EP0000557A1 - Semiconductor laser device - Google Patents
Semiconductor laser device Download PDFInfo
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- EP0000557A1 EP0000557A1 EP78100461A EP78100461A EP0000557A1 EP 0000557 A1 EP0000557 A1 EP 0000557A1 EP 78100461 A EP78100461 A EP 78100461A EP 78100461 A EP78100461 A EP 78100461A EP 0000557 A1 EP0000557 A1 EP 0000557A1
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- semiconductor layer
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/12—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
- H01S5/223—Buried stripe structure
- H01S5/2232—Buried stripe structure with inner confining structure between the active layer and the lower electrode
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
- H01S5/223—Buried stripe structure
- H01S5/2232—Buried stripe structure with inner confining structure between the active layer and the lower electrode
- H01S5/2234—Buried stripe structure with inner confining structure between the active layer and the lower electrode having a structured substrate surface
Definitions
- This invention relates to a novel semiconductor laser device. It provides a semiconductor laser device in which longitudinal and transverse modes are stabilized.
- Semiconductor laser devices have many merits such as small size, operation at high efficiency, and capability of direct modulation by a drive current. There are therefore hopeful as light sources for optical communication, optical information processing etc.
- the distributed-feedback semiconductor laser has a corrugated surface therein. It achieves mode stabilization by exploiting a sharp oscillation mode selectivity which is produced by the diffraction effect of light based on the corrugated surface.
- Figs. 1 and 2 of the accompanying drawings show an example of the distributed-feedback semiconductor laser device.
- Fig. 1 is a sectional view taken orthogonally to the travelling direction of light
- Fig. 2 is a sectional view taken along the travelling direction of light.
- numeral 1 designates an n-GaAs substrate
- numeral 2 an n-Ga 1 -x Al x As layer (x ⁇ 0.3)
- numeral 3 a GaAs active layer
- numeral 4 a p-Ga 1-x Al x As layer and numeral 5 periodic corrugations which are provided at the boandary between the semiconductor layer 3 and the semiconductor layer 4.
- Numerals 6 and 7 indicate ohmic electrodes.
- the layers 2, 3 and 4 constitute an optical waveguide. Light given forth in active layer 3 is guided centering around the layer 3, and is subjected to the Bragg reflection of 130° by the periodic corrugations 5 formed at the boundary between the layers 3 and 4.
- the distributed-feedback semiconductor laser device oscillates at a single longitudinal mode and exhibits a spectral width of 0.5 ⁇ or less, so that it is excellent in monochromaticity. In addition, the temperature-dependency of the osicllation wavelength is low.
- the buried heterostructure semiconductor laser device has been proposed as a typical semiconductor laser device.
- a structure provided with an optical waveguide which produces the effect of confining lateral carriers and light in the direction of the thickness of an active layer.
- An example of the buried heterostructure semiconductor laser device of this sort is described in U.S. patent application Serial No. 786,758.
- This invention has for its object to provide a novel semiconductor laser device in which a longitudinal and transverse mode is stabilized singly and in which any excess optical noise component for a modulated signal is not generated by mode competition.
- a structure as stated below is employed.
- a first semiconductor layer is disposed, and second and third semiconductor layers which are greater in the band gap and lower in the index of refraction than the first semiconductor layer are disposed in a manner to sandwich the first semiconductor layer therebetween, whereby a double-heterostructure is constructed.
- light is confined in the vinicity of the active layer.
- a substrate semiconductor on which the respective semiconductor layers are not carried is naturally prepared.
- a semiconductor layer or layers are further stacked besides the semiconductor layers constituting the double-heterostructure.
- the basic optical confinement is effected by the structure as described above.
- that region of at least one of the second and third semiconductor layers which is remote from the first semiconductor layer is made a semiconductor layer which corresponds substantially to a radiation region and which functions as a light non-absorptive region in the shape of a stripe.
- a semiconductor layer is disposed which has portions lying on both sides of the semiconductor layer remote from the first semiconductor layer and which makes a complex refractive index for laser light discontinuous at both ends of the semiconductor layer remote from the first semiconductor layer.
- Periodic corrugations which intersect orthogonally to the lengthwise direction of the stripe-shaped light non-absorptive region are formed in at least one interface among the aforesaid semiconductor layers.
- FIG. 3 is a perspective view of the typical example of this invention.
- an n-GaAs substrate 1 formed with a groove 9; an n-Ga 1-x Al x As (x 0.3) layer 2, a GaAs active layer 3 and a p-Ga 1-y Al y As (y ⁇ 0.3) layer 4 are successively formed by the well-known liquid-phase epitaxy.
- the upper surface of the semiconductor layer 4 is formed with periodic corrugations 8.
- Numerals 6 and 7 designate ohmic electrodes.
- the light generated in the active layer 3 is confined in the vertical direction around the active layer by the double-heterostructure Part of the light evanesces to the GaAlAs layers 2 and 4 on both the sides.
- the light having evanesced to the GaAlAs layer 2 reaches the GaAs substrate 1 in regions on both the sides of the groove 9 because the n-Ga 1-x Al x As layer 2 in these regions is thin.
- the complex refractive-index for the light becomes different between the region corresponding to the groove 9 and the regions corresponding to both the sides of the groove 9. For this reason, any higher-order mode oscillation spreading to outside of the groove and the deviation of the oscillation region are suppressed, and the effect that the light is stably confined only to the region of the groove 9 in the lateral direction is produced.
- the travelling direction of the light is taken in the z-direction.
- the laser light is diffracted, and where X: wavelength of the light, n : effective refractive index of waveguide, A: period of the corrugations and a order of the diffraction.
- X wavelength of the light
- n effective refractive index of waveguide
- A period of the corrugations and a order of the diffraction.
- the width of the stripe-shaped light non-absorptive region corresponding substantially to the radiation region is made 2 um to 8 um. With widths below 2 um, especially the threshold current density (the lowest current density necessary for attaining the laser oscillation) increases rapidly. With widths above 8 ⁇ m, especially the instability of the transverse mode increases.
- the quantity of evanescence of the light to the regions which exist on both sides of the light non-absorptive region and which make the complex refractive index for the laser beam discontinuous at least 3 x 10 -2 % of the whole quantity of the light, preferably 5 x 10 -2 % to 5 x 10 % of the same is appropriate.
