JPH10223976A - Semiconductor laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the laser light emitting efficiency of a electron beam pumping semiconductor laser used in the field of communication, sensor, display, etc., to narrow the lasing wave band of the laser, and to reduce the number of laser oscillation modes of the laser. SOLUTION: A semiconductor laser has a diffracting area 13 in which a diffraction grating 12 having the optical distance period corresponding to a half or integer multiple of the wavelength of the oscillated light of the laser is formed perpendicularly to the winding direction of light above, below, or in part of or the entire area of a semiconductor optical waveguide layer 9, and emits laser light having a narrow wavelength band when at least part of the area 13 is irradiated with an electron beam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser used in the fields of communication, sensors, displays and the like.

[0002]

2. Description of the Related Art Semiconductor lasers can be classified into three types, a current injection type laser, an electron beam pumped laser, and an optically pumped laser, according to the pumping method. Among them, the electron beam pumped laser can use all direct transition type semiconductors as its material, and can emit laser light in a short wavelength region, particularly in a wavelength region where it is difficult to form a current injection type laser. In this respect, it is advantageous in application.

Therefore, the above-mentioned electron beam pumped laser will be described below with reference to the drawings. FIG. 8 is a configuration diagram showing a conventional semiconductor laser using an electron beam as an excitation source. In FIG. 8, an electron beam 2 emitted from an electron gun 1 is shown.
Is irradiated onto the optical resonator 3. The shape, area, and the like of the electron beam irradiation area on the optical resonator 3 are determined by the electron lens 4. The above-described optical resonator 3 is formed on the substrate 5, and reflection surfaces 6 and 7 are formed at both ends of the resonator by cleavage. Generally, an optical waveguide 9 including an active layer 8 therein is formed in the resonator. Cavity length 10 is 300-1
It is about 000 μm. GaAs as a material of the substrate 5
s, GaSb, InP, sapphire, or the like is used.
As a material of the active layer 8, IIb- such as ZnS and CdS is used.
IIIb of group VI compound semiconductor, AlAs, GaP, etc.
A group V compound semiconductor, a chalcogenide compound such as MgS or MnS, or a mixed crystal thereof is mainly used. Active layer 8 excited by irradiation with electron beam 2
Laser light 11 is emitted.

[0004]

However, the above-mentioned conventional electron beam pumped semiconductor lasers have problems such as low luminous efficiency, multimode laser oscillation, and laser oscillation in a wide wavelength range. Laser oscillation in a wide wavelength band has limited the application of electron beam pumped semiconductor lasers in fields such as communication and sensors.

In view of the above problems, the present invention has as its first object to improve the luminous efficiency of an electron beam pumped semiconductor laser, and to reduce the laser oscillation wavelength width and reduce the number of laser oscillation modes. This is the second purpose.

[0006]

According to a first aspect of the present invention, there is provided an optical waveguide comprising: a part of an optical waveguide;
Alternatively, a diffraction grating is formed perpendicular to the light guiding direction at one half of the wavelength of the laser oscillation light or at a period of an optical distance corresponding to an integral multiple of the above-mentioned length. A semiconductor laser having a diffraction region that emits a laser beam by irradiating at least a part of the diffraction region with an electron beam.

By employing this configuration, it is possible to increase the efficiency of the laser and to narrow the wavelength band of the laser oscillation.

In the present invention, forming the diffraction grating in the diffraction region at a period of an optical distance corresponding to one half of the wavelength of the laser oscillation light has a probability of laser oscillation in a single mode. It is more preferable in terms of improvement.

[0009] A second invention is to achieve the above object,
A diffraction region in which a diffraction grating is formed at a period of an optical distance corresponding to a half of the wavelength of the laser oscillation light is provided in a part of the optical waveguide, or an upper part, a lower part, or an inside of the whole area. A semiconductor laser that emits laser light by irradiating at least a part of the diffraction region with an electron beam,
A reflecting surface formed perpendicular to the light guiding direction and separated by an optical distance corresponding to an integral multiple of one half of the wavelength of the laser oscillation light, and at least one of the reflecting surfaces is made highly reflective; It is characterized by doing.

By employing this configuration, it is possible to narrow the wavelength band of laser oscillation and improve the probability of laser oscillation in a single mode.

[0011] A third aspect of the present invention is to achieve the above object.
A diffraction region in which a diffraction grating is formed at a period of an optical distance corresponding to a half of the wavelength of the laser oscillation light is provided in a part of the optical waveguide, or an upper part, a lower part, or an inside of the whole area. An electron beam pumped semiconductor laser characterized in that the phase shift regions having the periods slightly different by a small amount are formed in the diffraction region.

