JP4439199B2 - Vertical cavity surface emitting semiconductor laser device, optical logic operation device, wavelength converter, optical pulse waveform shaping device, and optical transmission system using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vertical cavity surface emitting semiconductor laser device having a modulation function, and an optical logic operation device, a wavelength converter, an optical pulse waveform shaping device, and an optical transmission system using the same.
[0002]
[Prior art]
A vertical cavity surface emitting semiconductor laser device that emits laser light in a direction perpendicular to the substrate is expected to be a functional device for optical communication and optical information processing due to its low power consumption and the ability to form a two-dimensional array. Has been.
[0003]
As devices that perform a bistable operation by providing a saturable absorption region in a vertical cavity surface emitting semiconductor laser device, Japanese Patent Publication Nos. 7-112087 (Patent Document 1) and JP-A-8-18146 ( Japanese Patent Publication No. 6-29625 (Patent Document 3) has been proposed.
[0004]
In the above-described bistable vertical cavity surface emitting semiconductor laser device, the laser beam output hysteresis characteristics with respect to the injection current of the active layer and the laser beam output hysteresis characteristics with respect to the light input to the saturable absorption region are used. Stable operation is realized.
[0005]
Therefore, when light is input to the saturable absorption region, the light output is kept on even when the light input is turned off. In order to turn off the optical output, it is necessary to increase the absorption by reducing the injection current of the active layer or increasing the reverse bias electric field applied to the saturable absorption region.
[0006]
In Japanese Patent Publication No. 6-29625 (Patent Document 3), an optical waveguide structure is provided to couple externally injected light to the saturable absorption region. Thereby, the coupling efficiency of externally injected light to the saturable absorption region is increased, and the optical switch operation is realized with a smaller light input intensity.
[0007]
In Japanese Patent Publication No. 6-29625 (Patent Document 3), another external injection light is incident on the active layer, and the bistable laser is shifted to the non-oscillation state by the gain quenching of the active layer. .
[0008]
JP-A-6-302916 (Patent Document 4) and JP-A-9-107148 (Patent Document 5) are other conventional examples in which a saturable absorption region is provided in a vertical cavity surface emitting semiconductor laser device. Proposed. This is a self-pulsation type semiconductor laser using a phenomenon that the saturable absorption region is absorbed and saturated by the light of the vertical cavity surface emitting semiconductor laser itself.
[0009]
Furthermore, Japanese Patent Laid-Open No. 5-152673 (Patent Document 6) proposes a structure in which an external modulator that changes the light absorption rate by electroabsorption is integrated in a vertical cavity surface emitting laser device.
[0010]
[Patent Document 1]
Japanese Patent Publication No.7-112087
[Patent Document 2]
JP-A-8-18146
[Patent Document 3]
Japanese Patent Publication No. 6-29625
[Patent Document 4]
JP-A-6-302916
[Patent Document 5]
JP-A-9-107148
[Patent Document 6]
JP-A-5-152673
[0011]
[Problems to be solved by the invention]
In the bistable vertical cavity surface emitting semiconductor laser device disclosed in Japanese Patent Publication No. 7-112087 (Patent Document 1) and Japanese Patent Laid-Open No. 8-18146 (Patent Document 2), light is input to the saturable absorption region. Is input, the light output remains on even when the light input is turned off. In order to turn off the optical output, it is necessary to increase the absorption by reducing the injection current of the active layer or increasing the reverse bias electric field applied to the saturable absorption region. Therefore, the output light cannot be turned on / off only by light input.
[0012]
In Japanese Patent Publication No. 6-29625 (Patent Document 3), the externally injected light is incident on the active layer separately from the externally injected light for turning on the light output, so that the bistable laser device is in a non-oscillating state. Transition to. For this reason, two control lights are required.
[0013]
In the self-oscillation vertical cavity surface emitting semiconductor laser device disclosed in Japanese Patent Laid-Open No. 6-302916 (Patent Document 4) and Japanese Patent Laid-Open No. 9-107148 (Patent Document 5), data is transmitted as pulse light. The signal cannot be directly applied at the self-oscillation frequency.
[0014]
In addition, in a vertical cavity surface emitting laser integrated with an external modulator as disclosed in Japanese Patent Laid-Open No. 5-152673 (Patent Document 6), the light intensity is modulated with the electric field strength applied to the modulator. All-optical switch operation cannot be realized.
[0015]
  Therefore, each claim of the present invention has the following object.Have.
[0017]
  Claim1From10Invention described inIsAn object is to realize a high-performance optical signal processing device (vertical cavity surface emitting semiconductor laser device, optical logic operation device, wavelength converter, optical pulse waveform shaping device, and optical transmission system using the same).
[0018]
[Means for Solving the Invention]
In order to achieve the above object, the present invention employs the following configuration. The characteristics of each claim will be described below.
[0022]
aClaim1The described invention includes, on a substrate, a resonator including an active layer, a distributed Bragg reflector formed above and below the resonator, and a light absorption layer that absorbs light of the active layer, and a laser perpendicular to the substrate. In a surface-type vertical cavity surface emitting semiconductor laser device that outputs oscillation light,SaidOf laser oscillation lightBasic transverse mode and primary higher-order modeIs modulated by the external input light intensity.
[0023]
bClaim2The described invention includes a resonator including an active layer on a substrate, a distributed Bragg reflector formed above and below the resonator, and a light absorbing layer that absorbs light of the active layer, and is perpendicular to the substrate. A surface-type semiconductor light-emitting device that outputs laser oscillation light and an electroabsorption optical modulator are monolithically integrated in a direction perpendicular to the substrate,SaidOf laser oscillation lightBasic transverse mode and primary higher-order modeModulated by external input light intensityDoThis is a vertical cavity surface emitting semiconductor laser device.
[0024]
cClaim3The invention described in claim 1Or 2The vertical cavity surface emitting semiconductor laser device described in 1) has a mechanism for sweeping the output light wavelength.
[0025]
dClaim4The invention described is from claim 13The vertical cavity surface emitting semiconductor laser device according to any one of the above is characterized in that intersubband absorption is used for light absorption of the light absorption layer.
[0026]
eClaim5The invention described is from claim 14In the vertical cavity surface emitting semiconductor laser device according to any one of the above, a mixed crystal semiconductor containing nitrogen and another group V element is used as a material for the light absorption layer and / or the active layer. It is said.
[0027]
fClaim6The invention described is from claim 15An optical logic operation device using the vertical cavity surface emitting semiconductor laser device according to any one of the above.
[0028]
gClaim7The invention described is from claim 15A wavelength converter using the vertical cavity surface emitting semiconductor laser device according to any one of the above.
[0029]
hClaim8The described invention is claimed.7The described wavelength converter is characterized by converting an optical signal having a wavelength of 0.85 μm and an optical signal having a wavelength of 1.3 μm.
[0030]
iClaim9The invention described is from claim 15An optical pulse waveform shaping device using the vertical cavity surface emitting semiconductor laser device according to any one of the above.
[0031]
jClaim10The invention described is from claim 15The vertical cavity surface emitting semiconductor laser device according to claim 1,6Claims optical logic operation device, claim7Or8The wavelength converter according to claim 1 or claim9An optical transmission system using the described optical pulse waveform shaping device.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
(1) FirstReference form
  The first of the present inventionreferenceAs shown in FIG. 1, a resonator 603 including an active layer 605 on a substrate 601, distributed Bragg reflectors 602 and 608 formed above and below the resonator 603, and an active layer 605 are formed. The present invention relates to a light modulation method for modulating the output light intensity of a vertical cavity surface emitting semiconductor laser device including a light absorption layer 604 that absorbs light.
[0033]
Here, description will be made using the structure shown in FIG. 1, but the optical modulation method described here is shown in FIGS. 10, 11, 12, 13, 14, 16, 16, and 19 described later. The present invention can also be applied to the structure of the vertical cavity surface emitting semiconductor laser device shown.
[0034]
  BookExampleFor example, by adopting a structure having the light absorption layer 604 structure as shown in FIG. 1, when input light is incident from the outside, the resonator loss is reduced due to absorption saturation of the light absorption layer 604, and the threshold value is reduced. When the current decreases, the output light intensity increases, and when the input light from the outside is blocked, the resonator loss due to the light absorption layer 604 increases and the threshold current increases, thereby decreasing the output light intensity. Light modulation is realized using the action. More detailed explanation will be described later.referenceSee Example 1.
[0035]
FIG. 2 is a diagram for explaining the light modulation operation, and shows the relationship between the injection current (Iop) to the active layer 605 and the light output.
[0036]
As shown in FIG. 1, by providing the light absorption layer 604 that absorbs the light of the active layer 605 in the vertical cavity surface emitting semiconductor laser element, the light absorption loss increases as shown in FIG. The threshold current of the semiconductor laser increases as compared with the case where no light absorption layer is provided.
[0037]
Here, when light having a wavelength that is absorbed by the light absorption layer 604 is injected from the outside, the light absorption layer 604 absorbs externally injected light. Since carriers are generated in the light absorption layer 604 by the absorbed light, absorption saturation of the light absorption layer 604 occurs when the external injection light intensity is increased. Thereby, since the absorption coefficient of the light absorption layer 604 is reduced, the light absorption loss for the light generated in the active layer 605 is reduced.
[0038]
As a result, the threshold current of the semiconductor laser is lower than when no light is injected from the outside. Therefore, if the injection current (Iop) to the active layer 605 is kept constant, the intensity of the laser beam output by injecting light from the outside as shown in FIG. Will increase.
[0039]
Then, when the external injection light is turned off again, the carriers photoexcited in the light absorption layer are reduced, and the absorption of the active layer with respect to the light is increased. Therefore, as shown in FIG. 2B, the threshold current of the semiconductor laser increases and the light output decreases.
[0040]
In particular, the difference in output light intensity is increased by setting the operating current Iop to oscillate when there is input light from the outside and not to oscillate when there is no input light from the outside. Therefore, the S / N ratio of modulation can be increased.
[0041]
With the above operation, it is possible to control and modulate the intensity of the laser beam output from the vertical cavity surface emitting semiconductor laser by turning on / off the optical signal input from the outside.
[0042]
In the above method, unlike the methods shown in Patent Document 1, Patent Document 2, and Patent Document 6, the intensity of the laser beam output from the vertical cavity surface emitting semiconductor laser is not an electrical signal but an optical signal. It is possible to modulate.
[0043]
Further, unlike the method disclosed in Patent Document 3, the output light intensity can be modulated with only one control light, so that the system configuration is simplified.
[0044]
As described above, this method does not use the hysteresis characteristic of injection current-light output or light input-light output (see FIG. 2). The hysteresis of the injection current-light output characteristic appears because the absorption saturation of the light absorption layer is caused by the light itself generated in the active layer. In this method, the operation is performed in such a range that the absorption saturation of the light absorption layer is sufficiently small for the light generated in the active layer and large for the externally injected light.
[0045]
In the bistable laser using the hysteresis characteristic, the output light intensity remains strong because the laser oscillation state is maintained even when the external injection light is turned off. On the other hand, in this method, as shown in FIG. 2B, when the external injection light is turned off, the output light intensity is lower than when the external injection light is input. can do. In this respect, the operation is different from that of the bistable laser.
[0046]
Further, by providing the position of the light absorption layer outside the path for injecting current into the active layer, the change in the absorption coefficient of the light absorption layer does not depend on the carrier density in the active layer. Therefore, self-excited oscillation as shown in Patent Document 5 can be suppressed.