- in both the regions is preferably made 10 -3 to 10 -2 .
- the thickness d of the active layer 3 and the thickness t of the semiconductor layer 2 need to be selected.
- the thickness of the active layer is ordinarily set at 0.05 ⁇ m to 0.15 ⁇ m.
- the thickness d of the active layer is 0.1 ⁇ m, it is favorable to make the thickness t at most 0.5 ⁇ m; when the thickness d is 0.15 ⁇ m, it is favorable to make the thickness t at most 0.2 ⁇ m; when the thickness d is 0.05 ⁇ m, it is favorable to make the thickness t at most 0.7 ⁇ m.
- the thickness of the semiconductor layer 2 may be set by the interpolation with the aforecited values.
- the distance c between the active layer 3 and the periodic corrugations 8 which are provided at the interface between the semiconductor layers 4 and 5 is made at most 1 ⁇ m, preferably at most 0.5 ⁇ m, and at least 0.03 ⁇ m.
- the distance c is below 0.03 ⁇ m, the carrier confinement effect owing to the semiconductor layer 4 becomes insufficient, and an increase of the threshold current density is incurred.
- the distance c is above 1 ⁇ m, the degree to which the radiation in the active layer senses the periodic corrugations decreases abruptly, so that the laser oscillation of the distributed feedback type does not take place.
- the depth L of the corrugations is desirably selected in a range of 0.01 ⁇ m to 0.5 ⁇ m.
- the depth L is less than 0.01 ⁇ m, the Bragg reflection of the light owing to the periodic corrugation structure becomes insufficient, and the laser oscillation of the distributed feedback type becomes difficult.
- the depth L is selected to be greater than 0.5 ⁇ m, the light is distributed in a limited range centering around the active layer, so that the intensity of the Bragg reflection becomes substantially constant and the effect based on the increase of the depth L diminishes.
- the semiconductor layer corresponding to the semiconductor substrate 1 in Fig. 3 may consist of a plurality of layers. It is also allowed to form a separate semiconductor layer on the semiconductor substrate and to provide a recess in tne semiconductor layer, the recess being used as the groove 9 in Fig. 3. The purpose can be achieved even when a discontinuity in only the refractive index (corresponding to the real part of the complex refractive index) is produced. In any case, however, the technical items previously described may be conformed with.
- a GaAs-GaAlAs conductor will be referred to as a semiconductive material
- the present invention concerns the property of a laser resonator including an optical waveguide and that it is independent of materials.
- This invention is accordingly applicable, not only to semiconductor lasers employing the above-mentioned semiconductor, but also to semiconductor lasers employing e.g. a ternary system compound semiconductor such as GaInP, GaAsP and GaAlSb and a quaternary system compound semiconductor such as GaInAsP and GaAlAsSb.
- n-GaAs substrate 1 Te-doped, electron concentration n 1 x 10 18 /cm 3
- a groove 9 having a depth of 1.5 ⁇ m and a desired width in the range of 2 ⁇ m to 8 ⁇ m was formed in the (011) orientation.
- the conventional photolithography may be employed.
- photoresist was directly used as an etching mask. The chemical etching was conducted at 20°C for about 140 seconds with a mixed solution which contained phosphoric acid, hydrogen peroxide solution and ethylene glycol at 1: 1 : 3.
- GaAlAs system material it is common to employ Ga 1-z Al z As (0 ⁇ z ⁇ 0.3) for the first semi- conductor layer, Ga 1-x Al x As (0.1 ⁇ x ⁇ 0.9) for the second semiconductor layer and Ga 1- Al As (0.1 ⁇ y ⁇ 0.9) for the third semiconductor layer, where x, y, > z; r > z; and y ⁇ r.
- corrugations 8 having a period of 3,700 ⁇ and a depth of 1,500 ⁇ were formed in the surface of the semiconductor layer 4.
- holographic photolithography employing a laser beam and chemical etching were used. More specifically, a film of the positive type photoresist as was 800 ⁇ thick was formed on the surface of the semiconductor layer 4. Subsequently, using an Ar laser at a wavelength of 4,579 ⁇ ] an interference fringe was formed on the photoresist. After completing exposure, development was carried out for about 1 min with a mixed solution consisting of a developer and water at 1 : 1. In this way, a diffraction grating made of the photoresist was formed.
- the diffraction grating made of the photoresist was used as a mask, and a mixed solution consisting of phosphoric acid, a solution of hydrogen peroxide and ethylene glycol at 1 : 1 : 8 was used as an etchant.
- Periodic corrugations 8 having a depth of 0.15 ⁇ m were formed by the etching at 20°C for 80 seconds. This method is disclosed in Japanese Laid-Open Patent Application No. 111344/1976.
- Zn was diffused into a desired region of the p-side surface of the specimen thus formed, whereupon Cr and Au were deposited by vacuum-evaporation so as to form an electrode.
- the substrate side was lapped down to about 150 ⁇ m, whereupon Au-Ge-rJi was brought into close contact to form an electrode.
- the laser length was made 300 ⁇ m.
- the width W of the groove 9, the thickness t of the semiconductor layer 2, the thickness d of the active layer 3, the distance C between the active layer and the periodic corrugations, the depth L of the periodic corrugations, etc. have influence on the oscillation characteristics.
- Fig. 4 shows the characteristics of semiconductor lasers employing various combinations between the width W of the groove 9 and the thickness t of the semiconductor layer 2. While values of 0.05 ⁇ m to 0.15 ⁇ m are often employed as the thickness d of the active layer 3, a value of 0.1 ⁇ m is given as a typical example.
- the depth L of the periodic corrugations is 1,500 ⁇ .
- Mark O indicates an example in which the laser device oscillated in a single mode longitudinally and transversely without any optical noise
- mark A an example in which the laser device oscillated in a single longitudinal mode, but excess optical noise was generated by mode competition
- mark X an example in which the laser device did not reach the continuous oscillation on account of the increase of the threshold current density.
- the width W of the groove 9 capable of achieving the object is 2 ⁇ m to 8 ⁇ m.
- a value of 0.05 ⁇ m or less is the limit to which the layer can be stably fabricated in the actual process, while a value of 0.45 ⁇ m or greater falls in a region in which a desired light absorption was not attainable.
- Figs. 5 to 8 illustrate the states of generation of excess optical noise attributed to mode competition.
