JPH08195525A - Semiconductor laser - Google Patents

Abstract

PURPOSE: To enhance power-optical output conversion efficiency and to obtain a large output in a small light emitting region by allowing the width of a flared structure semiconductor laser in which the widths of a ridge waveguide are varied in a resonator direction to alternately approach at wide and narrow parts and disposing it in an array state. CONSTITUTION: A p-type InP ridge clad layer 20 and a p-type InGaAs contact layer 7 in which wide and narrow parts of a taped shape with varying widths are made to approach in the longitudinal direction are formed on a semiconductor wafer. Then, an insulating film 21 is formed at the epitaxially grown layer side except the surface on the contact layer, and an n-type ohmic electrode 9 and a p-type ohmic electrode 8 are respectively formed at the substrate side and the grown layer. Subsequently, it is quarried in array laser chips, a highly reflecting film 10 is formed at the terminal surface of the wide side of the entire light emitting width, and a lowly reflecting film 15 is formed at the end face of the narrow side of the entire light emitting width as a flared structure semiconductor laser array.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser capable of operating up to a high output in the watt class, and more particularly to a semiconductor laser capable of obtaining a high output in a narrow light emitting region.

[0002]

2. Description of the Related Art In the field of optical measurement and the like, a point range finder for measuring a distance to a certain point has been developed, and a high-power laser diode that generates a watt-class optical output as a light source. R & D is becoming active.

As a first conventional example of a high-power laser diode that generates a watt-class optical output, a so-called broad area laser is used in which the width of the light emitting region is widened in order to increase the output of a single laser diode chip. It has been made into a diode, and the light emitting area width 60 by Yamanaka et al.
At 0 μm, an optical output of 6 W is obtained (Yamanaka et al., Laser Research, Vol. 18, p. 555, 1990).

Further, many laser elements are arranged in an array, and the like.
gei) et al.
A light output of 0 W or more is obtained (Applied Physics Letter, Vol. 49, page 1418, 1986,
G. L. Harnagei et al. , Appl.
Phys Lett. , Vol. 49, pp. 141
8, 1986. ).

As a second conventional example, there is a method in which a semiconductor laser with a flare structure having a shape in which the active layer width is widened in the cavity direction is used to perform a stable large output operation in the transverse fundamental mode up to the watt class. . Such semiconductor lasers are expected to have various applications such as optical measurement systems.

FIG. 12 shows a report by Kamohara et al. (1
Electronics Letters Magazine, 1988, No. 24
Vol. 18, No. 18, pp. 1182 to 1183) shows a perspective view of a flare structure semiconductor laser. In this example, after the buffer layer 2 and the current blocking layer 3 are grown on the substrate 1, a part of the current blocking layer is etched and removed into a shape whose width changes in the cavity direction as shown in FIG. A lower clad layer 4, an active layer 5, an upper clad layer 6, and a contact layer 7 are sequentially laminated on the entire surface, electrodes 8 and 9 are formed on the substrate side and the epi growth layer side, and the width of the current block layer 3 is removed. A high-reflection film is formed on the end face on the narrow side of to obtain a desired flare structure semiconductor laser.

Since the current is injected only into the removed portion of the current blocking layer 3, the width of the light emitting region 11 changes in the resonance direction of light in the plan view of the device shown in FIG. Spread) shape. Using such a device, a light output of 4 W was obtained in a light emitting region having a width of 200 μm (issued in 1993, IE Photonics Technology Letters, Vol. 5, 605).
Page, E. S. Kintzer et al. , IEEE
Photon. Technol. Lett. , 5, p
p. 605, 1993. ). In particular, in this method, since the light output of a portion having a wide active region is equal to that of a narrow portion, a large output can be obtained in a narrow light emitting region by setting the region having a narrow active region as a light emitting end.

Further, as a third conventional example, a master oscillator power amplifier (Master) in which an amplifier is integrated is provided.
Oscillator Power Amplifier
r: MOPA: For example, literature EE Photonics Technology Letters, Vol. 5, pp. 297-300,
R. Parke et al. , IEEE Photo
n. Tech. Lett. vol. 5, pp. 297-
300. 2) in a light emitting region with a width of 200 μm.
The above optical output is obtained.