[0047]
A reverse bias electric field can be applied to the light absorption layer. Thereby, when the external injection light is turned off, the excited carriers remaining in the light absorption layer can be quickly discharged, so that the switch-off time can be further shortened.
[0048]
Also, the light injected from the outside can be two light beams, bias light and control light. That is, the light intensity of the bias light and the control light is adjusted so that the absorption saturation of the light absorption layer does not occur only with the bias light, and the absorption saturation occurs only when the bias light and the control light are combined. In this case, since the bias light may be CW light, the signal for modulating the intensity of the laser light output from the vertical cavity surface emitting semiconductor laser is only one control light.
[0049]
As the light absorption layer, in addition to the bulk semiconductor layer, a quantum well structure or a superlattice structure can be used.
[0050]
The light absorption layer can be provided in the resonator structure, in the lower distributed Bragg reflector, in the upper distributed Bragg reflector, or outside the distributed Bragg reflector.
When the light absorption layer is provided in the resonator structure, the light absorption layer can be brought close to the active layer, so that the light of the active layer can be efficiently absorbed.
[0051]
On the other hand, in order to suppress the self-excited oscillation, the light absorption layer needs to be provided outside the current injection path for the active layer. When the light absorption layer is provided in the distributed Bragg reflector, the electrode contact layer for injecting current into the active layer can be provided not in the resonator but in the distributed Bragg reflector away from the active layer. Therefore, an increase in element resistance can be suppressed.
[0052]
When the light absorption layer is provided in the upper or lower distributed Bragg reflector, it is preferable that the light absorption layer is provided in the distributed Bragg reflector within 5 cycles from the active layer side. This is because the peak intensity of the standing wave distribution of light in the device is greatly attenuated outside the five periods, and the efficiency of absorbing light generated in the active layer by the light absorption layer is reduced.
[0053]
Moreover, the light absorption efficiency by the light absorption layer can be improved by providing the position of the light absorption layer at an antinode position in the optical standing wave distribution in the vertical cavity surface emitting semiconductor laser element.
[0054]
(2) SecondReference form
  The second of the present inventionreferenceIn the embodiment, the substrate includes a resonator including an active layer, a distributed Bragg reflector formed above and below the resonator, and a light absorbing layer that absorbs light from the active layer, and is based on the intensity of input light from the outside. In the vertical cavity surface emitting semiconductor laser device capable of modulating the output light intensity, the resonator length is formed so that a plurality of resonator modes are formed in the high reflection band of the distributed Bragg reflector. One of the plurality of resonator modes is a laser oscillation wavelength, and another resonator mode coincides with the input light wavelength.
[0055]
  SecondreferenceThe device of the form is the firstreferenceIt is possible to use the light modulation method shown in the embodiment.
[0056]
  SecondreferenceIn the apparatus of the embodiment, as shown in FIG. 3, the length of the resonator is formed so that a plurality of resonator modes (λ1, λ2, λ3) are formed in the high reflection band of the distributed Bragg reflector. ing.
[0057]
For example, in the 1.3 μm band, when a distributed Bragg reflector is formed with a GaAs / AlAs material system, if the optical wavelength of the resonator is 6λ or more, a plurality of resonator modes are formed in the high reflection band. . By making the gain wavelength of the active layer substantially coincide with one of the resonator modes, the output light wavelength of the vertical cavity surface emitting semiconductor laser can be determined.
[0058]
In addition, among the plurality of resonator modes, a resonator mode different from the oscillation wavelength is matched with the input light wavelength. As a result, the light input to the vertical cavity surface emitting semiconductor laser element passes through the distributed Bragg reflector and is provided in the resonator structure or in the upper or lower distributed Bragg reflector. Therefore, the coupling efficiency between the light absorption layer and the external input light can be improved. Therefore, it is possible to modulate the output light with a smaller input light intensity.
[0059]
  In addition, since the input light wavelength and the output light wavelength are different, it is easy to distinguish the input light from the output light when used in a reflective type that inputs and outputs light from one surface of the element.
  BookreferenceThe element of the example can be used not only in the reflection type but also in the transmission type in which the light is input from one surface of the wafer and output from the other surface.
[0060]
(3) ThirdReference form
  The third of the present inventionreferenceIn the embodiment, the substrate includes a resonator including an active layer, a distributed Bragg reflector formed above and below the resonator, and a light absorbing layer that absorbs light from the active layer, and is based on the intensity of input light from the outside. The vertical cavity surface emitting semiconductor laser device capable of modulating the output light intensity is characterized in that a window portion for inputting the input light to the light absorption layer without passing through the distributed Bragg reflector is formed.
[0061]
  ThirdreferenceIn the embodiment, since the window portion for inputting the input light to the light absorption layer without passing through the distributed Bragg reflector is formed, the light input to the vertical cavity surface emitting semiconductor laser element is distributed to the distributed Bragg reflector. The light absorption layer provided in the resonator structure or the upper or lower distributed Bragg reflector can be penetrated without being reflected by the light. Therefore, the coupling efficiency between the light absorption layer and the external input light can be improved. Therefore, it is possible to modulate the output light with a smaller input light intensity.
[0062]
Further, it is not necessary to limit the input light wavelength to a wavelength that matches the resonator mode. As a result, the wavelength range of the input light can be increased, and the system configuration is less restricted. In addition, it can be stably operated against fluctuations in the wavelength of the input light.
[0063]
In Patent Document 3, an optical waveguide structure is provided to couple externally injected light to the saturable absorption region. On the other hand, in this system, input light can be incident on the substrate from the vertical direction without being coupled by the waveguide. Therefore, the manufacturing process can be simplified and the integration density of the elements can be increased.
[0064]
It should be noted that the absorption saturation of the light absorption layer must be generated at a portion corresponding to the oscillation region of the active layer. Therefore, it is desirable that the window portion through which the input light is incident be positioned so as to be a distance within the carrier diffusion length in the in-plane direction with respect to the oscillation region of the active layer.
[0065]
(4) No.1Embodiments (claims)1)
  First of the present invention1The embodiment includes a resonator including an active layer on a substrate, a distributed Bragg reflector formed above and below the resonator, and a light absorbing layer that absorbs light of the active layer, and a laser perpendicular to the substrate. In a vertical cavity surface emitting semiconductor laser element that outputs oscillation light, the transverse mode of the laser oscillation light is modulated by the intensity of external input light.
[0066]
  First1In this embodiment, a light absorption layer that absorbs light of the active layer is provided in the vertical cavity surface emitting semiconductor laser element by patterning in the plane. For example, there is no light absorption layer in the concentric central part of the light emitting region, and the light absorption layer is provided only in the peripheral part. For this reason, when there is no external input light, light absorption loss increases in the peripheral portion of the oscillation region, so that oscillation is likely to occur in the fundamental transverse mode.
[0067]
When light having a wavelength that is absorbed by the light absorption layer is injected from the outside, absorption saturation occurs in the peripheral light absorption layer, thereby reducing the absorption loss of the light absorption layer. As a result, the transverse mode easily oscillates in the higher order mode. By setting the injection current value of the active layer to oscillate in the basic transverse mode when there is no external input light, and to oscillate in the higher-order transverse mode when external input light is input, It becomes possible to modulate the transverse mode of the laser oscillation light.
[0068]
The vertical cavity surface emitting laser element has a different radiation distribution of light output depending on the transverse mode. Therefore, by selectively capturing light in a direction substantially perpendicular to the substrate, the light intensity is strong in the basic transverse mode and the light intensity is lowered in the high-order transverse mode, so that the light intensity can be modulated. (See FIG. 4).
[0069]
Further, as shown in FIG. 5, by detecting the light output from the vertical cavity surface emitting laser element simultaneously from the vertical direction and the oblique direction with respect to the substrate, as shown in FIG. Accordingly, it is possible to take out two types of output signals, a normal signal and an inverted signal.
[0070]
As another application, by inputting a signal as an electric signal to be injected into the active layer of the vertical cavity surface emitting laser element, and detecting the output laser beam simultaneously from the substrate in the vertical direction and the oblique direction, As shown in FIG. 7, the path of the output signal can be changed by the external input light.
[0071]
As a result, an optical branching operation for separating one series of optical signals (input light) into two series of output lights 1 and 2 becomes possible. Further, the electroabsorption optical modulator and the light emitting device of this embodiment can be integrated.
[0072]
(5) No.2Embodiments (claims)2)
  First of the present invention2The embodiment includes, on a substrate, a resonator including an active layer, distributed Bragg reflectors formed above and below the resonator, and a light absorption layer that absorbs light of the active layer, and is perpendicular to the substrate. A surface-type semiconductor light-emitting device that outputs laser oscillation light and an electroabsorption optical modulator are monolithically integrated in a direction perpendicular to the substrate so that the transverse mode of the laser oscillation light can be modulated by the external input light intensity. This is a feature of a vertical cavity surface emitting semiconductor laser device.
[0073]
When no bias is applied in the electroabsorption optical modulator, it is transparent to the light emitted from the active layer. Therefore, the threshold current of the surface emitting semiconductor laser remains low.
[0074]
On the other hand, when a reverse bias is applied to the electroabsorption optical modulator, the light absorption coefficient increases, so that the threshold current of the surface emitting semiconductor laser increases. Therefore, the laser beam output intensity can be modulated by keeping the injection current to the active layer constant and modulating the electric field applied to the electroabsorption optical modulator.
[0075]
The modulation method by applying an electric field to the semiconductor optical modulator can increase the modulation frequency as compared with the case of directly modulating the current value injected into the active layer. Therefore, it is possible to modulate the surface emitting semiconductor laser device with a modulation frequency as high as 10 to 50 GHz.
[0076]
  In addition2In the embodiment,1As in the first embodiment, a light absorption layer for absorbing light of the active layer is provided in the vertical cavity surface emitting semiconductor laser element by patterning in the plane. For example, there is no light absorption layer in the concentric central part of the light emitting region, and the light absorption layer is provided only in the peripheral part. For this reason, when there is no external input light, light absorption loss increases in the peripheral portion of the oscillation region, so that oscillation is likely to occur in the fundamental transverse mode.
[0077]
When light having a wavelength that is absorbed by the light absorption layer is injected from the outside, absorption saturation occurs in the peripheral light absorption layer, thereby reducing the absorption loss of the light absorption layer. As a result, the transverse mode easily oscillates in the higher order mode. By setting the injection current value of the active layer to oscillate in the basic transverse mode when there is no external input light, and to oscillate in the higher-order transverse mode when external input light is input, It becomes possible to modulate the transverse mode of the laser oscillation light.
[0078]
In this light emitting device, the current value injected into the active layer is kept constant, the signal is input as an electric field applied to the electroabsorption optical modulator, and the output laser beam is simultaneously transmitted in the vertical direction and the oblique direction with respect to the substrate. By detecting, the path of the output signal can be changed by the external input light. Thereby, for example, an optical branching operation for separating a serial optical signal having a high modulation frequency of 10 to 50 GHz into two systems can be realized.
[0079]
(6) No.3Embodiments (claims)3)
  First of the present invention3Embodiments 1 to 12The vertical cavity surface emitting semiconductor laser device described in the embodiment has a mechanism for sweeping the output light wavelength.