- a square wave signal current having a pulse width of 8 ns, a pulse height of 160 mA (1.25 times a threshold value) and a recurrence frequency of 62.5 MHz was caused to flow through a semiconductor laser device having a threshold current of 130 mA, and the optical output of the semiconductor laser was observed.
- the optical output waveform is a result obtained by conversion into an electric signal with a photodiode of which the wavelength band was the oscillation wavelength ⁇ 1 ⁇ and the frequency band was 1 MHz to 0.8 GHz.
- Fig. 5 shows an example of the optical output waveform of the distributed-feedback semiconductor laser device exemplified in Fig. 1, Fig.
- FIG. 6 shows an example of the optical output waveform of a prior art buried heterostructure semiconductor laser device
- Fig. 7 shows an example of the optical output waveform of the semiconductor laser device of this invention
- Fig. 8 shows an example of the optical output waveform of a semiconductor laser device which has a structure similar to that of this invention but whose stripe-shaped non-absorptive region is as broad as 12 pm. It is apprehended from the observation of the optical output waveforms that the semiconductor laser device of this invention is excellent.
- the semiconductor laser device of the structure of this example is advantageous in that the deterioration is especially little and that the transverse mode is more easily stabilized. This originates in that the periodic corrugations can be formed after forming the active layer
- n-GaAs substrate 21 Te-doped, electron concentration n ⁇ 1 x 10 18 /cm 3 ) having the (100) face as its surface
- a groove 29 having a depth of about 1.5 ⁇ m and a desired width in a range of 2 ⁇ m to 8 ⁇ m was formed by the conventional photolithography and chemical etching.
- Photoresist was used for an etching mask.
- the chemical etching was conducted at 20°C for about 140 seconds with a mixed solution which consisted of phosphoric acid, hydrogen peroxide silation and ethylene glycol at 1 : 1 : 3.
- the surface of the grown layer was subjected to the chemical etching until the substrate 21 was exposed on both sides of the groove.
- the chemical etching was carried out at 20°C for about 70 seconds by the use of phosphoric acid, hydrogen peroxide solution and ethylene glycol at 1 : 1 : 3.
- corrugations 28 having a period of 3,750 ⁇ were formed in the direction orthogonal to the groove (in the (011) orientation) by the holographic photolithography employing a laser beam and the chemical etching.
- photoresist being about 800 ⁇ thick was used.
- a mixed solution consisting of phosphoric acid, a solution of hydrogen peroxide and ethylene glycol at 1 : 1 : 8 was employed as an etchant, and the etching was conducted at 20°C for 80 seconds.
- the corrugations 28 being 0.15 ⁇ m deep were formed in the crystal surface.
- the Al contents of the respective layers must be so set that, with respect to light produced in the active layer 23, the substrate 21 becomes an absorptive region, while the stripe-shaped buried layer 30 becomes a non-absorptive region.
- the composition ratio totwen the Ga 1-s Al s As layer 30 and the Ga 1-z Al z As layer 23 is made z ⁇ s, and it is desirable that (s - z) is approximately 0.01 or greater.
- the Al content s of the semiconductor layer 30 may, in principle, be made 0.01 ⁇ s ⁇ 0.9. However, s ⁇ 0.1 must be held in order that the crystal may be smoothly grown on this layer by the liquid-phase epitaxial growth generally employed.
- Zn was diffused into the p-side surface of this specimen by approximately 0.1 ⁇ m, whereupon Cr and Au were deposited by vacuum-evaporation so as to form an electrode 27.
- the substrate side was lapped down to approximately 150 ⁇ m, whereupon Au-Ge-Ni was evaporated to form an ohmic electrode 26.
- Fig. 11 is a graph showing the light output versus current characteristics of this embodiment, while Fig. 12 is a graph showing the far-field intensity distributions in the junction plane.
- the results were obtained in an example in which the semiconductor laser device had a length of 300 ⁇ m and a groove width of 7 ⁇ m.
- the threshold current value was 100 mA at room temperature, and the external differential quantum efficiency was about 35%.
- Fig. 11 corresponds to the light output versus current characteristics at this time.
- the laser oscillated in the fundamental transverse mode, and the transverse mode was stable up to above double the threshold value.
- Fig. 13 shows the lasing spectra of the embodiment.
- the oscillation arose at a wavelength of 8,360 ⁇ , and even when the current value was increased double the threshold value, no change was noted.
- Fig. 14 shows the pulse responses at the time when current pulses having a width of 7 ns were impressed on the present laser device. Since the transverse mode was stabilized, the relaxation oscillation to become an optical noise as observed in the prior art distributed-feedback semiconductor laser was not noted.
- Fig. 15 concerns another embodiment of this invention, and is a sectional view taken perpendicularly to the travelling direction of light within a laser.
- corrugations 28 were formed on only the surface of a layer 30 grown in a groove.
- the other features were the same as in the case of Fig. 9.
- the feedback of light owing to the diffraction effect is selectively attained only in the upper part of the groove, and the lasing occurs concentratedly in this part. Therefore, the transverse mode is further stabilized.
- the thickness of the active layer 23 was 0.1 ⁇ m and where the thickness of the layer 22 was 0.3 ⁇ m
- the laser oscillated in the fundamental transverse mode up to triple the threshold value. Any excess optical noise for a modulated signal at the time of modulation as otherwise generated by mode competition was not noted.
- Fig. 16 is a sectional view showing another embodiment of this invention.
- an n-Ga 1-y Al y As layer 33 was grown on the whole surface of an n-GaAs substrate 21 in a manner to fill up the groove of the substrate, and corrugations 34 were formed thereon.
- the other features were the same as in Example 1.
- the sum between the thickness of the layer 33 and the layer 22 nedded to be made 0.6 ⁇ m or less when the thickness of the active layer was 0.1 ⁇ m.
- the thickness of the layer 33 outside the groove was 0.2 ⁇ m
- the thickness of the layer 22 was 0.2 ⁇ m
- the thickness of the active layer was 0.1 pm
- the groove width was 7 ⁇ m and the length was 300 ⁇ m
- the threshold current value of the oscillation was 100 mA and each of the longitudinal and transverse modes was single and stable up to above double the threshold value.
Abstract
Description
- This invention relates to a novel semiconductor laser device. It provides a semiconductor laser device in which longitudinal and transverse modes are stabilized.