By employing this configuration, it is possible to narrow the wavelength band of laser oscillation and improve the probability of laser oscillation in a single mode.

In the present invention, the formation of a diffraction grating in which the total phase shift introduced into the diffraction region corresponds to an odd multiple of a quarter of the wavelength of the laser oscillation light is a single mode. It is more preferable from the viewpoint of improving the probability of laser oscillation.

It is more preferable to form an anti-reflection coating layer on both end faces of the optical waveguide from the viewpoint of improving the probability of laser oscillation in a single mode.

According to a fourth aspect of the present invention, in order to achieve the above object,
A diffraction grating having a period of an optical distance corresponding to one half of the wavelength of the laser oscillation light or an integral multiple of the above-mentioned length is provided on a part of the optical waveguide or on the upper part, the lower part, or the inside of the whole area, A diffraction grating having at least two or more types of diffraction regions formed perpendicular to the light waveguide direction, and formed in an active diffraction region that irradiates at least a part with an electron beam,
A semiconductor laser characterized in that diffraction efficiencies of diffraction gratings formed in a passive diffraction region not irradiated with an electron beam are different.

By adopting this configuration, it is possible to increase the efficiency of the laser, narrow the bandwidth of the laser oscillation wavelength, and improve the probability of laser oscillation in a single mode.

In the present invention, the period of the diffraction grating to be formed is an optical distance corresponding to one half of the wavelength of the laser oscillation light, in that the probability of laser oscillation in a single mode is improved. Is more preferable. Further, it is more preferable to form a diffraction grating having higher diffraction efficiency in the passive diffraction region than a diffraction grating formed in the active diffraction region in terms of improving the probability of laser oscillation in a single mode. Also, the medium in contact with the diffraction grating formed in the active diffraction region is a material having a smaller refractive index ratio to the waveguide material than the medium in contact with the diffraction grating formed in the passive diffraction region. It is more preferable from the viewpoint of improving the probability of laser oscillation in the above.

According to a fifth aspect, in order to achieve the above object,
A diffraction region in which a diffraction grating is formed at a period of an optical distance corresponding to an integral multiple of a half of the wavelength of the laser oscillation light at an upper part, a lower part, or an inside of a part of the optical waveguide. And a semiconductor laser that emits laser light by irradiating an area other than the diffraction area with an electron beam.

By employing this configuration, it is possible to increase the efficiency of the laser and to narrow the wavelength band of the laser oscillation.

According to a sixth aspect of the present invention, to achieve the above object,
A diffraction grating is formed concentrically or concentrically with a period of an optical distance corresponding to an integral multiple of one half of the wavelength of the laser oscillation light at any of the upper, lower and inner portions of the optical waveguide. A semiconductor laser having a diffraction region and using an electron beam as an excitation source.

By employing this configuration, the laser oscillation wavelength width can be narrowed. Further, there is an advantageous effect that the laser beam emitted by scanning the excitation electron beam can be scanned radially.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor laser according to an embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) First, a semiconductor laser according to Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram of a semiconductor laser according to the present embodiment, and in particular, FIG.
1 is a perspective view, and FIG. 1B is a side view.

As shown in FIG. 1A, the semiconductor laser according to the present embodiment is arranged such that a part of the semiconductor optical waveguide 9, the upper part, the lower part, or the inside of the whole area thereof has a wavelength of two minutes of the laser oscillation light. The diffraction grating 12 has a diffraction region 13 formed perpendicular to the waveguide direction of the laser oscillation light 11 at a period of an optical distance that is an integral multiple of 1 and at least a part of the diffraction region is an electron beam. This is an electron beam pumped semiconductor laser having a configuration for pumping.

More specifically, the diffraction region 1 is partially or entirely formed on the semiconductor optical waveguide 9 formed on the substrate 5.
3 are formed. The period Λ (Λ =
(λ / 2n) diffraction grating 12 is formed. Here, λ is a desired laser oscillation wavelength, and n is a refractive index of the optical waveguide. The reflection surface 6 was formed on the laser emission side of the diffraction region 13. In FIG. 1, the reflection surface 7 is formed on the end surface of the optical waveguide on the laser non-emission side, but this is not always necessary.

The material of the substrate 5 is Ga
Materials such as As, GaSb, InP, and sapphire are mainly used, and the material of the optical waveguide 9 is Zn
IIb-VI group compound semiconductors such as S and CdS, AlA
Materials such as IIIb-V group compound semiconductors such as s and GaP, chalcogenide compounds such as MgS and MnS, or mixed crystals thereof are mainly used.

Next, the device structure of this embodiment will be described in detail with reference to FIGS. 1 (a) and 1 (b).