[0080]
As a mechanism for changing the oscillation wavelength of the vertical cavity surface emitting semiconductor laser element, there is a method of providing a refractive index modulation layer in the resonator. The refractive index modulation layer is made of a bulk material or a superlattice material, and is transparent to the oscillation wavelength. The refractive index can be changed by applying an electric field to the refractive index modulation layer or injecting a current. Thereby, it is possible to change the resonance wavelength by changing the optical length of the resonator.
[0081]
It is also possible to change the oscillation wavelength by providing a gap in the resonator, between the resonator and the reflecting mirror, or in the reflecting mirror and changing the interval.
[0082]
  1st to 1st of the present invention2In the vertical cavity surface emitting semiconductor laser device described in the embodiment, the input light wavelength range can be widened. However, as for the output light wavelength, only one wavelength can be output by the element.
[0083]
  However, the second3In this embodiment, the output light wavelength can also be changed. That is, the output light wavelength can be selected and emitted by the same element, such as wavelengths λ1, λ2,. For this reason, when light of wavelength λ1 is input, not only is wavelength converted to λ2 and output, but also when light of wavelength λ2 is input, it can be converted to λ1 and output.
[0084]
  No. described later7In this embodiment, it is necessary to use different elements having different structures for the element that converts the wavelength from λ1 to λ2 and the element that converts the wavelength from λ2 to λ1. However, in this embodiment, it is possible to mutually convert the optical signals of λ1 and λ2 with the same element.
[0085]
In addition, by making this element into a monolithic array, a small wavelength conversion switch that can output different wavelengths can be easily configured.
[0086]
(7) No.4Embodiments (claims)4)
  First of the present invention4In the embodiment, the first to the first3The vertical cavity surface emitting semiconductor laser device described in the embodiment is characterized in that intersubband absorption is used for light absorption of the light absorption layer.
[0087]
Intersubband absorption is absorption caused by transition between quantum levels in the conduction band (or valence band) in a quantum well structure, unlike absorption due to interband transition between the normal conduction band and valence band. is there. Since the intersubband absorption has a carrier relaxation time faster than the interband transition, the recovery time from the absorption saturation can be shortened when the intersubband absorption is used for the light absorption of the light absorption layer. Therefore, light modulation can be performed at higher speed.
[0088]
(8) No.5Embodiments (claims)5)
  First of the present invention5In the embodiment, the first to the first4The vertical cavity surface emitting semiconductor laser element described in the embodiment is characterized in that a mixed crystal semiconductor containing nitrogen and another group V element is used as a material for the light absorption layer and / or the active layer. .
[0089]
A mixed crystal semiconductor containing nitrogen and another group V element is known as a nitrogen-based group V mixed crystal semiconductor. This is a mixed crystal semiconductor containing any one or a plurality of elements of Ga, In, Al as a group III element and any one or a plurality of elements of As, P, Sb in addition to nitrogen (N) as a group V element.
[0090]
GaNAs, GaNASSb, GaInNAs, GaInNAsSb, GaInNAsP, GaInNAsPSb, etc. can be epitaxially grown on a GaAs substrate. And in the range with a small nitrogen composition, it has the characteristic that an energy band gap becomes small compared with the original crystal | crystallization which does not contain nitrogen. Thereby, an active layer having a long wavelength band of 1.2 μm to 1.6 μm or a light absorption layer can be formed on the GaAs substrate. Accordingly, a vertical cavity surface emitting semiconductor laser element suitable for the wavelength used in optical communication can be configured.
[0091]
By using a GaAs substrate, a high performance distributed Bragg reflector made of an AlGaAs material system can be used. Therefore, the characteristics of the vertical cavity surface emitting laser that is the basis of the configuration of the present invention are improved.
[0092]
Nitrogen is known to be highly immiscible with other group V elements such as As and P. Therefore, by increasing the nitrogen composition in the light absorption layer, non-radiative recombination centers can be increased and the carrier life can be shortened. Therefore, the carrier relaxation time can be shortened and the light can be modulated at a higher speed, similar to the effect of high concentration doping in the light absorption layer.
[0093]
In addition, when nitrogen is added with a small composition to a semiconductor whose main element is As or P as a group V element, the band edge position of the conduction band is greatly lowered. For example, Ga containing 1% N_0.7In_0.3N_0.01As_0.99Has been reported to have a conduction band edge discontinuity of 350 meV with respect to GaAs (IEEE Journal of Selected Topics of Quantum Electronics, Vol. 3, No. 3, p719).
[0094]
Due to this effect, when a mixed crystal semiconductor containing nitrogen and another group V element is used for the well layer, the conduction band discontinuity can be expanded, and the light absorption layer utilizing intersubband absorption in the conduction band. It is also possible to configure.
[0095]
(9) No.6Embodiments (claims)6)
  First of the present invention6Embodiments 1 to 15This is an optical logic operation device using the vertical cavity surface emitting semiconductor laser device according to the embodiment.
[0096]
As an example, a case where two light absorption layers that absorb light of the active layer are provided will be described. The external input light A is input to the first light absorption layer and saturates the light absorption coefficient of the first light absorption layer. Further, the external input light B is input to the second light absorption layer and saturates the light absorption coefficient of the second light absorption layer.
[0097]
When external input light A and B are input at the same time, the absorption loss of the light absorption layer is reduced and laser oscillation occurs, and when there is no external input light or when only one input is input, laser oscillation does not occur. The injection current of the active layer is controlled. As a result, it is possible to output light corresponding to an AND logical operation for two input optical signals.
[0098]
Further, the injection current of the active layer can be set so that laser oscillation occurs when one or both of the external input light is input and laser oscillation does not occur when there is no external input light. In this case, it is possible to output light corresponding to an OR logical operation for two input optical signals.
[0099]
Therefore, by controlling the current value injected into the active layer, an optical logic operation element that can realize both the AND operation and the OR operation can be configured.
[0100]
Furthermore, multi-valued logical operations can be performed by providing three or more light absorption layers. Further, even when there is only one light absorption layer, it is possible to execute a logical operation by adjusting the intensity of each input signal.
[0101]
(10) No.7Embodiments (claims)7)
  First of the present invention7Embodiments 1 to 15A wavelength converter using the vertical cavity surface emitting semiconductor laser device according to the embodiment.
[0102]
  A vertical cavity surface emitting semiconductor laser device including a resonator including an active layer, a distributed Bragg reflector formed above and below the resonator, and a light absorption layer that absorbs light of the active layer is used on a substrate. And the firstreferenceThe light modulation method described in the embodiment can be realized. At this time, the input light wavelength from the outside and the output light wavelength of the laser can be set to different wavelengths. SecondreferenceForm to No.5Also in the vertical cavity surface emitting semiconductor laser device described in the embodiment, the wavelength of the input light from the outside and the output light wavelength of the laser can be set to different wavelengths.
[0103]
  FirstreferenceIn the modulation system described in the embodiment, an on / off signal having an input light intensity can be converted into an on / off signal having an output light intensity as it is, so that an optical signal can be converted to a different wavelength. At this time, since both the input light wavelength and the output light wavelength need to be absorbed by the light absorption layer, the input light wavelength and the output light wavelength need to be the same as or shorter than the band gap wavelength of the light absorption layer. (See FIG. 8).
[0104]
Within this range, the input light wavelength may be shorter (λ2) or longer (λ3) than the output light wavelength (λ1). Therefore, in the wavelength conversion device of the present embodiment, by appropriately selecting and configuring the wavelengths of the input light and the output light, not only the wavelength conversion from the short wavelength (λ2) to the long wavelength (λ1) but also the long wavelength Conversion from (λ3) to a short wavelength (λ1) is also possible. For example, light having a wavelength of 0.85 μm and light having a wavelength of 1.3 μm can be converted.
[0105]
Further, by connecting this apparatus in two stages, it is possible to return the optical signal to the same wavelength.
[0106]
When the input light wavelength is shorter than the output light wavelength, when the input light is input to the active layer, the light is also absorbed in the active layer and photoexcited carriers are generated in the active layer. Therefore, even if the injection current applied to the active layer is constant, the light output increases because carriers due to photoexcitation are injected into the active layer. Accordingly, the external input light can modulate the output light intensity more greatly by the effect of photoexciting the active layer in addition to the function of absorbing and saturating the light absorption layer.
[0107]
(11) No.8Embodiments (claims)8)
  First of the present invention8The embodiment of the first7The wavelength conversion device according to the embodiment is characterized in that it converts an optical signal having a wavelength of 0.85 μm and an optical signal having a wavelength of 1.3 μm.
[0108]
When converting an input optical signal in the 0.85μm band to an output optical signal in the 1.3μm band, the band gap wavelength of the active layer is set to 1.3μm band, and the band gap wavelength of the light absorption layer is equal to or less than 1.3μm. Also set a longer wavelength. When input light having a wavelength of 0.85 μm is incident on the light absorption layer, the absorption coefficient is saturated in the light absorption layer, so that the intensity of the output light in the 1.3 μm band changes.
[0109]
Conversely, when converting an input optical signal in the 1.3 μm band into an output optical signal in the 0.85 μm band, the band gap wavelength of the active layer is set to 0.85 μm, and the band gap wavelength of the light absorption layer is equal to 1.3 μm. , Set to a longer wavelength. When input light having a wavelength of 1.3 μm is incident on the light absorption layer, the absorption coefficient is saturated in the light absorption layer, so that the intensity of output light in the 0.85 μm band changes.
[0110]
In the present invention, the input / output wavelength can be largely wavelength-converted from the 0.85 μm band to the 1.3 μm band, or from the 1.3 μm band to the 0.85 μm band. This is because the active layer and the light absorption layer are integrated in the stacking direction, and the respective band gaps can be arbitrarily changed. Due to this feature, the wavelength difference between the input light wavelength and the output light wavelength can be increased.
[0111]
The light in the 1.3 μm band corresponds to a wavelength with a small transmission loss in a single mode silica optical fiber, and is suitable for optical transmission between a relatively long distance LAN and equipment. On the other hand, the light in the 0.85 μm band can be used for optical wiring in equipment using multimode quartz optical fibers.
[0112]
By using the wavelength converter of the present embodiment, the 0.85 μm band optical signal used for the optical wiring in the device is converted into the 1.3 μm band optical signal outside the device without converting it to electricity once. Input / output is possible. Thereby, the transmission throughput can be greatly improved.
[0113]
(12) No.9Embodiments (claims)9)
  First of the present invention9Embodiments 1 to 15An optical pulse waveform shaping device using the vertical cavity surface emitting semiconductor laser device according to the embodiment.
[0114]
  First9Also in the optical pulse waveform shaping device of the embodiment, basically the firstreferenceThe optical modulation system described in the embodiment is used for operation.
[0115]
As shown in FIG. 9, two types of light, clock light and signal light, are used as light input to the element from the outside. Consider a case in which the signal light is not rectangular due to the influence of dispersion caused by optical transmission, and the rising and falling edges have a trailing edge due to deterioration. On the other hand, the clock light is a rectangular pulse and determines the timing of data extraction.
[0116]
When the optical pulse shape is distorted by transmission and the rising and falling edges of the pulse become trailing, intersymbol interference occurs and the code reading error increases. Therefore, it is necessary to shape the pulse waveform to suppress intersymbol interference.
