JPH07254752A - Optical semiconductor element - Google Patents

Abstract

PURPOSE:To enable constituting an inversion polarization structure for phase matching which is easy for manufacturing, regarding an optical parametric semiconductor element. CONSTITUTION:The optical semiconductor element is provided with a laminated semiconductor 1 in which a first intrinsic semiconductor layer 1a, an N-type semiconductor layer 1b, a second intrinsic semiconductor layer 1c and a P-type semiconductor layer ld are repeatedly laminated in order. A first depletion layer 2a containing the first intrinsic semiconductor layer 1a and a second depletion layer 2b containing the second intrinsic semiconductor layer 1c are formed. The distance (d) between the nearest depletion layer 2b and depletion layer 2a is set as d=(lambda4).costheta/(nAP-nAS where TRAP is the average refractive index to excited light generated between the two deplation layers, nAS is the average refractive index to a signal light generated between the two deplation layers, and theta is the angle which the excited light and the signal light propagating in the laminated semiconductor 1 form with the normal of the lamination surface of the laminated semiconductor 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical semiconductor device which is parametrically excited by optical excitation. It has been clarified that an element that parametrically excites by optical pumping, such as an optical parametric amplifier, can theoretically realize an amplifier with a high S / N ratio (J. Opt. Soc. Am. B / Vol. 4, No. 10 / Oc
tober 1987 Squeezed States feature article). In addition, wavelength conversion using idler light, and further, dispersion compensation of fiber transmission using the phase conjugate relationship between idler light and signal light can be performed.

As described above, an element for parametric excitation can realize characteristics that are difficult to realize by a conventional laser amplifier or electric amplifier, and is expected to bring about a dramatic improvement in performance of optical application equipment in the future. .

In particular, it is now widely used for communication.
The realization of an optical parametric amplifier in the 55 μm band is strongly expected because it enables long-distance communication or wavelength-division multiplex communication by realizing a high-sensitivity receiver.

[0004]

2. Description of the Related Art Conventionally, an insulating dielectric material such as LiNbO ₃ or KDP (KH ₂ PO ₄ ) has been used for an element which is parametrically excited by optical excitation. However,
These dielectrics have a very low second-order nonlinear susceptibility,
The interaction between the excitation light and the signal light is extremely weak. For this reason,
In order to perform sufficient optical amplification, a very strong excitation light and a long working area are required, which is not practical.

On the other hand, it is theoretically predicted that a large second-order nonlinear susceptibility is generated in a state where an electric field is applied to a semiconductor having a quantum well structure in which semiconductor thin films having different forbidden band widths are laminated. Therefore, it is considered that by using a semiconductor having such a quantum well structure as a dielectric, it is possible to realize an optical semiconductor device that can obtain a sufficient amplification degree with weak pumping light and a short working region. Is proposed.

The structure of a conventionally proposed optical semiconductor device that is parametrically excited by optical excitation will be described below. First, the structure of an optical parametric amplifier using a dielectric will be described.

FIG. 4 is a perspective view of a conventional example and shows the structure of an optical parametric amplifier using a dielectric. Referring to FIG. 4, ion-implanted regions 44 having a constant width are formed in stripes at equal intervals on the surface of a dielectric, for example, a LiNbO ₃ single crystal 45. Furthermore, the ion implantation region 44 is formed on the surface of the single crystal 45.
An optical waveguide 41 that is orthogonal to is formed. Input light 4 in which signal light and excitation light are superposed from one end of the optical waveguide 41
2, the signal light is amplified by the optical parametric amplification with the optical waveguide 41 as the working region, and the output light 43 is output from the other end.
Take out as.

The polarization direction 46 in the single crystal 45 is polarized so as to face the surface. On the other hand, in the ion implantation region 44, the polarization direction 46 is reversed with the ion implantation. Therefore, the light propagating in the optical waveguide 41 is transmitted through the dielectric region in which the polarization direction 46 is inverted for each period of the striped ion implantation region 41.
The reason why the polarization direction is required to be inverted is as follows.

FIG. 6 is a structural explanatory view of an optical parametric amplifier, showing a polarization inversion structure and its action. Figure 6
(A) shows the polarization structure of the optical parametric amplifier. The signal light 21 and the pumping light 23 are simultaneously superimposed and incident on a striped polarization structure in which the polarization direction is inverted at a constant distance d. The signal light 21 is parametrically excited by the pumping light 23, and is amplified on the way.