- Semiconductor laser devices have many merits such as small size, operation at high efficiency, and capability of direct modulation by a drive current. There are therefore hopeful as light sources for optical communication, optical information processing etc.
- Among various semiconductor lasers, the distributed-feedback semiconductor laser has a corrugated surface therein. It achieves mode stabilization by exploiting a sharp oscillation mode selectivity which is produced by the diffraction effect of light based on the corrugated surface.
- The distributed-feedback semiconductor laser devices have been reported in detail in "Appl. Phys. Lett.," vol. 27, pages 403 to 405, October 1975, by M. Nakamura et al., and in "IEEE J. Quantum Electron.," vol. QE-12, pages 597 to 603, October 1976, by K. Aiki et al. A typical example of the distributed-feedback semiconductor laser is disclosed in U.S. patent application Serial No. 512,969.
- Figs. 1 and 2 of the accompanying drawings show an example of the distributed-feedback semiconductor laser device. Fig. 1 is a sectional view taken orthogonally to the travelling direction of light, while Fig. 2 is a sectional view taken along the travelling direction of light. Here, numeral 1 designates an n-GaAs substrate,
numeral 2 an n-Ga1 -xAlxAs layer (x ≃0.3), numeral 3 a GaAs active layer, numeral 4 a p-Ga1-xAlxAs layer, andnumeral 5 periodic corrugations which are provided at the boandary between thesemiconductor layer 3 and thesemiconductor layer 4.Numerals layers active layer 3 is guided centering around thelayer 3, and is subjected to the Bragg reflection of 130° by theperiodic corrugations 5 formed at the boundary between thelayers - The distributed-feedback semiconductor laser device oscillates at a single longitudinal mode and exhibits a spectral width of 0.5 Å or less, so that it is excellent in monochromaticity. In addition, the temperature-dependency of the osicllation wavelength is low.
- Even in the distributed-feedback semiconductor laser device controlled to the single longitudinal mode, nowever, the generation of excess optical noise especially for a modulated signal due to transverse mode instability is not avoided yet.
- On the other hand, the buried heterostructure semiconductor laser device has been proposed as a typical semiconductor laser device. In this case, there has also been proposed a structure provided with an optical waveguide which produces the effect of confining lateral carriers and light in the direction of the thickness of an active layer. An example of the buried heterostructure semiconductor laser device of this sort is described in U.S. patent application Serial No. 786,758.
- Even in the buried heterostructure semiconductor laser devices oscillating at a single transverse mode, however, the generation of the excess optical noise due to mode competition is not avoided.
- This invention has for its object to provide a novel semiconductor laser device in which a longitudinal and transverse mode is stabilized singly and in which any excess optical noise component for a modulated signal is not generated by mode competition.
- In order to accomplish the object, a structure as stated below is employed. A first semiconductor layer is disposed, and second and third semiconductor layers which are greater in the band gap and lower in the index of refraction than the first semiconductor layer are disposed in a manner to sandwich the first semiconductor layer therebetween, whereby a double-heterostructure is constructed. With this structure, light is confined in the vinicity of the active layer.
- A substrate semiconductor on which the respective semiconductor layers are not carried is naturally prepared. In some cases, a semiconductor layer or layers are further stacked besides the semiconductor layers constituting the double-heterostructure. Anyway, however, the basic optical confinement is effected by the structure as described above. Subsequently, that region of at least one of the second and third semiconductor layers which is remote from the first semiconductor layer is made a semiconductor layer which corresponds substantially to a radiation region and which functions as a light non-absorptive region in the shape of a stripe. Further, a semiconductor layer is disposed which has portions lying on both sides of the semiconductor layer remote from the first semiconductor layer and which makes a complex refractive index for laser light discontinuous at both ends of the semiconductor layer remote from the first semiconductor layer. Periodic corrugations which intersect orthogonally to the lengthwise direction of the stripe-shaped light non-absorptive region are formed in at least one interface among the aforesaid semiconductor layers.
- Preferred embodiments of the invention will now be described with reference to the drawings, in which:
- Figs. 1 and 2, which have been referred to above, are sectional views of a distributed-feedback semiconductor laser device of a prior art structure, which arc respectively taken perpendicularly to, and along, the travelling direction of light;
- Fig. 3 is a perspective view of a semiconductor laser device according to this invention;
- Fig. 4 is a graph showing the relationship between the groove width and the distance from an active layer to a light absorptive region;
- Figs. 5 to 8 are diagrams showing the states of generation of excess optical noise ascribable to mode competition in various semiconductor laser devices;
- Figs. 9 and 10 are sectional views of a device of another embodiment of this invention, which are respectively taken perpendicularly to, and along, the travelling direction of light;
- Fig. 11 is a graph showing the light output versus current characteristics of one embodiment of the present invention;
- Fig. 12 is a graph showing far-field intensity distributions in the junction plane;
- Fig. 13 shows the lasing spectra of one embodiment of the present invention operating under d.c. bias;
- Fig. 14 shows the pialse response of one embodiment of the present invention at different excitation levels; and
- Figs. 15 and 16 are sectional views of devices of further embodiments of this invention as taken perpendicularly to the travelling direction of light.
- This invention will be described in detail with reference to a typical example. Fig. 3 is a perspective view of the typical example of this invention.
- On an n-GaAs substrate 1 formed with a
groove 9; an n-Ga1-xAlxAs (x = 0.3)layer 2, a GaAsactive layer 3 and a p-Ga1-yAlyAs (y ≃ 0.3)layer 4 are successively formed by the well-known liquid-phase epitaxy. The upper surface of thesemiconductor layer 4 is formed with periodic corrugations 8.Numerals - In the present structure, light generated in the
active layer 3 is confined in the vertical direction around the active layer by the double-heterostructure Part of the light evanesces to the GaAlAslayers layer 2 reaches the GaAs substrate 1 in regions on both the sides of thegroove 9 because the n-Ga1-xAlxAslayer 2 in these regions is thin. In consequence, the complex refractive-index for the light becomes different between the region corresponding to thegroove 9 and the regions corresponding to both the sides of thegroove 9. For this reason, any higher-order mode oscillation spreading to outside of the groove and the deviation of the oscillation region are suppressed, and the effect that the light is stably confined only to the region of thegroove 9 in the lateral direction is produced. - On the other hand, the periodic corrugations 8 are provided at the interface between the
semiconductor layers active layer 3 varies periodically in the travelling direction of the light. ne can approximately be expressed as follows: - The travelling direction of the light is taken in the z-direction.