[0117]
When the clock light and the signal light are input at the same time, the intensity of the input light becomes strong at the portion of the signal light that overlaps the clock light, and the strength of the portion that does not overlap is low. Then, the output light intensity of the vertical cavity surface emitting laser becomes strong (oscillation state) in the portion where the clock light and the signal light overlap, and the output light intensity of the vertical cavity surface emitting laser is low in the portion where it does not overlap. The optical output threshold value (Pth) is set so that (oscillation is stopped).
[0118]
As a result, the input intensity is lower than Pth at the rising and falling portions of the signal light, so that the output intensity remains low, and output light corresponding to the pulse width of the clock light is obtained.
[0119]
Further, by setting the light intensity of the clock light lower than Pth, the output light intensity of the vertical cavity surface emitting laser can be kept low in the case of only the clock light to which no signal light is input. Thereby, the on / off information of the signal light is directly inherited by the output light. Note that this optical pulse waveform shaping operation applies a logical operation using light as an input / output signal.
[0120]
With the above operation, it is possible to shape and output an optical pulse waveform that is degraded and has a tail at the rising and falling edges of the pulse.
[0121]
  The optical pulse waveform shaping device of the present embodiment has first to first5The vertical cavity surface emitting semiconductor laser device in the embodiment is basically used. Therefore, an optical pulse waveform shaping device can be formed by taking advantage of the features of the vertical cavity surface emitting semiconductor laser device, such as low power consumption, low cost, and easy two-dimensional array.
[0122]
(13) No.10Embodiments (claims)10)
  First of the present invention10In the optical transmission system according to the embodiment, the first to the first5Vertical cavity surface emitting semiconductor laser device according to any of the embodiments,6Optical logic unit of the embodiment,7Or second8Wavelength converter of the embodiment, or9The optical transmission system characterized by using the optical pulse waveform shaping device of the embodiment is used.
[0123]
As a result, a high-performance optical transmission system having optical information processing functions such as optical logic operation, wavelength conversion, optical pulse waveform shaping, and sequence separation can be configured. Since the basic element of a semiconductor light emitting device that performs optical information processing is a vertical cavity surface emitting semiconductor laser device, a system can be constructed with low power consumption and low cost. Also, a two-dimensional array is possible, and the structure is suitable for optical parallel information processing.
[0124]
  Next, it demonstrates more concretely using the detailed Example of this invention.
  First, a reference example of the present invention will be described, and then an example will be described.
(referenceExample 1)
  FIG. 1 illustrates the present invention.reference1 is a cross-sectional view of a vertical cavity surface emitting semiconductor laser device having a modulation function according to Example 1. FIG.
[0125]
Referring to FIG. 1, an n-type lower distributed Bragg reflector (DBR) 602 is stacked on an n-type GaAs substrate 601. The n-type lower DBR 602 has a high refractive index layer of GaAs and a low refractive index layer of AlGaAs, for example, Al._0.8Ga_0.2It is formed by alternately laminating as As.
[0126]
A resonator structure 603 is formed on the n-type lower DBR 602. In the resonator structure 603, a light absorption layer 604 having an InGaAs / GaAs multiple quantum well (MQW) structure, an InGaAs / GaAs-MQW active layer 605, and an AlAs layer 606 are provided from the substrate side. In the resonator structure, the light absorption layer 604, the active layer 605, and the AlAs layer 606 are each composed of a GaAs spacer layer.
[0127]
The band gap of the InGaAs well layer of the light absorption layer 604 is the same as or smaller than the band gap of the InGaAs well layer of the active layer 605 so that the light generated in the active layer 605 can be absorbed.
[0128]
The active layer 605 and the light absorption layer 604 are provided at antinode positions in the standing wave distribution of light in the resonator structure. This is to increase the coupling efficiency between the active layer and the light absorption layer and light. The AlAs layer 606 is provided at the position of a node in the standing wave distribution of light in the resonator structure.
[0129]
A p-type upper DBR 608 is stacked on the resonator structure 603. The p-type upper DBR 608 has a high refractive index layer of GaAs and a low refractive index layer of AlGaAs, for example, Al._0.8Ga_0.2It is formed by alternately laminating as As.
[0130]
A rectangular or cylindrical mesa structure is formed by etching from the surface of the laminated structure to between the active layer 605 and the light absorption layer 604. A p-side electrode 609 is formed on the top of the mesa structure except for the light emitting portion, and an n-side electrode 610 is formed in the middle of the resonator structure 603 whose surface is exposed by mesa etching. Although not shown, the n-side electrode 610 is formed on the n-type GaAs contact layer in the resonator structure.
[0131]
The AlAs layer 606 is selectively oxidized from the mesa-etched side surface to form an insulating region 607.
[0132]
When a forward bias is applied to the p-side electrode 609 and the n-side electrode 610, the current is confined in the insulating region 607, passes through the opening of the unoxidized AlAs layer 606, and the InGaAs / GaAs-MQW active layer 605. A current is injected into the light, and light is emitted at a wavelength of 0.98 μm.
[0133]
The light generated in the active layer 605 resonates in the resonator structure 603 sandwiched between the lower DBR 602 and the upper DBR 608, and oscillates and is output upward in the direction perpendicular to the substrate. That is, the semiconductor light emitting device of FIG. 1 operates as a vertical cavity surface emitting semiconductor laser.
[0134]
In the vertical cavity surface emitting semiconductor laser device of FIG. 1, a light absorption layer 604 that absorbs light of the active layer 605 is provided in the resonator. Therefore, as shown in FIG. 2B, the absorption loss of the resonator is increased by the light absorption layer 604, and the threshold current of the semiconductor laser is increased as compared with the case where the light absorption layer 604 is not provided.
[0135]
Here, light having a wavelength absorbed by the light absorption layer 604, for example, light having a wavelength of 0.98 μm, is injected from the outside (substrate side). Since GaAs is transparent to light having a wavelength of 0.98 μm, the externally injected light is transmitted through the n-type GaAs substrate 601 and incident on the light absorption layer 604, and the light is absorbed. Since carriers are generated in the light absorption layer 604 due to the absorbed light, absorption saturation of the light absorption layer 604 occurs when the external input light intensity is increased.
[0136]
Thereby, since the absorption coefficient of the light absorption layer 604 is reduced, the light absorption loss for the light generated in the active layer 605 is also reduced. As a result, the threshold current of the semiconductor laser is lower than when no light is injected from the outside. Therefore, if the injection current (Iop) to the active layer 605 is kept constant, the intensity of the laser beam output by injecting light from the outside as shown in FIG. Will increase.
[0137]
When the external input light is turned off again, the carriers photoexcited in the light absorption layer 604 decrease, and the absorption of light in the active layer 605 increases. Therefore, as shown in FIG. 2B, the threshold current of the semiconductor laser increases and the light output decreases.
[0138]
With the above operation, it is possible to control and modulate the intensity of the laser beam output from the vertical cavity surface emitting semiconductor laser device by turning on / off the optical input signal from the outside.
[0139]
In the structure shown in FIG. 1, it is possible to form an electrode on the back surface of the n-type GaAs substrate 601 and apply a reverse bias electric field to the light absorption layer 604. Thereby, when the external injection light is turned off, the excited carriers remaining in the light absorption layer 604 can be quickly discharged, so that the switch-off time can be further shortened.
[0140]
(referenceExample 2)
  FIG. 10 illustrates the present invention.reference6 is a sectional view of a vertical cavity surface emitting semiconductor laser device according to Example 2. FIG.
[0141]
Referring to FIG. 10, an n-type lower GaAs / AlGaAs-DBR 602 is stacked on an n-type GaAs substrate 601. A resonator structure 603 is formed on the n-type lower DBR 602.
[0142]
In the resonator structure 603, an InGaAs / GaAs-MQW active layer 605, an AlAs layer 606, and an InGaAs / GaAs-MQW light absorption layer 604 are provided from the substrate side. In the resonator structure, the active layer 605, the AlAs layer 606, and the light absorption layer 604 are each composed of a GaAs spacer layer.
[0143]
The band gap of the InGaAs well layer of the light absorption layer 604 is the same as or smaller than the band gap of the InGaAs well layer of the active layer 605 so that the light generated in the active layer 605 can be absorbed.
[0144]
The active layer 605 and the light absorption layer 604 are provided at antinode positions in the standing wave distribution of light in the resonator structure. The AlAs layer 606 is provided at the position of a node in the standing wave distribution of light in the resonator structure. A p-type upper GaAs / AlGaAs-DBR 608 is stacked on the resonator structure 603.
[0145]
A rectangular or cylindrical first mesa structure is formed by etching from the surface of the laminated structure to between the light absorption layer 604 and the AlAs layer 606. Further, the second mesa structure is formed by etching with a mesa size larger than that of the first mesa structure until the n-type lower DBR 602 is reached.
[0146]
A p-side electrode 609 is formed in the middle of the resonator structure whose surface is exposed by the etching of the first mesa structure, and an n-side electrode 610 is formed on the back surface of the n-type GaAs substrate 601. Although not shown, the p-side electrode 609 is formed on the p-type GaAs contact layer in the resonator structure.
[0147]
The AlAs layer 606 is selectively oxidized from the mesa side surface exposed by the etching of the second mesa structure to form an insulating region 607.
[0148]
Also in the vertical cavity surface emitting semiconductor laser device of the second embodiment shown in FIG. 10, as in the first embodiment, the vertical cavity surface emitting semiconductor laser device is turned on / off by turning on / off an optical input signal from the outside. It is possible to control and modulate the intensity of the laser beam output from. In Example 1, the transmission type is configured to input light from the back surface of the substrate and output light from the substrate surface. However, in Example 2, both input light and output light are input from the substrate surface. Reflective type to output.
[0149]
Furthermore, the vertical cavity surface emitting semiconductor laser device shown in FIG. 10 is characterized in that a plurality of resonator modes are formed in the high reflection band of the DBR by increasing the cavity length. . In this embodiment, the optical thickness of the entire resonator structure is 10λ, and three resonator modes of 950.5 nm, 980 nm, and 1012 nm are formed.
[0150]
By making the band gap wavelength of the active layer 605 substantially coincide with 980 nm, the output light wavelength of the vertical cavity surface emitting semiconductor laser device is set to 980 nm.
[0151]
Further, among the plurality of resonator modes, the input light wavelength is matched with the resonator mode 950.5 nm different from the oscillation wavelength 980 nm. As a result, light input to the vertical cavity surface emitting semiconductor laser device can pass through the p-type DBR 608 and enter the light absorption layer 604 provided in the resonator structure 603. The coupling efficiency between the layer 604 and the input light can be improved. Therefore, it is possible to modulate the output light with a smaller input light intensity.
[0152]
In this embodiment, the reflection type is used to input and output light from one surface of the element. However, since the input light wavelength and the output light wavelength are different, the signal separation between the input light and the output light is very high. Easy.
[0153]
(referenceExample 3)
  FIG. 11 shows the present invention.reference6 is a sectional view of a vertical cavity surface emitting semiconductor laser device according to Example 3. FIG.
[0154]
Referring to FIG. 11, a first n-type GaAs / AlGaAs lower DBR 801 is stacked on an n-type GaAs substrate 601. A light absorption layer 604 having an InGaAs / GaAs-MQW structure is formed on the n-type lower DBR 801, and a second n-type GaAs / AlGaAs lower DBR 802 and a GaAs lower spacer layer 803 are formed on the light absorption layer 604. InGaAs / GaAs-MQW active layer 605, GaAs upper spacer layer 804, AlAs layer 606, and p-type GaAs / AlGaAs upper DBR 608 are sequentially stacked.