[0009]

A method of increasing the light output by widening the light emitting region width of the semiconductor laser of the first conventional example or increasing the number of semiconductor lasers arranged in an array, or In the method of increasing the light output by increasing the width of the light emitting area of the array as in the conventional example of 3, the light emitting area is mainly increased. Therefore, when the device for optical measurement is configured, the optical system is large. There was a drawback that it would be.

In the flare structure semiconductor laser of the second conventional example, light is extracted from a portion having a narrow active region width and the light emitting region width of the portion having a wide active region width is expanded to increase the light output, so that the resonance occurs. You need to make the vessel longer,
The power-light output conversion efficiency is reduced. Therefore, when constructing a device for optical measurement, there is a drawback that the capacity of the current source for driving the laser increases.

The semiconductor laser of the present invention is intended to be applied to optical measurement and the like, and to provide a semiconductor laser having a high power-light output conversion efficiency and a large output in a narrow light emitting region. The purpose is.

[0012]

In the semiconductor laser of the present invention, the active waveguide has a ridge waveguide structure, and the flare structure semiconductor laser in which the width of the ridge waveguide changes in the cavity direction is used. And narrow portions are arranged in close proximity to each other in an array. Further, it is characterized by having a radiation mode prevention region in which the outside of the active waveguide is partially removed.

[0013] The semiconductor laser having a flare structure in which the width of the active layer changes in the direction of the resonator is arranged in an array such that a wide portion and a narrow portion are close to each other.
Further, a diffraction grating is formed in the narrower width of the flare structure semiconductor laser in which the width of the active layer or the ridge waveguide part changes, and the narrow parts of the flare structure semiconductor laser are arranged close to each other.

Further, the integrated semiconductor laser of the present invention has a semiconductor laser, an optical amplifier for amplifying light from the semiconductor laser to enlarge a spot size, and a laser intensity for the enlarged spot size on a semiconductor substrate. It is characterized in that a spot size conversion device that reduces the spot size without being integrated is integrated.

[0015]

According to the semiconductor laser of the present invention, a plurality of flared semiconductor lasers are arranged in an array in such a manner that wide portions and narrow portions of the flared semiconductor laser are alternately brought close to each other. An optical output is obtained by combining the light from the large emission width of the light emitting region of the central flare structure semiconductor and the light from the small emission width of the light emitting region of the flare structure semiconductor on both sides thereof.
Therefore, the light emitting region can obtain a large amount of light output only by being slightly larger than the light emitting region of the central flare structure semiconductor.

In a semiconductor laser using a flare structure semiconductor laser in which the active waveguide has a ridge waveguide structure, the active waveguide is removed along at least a part of the outside of the ridge structure active waveguide. A radiation mode prevention region is formed. This prevents radiation modes in the active waveguide and improves the power-to-light output conversion efficiency.

According to the semiconductor laser of the present invention, a plurality of flare structure semiconductor lasers are arranged close to each other in a portion having a narrow active layer width, and a diffraction grating is formed in the narrow portion, whereby a narrow light emitting region is concentrated in a part. , A large output light is emitted in a direction perpendicular to the substrate. With this structure, light with a larger output than in the past can be emitted in a narrow light emitting region.

Further, the semiconductor laser of the present invention is a MOPA in which a semiconductor laser having a taper electrode structure capable of high-power operation is integrated with a semiconductor laser, and the semiconductor laser of the present invention has a tapered laser emitting end at the light emitting end. Integrated spot size converter. A direct current in the forward direction is independently applied to the laser, the optical amplifier, and the spot size converter to amplify the intensity of the laser light generated by the laser and increase the spot size of the laser light. After that, the spot size is reduced and emitted so that the intensity of the laser beam amplified by the spot size converter is not reduced. By doing this,
A semiconductor laser capable of obtaining a large output in a narrow light emitting region can be provided.

[0019]

Embodiments of the present invention will now be described with reference to the drawings.