GaAs was used as the substrate 5. Zn _{0. 6} as a cladding layer 14 on the substrate 5 Next Mg _0.4 S _0.6 Se
_0.4 , the optical waveguide 9 Zn _0.95 Mg _0.05 S _0.1 Se _0.9 ,
Again as the cladding layer 14, Zn _0.6 Mg _0.4 S _0.6 Se _0.4
Was formed by a molecular beam epitaxial growth method. Each of the cladding layers 14 has a thickness of 0.3 μm,
Was 0.3 μm in thickness.

On the other hand, the reflecting surfaces 6 and 7 were formed by cleavage.
The distance 16 between the reflecting surfaces was 350 μm. After cleavage, Ga
A diffraction grating was formed parallel to the cleavage plane by a constant-frequency gain modulation structure formed by selective focused beam injection of ions. Ga ions were implanted under the conditions that the acceleration voltage of Ga ions was 130 kV, the ion current was 10 pA, the diameter of the ion beam was 30 nm, and the ion implantation dose was 3 × 10 ⁶ per cm. Due to the ion beam implantation, the crystallinity is deteriorated in the implantation region, the life of carriers is shortened,
A periodic modulation of the optical gain is obtained.

The period 17 of the diffraction grating is set to 92, 184, 2
Three types of semiconductor lasers 1-1 to 3 (sample numbers) having a wavelength of 76 nm were produced. Laser 1 is used except for the formation of the diffraction region.
Laser 1-4 (sample number) having the same structure as -1 to 3
It was prepared for confirming the effect of the present invention.

The above four types of semiconductor lasers are accelerated at an acceleration voltage of 15
Excitation was performed with an electron beam having an electron beam diameter of 50 μm at kV, and laser light oscillation was obtained. The characteristics such as the oscillation wavelength, oscillation wavelength width, oscillation threshold value, and output efficiency are as shown in the following table.

[0032]

[Table 1]

As shown in the above (Table 1), the laser oscillation wavelength width is narrowed by adopting the present embodiment, but this is because of the selective gain for the light in the narrow wavelength band by the periodic gain modulation structure. Due to a significant gain improvement. Since the single-mode oscillation probability is improved by improving the selectivity of the gain, the period of the diffraction grating to be introduced is preferably short, and the period of the diffraction grating to be introduced is one half of the wavelength of the laser oscillation light in the waveguide. It is particularly preferred to introduce a periodic grating.

As shown in (Table 1), the threshold current value of laser oscillation is reduced and the output efficiency is improved by the present embodiment. This is because the distributed feedback structure is adopted. This is because the loss in the non-excitation region between the cavities in the conventional electron beam pumped semiconductor laser is reduced, and the wavelength selectivity of the effective reflectance for a specific wavelength is improved. In conventional electron beam pumped lasers, in which the cavity length is determined by the crystal cleavage technology, the region excited by the electron beam occupies only a small area of the cavity length, and the effect of absorption in the non-excited region is affected by laser oscillation. This led to an increase in the threshold current value and a decrease in the luminous efficiency. However, this embodiment has solved this problem.

The structure of the optical waveguide 9 is shown in FIG.
As shown in (a), Zn _0.95 Mg _0. containing ₀₅ S _0.1 Se _0.9 quantum well 15, the Zn _0.93 Mg _0.07 S _0.14 Se _0.86 waveguide layer 11, a multiple quantum well sandwiched thickness direction by the cladding layer 14 When the structure is adopted, the same effect as that of the present embodiment is obtained. Hereinafter, the wafer having this configuration is referred to as a wafer 1. Further, even when the cladding layer is not formed on the optical waveguide 9 as in the wafer structure shown in FIG.

As described above, according to the present embodiment, the advantageous effects of increasing the efficiency of high-efficiency laser oscillation and narrowing the laser oscillation wavelength width can be obtained.

(Embodiment 2) Next, Embodiment 2 of the present invention.
Will be described with reference to FIG.

FIG. 3A is a perspective view of a semiconductor laser according to the second embodiment of the present invention, and FIG. 3B is a side view of the semiconductor laser of the present embodiment. FIG. 3 (a)
As shown in the figure, in the electron beam pumped semiconductor laser according to the present embodiment, the diffraction grating is provided at any one of the upper part, the lower part, and the inside of the optical waveguide at a period of an optical distance of half the wavelength of the laser oscillation light. It has a diffraction region formed perpendicularly to the light guiding direction, and has a reflection surface on both end surfaces of the optical waveguide separated by an optical distance corresponding to an integral multiple of half the wavelength of the laser oscillation light. 6 and 7 are formed, and at least one of the reflection surfaces is highly reflective.