[0155]
A region where the GaAs lower spacer layer 803, the InGaAs / GaAs-MQW active layer 605, and the GaAs upper spacer layer 804 are combined has a resonator structure. The active layer 605 is provided at an antinode position in the standing wave distribution of light in the resonator structure. In addition, the AlAs layer 606 is provided at a node position in the standing wave distribution of the light of the element.
[0156]
The band gap of the InGaAs well layer of the light absorption layer 604 is the same as or smaller than the band gap of the InGaAs well layer of the active layer 605 so that the light generated in the active layer 605 can be absorbed.
[0157]
A rectangular or cylindrical mesa structure is formed by etching from the surface of the laminated structure to the middle of the second n-type GaAs / AlGaAs lower DBR 802. A p-side electrode 609 is formed on the top of the mesa structure except for the light emitting portion, and an n-side electrode 610 is formed on the surface exposed by mesa etching.
[0158]
Further, a portion of the n-side electrode 610 is removed, and a window portion 805 for inputting light from the outside is formed. The distance between the light absorption layer 604 and the surface of the window portion 805 was made to be thinner than λ / 4 in terms of optical distance.
[0159]
The AlAs layer 606 is selectively oxidized from the mesa-etched side surface to form an insulating region 607.
[0160]
In the vertical cavity surface emitting semiconductor laser device of FIG. 11, a window portion 805 is provided so that light is input from the outside to the light absorption layer 604 without passing through the distributed Bragg reflector. Therefore, the input light is not reflected by the distributed Bragg reflector and can enter the light absorption layer 604 provided in the lower DBR. Therefore, the coupling efficiency between the light absorption layer 604 and the external input light can be improved. Therefore, it is possible to modulate the output light with a smaller input light intensity.
[0161]
Further, it is not necessary to limit the input light wavelength to a wavelength that matches the resonator mode. Therefore, the wavelength range used as input light can be increased, and the system configuration is less restricted. In addition, it can be stably operated against fluctuations in the wavelength of the input light.
[0162]
  the abovereferenceIn the example, the distance between the light absorption layer 604 and the surface of the window portion 805 is made to be thinner than λ / 4 in terms of optical distance. However, a thin DBR may be provided between the light absorption layer 604 and the window portion 805 surface.
[0163]
By reducing the DBR period between the light absorption layer 604 and the surface of the window portion 805 to 1 to 2 periods, the reflection of the input light is suppressed and the coupling efficiency between the light absorption layer 604 and the input light is improved. However, as the DBR period between the light absorption layer 604 and the surface of the window portion 805 increases, the band in which the light absorption layer 604 can enter becomes narrower. Therefore, it is preferable to reduce the layer thickness.
[0164]
  Next, wavelength conversion operation using the vertical cavity surface emitting semiconductor laser device of FIG. 11 will be described.
  In the element of FIG.referenceAs in Example 1, the laser output light intensity can be modulated by turning on / off the input light intensity. Therefore, a digital signal based on the intensity modulation of the input light can be converted into a digital signal based on the intensity of the output light as it is.
[0165]
Both the wavelength of the input light and the wavelength of the output light need to be the same or shorter than the band gap wavelength of the light absorption layer 604. This is because the light absorption layer 604 can absorb the input light and the light generated in the active layer 605. In this embodiment, the band gap wavelength of the light absorption layer 604 is 1100 nm, and the wavelength of output light is 980 nm.
[0166]
On the other hand, since the input light is coupled to the light absorption layer 604 without passing through the DBR, the input light wavelength is not limited by the resonance mode. Therefore, the selection range of the input light wavelength is widened.
[0167]
When light having a wavelength of 950 nm is used as the input light wavelength, the input light is shorter than the band gap wavelength of the light absorption layer 604 and thus is absorbed by the light absorption layer 604. Therefore, it is possible to convert a 950 nm optical signal into a 980 nm optical signal.
[0168]
Even when light having a wavelength of 1020 nm is used as the input light wavelength, the input light is shorter than the band gap wavelength of the light absorption layer 604 and thus is absorbed by the light absorption layer 604. Therefore, it is possible to convert a 1020 nm optical signal into a 980 nm optical signal.
[0169]
That is, using the same element, wavelength conversion from a short wavelength to a long wavelength and conversion from a long wavelength to a short wavelength are possible. Therefore, wavelength conversion processing in wavelength division multiplex communication can be easily performed.
[0170]
  Next, examples of the present invention will be described.
(Example1)
  FIG. 12 shows an embodiment of the present invention.11 is a cross-sectional view of a vertical cavity surface emitting semiconductor laser device according to FIG.
[0171]
Referring to FIG. 12, an n-type GaAs / AlGaAs lower DBR 602 is stacked on an n-type GaAs substrate 601. On the n-type lower DBR 602, a GaAs lower spacer layer 803, a GaInNAs / GaAs-MQW active layer 1001, a GaAs upper spacer layer 804, an AlAs layer 606, and a p-type GaAs / AlGaAs upper DBR 608 are sequentially stacked.
[0172]
A cylindrical mesa structure is formed by etching from the surface of the laminated structure until it reaches the n-type GaAs / AlGaAs lower DBR 602. A ring-shaped p-side electrode 609 is formed on the top of the mesa structure except for the light emitting portion. An n-side electrode 610 is formed on the back surface of the n-type GaAs substrate 601.
[0173]
Further, as a feature of the element of FIG. 12, a GaInNAs / GaAs-MQW light absorption layer 1002 is formed in a ring shape at the opening of a circular p-side electrode 609 formed at the top of the mesa structure.
[0174]
In addition, the AlAs layer 606 is selectively oxidized from the mesa-etched side surface to form an insulating region 607.
[0175]
In the vertical cavity surface emitting semiconductor laser device of FIG. 12, a light absorption layer 1002 that absorbs light generated in the active layer 1001 is formed in a ring shape. Therefore, when there is no external input light, the optical absorption layer 1002 increases the optical absorption loss in the periphery of the oscillation region. Therefore, the higher-order transverse mode has a larger loss than the fundamental transverse mode, and the fundamental mode oscillates. It becomes easy.
[0176]
On the other hand, when light having a wavelength that is absorbed by the light absorption layer 1002 is injected from the outside, absorption saturation occurs in the light absorption layer 1002, thereby reducing absorption loss of the light absorption layer 1002. For this reason, there is no difference in absorption loss between the central portion and the peripheral portion of the oscillation region, and oscillation in the high-order transverse mode is facilitated.
[0177]
Therefore, by setting the injection current value of the active layer to oscillate in the fundamental transverse mode when there is no external input light, and to oscillate in the high-order transverse mode when external input light is input, It becomes possible to modulate the transverse mode of the laser oscillation light with light.
[0178]
An example of the radiation distribution of the output light in the vertical cavity surface emitting laser device is shown in FIG. In the case of the basic transverse mode, the light intensity is highest in the direction perpendicular to the substrate. On the other hand, in the high-order (primary) mode, the intensity is small in the direction perpendicular to the substrate, and the light intensity is high in the direction inclined by 10 to 15 degrees. Therefore, when the light output from the element of FIG. 12 is detected from the vertical direction or the oblique direction, the light intensity is modulated by the transverse mode.
[0179]
In this case, when the light output from the element of FIG. 12 is detected from the direction perpendicular to the substrate, the output code is inverted with respect to the input code and output. On the other hand, when detected from an oblique direction with respect to the substrate, it is output as it is without being inverted.
[0180]
In this embodiment, GaInNAs is used as the well layer material of the active layer 1001. GaInNAs can be epitaxially grown on a GaAs substrate, and has a characteristic that the energy band gap is smaller than GaInAs not containing nitrogen in a range where the nitrogen composition is small.
[0181]
Thereby, an active layer having a long wavelength band of 1.2 μm to 1.6 μm can be formed on the GaAs substrate. Therefore, a semiconductor light emitting device suitable for the wavelength band used in optical communication can be configured. In this embodiment, the output light wavelength is 1.3 μm.
[0182]
Further, by using a GaAs substrate, a high-performance DBR composed of a GaAs / AlGaAs material system can be used. Therefore, the characteristics of the vertical cavity surface emitting laser that is the basis of the configuration of the present invention are improved. That is, a long-wavelength surface emitting laser with low power consumption and good temperature characteristics can be manufactured.
[0183]
In this embodiment, GaInNAs is also used for the well layer material of the light absorption layer 1002. Since nitrogen (N) is highly immiscible with As, which is another group V element, the carrier life can be shortened by making the nitrogen composition higher in the light absorption layer 1002 than in the active layer. Thereby, the carrier relaxation time in the light absorption layer 1002 can be shortened, and light can be modulated at higher speed.
[0184]
(Example2)
  FIG. 13 shows an embodiment of the present invention.2It is sectional drawing of the semiconductor light-emitting device based on.
  Referring to FIG. 13, a p-type GaAs / AlGaAs lower DBR 1502 is stacked on a p-type GaAs substrate 1501. On the p-type lower DBR 1502, a light absorption layer 1503 and an n-type GaAs / AlGaAs lower DBR 1504 are stacked.
[0185]
An AlAs layer 1505 is provided in the middle of the n-type GaAs / AlGaAs lower DBR 1504. Further, on the n-type GaAs / AlGaAs lower DBR 1504, a GaAs lower spacer layer 803, a GaInNAs / GaAs-MQW active layer 1001, a GaAs upper spacer layer 804, an AlAs layer 606, and a p-type GaAs / AlGaAs upper DBR 608 are sequentially stacked. ing.
[0186]
A cylindrical mesa structure is formed by etching from the surface of the laminated structure until reaching the n-type GaAs / AlGaAs lower DBR 1504. A ring-shaped p-side electrode 609 is formed on the top of the mesa structure except for the light emitting portion.
[0187]
Further, a GaInNAs / GaAs-MQW light absorption layer 1002 is formed in a ring shape at the opening of the circular p-side electrode 609 formed at the top of the mesa structure.
[0188]
Reference numeral 1506 denotes an n-side electrode formed on the n-type GaAs / AlGaAs lower DBR 1504 whose surface is exposed by etching, and 1507 denotes a p-side electrode (610) formed on the back surface of the p-type GaAs substrate 1501.
[0189]
Also, the AlAs layers 606 and 1505 are selectively oxidized from the side surfaces to form an insulating region 607.
[0190]
In the semiconductor light emitting device of FIG. 13, by applying a forward bias between the electrode 609 and the electrode 1506, current is injected into the active layer 1001 to emit light. At this time, since the current passes through a region where the AlAs layer 606 is not selectively oxidized, the current can be narrowed corresponding to the opening diameter of the oxidation.
[0191]
The light emitted from the active layer 1001 resonates between the DBR 608, the DBR 1504, and the DBR 1502, and laser oscillates in a direction perpendicular to the substrate when the gain exceeds the loss.
[0192]
Further, the light absorption layer 1503 constitutes an electroabsorption optical modulator. By applying a reverse bias between the electrode 1506 and the electrode 1507, an electric field is applied to the light absorption layer 1503 in the laser oscillation region through the AlAs layer 1505 that is not selectively oxidized.