(Embodiment 1) FIG. 1 is a plan view of an element of a flare structure semiconductor laser according to the present invention, and FIG.
The sectional structural views at the A 'portion are respectively shown. Such an element can be manufactured by the following procedure. First, n-In
An n-InP buffer layer 2 (0.2 μm thick) is formed on a P substrate 1.
), The active layer 5, and the cladding layer 6 (thickness 0.3 μm) are sequentially grown. Here, the active layer 5 has a multiple quantum well structure whose energy band structure is shown in FIG.
% InGaAsP well layers 25 (thickness: 8 nm) with a compressive strain of 5%, InGaAs with an emission wavelength of 1.2 μm
The P barrier layer 26 (thickness: 6 nm) and the InGaAsP SCH layer 27 (thickness: 50 nm) having an emission wavelength of 1.2 μm were used. The emission wavelength of the active layer 5 is 1.5 μm. After forming an SiO ₂ insulating film on such a semiconductor wafer, a taper shape whose width changes in the length direction is patterned into an array arrangement to selectively form the p-InP ridge cladding layer 20 (thickness: 2.5 μm). ), A p-InGaAs contact layer 7 (having a thickness of 0.5 μm) having an emission wavelength of 1.64 μm is grown. The ridge waveguide structure has widths of 4 μm and 100 μm in a narrow region and a wide region, respectively, and a length of 900 μm.
The width was changed from 4 μm to 100 μm. The array spacing was 10 μm. After that, the insulating film 21 is formed on the epitaxial growth layer side except the contact layer upper surface,
Further, an n-type ohmic electrode 9 and a p-type ohmic electrode 8 are formed on the substrate side and the growth layer side, respectively. Finally, the laser chip of the array was cut out, and the high reflection film 10 (reflectance 90%) was formed on the terminal surface on the side where the total emission width was wide, and the low reflection film 15 (reflection rate 10%) was formed on the end surface on the side where the total emission width was narrow. Each is formed to obtain a desired flare structure semiconductor laser array. The total length of the element is 1 mm, and 50 μm on both sides of the 900 μm long tapered region.
The configuration is such that m linear waveguides are formed.

In such a semiconductor laser, the width is 20n.
By applying a pulse current of 10 kHz repeatedly at s, a luminescence far-field image with a single peak and no ripple up to a peak light output of 50 W was obtained. The oscillation threshold current and slope efficiency were 3 A and 0.25 W / A, respectively, and the total light emitting region width was 128 μm.

In a conventional broad area laser having a light emitting region width of 128 μm, in a device having a cavity length of 1000 μm,
The maximum light output was 33 W at a slope efficiency of 0.25 W / A, and the maximum light output was improved by 1.5 times. In addition, resonator length 1
Slope efficiency of 0.18 W / in a device of 500 μm
The maximum light output at A was 50 W, and the efficiency was improved by 1.4 times.

(Embodiment 2) FIG. 4 is a plan view of an element of a flare structure semiconductor laser according to the present invention, and FIG. 5 is B- in FIG.
The cross-sectional structural views at the portion B'are respectively shown. Such an element can be manufactured by the following procedure. First, n-In
An n-InP buffer layer 2 (0.2 μm thick) is formed on a P substrate 1.
), The active layer 5, and the cladding layer 6 (thickness 0.3 μm) are sequentially grown. Here, the active layer 5 has a multiple quantum well structure whose energy band structure is shown in FIG.
% InGaAsP well layers 25 (thickness: 8 nm) with a compressive strain of 5%, InGaAs with an emission wavelength of 1.2 μm
The P barrier layer 26 (thickness: 6 nm) and the InGaAsP SCH layer 27 (thickness: 50 nm) having an emission wavelength of 1.2 μm were used. The emission wavelength of the active layer 5 is 1.5 μm. After forming an SiO ₂ insulating film on such a semiconductor wafer, a taper shape whose width changes in the length direction is patterned into an array arrangement to selectively form the p-InP ridge cladding layer 20 (thickness: 2.5 μm). ), A p-InGaAs contact layer 7 (having a thickness of 0.5 μm) having an emission wavelength of 1.64 μm is grown. The ridge waveguide structure has widths of 4 μm and 100 μm in a narrow region and a wide region, respectively, and a length of 900 μm.
The width was changed from 4 μm to 100 μm. The spacing between the arrays was 25 μm. Then, the active layer 5 is removed by etching while leaving the outer region of the ridge cladding layer 20 by 10 μm each. Thereafter, an insulating film 21 is formed on the epitaxial growth layer side except for the upper surface of the contact layer, and further, an n-type ohmic electrode 9 and a p-type ohmic electrode 8 are formed on the substrate side and the growth layer side, respectively. Finally, the laser chip of the array is cut out, and a high-reflection film 1
The desired flare structure semiconductor laser array is obtained by forming the low reflection film 15 (reflectance 10%) on the end face of 0 (reflectance 90%) and the side where the total emission width is narrow. The total length of the device was 1 mm, and linear waveguides of 50 μm each were formed on both sides of a 900 μm long tapered region.