As the material of the substrate 5 and the optical waveguide 9, as described in the first embodiment, the same material as the conventional one is used.

In the following, the wafer structure of the semiconductor laser of the present embodiment will be described in detail with reference to FIG. 2B and the device structure of the present embodiment with reference to FIGS. 3A and 3B. I do.

GaAs was used as the substrate 5. Then Zn _{0. 74} as a cladding layer 14 on the substrate 5 Mg _0.26 S _0.33 S
e _0.67 and Zn _0.95 Mg _0.05 S _0.1
The Se _{0 .9,} was formed by molecular beam epitaxial growth method. The thickness of the cladding layer 14 was 1 μm, and the thickness of the waveguide 9 was 0.5 μm. Hereinafter, the wafer having this configuration is referred to as a wafer 2.

The wafer 2 was cleaved at the crystal plane, and parallel reflection surfaces 6 and 7 were obtained. The distance 16 between the reflecting surfaces was set to 350 μm. A diffraction grating 12 having a constant period was formed on the waveguide surface in parallel with the cleavage plane.

In the present embodiment, the diffraction grating is formed by forming an uneven shape using the method of electron beam exposure and immersion etching. A resist was spin-coated on the waveguide, and the diffraction pattern was transferred onto the resist by electron beam exposure. After developing the resist pattern, a diffraction grating was formed by immersion etching with an ethylene glycol solution of Br ₂ .

Setting of a constant period of 92 nm and a depth of 30 nm
And a laser 2-1 having a diffraction grating formed uniformly between the reflection surfaces.
(Sample No.) was prepared. Furthermore, a film thickness of 77.5 nm
SiO _Two, 45 nm thick TiO_TwoA few pairs alternately, light guide
By vapor deposition with the wave direction as the thickness direction, high reflection
The gate layer 19 is provided on the laser non-emitting side reflection surface of the laser 2-1.
Girder lasers 2-2 to 4 (sample numbers) were produced. here
Then, with the lasers 2-2 to -4, the effect of the high reflection coating layer 19 is
To confirm, we changed the number of dielectric
It was manufactured by changing the reflectance of the layer.

The above-mentioned semiconductor laser is supplied with an acceleration voltage of 15 k
V, excitation with an electron beam having an electron beam diameter of 50 μm was performed, and laser light oscillation was obtained. The oscillation characteristics such as the element structure, oscillation wavelength width, oscillation threshold value, output efficiency, and single mode oscillation probability when a plurality of lasers are manufactured are as shown in the following table.

[0046]

[Table 2]

From the difference between the oscillation wavelength widths of the laser 2-1 and the lasers 2-2 to -4, it can be seen that the single mode oscillation probability is increased by increasing the reflection of the reflection surfaces provided at both ends of the diffraction region. This is because when a diffraction grating is formed by the formation of a periodic uneven shape or the formation of a periodic refractive index modulation structure by impurity doping, etc.
Although the gains of the two degenerate maximum gain modes become almost the same, two-mode oscillation occurs. However, the phase of the diffracted wave determined by the diffraction grating is disturbed by the reflected waves from the high-reflectance reflecting surfaces provided at both ends of the diffraction region. This causes the mode to be degenerated.

From the comparison of the oscillation characteristics of the lasers 2-2 to -4, by making the reflection surface on the laser non-emission side highly reflective,
It can be seen that an advantageous effect of improving luminous efficiency can be obtained. This is due to an increase in laser light extraction efficiency on the low-reflectance end face side due to the asymmetry of the end face reflectivity.

As described above, according to the present embodiment, it is possible to improve the single mode laser oscillation probability.

(Embodiment 3) Next, Embodiment 3 of the present invention.
Will be described with reference to FIG. FIG. 4 is a side view of a semiconductor laser according to the third embodiment of the present invention.

As shown in FIG. 4, in the electron-beam-pumped semiconductor laser according to the present embodiment, the wavelength of the laser oscillation light is set at the upper, lower, or inside of the diffraction region 13 formed in the semiconductor optical waveguide. A diffraction grating having a period of one-half optical distance is formed perpendicular to the light waveguide direction, and a phase shift region 20 whose period is slightly different from that of the diffraction grating is partially provided in the diffraction region.

As the material of the substrate 5 and the optical waveguide 9, as described in the first embodiment, the same material as the conventional one is used.

Hereinafter, a specific element structure of the semiconductor laser shown in FIG. 4 will be described in detail.