[0193]
When an electric field is applied to the light absorption layer 1503, the band gap of the light absorption layer 1503 is reduced. The band gap of the light absorption layer 1503 was set so that it was transparent to the light of the active layer 1001 when no electric field was applied, and the light of the active layer 1001 was absorbed when the electric field was applied.
[0194]
When no bias is applied to the light absorption layer 1503, the threshold current of the surface emitting semiconductor laser remains low because it is transparent to the light emitted from the active layer 1001.
[0195]
On the other hand, when a reverse bias is applied to the light absorption layer 1503, the light absorption loss increases, so that the threshold current of the surface emitting semiconductor laser increases. Accordingly, the laser beam output intensity can be modulated by keeping the injection current to the active layer 1001 constant and modulating the electric field applied to the light absorption layer 1503.
[0196]
The method of applying and modulating an electric field to an electroabsorption optical modulator composed of the light absorption layer 1503 can increase the modulation frequency as compared with the case of directly modulating the current value injected into the active layer 1001. Therefore, it is possible to modulate the surface emitting semiconductor laser device with a modulation frequency as high as 10 to 50 GHz.
[0197]
As the light absorption layer 1503, a bulk layer or a quantum well structure can be used. In this embodiment, the light absorption layer 1503 is configured with a GaInNAs / GaAs-MQW structure.
[0198]
In FIG. 13, another light absorption layer 1002 that absorbs light generated in the active layer 1001 is formed in a ring shape. When there is no external input light, the optical absorption loss is increased by the light absorption layer 1002 in the periphery of the oscillation region. Therefore, the higher-order transverse mode has a larger loss than the fundamental transverse mode, and the fundamental mode easily oscillates. .
[0199]
On the other hand, when light having a wavelength that is absorbed by the light absorption layer 1002 is injected from the outside, absorption saturation occurs in the light absorption layer 1002, thereby reducing absorption loss of the light absorption layer 1002. For this reason, there is no difference in absorption loss between the central portion and the peripheral portion of the oscillation region, and oscillation in the high-order transverse mode is facilitated.
[0200]
Therefore, by setting the injection current value of the active layer to oscillate in the fundamental transverse mode when there is no external input light, and to oscillate in the high-order transverse mode when external input light is input, It becomes possible to modulate the transverse mode of the laser oscillation light with light.
[0201]
With the above structure, the semiconductor light emitting device in FIG. 13 modulates the output light intensity by the electric field applied to the light absorption layer 1503 and modulates the transverse mode of the laser oscillation light by the external light input to the light absorption layer 1002. Can do. Each modulation can be controlled independently.
[0202]
The current value injected into the active layer 1001 is kept constant, a signal is input as an electric field to be applied to the light absorption layer 1503, and the output laser beam is detected simultaneously from the direction perpendicular to the substrate and from the oblique direction. The path of the output signal can be changed by the input light. Thereby, for example, an optical branching operation for separating a serial signal having a high modulation frequency of 10 to 50 GHz into two series can be realized.
[0203]
(Example3)
  FIG. 14 shows an embodiment of the present invention.3It is sectional drawing of the semiconductor light-emitting device based on.
  Referring to FIG. 14, first lower distributed Bragg reflectors (DBR) 1701 and 1703 are stacked on an n-type GaAs substrate 601. In the lower DBR, a light absorption layer 1702 is provided.
[0204]
On the lower DBR 1703, an n-type GaAs spacer layer 1704, a GaInNAs / GaAs-MQW active layer 1001, a p-type GaAs spacer layer 1705, an AlAs layer 606, and a p-type GaAs spacer layer 1706 are sequentially stacked.
[0205]
Further, an upper DBR 1709 is provided on the p-type GaAs spacer layer 1706 via an air gap 1707. A region sandwiched between the lower DBR 1703 and the upper DBR 1709 forms a resonator structure 1708.
[0206]
A mesa structure is formed by etching from the surface of the laminated structure until reaching the lower DBR 1703. A p-side electrode 1710 is formed on the top of the mesa structure except for the light emitting portion. An n-side electrode 1711 is formed on the etched bottom surface of the mesa structure.
[0207]
The AlAs layer 606 is selectively oxidized from the etched side surface to form an insulating region 607.
[0208]
When a forward bias is applied to the p-side electrode 1710 and the n-side electrode 1711, a current is injected into the active layer 1001 through the opening of the AlAs layer 606, and light is emitted in the 1.3 μm band. The light generated in the active layer 1001 resonates in the resonance mode selected by the resonator structure 1708, and a laser beam is output perpendicular to the substrate.
[0209]
In the element of FIG. 14, a light absorption layer 1702 that absorbs light of the active layer 1001 is provided. Therefore, the absorption loss increases, and the threshold current is higher than when the light absorption layer 1702 is not provided. Here, if external input light having a wavelength that is absorbed by the light absorption layer 1702 is injected from the bottom surface of the second mesa structure etching, the absorption coefficient of the light absorption layer 1702 is saturated and the light absorption loss is reduced.
[0210]
As a result, the threshold current is lower than when light is not injected from the outside. Therefore, the intensity of the laser beam output from the surface emitting semiconductor laser can be modulated by an optical input signal from the outside. At this time, the wavelength conversion operation can be realized by setting the input light wavelength to a wavelength different from the output light wavelength.
[0211]
Further, an air gap 1707 is provided inside the resonator 1708 of FIG. By changing the interval of the air gap 1707, the length of the resonator 1708 changes, so that the resonance mode wavelength of the surface emitting laser can be shifted.
[0212]
Thereby, a wavelength conversion element capable of sweeping the output light wavelength can be realized. The distance between the air gaps 1707 can be controlled from the outside using electrostatic attraction or a piezoelectric element.
[0213]
FIG. 15 shows an example of an optical switching device configured using the wavelength conversion element of FIG.
[0214]
In FIG. 15, optical signals of wavelengths λ 1, λ 2, λ 3, and λ 4 input from an optical fiber 1801 are spatially separated for each wavelength by a wavelength demultiplexer 1802. Each of the separated optical signals is wavelength-converted by the wavelength conversion element 1803 and then recombined by the multiplexer 1804 and output from one optical fiber 1801.
[0215]
FIG. 15 shows an operation of converting λ1 to λ4, λ2 to λ3, λ3 to λ2, and λ4 to λ1 as an example. However, each wavelength conversion element can output at any wavelength of wavelengths λ1 to λ4, and the combination of output wavelengths can be switched freely.
[0216]
In FIG. 15, a single optical fiber is transmitted with an optical signal having four wavelengths, and a wavelength division multiplexing transmission system is used. For example, four wavelengths of 1290 nm, 1295 nm, 1300 nm, and 1305 nm were used as the wavelengths from λ1 to λ4.
[0217]
By making the band gap wavelength of the light absorption layer 1702 in FIG. 14 longer than 1305 nm, all wavelengths from λ1 to λ4 can be absorbed. The band gap wavelength of the active layer 1704 was set to 1295 nm. Further, by changing the air gap 1707, the oscillation wavelength can be changed from 1290 to 1305 nm.
[0218]
Therefore, by using the wavelength conversion element shown in FIG. 14, it is possible to input arbitrary light of wavelengths λ1 to λ4, convert it to arbitrary light of wavelengths λ1 to λ4, and output it with the same element structure. . Therefore, it is possible to monolithically integrate four wavelength conversion elements. Thereby, the size of the wavelength converter can be reduced.
[0219]
(Example4)
  FIG. 16 shows an embodiment of the present invention.41 is a cross-sectional view of a vertical cavity surface emitting semiconductor laser device according to FIG.
[0220]
The configuration of the vertical cavity surface emitting semiconductor laser device shown in FIG. 16 is similar to the configuration shown in FIG. The difference from the configuration of FIG. 11 is that the active layer 1001 uses a GaInNAs / GaAs-MQW structure with a wavelength of 1.3 μm band. Thereby, it is possible to operate at a wavelength suitable for optical communication.
[0221]
Further, the light absorption layer 1101 is characterized by using a GaInNAs / AlAs-MQW structure. For example, the conduction band (Γ band) discontinuity between GaInNAs and AlAs having an In composition of 0.1 and a nitrogen composition of 2% is about 1.43 eV.
[0222]
In a quantum well structure with a well width of 4.6 nm, the energy difference between the ground level (0th order) and the third level of the quantum level formed in the conduction band is about 950 meV, which corresponds to a wavelength of 1.3 μm. . By using absorption between subbands in this conduction band, light of 1.3 μm can be absorbed.
[0223]
Ga_0.9In_0.1N_0.02As_0.98The band gap wavelength of the well layer is about 1.23 μm, which is shorter than 1.3 μm. Therefore, there is almost no interband absorption between the conduction band and the valence electrons.
[0224]
By using intersubband absorption within the conduction band as the absorption process of the light absorption layer 1101, the recovery time from absorption saturation can be shortened, so that light modulation that operates at higher speed can be realized. .
[0225]
In the light absorption layer 1101, GaAs of about 1 nm can be provided as an intermediate layer at the interface between the GaInNAs well layer and the AlAs barrier layer. Thereby, the interface flatness between the GaInNAs well layer and the AlAs barrier layer can be remarkably improved.
[0226]
In the above embodiments, the description has been made using an example in which an n-type GaAs substrate is used as the substrate. However, a p-type or (semi) insulating substrate can be used as the conductivity type of the substrate. In addition to GaAs, various single crystal substrates such as GaP, InP, GaSb, InAs, GaN, sapphire, SiC, ZnO, and Si can be used.
[0227]
In addition to the AlGaAs system, an InGaAsP system, an AlGaInP system, an AlGaInAs system, an AlGaN system, or the like can be used as a semiconductor material constituting the DBR. Alternatively, a dielectric multilayer film can be used for the upper DBR structure.
[0228]
In addition, the light absorption layer is not limited to a single layer, and a plurality of light absorption layers may be provided in the element. In addition, the wavelength of the output light can be changed by providing a wavelength sweeping mechanism in the vertical cavity surface emitting semiconductor laser element.
[0229]
(Example5)
  FIG. 17 shows an embodiment of the present invention.5It is sectional drawing of the semiconductor light-emitting device based on.
[0230]
Referring to FIG. 17, lower distributed Bragg reflectors (DBR) 1601, 1603, and 1605 are stacked on an n-type GaAs substrate 601. In the lower DBR, a first light absorption layer 1602 and a second light absorption layer 1604 are provided.
[0231]
On the lower DBR 1605, a lower GaAs spacer layer 803, an InGaAs / GaAs-MQW active layer 605, an upper GaAs spacer layer 804, an AlAs layer 606, and a p-type GaAs DBR 608 are provided.
[0232]
A rectangular or cylindrical mesa structure is formed by etching from the surface of the laminated structure to the middle of the lower DBR 1605. A p-side electrode 609 is formed on the top of the mesa structure except for the light emitting portion, and an n-side electrode 610 is formed on the lower DBR 1605 whose surface is exposed by mesa etching. The AlAs layer 606 is selectively oxidized from the mesa-etched side surface to form an insulating region 607.
[0233]
When a forward bias is applied to the p-side electrode 609 and the n-side electrode 610, the current is injected into the InGaAs / GaAs-MQW active layer 605 through the opening of the unoxidized AlAs layer 606, and the wavelength is 0.98. Emits light in the μm band. The light generated in the active layer 605 resonates in a resonator structure sandwiched between the lower DBRs 1601, 1603, and 1605 and the upper DBR 608, and laser light is output in the upward direction perpendicular to the substrate.