However, due to the dispersion of the refractive index of the dielectric, the signal light 21 and the pumping light 23 having different wavelengths have different refractive indexes, and the optical path difference is different even if they travel the same distance. A phase difference occurs with 23. FIG. 6B shows the phase difference between the signal light and the excitation light with respect to the traveling distance. The phase difference is expressed in radians with the phase of the signal light as a unit. Figure 6 (b) during uniform polarization
Referring to, the phase difference between the signal light and the pump light increases in proportion to the traveling distance. As a result, at the traveling distance d, the phase difference becomes π / 2 radians, that is, λ _s / 4. Where λ
_s is the wavelength of the signal light.

FIG. 6 (c) is a comparison of polarization states when a phase difference of π / 2 radians is generated. (C-
1) and (c-3) show the electric field strengths of the signal light and the pumping light when the phase difference is 0 and π / 2, respectively (c-2) and (c-2).
-4) represents the magnitude of polarization excited by light when the phase difference is 0 and π / 2, respectively. It should be noted that FIG. 6C is an example when the wavelength of the pumping light is ½ of the signal light.

Referring to FIGS. 6C-1 and 6C-3, the phase of the pump light 23 with respect to the signal light 21 is π of the signal light.
Delayed by / 2. Therefore, FIGS. 6C-2 and 6C-
4), the sum E of the electric field strengths of the pumping light 21 and the signal light E
The phase of the square of E ² is delayed by π. Since the magnitude of the polarization excited by the electric field is proportional to E ² , the time change of the polarization is delayed by π.

As a result, at a place separated by the traveling distance d,
The polarization direction is opposite to that of the signal light, and acts so as to attenuate the signal light. The inverted striped polarization structure is for eliminating such inconvenience.

That is, the inverted polarization structure is formed in a striped pattern having a width of a distance d at which the phase difference between the signal light and the pump light reaches π / 2 with reference to FIG. 6B. Therefore, the polarization directions are always opposite at the two points where the phase difference is π / 2. In this way, when the polarization directions are opposite, the sign of the second-order nonlinear susceptibility is reversed, and the magnitude of the polarization excited by the electric field is the opposite of positive and negative.
That is, the phase is advanced by π, and the phase difference between the polarization excited by the electric field and the signal light disappears. Therefore, even if there is a phase difference between the signal light and the pump light, it is possible to continue amplification along the waveguide.

The same applies to the device using the semiconductor. FIG. 5 is a cross-sectional view of a conventional example, showing the structure of an optical parametric amplifier using a semiconductor. Note that FIG. 5 (a) is an example thereof, and FIG. 5 (b) is a further improved example.

Referring to FIG. 5A, an optical waveguide 41 having an electric field applying layer 47 made of a semiconductor provided on the upper and lower sides is formed on a semiconductor substrate 49. The optical waveguide 41 is made of a semiconductor having a quantum well structure and is polarized by the application of an electric field.
It has the following non-linear susceptibility. The electric field applying layer 47 is a semiconductor layer in which n-type regions and p-type regions are alternately arranged at equal intervals along the optical waveguide 41.
These regions are formed such that the n-type and p-type regions face regions of opposite conductivity type. Also, two wirings 48 are provided which are connected to the n-type and p-type regions, respectively.

In this element, a voltage is applied between the n-type region and the p-type region facing the upper and lower sides of the optical waveguide 41 to generate an electric field in the vertical direction in the optical waveguide 41. This electric field is n
Since the inversion occurs depending on the distance between the striped regions of the mold region and the p-type region, a polarization structure in which the inverted polarization regions are arranged in stripes along the optical path as shown in FIG. 6A is realized. Therefore, the width between the n-type region and the p-type region is set so that the phase difference between the signal light and the pump light is π / 2.
By doing so, optical parametric amplification can be performed.

However, it is extremely difficult to form the optical waveguide 41 on the electric field applying layer 47 from the viewpoint of crystallinity and impurity distribution. Further, it is not easy to form the wiring 48 connected to the lower electric field application layer 47. Therefore, an improved structure was devised so that it could be easily manufactured.