In such a semiconductor laser, the width is 20n.
By applying a pulse current of 10 kHz repeatedly at s, a luminescence far-field image with a single peak and no ripple up to a peak light output of 50 W was obtained. The oscillation threshold current and the slope efficiency were 3 A and 0.25 W / A, respectively, and the total light emitting region width was 158 μm.

(Embodiment 3) FIG. 6 is a plan view of an element of a flare structure semiconductor laser according to the present invention, and FIG. 7 shows C- in FIG.
The sectional structural views at the C 'portion are respectively shown. Such an element can be manufactured by the following procedure. First, n-In
An n-InP buffer layer 2 (0.2 μm thick) is formed on a P substrate 1.
), The active layer 5, the cladding layer 6 (thickness 2 μm), and the p-InGaAs contact layer 7 (thickness 0.5 μm) having an emission wavelength of 1.64 μm are sequentially grown. Here, the active layer 5 is shown in FIG.
InGaAs with + 0.8% compressive strain and multiple quantum well structure showing its energy band structure
5 P-well layers 25 (8 nm thick), emission wavelength 1.2 μm
InGaAsP SCH layer 27 having composition of InGaAsP barrier layer 26 (thickness: 6 nm) and emission wavelength of 1.2 μm
(Thickness: 50 nm). The emission wavelength of the active layer 5 is 1.5 μm. After an SiO ₂ insulating film is formed on such a semiconductor wafer, a taper shape whose width changes in the length direction is patterned into an array arrangement to form an SiO ₂ etching mask. The structure of the tapered waveguide is 4 μm and 100 μm in the narrow and wide regions, respectively.
And a width of 4 μm to 100 over a length of 900 μm.
The shape changed to μm. The spacing between the arrays was 25 μm. After that, the outer region of the tapered mask is removed by etching down to the active layer 5, and the p-type InP layer 31 and the n-type InP layer 30 are buried and regrown. Next, the SiO ₂ etching mask is removed, the insulating film 21 is formed on the epi growth layer side except the contact layer upper surface, and the n-type ohmic electrode 9 and the p-type ohmic electrode 8 are further formed on the substrate side and the growth layer side, respectively. Form. Finally, the laser chip of the array was cut out, and the high reflection film 10 (with a reflectance of 90
%), And the low reflection film 15 (reflectance 10%) is formed on the end face on the side where the total emission width is narrow, to obtain a desired flare structure semiconductor laser array. The total length of the device was 1 mm, and linear waveguides of 50 μm each were formed on both sides of a 900 μm long tapered region.

In such a semiconductor laser, the width is 20n.
By applying a pulse current of 10 kHz repeatedly at s, a luminescence far-field image with a single peak and no ripple up to a peak light output of 50 W was obtained. The oscillation threshold current and the slope efficiency were 3 A and 0.25 W / A, respectively, and the total light emitting region width was 158 μm.