[0234]
The light absorption layers 1602 and 1604 have the same or smaller band gap as that of the active layer 605 and absorb light generated in the active layer 605. In this example, the band gap wavelength of the light absorption layer 1602 was 1.0 μm, and the band gap wavelength of the light absorption layer 1604 was 1.1 μm.
[0235]
The light absorption layer 1602 was provided at the antinode position in the standing wave distribution of the light of the element. As a result, the coupling efficiency between the light constituting the standing wave in the element and the light absorption layer 1602 increases. On the other hand, the light absorption layer 1604 is provided in the vicinity of the position of the node in the standing wave distribution of the light of the element.
[0236]
Next, the operation of the semiconductor light emitting device of FIG. 17 will be described.
The eighth embodiment operates as an optical logic operation element that inputs two input lights A and B to the element and obtains the logical operation result as output light.
[0237]
The input light A is 0.98 μm, which is the same as the output light wavelength, and is input to the element from the back surface of the substrate. On the other hand, the input light B has a wavelength of 1.05 μm and is input from the window portion of the lower DBR 1605 exposed by etching.
[0238]
Since the input light A is phase-matched with the resonator mode of the element, it is coupled and absorbed by the light absorption layer 1602 provided at the antinode position in the standing wave distribution. On the other hand, since the light absorption layer 1604 is provided in the vicinity of the node position, the coupling efficiency with the input light A is low.
[0239]
The wavelength of the input light B is longer than the band gap wavelength of the light absorption layer 1602 and shorter than the band gap wavelength of the light absorption layer 1604. Therefore, it is absorbed by the light absorption layer 1604, but is transparent to the light absorption layer 1602. Therefore, the input light A is combined with the light absorption layer 1602 and the input light B is combined with the light absorption layer 1604.
[0240]
When the input lights A and B from the outside are input simultaneously, the absorption coefficients of the light absorption layers 1602 and 1604 are saturated, and the absorption loss is reduced. As a result, laser oscillation occurs and output light is emitted above the substrate.
[0241]
On the other hand, when there is no external input light or only one is input, the injection current of the active layer is controlled so as not to cause laser oscillation due to absorption loss due to the light absorption layer. As a result, it is possible to output light corresponding to the logical operation of AND for the two input optical signals A and B.
[0242]
In addition, the injection current of the active layer can be set so that laser oscillation occurs when one or both of the external input lights A and B are input and laser oscillation does not occur when there is no external input light. In this case, it is possible to output light corresponding to an OR logical operation for two input optical signals.
[0243]
(Example6)
  FIG. 18 shows an embodiment of the present invention.6It is a block diagram of the wavelength converter which concerns on.
  In FIG. 18, wavelength conversion elements 1404 and 1405 are provided on a substrate 1401. 1402 is a single mode silica optical fiber, 1403 is a multimode silica optical fiber, and 1406 is an optical multiplexer.
[0244]
In FIG. 18, a single mode silica optical fiber 1402 is connected to an external LAN and transmits an optical signal bidirectionally with light having a wavelength of 1.3 μm. An optical signal input from the outside to the single mode silica optical fiber 1402 is input to the wavelength conversion element 1404 through the optical multiplexer 1406.
[0245]
Here, after being converted from an optical signal having a wavelength of 1.3 μm to 0.85 μm, it is output to the multimode quartz optical fiber 1403. The multimode quartz optical fiber 1403 is optically connected to units in the device and is used as an optical wiring between the units.
[0246]
On the other hand, an input signal from the multimode silica optical fiber 1403 is wavelength-converted from a wavelength of 0.85 μm to 1.3 μm by the wavelength conversion element 1405, passes through the optical multiplexer 1406, and is output to the single mode silica optical fiber 1402.
[0247]
In the in-apparatus optical wiring having a relatively short wiring length, a multimode quartz optical fiber 1403 that is easy to mount is used, and the wavelength of the optical signal is 0.85 μm. On the other hand, when connecting to an external LAN, the wavelength of the optical signal is 1.3 μm using a single mode quartz optical fiber 1402 having a low transmission loss even when the transmission distance is long. The wavelength conversion apparatus of this embodiment functions to convert optical signals having different wavelengths inside and outside the apparatus.
[0248]
  The structure of the wavelength conversion element isreferenceThe semiconductor light emitting device of FIG. 1 shown in Example 1 has almost the same structure. In the wavelength conversion element 1405 that converts an optical signal of 0.85 μm into an optical signal of 1.3 μm, the active layer is made of a GaInNAs material, so that the band gap wavelength is 1.3 μm. Then, the layer thickness of the distributed Bragg reflector and the resonator length is set so that laser oscillation occurs at 1.3 μm.
[0249]
The band gap wavelength of the light absorption layer is set to be equal to or longer than 1.3 μm so as to absorb the light of the active layer. When input light having a wavelength of 0.85 μm is incident on the light absorption layer, the absorption coefficient is saturated in the light absorption layer, so that the output light intensity of 1.3 μm can be modulated.
[0250]
In the layer where external light having a wavelength of 0.85 μm reaches the light absorption layer, the band gap of each laminated structure is made transparent to light having a wavelength of 0.85 μm. When external light is input from the substrate side, it is necessary to remove the GaAs substrate by etching to form an input window portion.
[0251]
In the wavelength conversion element 1404 that converts a 1.3 μm optical signal into a 0.85 μm optical signal, the active layer is made of a GaAs material, and the band gap wavelength is 0.85 μm. The light absorption layer is made of a GaInNAs material, and the band gap wavelength is set to be equal to or longer than 1.3 μm.
[0252]
When input light having a wavelength of 1.3 μm is incident on the light absorption layer, the absorption coefficient is saturated in the light absorption layer, so that the output light intensity of 0.85 μm can be modulated. When output light is emitted from the substrate side, it is necessary to remove the GaAs substrate by etching to form an output window portion.
[0253]
In the wavelength conversion apparatus of FIG. 18, the optical signal is converted into electricity once and then converted again without returning to the optical signal. Therefore, the apparatus configuration can be simplified. Further, since the delay time required for signal conversion is shortened, the signal transmission throughput can be improved.
[0254]
(Example7)
  FIG. 19 shows an embodiment of the present invention.71 is a cross-sectional view of a vertical cavity surface emitting semiconductor laser device according to FIG.
[0255]
Referring to FIG. 19, an n-type lower GaAs / AlGaAs-DBR 602 is stacked on an n-type GaAs substrate 601. On the n-type lower DBR 602, a GaAs lower spacer layer 803, an InGaAs / GaAs-MQW active layer 605, a GaAs upper spacer layer 804, an AlAs layer 606, a first p-type upper GaAs / AlGaAs-DBR 901, InGaAs / GaAs. The -MQW light absorption layer 604 and the second p-type upper GaAs / AlGaAs-DBR 902 are sequentially stacked.
[0256]
A rectangular or cylindrical first mesa structure is formed by etching from the surface of the laminated structure to the middle of the second p-type upper GaAs / AlGaAs-DBR 902. Further, the second mesa structure is formed by etching halfway through the first p-type upper GaAs / AlGaAs-DBR 901 with a larger mesa size than the first mesa structure. Further, the third mesa structure is formed by etching until reaching the n-type lower GaAs / AlGaAs-DBR 602 with a size larger than that of the second mesa structure.
[0257]
A p-side electrode 609 is formed in the middle of the first p-type upper GaAs / AlGaAs-DBR 901 whose surface is exposed by the etching of the second mesa structure, and the n-side GaAs substrate 601 has an n-side on the back surface. An electrode 610 is formed.
[0258]
The AlAs layer 606 is selectively oxidized from the side surface exposed by etching of the third mesa structure to form an insulating region 607.
[0259]
When a forward bias is applied to the p-side electrode 609 and the n-side electrode 610, the current is confined in the insulating region 607, passes through the opening of the unoxidized AlAs layer 606, and the InGaAs / GaAs-MQW active layer 605 A current is injected into the light, and light is emitted in the wavelength band of 0.98 μm. The light generated in the active layer 605 resonates between the lower DBR 602 and the upper DBRs 901 and 902, and oscillates and is output from the top of the first mesa structure in a direction perpendicular to the substrate.
[0260]
The bottom surface exposed by the etching of the first mesa structure is a window portion 805 for inputting light to the light absorption layer 604 from the outside. The distance between the light absorption layer 604 and the surface of the window portion 805 was made to be thinner than λ / 4 in terms of optical distance.
[0261]
Thereby, the coupling efficiency between the light absorption layer 604 and the external input light can be improved, and the output light can be modulated with a smaller input light intensity. In addition, the wavelength range used as input light can be increased.
[0262]
Next, an optical pulse waveform shaping operation using the vertical cavity surface emitting semiconductor laser device of FIG. 19 will be described.
[0263]
Two types of light, clock light and signal light, are used as light input to the element from the outside. Consider a case where the pulse shape of signal light is degraded rather than rectangular due to the influence of dispersion caused by optical transmission. On the other hand, the clock light is a rectangular pulse and determines the timing of data extraction. In FIG. 19, the clock light is input light 1 and the signal light is input light 2.
[0264]
When the clock light and the signal light are input at the same time, the intensity of the input light input to the light absorption layer 604 is strong in the portion of the signal light that overlaps the clock light, and the strength of the portion that does not overlap is low.
[0265]
Then, in the portion where the clock light and the signal light overlap, the vertical cavity surface emitting laser is in an oscillation state, and in the portion where the clock light does not overlap, the vertical cavity surface emitting laser is in an oscillation stop state. Pth).
[0266]
As a result, the input intensity is lower than Pth at the rising and falling portions of the signal light, so that the output intensity remains low, and output light having a pulse width corresponding to the pulse width of the clock light is obtained.
[0267]
Further, by setting the light intensity of the clock light to be lower than Pth, the output light intensity of the vertical cavity surface emitting laser device can be kept low in the case of only the clock light to which no signal light is input. Thereby, the on / off information of the signal light is directly inherited by the output light.
[0268]
By using the optical pulse waveform shaping device described above as a relay device of an optical transmission system, an optical signal deteriorated by optical fiber transmission can be amplified and shaped and output, so that the transmission distance can be extended. In addition, since the optical pulse waveform shaping device is composed of a vertical cavity surface emitting laser device, the manufacturing cost of the device can be reduced.
[0269]
(Example8)
  20 uses the vertical cavity surface emitting semiconductor laser device (wavelength conversion element) shown in FIG. 1, FIG. 10, FIG. 11, FIG. 12, FIG. It is an example of an optical transmission module.
[0270]
In FIG. 20, 1201 is an input optical fiber array, 1202 is a wavelength conversion element, 1203 is a multiplexer, and 1204 is an output optical fiber.
[0271]
The parallel optical signals (wavelength λ0) input from the optical fiber array 1201 in which four optical fibers are arrayed are converted into wavelengths λ1, λ2, λ3, and λ4 by the four wavelength conversion elements 1202, respectively. The wavelength-converted optical signal is coupled to one optical waveguide by an optical multiplexer 1203 and is output from one optical fiber 1204 by a wavelength division multiplexing system with four wavelengths. Thereby, an optical signal can be converted at high speed from the parallel transmission system to the wavelength division multiplexing system.
[0272]
(Example9)
  21 uses the vertical cavity surface emitting semiconductor laser device (wavelength conversion element) shown in FIGS. 1, 10, 11, 12, 13, 13, 14, 16, 17, and 19. FIG. 3 shows another configuration example of the optical transmission module.