With reference to FIG. 5B, in the improved structure, the lower electric field applying layer 47 is not provided. And the electric field is
It is generated by the potential applied between the p and n regions in the electric field applying layer 47 on the optical waveguide 41 and the substrate 49.

This structure is easy to manufacture. However,
In order to utilize the substrate 49 as one of the electrodes, the substrate 49 must be conductive, for example n-type. As a result, a large electric field is generated in the p-type region having the opposite conductivity type to the substrate 49 even if a small potential is applied, while a large potential is applied to the n-type region having the same conductivity type as the substrate 49. If so, the necessary electric field is not generated in the optical waveguide 41. Under such circumstances, it was practically difficult to realize an element having a structure having a required breakdown voltage.

As described above, it is extremely difficult to use a semiconductor for an optical device that utilizes parametric excitation of optical excitation. Furthermore, since the above-mentioned device utilizes the inverted polarization structure formed on the surface, it requires an optical waveguide formed near the surface and is not suitable for constructing a three-dimensional optical system.

[0022]

As described above, the conventional optical device for forming an optical waveguide and a region where the polarization is inverted on the dielectric surface, which is parametrically excited by photoexcitation, requires strong excitation light and a long working range. There is a problem of doing.

Further, in an optical semiconductor device using a semiconductor, the structure for generating an inverted polarization structure has a drawback that the device fabrication is difficult. Further, since these optical elements utilize the optical waveguide on the surface, there is a drawback that they are not suitable for the construction of a three-dimensional optical system.

According to the present invention, semiconductor layers including alternating p-layers and n-layers are stacked and polarized by utilizing the electric field in the depletion layer generated between the p-layers and the n-layers. To provide an optical semiconductor device that can be easily manufactured by using a semiconductor, has a structure that can operate in a short action region and weak excitation light using a semiconductor, and can handle light incident from the semiconductor surface, and that is parametrically excited by optical excitation. I am trying.

[0025]

FIG. 1 illustrates the principle of the present invention.
FIG. 1A is a cross-sectional view of a part of the laminated semiconductor and FIG.
The traveling directions of the excitation light and the signal light are shown. Figure 1
(B) is the energy of the laminated semiconductor between AB in FIG. 1 (a).
It represents the geeband structure. In the figure, E_CE _VE
_FIs the conduction band bottom, valence band top, and Fermi, respectively.
It represents energy.

FIG. 2 is a sectional view of an embodiment of the present invention.
(A) shows the structure of the optical parametric amplifier according to the first embodiment. In order to solve the above-mentioned problems, referring to FIG. 1, the first configuration of the present invention is an optical semiconductor device in which pumping light and signal light having a wavelength λ are superposed and incident to perform parametric excitation. The first intrinsic semiconductor layer 1a transparent to the signal light, the n-type semiconductor layer 1b, the second intrinsic semiconductor layer 1c transparent to the excitation light and the signal light, and the p-type semiconductor layer 1d are The laminated semiconductor 1 is formed by repeatedly stacking a plurality of times in order, and the p-type semiconductor layer 1d that is in contact with the first intrinsic semiconductor layer 1a is in contact with the p-type semiconductor layer 1d that is in contact with the first intrinsic semiconductor layer 1a. A first depletion layer 2a is formed between the n-type semiconductor layer 1b and the n-type semiconductor layer 1b which is in contact with the second intrinsic semiconductor layer 1c and above the second intrinsic semiconductor layer 1c. A second depletion layer 2b is formed between the contacting p-type semiconductor layer 1d and the p-type semiconductor layer 1d. Layer 2a, the depletion layer 2b nearest from 2b top, the distance d that leads to 2a top,
An average refractive index for the excitation light during that period is n _AP , an average refractive index for the signal light during that period is n _AS , and the excitation light and the signal light propagating in the laminated semiconductor 1 are laminated surfaces of the laminated semiconductor 1. The angle formed with the normal of is θ, and d = (λ / 4) · sin θ / (n _AP −n _AS ), and the second configuration is
In the optical semiconductor device having the first structure, the first intrinsic semiconductor layer 1a and the second intrinsic semiconductor layer 1c have a quantum well structure formed by stacking semiconductor thin films having different forbidden band widths. As a feature, and the third configuration is
In the optical semiconductor element having the first or second configuration, the n-type semiconductor layer 1b and the p-type semiconductor layer 1d have a thickness such that the n-type semiconductor layer 1b and the p-type semiconductor layer 1d are depleted. And a fourth configuration is an optical semiconductor device of the first, second or third configuration, wherein at least one of the n-type semiconductor layer 1b and the p-type semiconductor layer 1d is The first intrinsic semiconductor layer 1a and the second intrinsic semiconductor layer 1c are characterized by having a larger forbidden band width, and the fifth constitution is described with reference to FIG. In the optical semiconductor element having the first, second, third or fourth configuration, the laminated semiconductor 1 is characterized in that it is provided on a reflective layer 3 which transmits the excitation light and reflects the signal light. .

