A semiconductor laser emitter

Abstract

The application provides a semiconductor laser emitter, characterized by comprising a first DBR layer, a second DBR layer, a resonance part located above the first DBR layer, and a quantum well active region arranged between the first DBR layer and the second DBR layer, and the first DBR layer is further connected with a substrate layer; by the design, the N-DBR pair number can be reduced from 22-26 pairs to 8-10 pairs, and the N-DBR resistance and the Joule heat generated in the working process can be effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser, in particular to a semiconductor laser emitter. BACKGROUND

[0002] Semiconductor laser, due to its excellent controllable performance, and very easy to realize the integration design of array type, through the control of voltage and other characteristics can also be more convenient to realize the adjustment of laser parameters, is very advantageous for the whole system, semiconductor laser refers to the laser with semiconductor material as the working substance, also known as semiconductor laser diode (LD), is a kind of laser developed in the 1960s. There are dozens of semiconductor laser materials, such as gallium arsenide (GaAs), cadmium sulfide (CdS) and so on, and the main excitation methods are electric injection, optical pumping and high energy electron beam excitation. The advantages of semiconductor laser mainly include the following aspects: 1) small size, light weight. 2) injection excitation: only a few volts of voltage injection of milliamperes of current can drive. Except for the power supply device, no other excitation equipment and parts are needed. The electric power is directly converted into optical power, and the energy efficiency is high. 3) wide wavelength range: appropriate selection of materials and alloy ratio can realize laser with any wavelength in a wide wavelength range of infrared and visible light. 4) direct modulation: superimposing the signal on the driving current, the oscillation intensity, frequency and phase can be modulated in the range of direct current to G Hz. 5) high coherence: single transverse mode laser can obtain high spatial coherence of output light. In the distributed feedback (DFB) and distributed Bragg reflection (DBR) lasers, stable single longitudinal mode oscillation can be obtained, and high temporal coherence can be obtained.

[0003] At present, one of the most commonly used semiconductor lasers is surface emitting semiconductor laser, which has many advantages compared with traditional edge emitting semiconductor laser. Among the surface emitting semiconductor lasers, vertical cavity surface emitting laser (VCSEL) has low threshold, circular beam, easy coupling and two-dimensional integration, and has the advantages of high side mode suppression ratio, low threshold, small size, easy integration and high output power. It has become a hot spot in the field of optoelectronics. In the optical fiber communication system, long wavelength vertical cavity surface emitting laser source with dynamic single mode operation is an indispensable key component. It is mainly used in medium and long distance high speed data communication and optical interconnection, optical parallel processing, optical recognition system, and has important application in metropolitan area network and wide area network.

[0004] The basic structure of vertical cavity surface emitting laser (VCSEL) is as follows Figure 1As shown, including upper and lower distributed Bragg reflector (DBR), oxidation limited hole, multi-quantum well active region and ohmic contact electrode. Quantum well active region is located between n-type doped and p-type doped DBR. DBR mirror has a reflectivity greater than 99%, which is alternately epitaxially grown by high and low refractive index medium or semiconductor material, and the optical thickness of each layer of material is 1 / 4 of the laser wavelength. The optical thickness of the active region is an integer multiple of 1 / 2 (or (2k+1)*1 / 2) of the laser wavelength, and the photons generated by injecting current into the active region through the P-contact are reciprocally reflected and resonantly amplified in the DBR, thereby forming a laser.