In this embodiment, the wafer 2 used in the second embodiment is used as a wafer. Both end faces of the diffraction region were formed by cleavage. Here, the distance 16 between the end faces is set to 350 μm.
Set to. A diffraction grating having a constant period of 92 nm and a depth of 30 nm was formed on the waveguide as in the second embodiment. Here, a phase shift region 20 in which the diffraction grating period was changed only at one location was provided at the center between the two reflection surfaces. Constant period 92n
The phase shift amount from m is −46 nm, −23 nm, +2
Lasers 3-1, 2, 3, 4 with 3 nm and +46 nm
(Sample No.) were prepared. In addition, except that the total phase shift amount is set to +46 nm and the phase shift region including two diffraction gratings with a period of 23 nm is provided, the laser 3-1 is used.
Lasers 3-5 (sample numbers) having the same structures as in Nos. 4 to 4 were produced.
In addition, a dielectric multilayer film was deposited on the laser emission side end face of the laser 3-4, and a non-reflective laser 3-6 (sample number) was produced. In addition, a laser 3-7 (sample number) was prepared by depositing a dielectric multilayer film on both end surfaces on the laser emission side and on the non-emission side of the diffraction region of the laser 3-4 to make it non-reflective. In addition, except that the phase shift area is not provided,
Lasers 3-8 (sample numbers) having the same structure as 1-4 were produced for confirming the effects of the embodiment.

The above eight types of semiconductor lasers were set to an acceleration voltage of 1
It was excited by an electron beam having an electron beam diameter of 5 μm and an electron beam diameter of 50 μm, and laser light oscillation was obtained. The oscillation characteristics such as the distance between the diffraction gratings in the phase shift region, the presence or absence of a non-reflection coating layer, the output efficiency, and the probability of single mode oscillation when a plurality of elements were manufactured were as shown in the following table.

[0056]

[Table 3]

From the difference in oscillation characteristics between the laser 3-8 and the lasers 3-1 to -4, it can be seen that the single mode oscillation probability is increased by employing this embodiment. This is because, when a diffraction grating is formed by a refractive index modulation structure, the gains of the two degenerate maximum gain modes become almost the same, resulting in two-mode oscillation. However, the phase of the diffraction grating that determines the phase of the diffracted wave is partially changed. Is caused by the fact that the mode has been degenerated.

From the single mode oscillation probability characteristics of the lasers 3-1 to -4, it is preferable to introduce a phase shift corresponding to one quarter or three quarters of the laser oscillation light wavelength in the diffraction region. Further, from the single mode oscillation probability characteristics of the laser 3-4 and the laser 3-5, the diffraction grating existing in the phase shift region does not need to have a single period. From the comparison of the output efficiencies of the laser 3-6 and the laser 3-4, it is preferable to provide a reflection surface on the laser emission side of the diffraction region to further reduce the reflection.

From the single mode oscillation probability characteristics of the lasers 3-7 and 3-4, by making both end faces of the diffraction region non-reflective, single mode oscillation can be obtained with high probability.
More preferred. This is because the influence of the reflected wave from the end face, which disturbs the phase of the single mode diffracted wave and is determined by the refractive index modulation structure provided with the phase shift region, is removed.

As described above, by adopting this embodiment,
The single mode laser oscillation probability can be improved.

(Embodiment 4) Next, Embodiment 4 of the present invention.
Will be described with reference to FIG.

FIGS. 5A and 5B are side views of a semiconductor laser according to the fourth embodiment of the present invention.
In the electron beam pumped semiconductor laser according to the present embodiment, an integer equal to one half of the wavelength of the laser oscillation light is provided in any of the upper, lower, and inner portions of the active diffraction region 21 formed in a part of the semiconductor optical waveguide 9. A diffraction grating having a period of twice the optical distance is formed, and a passive diffraction region 22 is provided at least before or after the active diffraction region. Since the period of the optical distance is an integer multiple of 1, a diffraction grating having a diffraction efficiency different from that of the active diffraction region is formed.

As the material of the substrate 5 and the optical waveguide 9, as described in the first embodiment, the same material as the conventional one is used.

Hereinafter, a specific element structure of the semiconductor laser shown in FIG. 5 will be described in detail.