[0027]

In the first structure of the present invention, referring to FIG. 1A, the n-type semiconductor layer 1b is sandwiched by the intrinsic semiconductor layers 1a and 1c.
And p-type semiconductor layers 1d are alternately stacked. Therefore, pn junctions sandwiching the intrinsic semiconductors 1a and 1c are formed, and referring to FIG. 1B, the energy bands of the intrinsic semiconductor layers 1a and 1c are inclined and the intrinsic semiconductor layers 1a and 1c are depleted.

The electric field generated in the depleted intrinsic semiconductor layers 1a and 1c polarizes the intrinsic semiconductor layers. The electric field in the depletion layer changes from the n-type semiconductor layer 1b to the p-type semiconductor layer 1b.
Since it is oriented in the direction of d, referring to FIG. 1A, the polarization direction is downward in the first intrinsic semiconductor layer 1a and upward in the second intrinsic semiconductor layer 1c. Therefore, in the laminated semiconductor 1, there is formed a polarization structure composed of layered polarization layers which are inverted at the installation period of the intrinsic semiconductor layers 1a and 1c.

The polarization layer is generated by the polarization of the semiconductor by the electric field in the depletion layer, and is formed in parallel at equal distances d between the depletion layers. Note that it is preferable to make the p-type and n-type semiconductor layers 1b and 1d thinner than the intrinsic semiconductor layers 1a and 1c, as described later. At this time, the distance d is substantially equal to the distance between the intrinsic semiconductor layers 1a and 1c.

The excitation light and the signal light incident as the incident light 42 from the upper surface of the laminated semiconductor 1 are superposed in the laminated semiconductor 1 to cause polarization, and the amplification and modulation of the signal light due to parametric excitation are caused. Done.

Since the refractive index n ^P of the excitation light and the refractive index n ^S of the signal light in the laminated semiconductor 1 are different, Δ = ∫ while propagating from one layer of the layered polarization structure to the next inverted polarization layer. An optical path difference Δ of (n ^P −n ^S ) ds, is generated. Here, the integration is performed along the propagation path that passes through the polarization interlayer distance.

In the present configuration, the average refractive index between the polarization layers of the excitation light and the signal light that is incident on the laminated surface of the laminated semiconductor 1 at the incident angle θ, that is, is incident on the polarized layer at the incident angle θ, n _AP = ( 1 / d) · ∫n ^P · cosθ · ds, n _AS = (1 / d) · ∫n ^S · cosθ · ds, the depletion layer spacing d is

[0033]

## EQU1 ## The laminated semiconductor 1 is configured so as to satisfy the relationship of d = (λ / 4) · cos θ / (n _AP −n _AS ). Under this condition, Δ = λ / 4. Here, λ is the wavelength of the signal light in the laminated semiconductor. The wavelength λ varies depending on the refractive index, and λ / 4 here means that the phase difference is π / 2 radians.

Therefore, when the signal light amplified by the polarization layer having the upward or downward polarization is incident on the next polarization layer polarized in the opposite direction, the phases of the excitation light and the signal light are inverted. . On the other hand, since the polarization direction of the incident polarization layer is also inverted, the inverted phase is compensated in the upper layer, and the amplification and the like are performed subsequently to the amplification and the like of the upper layer.

As described above, since the depletion layer is formed by the pn junction, the depletion layer distance d that determines the distance between the polarization layers is determined by the thickness of the intrinsic semiconductor layers 1a and 1c, the thickness of the p-type and n-type semiconductor layers. And the concentration of impurities and the energy band structure of these layers.