- Therefore, the laser light is diffracted, and
- In the above, the fundamental operation of the semiconductor laser of this invention has been explained. In order to reallse the semiconductor laser intended by this invention wherein a longitudinal and transverse mode is stabilized, especially any excess optical noise com- ponenet for a modulated signal is not generated by mode competition, a construction as described below is required.
- The width of the stripe-shaped light non-absorptive region corresponding substantially to the radiation region is made 2 um to 8 um. With widths below 2 um, especially the threshold current density (the lowest current density necessary for attaining the laser oscillation) increases rapidly. With widths above 8 µm, especially the instability of the transverse mode increases.
- As to the quantity of evanescence of the light to the regions which exist on both sides of the light non-absorptive region and which make the complex refractive index for the laser beam discontinuous, at least 3 x 10-2% of the whole quantity of the light, preferably 5 x 10-2% to 5 x 10 % of the same is appropriate. Thus, the absolute value of the index different |An| in both the regions is preferably made 10-3 to 10-2. When the quantity of evanescence of the light is too small, especially the effect of confinement in the lateral direction is unsatisfactory. On the other hand, when the quantity of evanescence of the light is too large, the quantity of absorption of the light increases, and the increase of the thrreshold current density is incurred. Therefore, the thickness d of the
active layer 3 and the thickness t of thesemiconductor layer 2 need to be selected. The thickness of the active layer is ordinarily set at 0.05 µm to 0.15 µm. When the thickness d of the active layer is 0.1 µm, it is favorable to make the thickness t at most 0.5 µm; when the thickness d is 0.15 µm, it is favorable to make the thickness t at most 0.2 µm; when the thickness d is 0.05 µm, it is favorable to make the thickness t at most 0.7 µm. Regarding any intervening thickness of the active layer, the thickness of thesemiconductor layer 2 may be set by the interpolation with the aforecited values. - On the other hand, the distance c between the
active layer 3 and the periodic corrugations 8 which are provided at the interface between the semiconductor layers 4 and 5 is made at most 1 µm, preferably at most 0.5 µm, and at least 0.03 µm. When the distance c is below 0.03 µm, the carrier confinement effect owing to thesemiconductor layer 4 becomes insufficient, and an increase of the threshold current density is incurred. When the distance c is above 1 µm, the degree to which the radiation in the active layer senses the periodic corrugations decreases abruptly, so that the laser oscillation of the distributed feedback type does not take place. - The depth L of the corrugations is desirably selected in a range of 0.01 µm to 0.5 µm. When the depth L is less than 0.01 µm, the Bragg reflection of the light owing to the periodic corrugation structure becomes insufficient, and the laser oscillation of the distributed feedback type becomes difficult. Even when the depth L is selected to be greater than 0.5 µm, the light is distributed in a limited range centering around the active layer, so that the intensity of the Bragg reflection becomes substantially constant and the effect based on the increase of the depth L diminishes.
- In the above, the fundamental concept of this invention has been described in connection with the typical example of this invention illustrated in Fig. 3.
- Various modifications can be contrived as to how the light non-absorptive region in the vicinity of the active layer and the retions situated on both the sides of the non-absorptive region for making the complex refractive index for the laser beam discontinuons are provided, at which interface among the stacked semiconductor layers the periodic corrugation is provided at, etc. By way of example, the semiconductor layer corresponding to the semiconductor substrate 1 in Fig. 3 may consist of a plurality of layers. It is also allowed to form a separate semiconductor layer on the semiconductor substrate and to provide a recess in tne semiconductor layer, the recess being used as the
groove 9 in Fig. 3. The purpose can be achieved even when a discontinuity in only the refractive index (corresponding to the real part of the complex refractive index) is produced. In any case, however, the technical items previously described may be conformed with. - Although, in examples to be stated later, a GaAs-GaAlAs conductor will be referred to as a semiconductive material, it is obvious that the present invention concerns the property of a laser resonator including an optical waveguide and that it is independent of materials. This invention is accordingly applicable, not only to semiconductor lasers employing the above-mentioned semiconductor, but also to semiconductor lasers employing e.g. a ternary system compound semiconductor such as GaInP, GaAsP and GaAlSb and a quaternary system compound semiconductor such as GaInAsP and GaAlAsSb.
- Hereunder, this invention will be described more in detail in connection with examples.
- Description will be made with reference to Fig. 3. In an n-GaAs substrate 1 (Te-doped, electron concentration n 1 x 1018/cm3) having the (100) face as its surface, a
groove 9 having a depth of 1.5 µm and a desired width in the range of 2 µm to 8 µm was formed in the (011) orientation. In the formation, the conventional photolithography may be employed. As an etching mask, photoresist was directly used. The chemical etching was conducted at 20°C for about 140 seconds with a mixed solution which contained phosphoric acid, hydrogen peroxide solution and ethylene glycol at 1: 1 : 3. - On the resultant substrate 1, an n-Ga1-xAlxAs layer 2 (x = 0.3, electron concentration
- n ≃ 5 x 1017 cm-3) being 0.3 µm thick, a
GaAs layer 3 being 0.1 µm thick, and a p-Ga1-yAlyAs layer 4 (y = 0.3, hole concentration - p = 5 x 1017 cm-3) being 0.2 µm thick, were continuously grown by the conventional liquid-phase epitaxy employing a slide boat.
- As regards the GaAlAs system material, it is common to employ Ga1-zAlzAs (0 < z < 0.3) for the first semi- conductor layer, Ga1-xAlxAs (0.1 ≤ x ≤ 0.9) for the second semiconductor layer and Ga1-Al As (0.1 < y ≦ 0.9) for the third semiconductor layer, where x, y, > z; r > z; and y ≠ r.