[0005] During the operation of the VCSEL, on the one hand, the upper and lower DBRs and the active region generate heat due to the Joule heat and the carrier leakage mechanism; on the other hand, a large amount of heat is generated due to the spontaneous radiation absorption of the active region and the scattering absorption in the DBR; especially for high-power lasers in continuous operation mode, internal heat accumulation is generated, and the temperature of the active region rises sharply, thereby causing the performance of the VCSEL laser to decrease, such as ① the output power of the VCSEL decreases or even a burn-through effect occurs; ② the threshold current increases due to the enhancement of non-radiative carrier recombination at high temperature; ③ the radiation wavelength changes due to the change of the band gap width of the quantum well in the active region and the change of the refractive index of the upper and lower DBRs with the change of the temperature; ④ in addition to the influence on the performance, the continuous high temperature inside the VCSEL also affects the reliability of the entire device, and the defects in the active region and the DBR further grow and expand at high temperature, causing the performance of the device to decrease or even an optical catastrophe, thereby causing the device to fail. Therefore, it is an urgent problem to develop a laser scheme that can reduce the heat generated by the device and has a relatively low cost. SUMMARY

[0006] The purpose of the present application is to solve the problems caused by too many DBR layers, too much resistance of the DBR and too much heat generated during the operation of the DBR in the related art, which seriously even causes the entire laser emitter to be unable to be used.

[0007] To achieve the above object, the technical scheme adopted by the embodiments of the present application is as follows:

[0008] The semiconductor laser emitter provided by the embodiments of the present application comprises:

[0009] The semiconductor laser emitter comprises:

[0010] The first DBR layer, the second DBR layer, the resonant part above the first DBR layer, and the quantum well active region arranged between the first DBR layer and the second DBR layer, and the substrate layer connected with the first DBR layer.

[0011] Optionally, the resonant part penetrates the whole substrate layer.

[0012] Optionally, the first DBR layer is N-doped, and the second DBR layer is P-doped.

[0013] Optionally, the resonant part comprises an external cavity mirror and a transparent conductive layer.

[0014] Optionally, the transparent conductive layer is indium tin oxide.

[0015] Optionally, the thickness of the transparent conductive layer is 80-160 um.

[0016] Optionally, the external cavity mirror layer is curved.

[0017] Optionally, the curvature radius of the external cavity mirror layer is 20-160 um.

[0018] Optionally, the light emitting size of the resonant part is 20-160 um.

[0019] Optionally, the thickness of the external cavity mirror layer is 10-50 um.

[0020] The semiconductor laser emitter provided by the application has the advantages that: the N-DBR pairs can be reduced from the original 22-26 pairs to 8-10 pairs, and the N-DBR resistance and the Joule heat generated in the working process can be effectively reduced. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments, and it should be understood that the following drawings only show some of the embodiments of the application, and therefore should not be regarded as a limitation to the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0022] Figure 1 A structural schematic diagram of a laser emitter provided in the prior art;

[0023] Figure 2A structural schematic diagram of a laser emitter provided in the prior art;

[0024] Figure 3 A structural schematic diagram of a laser emitter provided in the embodiment of the present application;

[0025] Figures 4-11 A process implementation schematic diagram provided in the embodiment of the present application. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the embodiment of the present application more clear, the technical scheme in the embodiment of the present application will be described clearly and completely below with reference to the drawings in the embodiment of the present application. Obviously, the described embodiment is a part of the embodiments of the present application, rather than all the embodiments of the present application.