As is well known, these thicknesses,
The concentration and energy band structure can be precisely manufactured by depositing and manufacturing a semiconductor layer. For example, a molecular beam epitaxial method, a metal organic vapor phase deposition method, a vapor phase growth method in which each atomic layer is deposited, and an ordinary vapor phase growth method can be used to easily superimpose layers with precise thicknesses. You can

Further, in the present structure, in order to manufacture the polarized structure, it is not necessary to form a special diffusion region or surface processing, and it is sufficient to precisely deposit the semiconductor layer as described above. Is simple and can have a precise structure.

In this configuration, the first intrinsic semiconductor layer 1a and the second intrinsic semiconductor layer 1c do not have to have the same thickness. The depletion layer distance d may also be different. Even in such a case, a laminated semiconductor having a structure in which the average refractive index and d satisfy the above formula 1 may be used.

In this structure, the intrinsic semiconductor layers 1a and 1c are made of a semiconductor having a wide band gap which is transparent to the excitation light and the signal light. On the other hand, the n-type and p-type semiconductor layers 1b and 1d
Is usually thinner than the intrinsic semiconductor layers 1a and 1c,
Even if there is some absorption, absorption of the excitation light and the signal light passing through the laminated semiconductor 1 does not substantially pose a problem.

In the second configuration of the present invention, the intrinsic semiconductor layer 1
Each of a and 1c includes a layer having an energy band of a quantum well structure in which semiconductor thin films having different forbidden band widths are stacked. A semiconductor having such a quantum well structure has a very large second-order nonlinear susceptibility as is known. Therefore, the optical semiconductor device of this configuration is sufficiently excited by weak excitation light, and is sufficiently amplified even in a short working range, so that the device can be downsized.

Even in the case of a semiconductor having a quantum well structure in which such thin layers are laminated, this structure can be easily manufactured only by the step of depositing the semiconductor layer. In the third configuration of the present invention, the n-type semiconductor layer 1b and the p-type semiconductor layer 1d are thin layers whose entire thickness is depleted. As a result, carriers in the n-type and p-type semiconductor layers 1b and 1d are ejected,
An optical semiconductor device with low light absorption and low loss is realized.

In the fourth structure of the present invention, one or both of the n-type and p-type semiconductor layers 1b and 1d is used as the intrinsic semiconductor layer 1a,
It is composed of a semiconductor having a forbidden band width larger than 1c. In this configuration, the n-type and p-type semiconductor layers 1 for pumping light and signal light are
Absorption at b and 1d is small.

Further, since the inclination of the energy band becomes large, the n-type and p-type semiconductor layers 1b and 1d are easily depleted. Therefore, by increasing the thickness of the n-type and p-type semiconductor layers 1b and 1d, the electric field of the depletion layer can be increased even if the impurity concentration is the same.

In the fifth configuration of the present invention, referring to FIG. 2A, a reflection layer 3 which transmits the excitation light and reflects the signal light is provided below the laminated semiconductor 1 layer in which parametric excitation is performed.
To provide.

With respect to the excitation light and the signal light incident from the upper surface of the laminated semiconductor 1, only the signal light is reflected by the reflective layer 3, and the signal light 22 is emitted again from the upper surface of the laminated semiconductor 1.
On the other hand, the excitation light passes through the reflection layer 3 and is reflected by the signal light 2
Separated from 2.

Since this structure needs only to handle the reflected light of the laminated semiconductor 1, it can be manufactured only by depositing the reflective layer 3 and the laminated semiconductor 1, and has an advantage that the element structure is simple and easy to manufacture. In addition, the pumping light 23 is added to the output signal light 22.
Therefore, it is convenient to use the optical semiconductor element according to this configuration as an optical element.

The above-described configuration of the present invention does not require a means for propagating the surface such as a surface waveguide. Therefore,
The device according to the present invention can be used in the same manner as an ordinary three-dimensional optical component and is convenient for constructing a three-dimensional optical system.

[0048]

EXAMPLES The present invention will be described with reference to examples. The first embodiment relates to a degenerate parametric amplifier in which the idler light and the signal light have the same wavelength. The production and use of the method will be described below.