- Subsequently, corrugations 8 having a period of 3,700 Å and a depth of 1,500 Å were formed in the surface of the
semiconductor layer 4. In forming the corrugations, holographic photolithography employing a laser beam and chemical etching were used. More specifically, a film of the positive type photoresist as was 800 Å thick was formed on the surface of thesemiconductor layer 4. Subsequently, using an Ar laser at a wavelength of 4,579 Å] an interference fringe was formed on the photoresist. After completing exposure, development was carried out for about 1 min with a mixed solution consisting of a developer and water at 1 : 1. In this way, a diffraction grating made of the photoresist was formed. The diffraction grating made of the photoresist was used as a mask, and a mixed solution consisting of phosphoric acid, a solution of hydrogen peroxide and ethylene glycol at 1 : 1 : 8 was used as an etchant. Periodic corrugations 8 having a depth of 0.15 µm were formed by the etching at 20°C for 80 seconds. This method is disclosed in Japanese Laid-Open Patent Application No. 111344/1976. - Subsequently, a p-Ga1-Y AlyAs layer 5 (γ = 0.1 and 17 in general, 0.05 < y ≤ 0.9; hole concentration p = 5 x 1017 cm-3) was formed to a thickness of 2.0 µm by employing the conventional liquid-phase epitaxial growth again. Zn was diffused into a desired region of the p-side surface of the specimen thus formed, whereupon Cr and Au were deposited by vacuum-evaporation so as to form an electrode. The substrate side was lapped down to about 150 µm, whereupon Au-Ge-rJi was brought into close contact to form an electrode. The laser length was made 300 µm.
- As a result, when the groove width was 7 µm, the laser device oscillated at a threshold value of 110 mA and a wavelength of 8,300 Å, and each of longitudinal and transverse modes was single and stable. Any excess optical noise otherwise generated by mode competition was not noted.
- It is as previously stated that, in the present structure the width W of the
groove 9, the thickness t of thesemiconductor layer 2, the thickness d of theactive layer 3, the distance C between the active layer and the periodic corrugations, the depth L of the periodic corrugations, etc. have influence on the oscillation characteristics. - Fig. 4 shows the characteristics of semiconductor lasers employing various combinations between the width W of the
groove 9 and the thickness t of thesemiconductor layer 2. While values of 0.05 µm to 0.15 µm are often employed as the thickness d of theactive layer 3, a value of 0.1 µm is given as a typical example. The depth L of the periodic corrugations is 1,500 Å. Mark O indicates an example in which the laser device oscillated in a single mode longitudinally and transversely without any optical noise, mark A an example in which the laser device oscillated in a single longitudinal mode, but excess optical noise was generated by mode competition, and mark X an example in which the laser device did not reach the continuous oscillation on account of the increase of the threshold current density. - From the results, it is understood that the width W of the
groove 9 capable of achieving the object is 2 µm to 8 µm. Regarding the thickness t of thesemiconductor layer 2, a value of 0.05 µm or less is the limit to which the layer can be stably fabricated in the actual process, while a value of 0.45 µm or greater falls in a region in which a desired light absorption was not attainable. - Figs. 5 to 8 illustrate the states of generation of excess optical noise attributed to mode competition. A square wave signal current having a pulse width of 8 ns, a pulse height of 160 mA (1.25 times a threshold value) and a recurrence frequency of 62.5 MHz was caused to flow through a semiconductor laser device having a threshold current of 130 mA, and the optical output of the semiconductor laser was observed. The optical output waveform is a result obtained by conversion into an electric signal with a photodiode of which the wavelength band was the oscillation wavelength ±1 Å and the frequency band was 1 MHz to 0.8 GHz. Fig. 5 shows an example of the optical output waveform of the distributed-feedback semiconductor laser device exemplified in Fig. 1, Fig. 6 shows an example of the optical output waveform of a prior art buried heterostructure semiconductor laser device, Fig. 7 shows an example of the optical output waveform of the semiconductor laser device of this invention, and Fig. 8 shows an example of the optical output waveform of a semiconductor laser device which has a structure similar to that of this invention but whose stripe-shaped non-absorptive region is as broad as 12 pm. It is apprehended from the observation of the optical output waveforms that the semiconductor laser device of this invention is excellent.
- The semiconductor laser device of the structure of this example is advantageous in that the deterioration is especially little and that the transverse mode is more easily stabilized. This originates in that the periodic corrugations can be formed after forming the active layer
- Description will be made with reference to Figs. 9 and 10.
- In the (011) orientation of an n-GaAs substrate 21 (Te-doped, electron concentration n ≃ 1 x 1018/cm3) having the (100) face as its surface, a
groove 29 having a depth of about 1.5 µm and a desired width in a range of 2 µm to 8 µm was formed by the conventional photolithography and chemical etching. Photoresist was used for an etching mask. The chemical etching was conducted at 20°C for about 140 seconds with a mixed solution which consisted of phosphoric acid, hydrogen peroxide silation and ethylene glycol at 1 : 1 : 3. - On the
resultant substrate 21, an n-Ga1-sAlsAs layer 30 ( s = Q.07, and in general, 0.1 < s ≦ 0.9; Sn- doped; electron concentration n = 5 x 1017/cm3) was grown to a thickness of 2.0 µm so as to fill up the groove flatly (to the extent that the thickness was about 0.5 µm outside the groove) by the conventional liquid-phase epitaxial growth employing a slide boat. - Subsequently, the surface of the grown layer was subjected to the chemical etching until the