(Embodiment 4) FIG. 8 is a plan view of an element of a flare structure semiconductor laser according to a fourth embodiment of the present invention, and FIG.
8A and 8B show cross-sectional structural views at DD 'and EE' portions in FIG. 8, respectively. Such an element can be manufactured by the following procedure. First, a second-order diffraction grating 12 is formed on the n-InP substrate 1 and InGaAs having an emission wavelength of 1.2 μm composition is formed.
P light guide layer 13 (thickness 0.1 μm), n-InP spacer layer 14 (thickness 40 nm), active layer 5, clad layer 6
(Thickness 0.3 μm) is successively grown. Here, the active layer 5 has a multi-quantum well structure whose energy band structure is shown in FIG. 3, and InGa with a compressive strain of + 0.8% is introduced.
AsP well layer 25 (thickness 8 nm) 5 layers, emission wavelength 1.2
InGaAsP barrier layer 26 (thickness 6 nm) of μm composition,
InGaAsP SCH layer 2 with an emission wavelength of 1.2 μm
7 (thickness: 50 nm). The emission wavelength of the active layer 5 is 1.5 μm. After forming an SiO ₂ insulating film on such a semiconductor wafer, a taper shape whose width changes in the length direction is patterned into an array arrangement to selectively form the p-InP ridge cladding layer 20 (thickness: 2.5 μm). ),
A p-InGaAs contact layer 7 (thickness 0.5 μm) having an emission wavelength of 1.64 μm is grown. The ridge waveguide structure has widths of 4 μm and 100 μm in narrow and wide areas, respectively.
m, with a width of 4 μm to 10 over a length of 900 μm
The shape was changed to 0 μm.

Thereafter, an insulating film 21 is formed on the epi-growth layer side except for the upper surface of the contact layer, and an n-type ohmic electrode 9 and a p-type ohmic electrode 8 are formed on the substrate side and the growth layer side, respectively.
To form. Finally cut out into laser chips of the array,
A highly reflective film 10 (having a reflectance of 90%) is formed on the end face to obtain a desired flare structure semiconductor laser array. The total length of each element is 1 mm, and 50 mm on each side of the 900 μm long tapered region.
The configuration is such that a linear waveguide of each μm is formed. The light is emitted in the direction perpendicular to the substrate 1. The light emitting area of each element is 4μm × 20μm, 50μm × 50μ
Four elements were integrated so that four light emitting areas were accommodated in the area of m 2.

In such a semiconductor laser, the width is 20n
By applying a pulse current of 10 kHz repeatedly at s, a luminescence far-field image with a single peak and no ripple up to a peak light output of 70 W was obtained. The oscillation threshold current and slope efficiency were 4 A and 0.25 W / A, respectively.

(Embodiment 5) FIG. 10 shows a plan view of an element of a flare structure semiconductor laser according to a fifth embodiment of the present invention, and FIG. 11 shows a sectional structure view at a portion FF ′ in FIG. Such an element can be manufactured by the following procedure. First, a first-order diffraction grating 12 is formed on an n-InP substrate 1, an InGaAsP optical guide layer 13 (thickness 0.1 μm) having an emission wavelength of 1.2 μm, an n-InP spacer layer 14 (thickness 40 nm), Active layer 5, clad layer 6 (thickness 2
.mu.m), and a p-InGaAs contact layer 7 (thickness 0.5 .mu.m) having an emission wavelength of 1.64 .mu.m is sequentially grown. Here, the active layer 5 has a multiple quantum well structure whose energy band structure is shown in FIG. 3, 5 layers of InGaAsP well layers 25 (thickness 8 nm) into which compressive strain of + 0.8% is introduced, emission wavelength 1.2 μm InGaAsP barrier layer 26 (thickness: 6 nm) having a composition, InGaAsP having an emission wavelength of 1.2 μm
The SCH layer 27 (thickness: 50 nm) was used. The emission wavelength of the active layer 5 is 1.5 μm. Thereafter, the DFB laser 32, the optical amplifier 33, and the spot size converter 3
The portion other than the portion 4 is selectively removed up to the optical guide layer 5, and the p-type InP layer 31 and the n-type InP layer 30 are buried and regrown. Next, an insulating film 21 is formed on the surfaces of the p-side contact layer 8 and the n-type InP buried regrowth layer 10, and the DFB laser 32, the optical amplification device 33, and the spot size converter 3 are formed.
4 regions are removed by etching. Then p
The side electrode 8 is formed and the electrodes are separated. After polishing the n-side substrate to a thickness of about 100 μm, the n-side electrode 9 is formed. Finally, a low-reflection film 15 is formed on the light-emitting side end face,
Cut into chips.