The wafer 2 used in the second embodiment was used as a wafer. Reflection surfaces were formed at both ends of the optical waveguide 9 by cleavage. The inter-plane distance 16 was set to 500 μm. A diffraction grating having a constant period of 92 nm was formed on the waveguide as in the second embodiment. Here, laser 4-1 (sample number)
In the active diffraction region 21 on the laser emission side, a depth of 30
A semiconductor laser was manufactured in which a diffraction grating having a depth of 50 nm was formed on a passive region 22 provided with a diffraction grating having a thickness of 50 nm on the laser non-emitting side of the active region. Here, the active diffraction region length 23 is set to 2
The length of the passive diffraction region 24 was set to 300 μm. FIG. 5A shows a side view of the laser 4-1. Also,
A laser 4 having a diffraction grating having a depth of 30 nm formed uniformly between the cleavage planes and further covering the active diffraction region 21 on the laser emission side with a region length of 200 μm with a medium 25 having a lower refractive index than the active layer. -2 (sample number). In this embodiment, SiO ₂ glass was used as a material having a lower refractive index than the active layer, and was deposited to a thickness of 45 nm. In order to prevent charge-up at the time of excitation, 20 nm of Ag, which is the conductive substance 26, was deposited on the SiO ₂ glass. FIG. 5B shows a side view of the laser 4-2. In addition, a laser 4-3 (sample number) in which a diffraction grating having a constant depth of 50 nm was uniformly formed in the active region and the passive region at a constant period of 92 nm was produced for confirming the effect of the embodiment.

The above three types of semiconductor lasers were set to an acceleration voltage of 1
It was excited by an electron beam having an electron beam diameter of 5 μm and an electron beam diameter of 50 μm, and laser light oscillation was obtained. The oscillation characteristics such as the output efficiency and the probability of single mode oscillation when a plurality of lasers are manufactured are as shown in the following table.

[0067]

[Table 4]

As shown in Table 4 above, the laser 4-
Comparing the oscillation characteristics of the lasers 1 and 4-2 with the oscillation characteristics of the laser 4-3, it can be seen that the adoption of the present embodiment enables stable laser oscillation in a single mode. This is because the refractive index modulation structure of the active diffraction region 21 has selectivity in the laser oscillation wavelength width, and the passive diffraction region 22 functions as an optical reflector having strong wavelength selectivity. I do. Here, it is effective to provide a diffraction grating deeper than the active diffraction region 21 in order to make the passive diffraction region 22 function as a reflecting mirror having a high reflectance.
It can be seen from the characteristic of -1. Similarly, by making the depth of the diffraction grating provided in the active diffraction region 21 substantially shallow, it is possible to make the passive diffraction region 22 function as a high-reflectance reflecting mirror by using the laser 4-2. It can be seen from the characteristics of Further, in comparison with the method of Embodiment 2 in which laser oscillation in a single mode is obtained by forming a high-reflection film on the end face of the active waveguide region on the laser non-emission side, the present embodiment applies a wafer-by-wafer fabrication process. It has the advantage of being able to. Further, as compared with the method of the third embodiment in which a single mode oscillation is obtained by providing a phase shift region in the active waveguide region, the present embodiment has an advantage that the light output efficiency is improved.

As described above, by adopting this embodiment,
It is possible to increase the efficiency of the laser and improve the probability of laser oscillation in a single mode.

(Embodiment 5) Next, Embodiment 5 of the present invention.
Will be described with reference to FIG.

FIG. 6A is a perspective view of a semiconductor laser according to the fifth embodiment of the present invention, and FIG. 6B is a side view of the semiconductor laser of the present embodiment. In the electron beam pumped semiconductor laser according to the present embodiment, an active waveguide region 27 that is excited by an electron beam is provided in a part of the optical waveguide, and the passive diffraction region 22 is provided at least one of before and after the active region.
And a diffraction grating having a period having an optical distance equal to an integral multiple of half the wavelength of the laser oscillation light is formed above, below, or inside the optical waveguide in the passive region.

As the material of the substrate 5 and the optical waveguide 9, as described in the first embodiment, the same material as that of the related art is used.

Hereinafter, a specific element structure of the semiconductor laser shown in FIG. 6 will be described in detail.

At the time of manufacturing, the wafer 2 used in the second embodiment was used as a wafer. By the cleavage, reflection surfaces were formed at both ends of the optical waveguide at an inter-surface distance of 500 μm 16. Here, the passive diffraction region 22 is provided on the non-laser light emission side of the active waveguide region 27. The active waveguide region length 28 is 200 μ
m, the passive diffraction region length 24 is 300 μm, and the depth is 30 n.
m, a diffraction grating having a constant period was formed on the passive diffraction region 22 perpendicular to the waveguide axis of the laser beam. Laser 5-1 (sample number) having a period of the diffraction grating of 92 nm and laser 5-2 (sample number) having a period of 184 nm were formed. Further, in order to confirm the effect of the present invention, a laser 5-3 (sample number) in which only the wafer was cleaved at a plane distance 16 of 300 μm was prepared.

The above three types of semiconductor lasers are supplied with an acceleration voltage of 1
It was excited by an electron beam having an electron beam diameter of 5 μm and an electron beam diameter of 50 μm, and laser light oscillation was obtained. The oscillation characteristics such as the period of the diffraction grating, the oscillation wavelength width, the oscillation threshold, the output efficiency, and the probability of single mode oscillation when a plurality of lasers are manufactured are as shown in the following table.