Referring to FIG. 2A, a reflective layer 3 made of a semiconductor multilayer film is deposited on an n-type GaAs substrate 4 by the MBE method (molecular beam epitaxial method). The reflection layer 3 reflects the signal light of the wavelength λ and transmits the excitation light of the wavelength λ / 2 of the incident light 42 that propagates in the semiconductor layer 1 and enters the reflection layer 3 at the incident angle θ. Form a type filter.

Next, the laminated semiconductor 1 is deposited on the reflective layer 3 by the MBE method. As shown in FIG. 1A, the laminated semiconductor 1 includes a first intrinsic semiconductor layer 1a and an n-type semiconductor layer 1
b, the second intrinsic semiconductor layer 1c and the p-type semiconductor layer 1d are
Fifty units are repeated with the four layers deposited in this order as a unit.

The first intrinsic semiconductor layer 1a and the second intrinsic semiconductor layer 1b are composed of a barrier layer of AlAs having a thickness of 5 nm and a thickness of 5 nm.
AlGaAs well layers are alternately deposited.
It is composed of 5 well layers and 14 barrier layers. The conduction electron concentration of the intrinsic semiconductor layers 1a and 1b is, for example, 1 ×
It is 10 ¹⁵ cm ^-3 .

The n-type semiconductor layer 1b is an n-type AlAs layer with a thickness of 5 nm deposited on the first intrinsic semiconductor layer 1a, and the conduction electron concentration thereof is, for example, 4 × 10 ¹⁸ cm ^-3 .
The p-type semiconductor layer 1d is formed of a p-type AlAs layer with a thickness of 5 nm deposited on the second intrinsic semiconductor layer 1a, and its hole concentration is, for example, 4 × 10 ¹⁸ cm ⁻³ . Such p-type and n
The entire type semiconductor layers 1b and 1d are depleted.

FIG. 3 shows an optical amplifier according to an embodiment of the present invention, and shows the configuration of a parametric optical amplifier using the optical semiconductor device according to the first embodiment. Referring to FIGS. 2A and 3, the signal light having a wavelength of 1.55 μm and the wavelength of 0.775 μm
The excitation light of m is superposed by using the three-way coupler 7 to be incident light 42, which is incident on the surface of the laminated semiconductor 1.

Initially, the incident angle was set to about 88 °, and while observing the intensity of the output signal light 22, the substrate 4 was rotated around the rotation axis perpendicular to the incident surface, and the incident angle satisfied the formula 1, The incident angle is set to maximize the intensity of the output signal light 22.

In the present embodiment, in the structure of the laminated semiconductor 1, even if the depletion interlayer distance d or the absolute value of the refractive index deviates from the design value, it is possible to easily set the optimum condition by fine adjustment of the incident angle. . Furthermore, it can be easily applied to signal light having a wavelength different from the designed value by simply changing the incident angle.

In the first embodiment, AlAs may be replaced by AlInP, and AlGaAs may be replaced by GaInP. As a result, signal light having a wavelength shorter than 1.55 μm, for example, signal light having a wavelength of 1.3 μm can be amplified.

The second embodiment of the present invention relates to a transmission type parametric amplifier. FIG. 2B shows the structure of the optical parametric amplifier according to the second embodiment of the present invention.

First, referring to FIG. 2B, the insulating Ga
The same laminated semiconductor 1 as that of the first embodiment is deposited on the As substrate 4 by the same method. Next, the central portion of the back surface of the substrate 4 (the surface on which the laminated semiconductor 1 is not deposited) is anisotropically etched to form a recess 6 having a trapezoidal cross section. As a result, the laminated semiconductor 1 has its periphery fixed on a frame formed from the substrate 1, and the substrate 1 thinned by etching adheres to the lower surface of the central portion. The thinned substrate is left to protect the laminated semiconductor 1 during etching.

The pumping light and the signal light are superimposed on each other to make incident light 42
Then, the light enters from the surface of the laminated semiconductor 1, passes through the thinned substrate 1 left on the upper surface of the recess 6, and is emitted below the substrate 1. The adjustment of the incident angle is the same as in the first embodiment.