[0273]
In FIG. 21, a parallel optical signal (wavelength λ 0) input from an optical fiber array 1201 in which four optical fibers are arrayed is collected by a microlens array 1301 and input to a wavelength conversion element 1202. . The wavelength conversion element 1202 converts the wavelengths of four types of optical signals into wavelengths λ1, λ2, λ3, and λ4.
[0274]
Here, a transmissive element structure was used as the wavelength conversion element. The wavelength-converted optical signals are combined into one by the surface optical multiplexer 1302, condensed by the condenser lens 1303, and output to the output optical fiber 1204. Thereby, similarly to the optical transmission module shown in FIG. 21, the optical signal can be converted from the parallel transmission system to the wavelength division multiplexing system at high speed.
[0275]
【The invention's effect】
The present invention has the following effects. Hereinafter, the effect will be described for each claim.
[0279]
aClaim1According to the described invention, since the transverse mode of the laser oscillation light is modulated by the external input light intensity, it is possible to form an inverted signal and to perform an optical branching operation that separates one series of optical signals into two series. .
[0280]
bClaim2According to the described invention, the substrate includes a resonator including an active layer, a distributed Bragg reflector formed above and below the resonator, and a light absorption layer that absorbs light of the active layer, and is perpendicular to the substrate. A surface-type semiconductor light emitting device that outputs laser oscillation light in the direction and an electroabsorption optical modulator are monolithically integrated in a direction perpendicular to the substrate, so that the transverse mode of the laser oscillation light can be modulated by the external input light intensity. As a result, it is possible to realize an optical branching operation that separates a serial optical signal having a high modulation frequency of 10 to 50 GHz into two series.
[0281]
c)Claim3According to the described invention, claim 1Or 2In the vertical cavity surface emitting semiconductor laser device described in 1), the output light wavelength can be changed with respect to various input light wavelengths by the same element and output by having a mechanism for sweeping the output light wavelength. Thereby, a wavelength conversion switch between signals in the wavelength division multiplex transmission system can be easily configured.
[0282]
dClaim4According to the described invention, from claim 13In the vertical cavity surface emitting semiconductor laser device according to any one of the above, by using intersubband absorption for the light absorption of the light absorption layer, the absorption recovery time from the absorption saturation can be shortened, Light modulation can be performed at higher speed.
[0283]
eClaim5According to the described invention, from claim 14In the vertical cavity surface emitting semiconductor laser device according to any one of the above, by using a mixed crystal semiconductor containing nitrogen and another group V element as the material of the light absorption layer and / or the active layer, A long-wavelength vertical cavity surface emitting semiconductor laser device suitable for a wavelength used in optical communication can be configured with high performance.
[0284]
In addition, by using a mixed crystal semiconductor containing nitrogen and another group V element for the light absorption layer, the carrier relaxation time can be shortened and light can be modulated at higher speed.
[0285]
In addition, if a mixed crystal semiconductor containing nitrogen and other group V elements is used for the well layer, the conduction band discontinuity can be expanded, and a light absorption layer using intersubband absorption in the conduction band is constructed. It is also possible to do.
[0286]
f)Claim6According to the described invention, from claim 15By configuring the optical logic operation device using the vertical cavity surface emitting semiconductor laser device according to any one of the above, by controlling the current value injected into the active layer, both the AND operation and the OR operation are performed. It is possible to realize an optical logic operation element that can realize the above.
[0287]
g) Claim7According to the described invention, from claim 15By using the vertical cavity surface emitting semiconductor laser device according to any one of the above, a wavelength conversion device capable of not only wavelength conversion from a short wavelength to a long wavelength but also a conversion from a long wavelength to a short wavelength Can be configured easily.
[0288]
h)Claim8According to the described invention, the claims7In the described invention, an optical transmission system between a relatively long-distance LAN or equipment using a single-mode quartz optical fiber by converting the wavelength of an optical signal having a wavelength of 0.85 μm and an optical signal having a wavelength of 1.3 μm. It is possible to connect an optical transmission system in a device using a multimode quartz optical fiber with high transmission throughput.
[0289]
iClaim9According to the described invention, from claim 15By using the vertical cavity surface emitting semiconductor laser device according to any one of the above, an optical pulse waveform shaping device with low power consumption, low cost, and easy two-dimensional array can be formed.
[0290]
jClaim10According to the described invention, from claim 15The vertical cavity surface emitting semiconductor laser device according to claim 1,6Claims optical logic operation device, claim7Or8The wavelength converter according to claim 1 or claim9By using the described optical pulse waveform shaping device, a high-performance optical transmission system having an optical information processing function such as sequence separation can be configured.
[0291]
Further, since the vertical cavity surface emitting semiconductor laser device is used as a basic element, a system can be constructed with low power consumption and low cost. A two-dimensional array is also possible.
[Brief description of the drawings]
[Figure 1]reference1 is a cross-sectional view of a vertical cavity surface emitting semiconductor laser device according to Example 1. FIG.
FIG. 2 is a diagram for explaining an optical modulation operation.
FIG. 3 is a diagram showing a reflection spectrum of a vertical cavity surface emitting semiconductor laser including a long cavity.
FIG. 4 is a diagram showing a relationship between a transverse mode and a light radiation distribution.
FIG. 5 is a configuration diagram of a transverse mode light modulator.
FIG. 6 is a diagram for explaining a pulse inversion operation.
FIG. 7 is a diagram for explaining a pulse sequence separation operation;
FIG. 8 is a diagram for explaining a relationship between an absorption coefficient of a light absorption layer and input light and output light wavelengths.
FIG. 9 is a diagram for explaining an operation of optical pulse waveform shaping.
FIG. 10reference6 is a sectional view of a vertical cavity surface emitting semiconductor laser device according to Example 2. FIG.
FIG. 11reference6 is a sectional view of a vertical cavity surface emitting semiconductor laser device according to Example 3. FIG.
FIG. 12 Example11 is a cross-sectional view of a vertical cavity surface emitting semiconductor laser device according to FIG.
FIG. 13 Example21 is a cross-sectional view of a vertical cavity surface emitting semiconductor laser device according to FIG.
FIG. 14 Example31 is a cross-sectional view of a vertical cavity surface emitting semiconductor laser device according to FIG.
15 is a configuration diagram of an optical switching apparatus according to Embodiment 6. FIG.
FIG. 16 Example41 is a cross-sectional view of a vertical cavity surface emitting semiconductor laser device according to FIG.
FIG. 17 Example51 is a cross-sectional view of a vertical cavity surface emitting semiconductor laser device according to FIG.
FIG. 18 Example6It is a block diagram of the wavelength converter which concerns on.
FIG. 19 Example71 is a cross-sectional view of a vertical cavity surface emitting semiconductor laser device according to FIG.
FIG. 20 Example8It is a structural example of the optical transmission module which concerns on this.
FIG. 21 Example9It is another structural example of the optical transmission module which concerns on this.
[Explanation of symbols]
  601: n-type GaAs substrate
  602: n-type GaAs / AlGaAsDBR
  603: Resonator structure
  604: InGaAs / GaAs-MQW light absorption layer
  605: InGaAs / GaAs-MQW active layer
  606: AlAs layer
  607: selectively oxidized insulating region
  608: p-type GaAs / AlGaAsDBR
  609: p-side electrode
  610: n-side electrode
  801: First n-type DBR
  802: Second n-type DBR
  803: Lower spacer layer
  804: Upper spacer layer
  805: Input window
  901: First p-type DBR
  902: Second p-type DBR
  1001: GaInNAs / GaAs-MQW active layer
  1002: GaInNAs / GaAs-MQW light absorption layer
  1101: GaInNAs / AlAs-MQW light absorption layer
  1201: Optical fiber array
  1202: Wavelength conversion element
  1203: Optical multiplexer
  1204: Optical fiber
  1301: Microlens array
  1302: Optical multiplexer
  1303: Condensing lens
  1401: Substrate
  1402: Single mode silica optical fiber
  1403: Multimode silica optical fiber
  1404: Wavelength conversion element A
  1405: Wavelength conversion element B
  1406: Optical multiplexer
  1501: p-type GaAs substrate
  1502: p-type GaAs / AlGaAs DBR
  1503: Light absorption layer
  1504: n-type GaAs / AlGaAsDBR
  1505: AlAs layer
  1506: n-side electrode
  1507: Back electrode
  1601: first lower DBR
  1602: First light absorption layer
  1603: second lower DBR
  1604: Second light absorption layer
  1605: Third lower DBR
  1701: first lower DBR
  1702: Light absorption layer 1702
  1703: Second lower DBR
  1704: n-type GaAs spacer layer
  1705: p-type GaAs spacer layer
  1706: p-type GaAs spacer layer
  1707: Air gap
  1708: Resonator
  1709: Upper DBR
  1710: p-side electrode
  1711: n-side electrode
  1801: Quartz optical fiber
  1802: Wavelength demultiplexer
  1803: Wavelength conversion element
  1804: multiplexer

Claims (10)

The substrate includes a resonator including an active layer, a distributed Bragg reflector formed above and below the resonator, and a light absorption layer that absorbs light from the active layer, and outputs laser oscillation light in a direction perpendicular to the substrate. In the vertical cavity surface emitting semiconductor laser device,
Vertical cavity surface emitting semiconductor laser device characterized by modulating the fundamental transverse mode and first-order high-order mode of the laser oscillation light by the external input light intensity. The substrate includes a resonator including an active layer, a distributed Bragg reflector formed above and below the resonator, and a light absorption layer that absorbs light from the active layer, and outputs laser oscillation light in a direction perpendicular to the substrate. a planar semiconductor light emitting device for modulation and electro-absorption optical modulator, monolithically integrated on the substrate and a vertical direction, and a fundamental transverse mode and first-order high-order mode of the laser oscillation light by the external input light intensity A vertical cavity surface emitting semiconductor laser device comprising: The vertical cavity surface emitting semiconductor laser device according to claim 1 or 2 ,
A vertical cavity surface emitting semiconductor laser device further comprising a mechanism for sweeping an output light wavelength. The vertical cavity surface emitting semiconductor laser device according to any one of claims 1 to 3 ,
A vertical cavity surface emitting semiconductor laser device using intersubband absorption for light absorption of the light absorption layer. The vertical cavity surface emitting semiconductor laser device according to any one of claims 1 to 4 ,
A vertical cavity surface emitting semiconductor laser device using a mixed crystal semiconductor containing nitrogen and another group V element as a material for the light absorption layer and / or the active layer. Optical logic unit, characterized in that using a vertical cavity surface emitting semiconductor laser device according to any one of claims 1 to 5. A wavelength converter using the vertical cavity surface emitting semiconductor laser device according to any one of claims 1 to 5 . In the wavelength converter of Claim 7 ,
A wavelength conversion device that converts an optical signal of a wavelength of 0.85 μm and an optical signal of a wavelength of 1.3 μm. An optical pulse waveform shaping device using the vertical cavity surface emitting semiconductor laser device according to any one of claims 1 to 5 . The vertical cavity surface emitting semiconductor laser device according to any one of claims 1 to 5 , the optical logic operation device according to claim 6 , the wavelength conversion device according to claim 7 or 8 , or the claim 9 . An optical transmission system using an optical pulse waveform shaping device.

Images