[0076]

[Table 5]

As shown in Table 5 above, the laser 5
From the difference in the oscillation characteristics between 1 and 5-2 and 5-3, it can be seen that the width of the laser oscillation wavelength is narrowed by adopting the present embodiment. This is because the passive region 22 has strong wavelength selectivity. This is because it functions as an optical reflecting mirror. As a result, an advantageous effect of reducing the laser oscillation threshold can be obtained. In order to reduce the number of laser oscillation modes, it is necessary to increase the wavelength selectivity of the passive region 22, and the diffraction grating provided in the passive region 22 corresponds to an optical distance of one half of the laser oscillation wavelength. It is preferable that the cycle be performed.

In the semiconductor laser according to the present embodiment, the diffraction grating for determining the laser oscillation wavelength is provided in a region different from the active region 12, so that it is affected by heat generated by electron beam irradiation. It is difficult to obtain the advantageous effect that stable laser oscillation at the same wavelength is possible.

As described above, by employing the present embodiment, it is possible to narrow the laser oscillation wavelength width.

(Embodiment 6) Next, Embodiment 6 of the present invention.
Will be described with reference to FIG.

FIG. 7 is a top structural view of a semiconductor laser according to the sixth embodiment of the present invention. The electron beam pumped semiconductor laser according to the present embodiment is characterized in that the diffraction grating formed in the passive diffraction region of the semiconductor laser according to the fifth embodiment is formed in a concentric or concentric arc shape.

As the material of the substrate 5 and the active layer 8, as described in the first embodiment, the same material as that of the related art is used.

Hereinafter, a specific element structure of the semiconductor laser shown in FIG. 7 will be described in detail.

The laser emitting surface 6 having a curvature was formed by a reactive ion etching method. Hereinafter, the reactive ion etching process will be specifically described.

A resist is spin-coated on the waveguide surface,
The pattern is transferred by electron beam exposure. After developing and forming a resist pattern, metal is vacuum deposited. After removing the metal on the resist with a solvent, the laser emitting surface 6 is formed by reactive ion etching.

The radius of curvature 29 of the laser emission surface is set to 700 μm.
The active waveguide region length 28 was set to 200 μm, and the passive diffraction region length 24 was set to 300 μm. A diffraction grating having a constant period of 92 nm and a depth of 50 nm is formed on the surface of the optical waveguide in the passive region.
A laser 6-1 formed concentrically with the laser emission surface was produced. In the laser 6-1, the diffraction grating forming angle 30 is 15
0 degrees.

The laser 6-1 was excited by the electron beam 2 having an acceleration voltage of 15 kV and an electron beam diameter of 50 μm, and laser light was emitted in two modes. The reduction in the number of laser oscillation modes is caused by the fact that the diffraction grating formed in the passive diffraction region acts as an optical reflecting mirror having strong wavelength selectivity, as in the fourth and fifth embodiments. Further, in the conventional semiconductor laser device, when the cavity structure has a curvature, it is difficult to perform a uniform high reflection by the reflection coating layer, and there is a problem that the output efficiency is not improved. The above-mentioned problem is solved at the same time by forming a passive diffraction region acting as a high reflection mirror. It goes without saying that the formation of the concentric and concentric arc diffraction gratings can be applied to the semiconductor lasers of the first to fourth embodiments.

Further, by scanning the irradiation position of the excitation electron beam, the emission direction of the laser beam 11 can be scanned in a fan shape. The laser beam that can be scanned in a circular shape obtained in the present embodiment is difficult to realize with a current injection type semiconductor laser that requires the formation of an electrode, and is capable of easily scanning an excitation electron beam. This is a mode that can be particularly realized by the method of line excitation.

As described above, according to the present embodiment, it is possible to scan a laser beam oscillating in a narrow wavelength band radially.

[0090]

As described above, according to the present invention, the advantageous effects of improving the laser emission efficiency, narrowing the laser oscillation wavelength width, and reducing the number of laser oscillation modes can be obtained.

[Brief description of the drawings]

FIG. 1A is a perspective view of a semiconductor laser according to a first embodiment of the present invention. FIG. 1B is a side view of the semiconductor laser according to the first embodiment of the present invention.

FIG. 2A is a cross-sectional view of a multiple quantum well structure used in an embodiment of the present invention. FIG. 2B is a cross-sectional view of a wafer used in an embodiment of the present invention.

3A is a perspective view of a semiconductor laser according to a second embodiment of the present invention. FIG. 3B is a side view of the semiconductor laser according to the second embodiment of the present invention.