In this embodiment, since it is a transmission type, it is convenient to construct a three-dimensional optical system. The output light of this embodiment is
It contains pumping light in addition to signal light. In order to reduce the excitation light in this output light, the sliced substrate can be formed from a semiconductor that transmits the signal light and absorbs the excitation light. For example, the laminated semiconductor 1 may be deposited after depositing an epitaxial layer having such absorption characteristics on the surface of the substrate. Further, an epitaxial layer having a forbidden band width larger than that of this substrate can be used as an etching stopper.

[0061]

As described above, according to the present invention, the laminated structure of the polarized layers having the inverted polarization is constituted by the laminated semiconductor. Therefore, an optical semiconductor device that is easy to manufacture can be realized.

Further, since it is possible to easily use a semiconductor having a quantum well structure having a large second-order non-linear susceptibility, it is possible to provide an optical semiconductor element which emits weak excitation light and operates sufficiently with a small element.

Therefore, the present invention greatly contributes to the performance improvement of the optical device.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of the present invention.

FIG. 2 is a sectional view of an embodiment of the present invention.

FIG. 3 is an optical amplifier according to an embodiment of the present invention.

FIG. 4 is a perspective view of a conventional example.

FIG. 5 is a sectional view of a conventional example.

FIG. 6 is a structural explanatory view of an optical parametric amplifier.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laminated semiconductor 1a 1st intrinsic semiconductor layer 1b n-type semiconductor layer 1c 2nd intrinsic semiconductor layer 1d p-type semiconductor layer 2a 1st depletion layer 2b 2nd depletion layer 3 reflective layer 4 substrate 5 polarization 6 depression 7 7 3 Directional coupler 21 Signal light 22 Output signal light 23 Excitation light 41 Optical waveguide 42 Incident light 43 Output light 44 Ion implantation region 45 Single crystal 46 Polarization direction 47 Electric field applying layer 48 Wiring 49 Substrate

Claims (5)

[Claims] 1. An optical semiconductor device in which pumping light and signal light having a wavelength λ are superposed and incident to perform parametric excitation,
A first intrinsic semiconductor layer (1a) transparent to the excitation light and the signal light, an n-type semiconductor layer (1b), and a second intrinsic semiconductor layer (1c transparent to the excitation light and the signal light. ) And p
The p-type semiconductor layer (1d) has a laminated semiconductor (1) formed by repeatedly laminating the type semiconductor layer (1d) a plurality of times in this order, and is in contact with the bottom of the first intrinsic semiconductor layer (1a).
And a first depletion layer (2a) is formed between the first intrinsic semiconductor layer (1a) and the n-type semiconductor layer (1b) in contact with the second intrinsic semiconductor layer (1c). The n touching under
-Type semiconductor layer (1b) and the second intrinsic semiconductor layer (1c)
A second depletion layer (2b) is formed between the upper surface of the depletion layer (2b) and the p-type semiconductor layer (1d) that is in contact with the upper surface of the depletion layer (2a, 2b). Distance to
Is the average refractive index for the pumping light during that period n _AP , the average refractive index for the signal light during that period is n _AS , and the excitation light and the signal light propagating through the laminated semiconductor (1) are the laminated semiconductor. An optical semiconductor device characterized in that d = (λ / 4) · cos θ / (n _AP −n _AS ), where θ is an angle formed with the normal to the laminated surface of (1). 2. The optical semiconductor element according to claim 1,
An optical semiconductor device characterized in that the first intrinsic semiconductor layer (1a) and the second intrinsic semiconductor layer (1c) have a quantum well structure formed by stacking semiconductor thin films having different forbidden band widths. . 3. The optical semiconductor device according to claim 1, wherein the n-type semiconductor layer (1b) and the p-type semiconductor layer (1d) are the n-type semiconductor layer (1b) and the p-type semiconductor layer. An optical semiconductor device, wherein the semiconductor layer (1d) has a depleting thickness. 4. The optical semiconductor element according to claim 1, 2 or 3, wherein at least one of the n-type semiconductor layer (1b) and the p-type semiconductor layer (1d) is the first semiconductor layer. The intrinsic semiconductor layer (1a) and the second intrinsic semiconductor layer (1
An optical semiconductor device having a forbidden band width larger than that of c). 5. An optical semiconductor element according to claim 1, claim 2, claim 3 or claim 4, wherein the laminated semiconductor (1)
Is a reflection layer (3) that transmits the excitation light and reflects the signal light
An optical semiconductor device provided on the above.