substrate 21 was exposed on both sides of the groove. The chemical etching was carried out at 20°C for about 70 seconds by the use of phosphoric acid, hydrogen peroxide solution and ethylene glycol at 1 : 1 : 3. - Subsequently, corrugations 28 having a period of 3,750 Å were formed in the direction orthogonal to the groove (in the (011) orientation) by the holographic photolithography employing a laser beam and the chemical etching. As a mask at this time, photoresist being about 800 Å thick was used. A mixed solution consisting of phosphoric acid, a solution of hydrogen peroxide and ethylene glycol at 1 : 1 : 8 was employed as an etchant, and the etching was conducted at 20°C for 80 seconds. As a result, the
corrugations 28 being 0.15 µm deep were formed in the crystal surface. - Subsequently, an n-Ga AlxAs layer 22 (x = 0.3; Sn- doped; electron concentration n ≃ 5 x 1017 cm ) being 0.4 µm thick, an n-Ga -zAlzAs active layer 23 (z ≃ 0.05; undoped;
n = 1 x 1016 cm-3) being 0.1 µm, a p-G1-xAlxAs layer 24 ( x ≃ 0.3, Ge-doped; hole concentration p = 1017 cm-3) being 2 µm thick, and a p-GaAs layer 25 (Ge-doped; hole concentration p = 5 x 1017 cm-3) being 1 µm thick were successively grown by employing the conventional liquid-phase epitaxial growth with the slide boat again. - Here, the Al contents of the respective layers must be so set that, with respect to light produced in the
active layer 23, thesubstrate 21 becomes an absorptive region, while the stripe-shaped buriedlayer 30 becomes a non-absorptive region. The composition ratio totwen the Ga1-sAlsAslayer 30 and the Ga1-zAlzAslayer 23 is made z < s, and it is desirable that (s - z) is approximately 0.01 or greater. On the other hand, the Al content s of thesemiconductor layer 30 may, in principle, be made 0.01 < s < 0.9. However, s < 0.1 must be held in order that the crystal may be smoothly grown on this layer by the liquid-phase epitaxial growth generally employed. When s > 0.1, the normal liquid-phase growth becomes difficult in practice. As described above,(s - z) should desirably be approximately 0.01 or greater. Therefore, even in case where theactive layer 23 is made a GaAs (z = O in Ga1-zAlzAs) layer it is necessary that s ≥ 0.01, and the lower limit value of s becomes 0.01. - Zn was diffused into the p-side surface of this specimen by approximately 0.1 µm, whereupon Cr and Au were deposited by vacuum-evaporation so as to form an
electrode 27. The substrate side was lapped down to approximately 150 µm, whereupon Au-Ge-Ni was evaporated to form anohmic electrode 26. - Fig. 11 is a graph showing the light output versus current characteristics of this embodiment, while Fig. 12 is a graph showing the far-field intensity distributions in the junction plane. The results were obtained in an example in which the semiconductor laser device had a length of 300 µm and a groove width of 7 µm. The threshold current value was 100 mA at room temperature, and the external differential quantum efficiency was about 35%. Fig. 11 corresponds to the light output versus current characteristics at this time. As apparent from the Figure, the laser oscillated in the fundamental transverse mode, and the transverse mode was stable up to above double the threshold value.
- Fig. 13 shows the lasing spectra of the embodiment. The oscillation arose at a wavelength of 8,360 Å, and even when the current value was increased double the threshold value, no change was noted. Fig. 14 shows the pulse responses at the time when current pulses having a width of 7 ns were impressed on the present laser device. Since the transverse mode was stabilized, the relaxation oscillation to become an optical noise as observed in the prior art distributed-feedback semiconductor laser was not noted.
- Fig. 15 concerns another embodiment of this invention, and is a sectional view taken perpendicularly to the travelling direction of light within a laser. In the present element, corrugations 28 were formed on only the surface of a
layer 30 grown in a groove. The other features were the same as in the case of Fig. 9. In this example, the feedback of light owing to the diffraction effect is selectively attained only in the upper part of the groove, and the lasing occurs concentratedly in this part. Therefore, the transverse mode is further stabilized. In case where the thickness of theactive layer 23 was 0.1 µm and where the thickness of thelayer 22 was 0.3 µm, the laser oscillated in the fundamental transverse mode up to triple the threshold value. Any excess optical noise for a modulated signal at the time of modulation as otherwise generated by mode competition was not noted. - Fig. 16 is a sectional view showing another embodiment of this invention. In the present laser device, an n-Ga1-yAlyAs
layer 33 was grown on the whole surface of an n-GaAs substrate 21 in a manner to fill up the groove of the substrate, andcorrugations 34 were formed thereon. The other features were the same as in Example 1. In this case, in order for light to evanesce to the substrate on the lateral outer sides, the sum between the thickness of thelayer 33 and thelayer 22 nedded to be made 0.6 µm or less when the thickness of the active layer was 0.1 µm. By way of example, in case of a laser wherein the thickness of thelayer 33 outside the groove was 0.2 µm, the thickness of thelayer 22 was 0.2 µm, the thickness of the active layer was 0.1 pm, the groove width was 7 µm and the length was 300 µm, the threshold current value of the oscillation was 100 mA and each of the longitudinal and transverse modes was single and stable up to above double the threshold value. - As regards the arrangement of the periodic corrugations and the means for bestowing a difference on the complex refractive index, only examples in which such means exists on the substrate side have been explained above. This invention, however, is not restricted to sach arrangement, but can adopt different constructions. For instance, a layer overlying an active layer is formed with periodic corrugations, whereupon a layer is formed which is provided with a protuberance corresponding sulhstantially to a radiation portion. The protuberant layer is made a light noa-absorptive layer. On this layer, a layer serving as a light absorptive layer is formed. With such a structure, the same effects as in the foregoing can be achieved. Concrete methods of setting the various constituents may conform with the methods stated in the general descrioption.