FIG. 4 is a side view of a semiconductor laser according to a third embodiment of the present invention.

5A is a side view of a semiconductor laser according to a fifth embodiment of the present invention. FIG. 5B is a side view of the semiconductor laser according to the fifth embodiment of the present invention.

6A is a perspective view of a semiconductor laser according to a fifth embodiment of the present invention, and FIG. 6B is a side view of the semiconductor laser according to the fifth embodiment of the present invention.

FIG. 7 is a top structural view of a semiconductor laser according to a sixth embodiment of the present invention.

FIG. 8 is a structural diagram of a conventional electron beam pumped semiconductor laser.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 electron gun 2 electron beam 3 optical resonator 4 electron lens 5 substrate 6 reflecting surface 7 reflecting surface 8 active layer 9 semiconductor optical waveguide 10 cavity length 11 laser beam 12 diffraction grating 13 diffraction region 14 cladding layer 15 quantum well 16 between reflection surfaces Distance 17 Period of gain modulation 18 Period of refractive index modulation 19 High reflection coating layer 20 Phase shift region 21 Active diffraction region 22 Passive diffraction region 23 Active diffraction region length 24 Passive diffraction region length 25 Medium having lower refractive index than active layer 26 Conductive substance 27 Active waveguide region 28 Active waveguide region length 29 Radius of curvature of laser emitting surface 30 Diffraction grating formation angle

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takao Nita 1006 Kazuma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (11)

[Claims] 1. An optical waveguide having an optical refractive index larger than that of an upper and lower medium, and a part of the optical waveguide, an upper part, a lower part, or an inside of the whole area, a half of a wavelength of laser oscillation light,
Or a diffraction region in which a diffraction grating having a period of an optical distance corresponding to an integral multiple of this length is formed perpendicular to the light guiding direction, and at least one of the optical waveguides in the diffraction region. A semiconductor laser that emits laser light by irradiating a part with an electron beam. 2. An optical waveguide having a reflecting surface formed perpendicular to a light guiding direction and separated by an optical distance corresponding to an integral multiple of half the wavelength of laser oscillation light, and at least one reflecting surface. 2. The semiconductor laser according to claim 1, wherein a high reflection coating layer is formed on said reflection surface. 3. A diffraction grating formed with a period of an optical distance corresponding to one half of the wavelength of the laser oscillation light, wherein at least one of the diffraction regions has a phase shift region in which the period is slightly different. 2. The semiconductor laser according to claim 1, wherein the semiconductor laser is provided. 4. The total phase shift amount of a diffraction grating introduced into a phase shift region from a predetermined period is an optical distance corresponding to an odd multiple of a quarter of the wavelength of laser oscillation light. 4. The semiconductor laser according to claim 3, wherein: 5. The semiconductor laser according to claim 4, wherein anti-reflection coating layers are formed on both end faces of the optical waveguide. 6. An optical waveguide having an optical refractive index larger than that of the upper and lower media, and a part of the optical waveguide, an upper part, a lower part, or an inside of the whole area, a half of a wavelength of laser oscillation light,
Alternatively, a diffraction grating having a period of an optical distance corresponding to an integral multiple of this length has at least two or more types of diffraction regions formed perpendicular to the light guiding direction, and at least a part of the diffraction regions. A semiconductor laser characterized in that a diffraction grating formed in an active diffraction region irradiated with an electron beam and a diffraction grating formed in a passive diffraction region irradiated with no electron beam have different diffraction efficiencies. 7. The semiconductor laser according to claim 6, wherein the diffraction efficiency of the passive diffraction region is higher than the diffraction efficiency of the active diffraction region. 8. A medium in which a diffraction grating introduced into an active diffraction region is in contact with a medium in contact with a diffraction grating introduced into a passive active region is a material having a smaller refractive index ratio with respect to a waveguide material. The semiconductor laser according to claim 7, wherein 9. An optical waveguide having an optical refractive index larger than that of the upper and lower media, and a half of the wavelength of the laser oscillation light or a length of one half of the wavelength of the laser oscillation light, which is provided at an upper part, a lower part, or inside a part of the optical waveguide. A diffraction grating having a period of an optical distance corresponding to an integral multiple of the diffraction region has a diffraction region formed perpendicular to the light waveguide direction, and irradiating an electron beam to a region other than the diffraction region. A semiconductor laser that emits laser light. 10. The semiconductor laser according to claim 1, wherein the diffraction grating is formed by a periodic gain modulation structure or a periodic refractive index modulation structure. 11. The semiconductor laser according to claim 1, wherein the diffraction grating is formed in a concentric shape or a concentric arc shape.