The structure is such that the width of the DFB laser 32 is 2 μm,
The length is 500 μm, and the length of the optical amplifier 33 is 200 μm.
The width of the connection with the DFB laser 32 was 2 μm, and the width of the connection with the spot size converter 34 was 200 μm. The spot size converter 34 had a length of 2000 μm and a light emitting area width of 2 μm.

Next, the driving method and operation of the semiconductor laser of the fifth embodiment will be described.

By supplying a direct current in the forward direction to each of the DFB laser 32, the optical amplifier 33 and the spot size converter 34 independently, a laser beam is generated in the DFB laser 32, and the intensity of the laser beam in the optical amplifier 33 is increased. And amplify the spot size. Then, in the spot size converter 34, the spot size is reduced so as not to reduce the intensity of the amplified laser light, and a large output light is obtained from the light emitting region 35.
At this time, the currents flowing through the DFB laser 32, the optical amplification device 33, and the spot size converter 34 are each 300 m.
By setting A, 20A, and 2A, the emission area width is 2 μm
In the above, a luminescence far-field image with a single peak and no ripple up to a peak light output of 10 W was obtained.

In the first to fifth embodiments of the present invention, an element having a wavelength of about 1.5 μm with InP as a substrate is shown, but the material used is not limited to this and Ga is used.
Various materials such as an As-based material and an InGaAlAs-based material can be used.

[0035]

According to the semiconductor laser of the present invention, the power consumption is
It is possible to realize a semiconductor laser that has a high light output conversion efficiency and can obtain a large output in a narrow light emitting region. Further, since the light emitting area can be narrowed, the optical system can be made small and a compact optical distance measuring device can be constructed.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a first embodiment of the present invention.

FIG. 3 is a diagram showing an energy band structure of an example of the present invention.

FIG. 4 is a schematic diagram showing a second embodiment of the present invention.

FIG. 5 is a schematic diagram showing a second embodiment of the present invention.

FIG. 6 is a schematic diagram showing a third embodiment of the present invention.

FIG. 7 is a schematic view showing a third embodiment of the present invention.

FIG. 8 is a schematic diagram showing a fourth embodiment of the present invention.

FIG. 9 is a schematic view showing a fourth embodiment of the present invention.

FIG. 10 is a schematic view showing a fifth embodiment of the present invention.

FIG. 11 is a schematic view showing a fifth embodiment of the present invention.

FIG. 12 is a schematic view showing a conventional technique.

FIG. 13 is a schematic diagram showing a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Buffer layer 3 Current block layer 4 Lower cladding layer 5 Active layer 6 Cladding layer 7 Contact layer 8 Electrode 9 Electrode 10 High reflection film 11 Light emitting area 12 Diffraction grating 13 Light guide layer 14 Spacer layer 15 Low reflection film 20 Ridge clad Layer 21 Insulating film 25 Well layer 26 Barrier layer 27 SCH layer 30 n-InP layer 31 p-InP layer 32 DFB laser 33 Optical amplifier 34 Spot size converter 35 Light emission area

Claims (5)

[Claims] 1. A flare structure semiconductor laser in which an active waveguide has a ridge waveguide structure, and a width of the ridge waveguide changes in a cavity direction, and a wide portion and a narrow portion are arranged close to each other in an array form. A semiconductor laser characterized by being arranged. 2. The semiconductor laser according to claim 1, further comprising a radiation mode prevention region formed by removing a part of the outside of the active waveguide. 3. A semiconductor laser comprising flare structure semiconductor lasers in which the width of an active layer changes in the cavity direction, and the wide and narrow portions are arranged close to each other in an array. 4. A flare structure semiconductor laser in which a width of an active layer or a ridge waveguide part changes has a narrower diffraction grating, and the narrow parts of the flare structure semiconductor laser are arranged close to each other. Characteristic semiconductor laser. 5. A semiconductor laser on a semiconductor substrate, an optical amplifying device that amplifies light from the semiconductor laser and enlarges the spot size, and a spot size of the enlarged spot size that is reduced without reducing the laser intensity. An integrated semiconductor laser characterized by integrating a spot size conversion device.