Claims (11)
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP9136877A JPS5427385A (en) | 1977-08-01 | 1977-08-01 | Semiconductor laser |
JP91368/77 | 1977-08-01 | ||
JP36912/78U | 1978-03-24 | ||
JP3691278U JPS54141881U (en) | 1978-03-24 | 1978-03-24 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0000557A1 true EP0000557A1 (en) | 1979-02-07 |
EP0000557B1 EP0000557B1 (en) | 1981-12-30 |
Family
ID=26376009
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP78100461A Expired EP0000557B1 (en) | 1977-08-01 | 1978-07-20 | Semiconductor laser device |
Country Status (4)
Country | Link |
---|---|
US (1) | US4257011A (en) |
EP (1) | EP0000557B1 (en) |
CA (1) | CA1105598A (en) |
DE (1) | DE2861465D1 (en) |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4302729A (en) * | 1979-05-15 | 1981-11-24 | Xerox Corporation | Channeled substrate laser with distributed feedback |
US4329658A (en) * | 1978-06-30 | 1982-05-11 | Hitachi, Ltd. | Semiconductor laser device |
EP0125608A2 (en) * | 1983-05-09 | 1984-11-21 | Nec Corporation | Single longitudinal mode semiconductor laser |
EP0178134A2 (en) * | 1984-10-09 | 1986-04-16 | Fujitsu Limited | Semiconductor laser |
EP0334209A2 (en) * | 1988-03-22 | 1989-09-27 | Siemens Aktiengesellschaft | Laser diode for the generation of strongly monochromatic laser light |
WO1992014286A1 (en) * | 1991-02-06 | 1992-08-20 | Eastman Kodak Company | Semiconductor diode laser |
Families Citing this family (18)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4342148A (en) * | 1981-02-04 | 1982-08-03 | Northern Telecom Limited | Contemporaneous fabrication of double heterostructure light emitting diodes and laser diodes using liquid phase epitaxy |
US4400813A (en) * | 1981-07-20 | 1983-08-23 | Bell Telephone Laboratories, Incorporated | Crenelated-ridge waveguide laser |
JPS5878487A (en) * | 1981-10-29 | 1983-05-12 | Kokusai Denshin Denwa Co Ltd <Kdd> | Distributed feedback type semiconductor laser |
US4573163A (en) * | 1982-09-13 | 1986-02-25 | At&T Bell Laboratories | Longitudinal mode stabilized laser |
US4606605A (en) * | 1984-06-29 | 1986-08-19 | At&T Bell Laboratories | Optical fiber having in-line polarization filter |
DE3580738D1 (en) * | 1984-10-03 | 1991-01-10 | Siemens Ag | METHOD FOR THE INTEGRATED PRODUCTION OF A DFB LASER WITH A COUPLED STRIP WAVE GUIDE ON A SUBSTRATE. |
JPS61113293A (en) * | 1984-11-07 | 1986-05-31 | Sharp Corp | Semiconductor laser array device |
US4633476A (en) * | 1984-11-16 | 1986-12-30 | Spectra Diode Laboratories, Inc. | Semiconductor laser with internal reflectors and vertical output |
US4777148A (en) * | 1985-01-30 | 1988-10-11 | Massachusetts Institute Of Technology | Process for making a mesa GaInAsP/InP distributed feedback laser |
US4722092A (en) * | 1985-01-30 | 1988-01-26 | Massachusetts Institute Of Technology | GaInAsP/InP distributed feedback laser |
US4691320A (en) * | 1985-03-11 | 1987-09-01 | Rca Corporation | Semiconductor structure and devices |
US4652333A (en) * | 1985-06-19 | 1987-03-24 | Honeywell Inc. | Etch process monitors for buried heterostructures |
GB8703743D0 (en) * | 1987-02-18 | 1987-03-25 | British Telecomm | Semiconductor laser structures |
JPS63258090A (en) * | 1987-04-15 | 1988-10-25 | Sharp Corp | Semiconductor laser device |
US5295150A (en) * | 1992-12-11 | 1994-03-15 | Eastman Kodak Company | Distributed feedback-channeled substrate planar semiconductor laser |
US5901168A (en) * | 1997-05-07 | 1999-05-04 | Lucent Technologies Inc. | Article comprising an improved QC laser |
US7457338B2 (en) * | 2006-04-19 | 2008-11-25 | Wisconsin Alumni Research Foundation | Quantum well lasers with strained quantum wells and dilute nitride barriers |
US7542503B2 (en) * | 2006-10-06 | 2009-06-02 | Applied Optoelectronics, Inc. | Distributed feedback laser with improved optical field uniformity and mode stability |
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US3978428A (en) * | 1975-06-23 | 1976-08-31 | Xerox Corporation | Buried-heterostructure diode injection laser |
US4023993A (en) * | 1974-08-22 | 1977-05-17 | Xerox Corporation | Method of making an electrically pumped solid-state distributed feedback laser |
FR2348589A1 (en) * | 1976-04-16 | 1977-11-10 | Hitachi Ltd | Semiconductor double hetero laser with stable reliable operation - has laser active zone in layer between layers with greater band sepn. (NL 18.10.77) |
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JPS51146196A (en) * | 1975-06-11 | 1976-12-15 | Hitachi Ltd | Diode laser |
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1978
- 1978-07-20 EP EP78100461A patent/EP0000557B1/en not_active Expired
- 1978-07-20 DE DE7878100461T patent/DE2861465D1/en not_active Expired
- 1978-07-24 CA CA307,988A patent/CA1105598A/en not_active Expired
- 1978-07-28 US US05/929,013 patent/US4257011A/en not_active Expired - Lifetime
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US4023993A (en) * | 1974-08-22 | 1977-05-17 | Xerox Corporation | Method of making an electrically pumped solid-state distributed feedback laser |
US3978428A (en) * | 1975-06-23 | 1976-08-31 | Xerox Corporation | Buried-heterostructure diode injection laser |
FR2348589A1 (en) * | 1976-04-16 | 1977-11-10 | Hitachi Ltd | Semiconductor double hetero laser with stable reliable operation - has laser active zone in layer between layers with greater band sepn. (NL 18.10.77) |
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Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4329658A (en) * | 1978-06-30 | 1982-05-11 | Hitachi, Ltd. | Semiconductor laser device |
US4302729A (en) * | 1979-05-15 | 1981-11-24 | Xerox Corporation | Channeled substrate laser with distributed feedback |
EP0125608A2 (en) * | 1983-05-09 | 1984-11-21 | Nec Corporation | Single longitudinal mode semiconductor laser |
EP0125608A3 (en) * | 1983-05-09 | 1986-08-20 | Nec Corporation | Single longitudinal mode semiconductor laser |
EP0178134A2 (en) * | 1984-10-09 | 1986-04-16 | Fujitsu Limited | Semiconductor laser |
EP0178134A3 (en) * | 1984-10-09 | 1987-05-20 | Fujitsu Limited | Semiconductor laser |
US4726031A (en) * | 1984-10-09 | 1988-02-16 | Fujitsu Limited | Semiconductor laser |
EP0334209A2 (en) * | 1988-03-22 | 1989-09-27 | Siemens Aktiengesellschaft | Laser diode for the generation of strongly monochromatic laser light |
DE3809609A1 (en) * | 1988-03-22 | 1989-10-05 | Siemens Ag | LASER DIODE FOR GENERATING STRICTLY MONOCHROMATIC LASER RADIATION |
EP0334209A3 (en) * | 1988-03-22 | 1989-12-06 | Siemens Aktiengesellschaft | Laser diode for the generation of strongly monochromatic laser light |
WO1992014286A1 (en) * | 1991-02-06 | 1992-08-20 | Eastman Kodak Company | Semiconductor diode laser |
Also Published As
Publication number | Publication date |
---|---|
US4257011A (en) | 1981-03-17 |
DE2861465D1 (en) | 1982-02-18 |
EP0000557B1 (en) | 1981-12-30 |
CA1105598A (en) | 1981-07-21 |
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