[0027] Figure 1For the prior art disclosed in an example diagram of a laser emitter, including a first electrode 101, the material of the first electrode can be gold (Au), germanium (Ge), silver (Ag), palladium (Pd), platinum (Pt), nickel (Ni), titanium (Ti), vanadium (V), tungsten (W), chromium (Cr), aluminum (Al), copper (Cu), zinc (Zn), tin (Sn) and indium (In) and the like, of course, not limited to metal materials, but also transparent electrodes formed by metal oxides, the first electrode is connected with a first DBR layer 102, wherein the first DBR layer 102 has a stacked structure in which low refractive index layers and high refractive index layers are alternately stacked. The low refractive index layer is, for example, a p-type AlX1Ga(1-X1)As (0X1<1) with an optical film thickness of λ / 4 (or (2k+1)*λ / 4). The high refractive index layer is, for example, a p-type AlX2Ga(1-X2)As (0≤X2X1) with an optical film thickness of λ / 4 (or (2k+1)*λ / 4). Here, this is only an example and is not a specific limitation on the implementation material. As long as the Bragg type structure is satisfied, in which the low refractive index and the high refractive index are alternately stacked, 107 is an oxidation limiting layer, which plays a role of limiting the generation of photons, so that the generated laser is more centered, and at the same time, it can reduce the refractive index of the resonator to increase the light loss of high-order transverse modes in this position and thus suppress oscillation, in which the strongest intensity can be obtained in the high-order transverse mode, thereby achieving better focusing effect, and the specific material is not limited here. 103 is the active region of the emitter, and the active region 103 has a quantum well structure in which quantum well layers with a thickness of 8 nm of undoped Al0.11As0.89GaAs quantum well layers and barrier layers with a thickness of 5 nm of undoped Al0.3Ga0.7As layers are alternately stacked. For example, the active region 103 is designed to have light emission with a wavelength of 780 nm, and the optical thickness of the active region 103 is an integer multiple of 1 / 2 of the laser wavelength. By injecting current into the active region through the P-contact first electrode 301, the generated excited radiation photons are reflected and resonantly amplified in the DBR, thereby forming a laser. The isolation layer formed by the undoped Al0.6Ga0.4As layer for forming a layer in the active region 3 includes a quantum well structure in the center thereof. The entire isolation layer has a film thickness as large as an integer multiple of λ / n r , where λ is the oscillation wavelength and n ris the refractive index of the medium, here only exemplary and not limiting the implementation material, thickness and the wavelength of the outgoing light and other characteristics, the other end of the active region 103 is connected to the second DBR layer 104, which has a laminated structure in which low refractive index layers and high refractive index layers are alternately stacked. The low refractive index layer is, for example, n-type AlX3Ga(1-X3)As (0X3<1) with an optical film thickness of λ / 4 (or (2k+1)*λ / 4). λ represents the oscillation wavelength of the semiconductor laser 1. The high refractive index layer is, for example, n-type AlX4Ga(1-X4)As (0≤X4X3) with an optical film thickness of λ / 4 (or (2k+1)*λ / 4). Similar to the structure of the first DBR layer 102, here the specific material is not limited, and other materials can also be used to form a Bragg structure in which low refractive index and high refractive index layers are alternately stacked. The DBR reflection region thus arranged can have a reflectivity greater than 99%. The second DBR layer 104 can further be connected to a substrate layer 105, for example, composed of a gallium arsenide (GaAs) substrate layer 105. The substrate layer 105 is made of a material that is transparent to the stacked structure (more specifically, a material that is transparent to the light generated by the active layer 103). The substrate layer 105 can be made of indium phosphide (InP), gallium nitride (GaN), indium gallium nitride (InGaN), sapphire, silicon (Si), silicon carbide (SiC), etc. Here, it is not limited to only the listed materials. Further, the substrate layer 105 is connected to a second electrode 106, which can be made of a material similar to the first electrode 101. By applying pressure through the electrodes, the VCSEL can be excited to work. During operation, on the one hand, Joule heat is generated due to the resistance of the first and second DBRs and the active region, and heat is generated due to the carrier leakage mechanism; on the other hand, a large amount of heat is generated due to the spontaneous radiation absorption of the active region and the scattering absorption in the DBR; especially for high-power lasers in continuous operation mode, internal heat accumulation occurs, the temperature of the active region rises sharply, and thus the performance of the VCSEL laser decreases, which will cause the following problems in the use of semiconductor lasers: ① the output power of the VCSEL decreases or even a burnout effect occurs; ② the threshold current increases due to the increase of non-radiative carrier recombination at high temperature; ③ the radiation wavelength drifts due to the change of the band gap width of the active region quantum well and the refractive index of the upper and lower DBRs with temperature; ④ the continuous high temperature inside the VCSEL not only affects the performance, but also affects the reliability of the entire device. Defects in the active region and the DBR grow and expand further at high temperature, causing the performance of the device to decrease or even optical catastrophe, leading to device failure.

[0028] Figure 2A structure diagram of a laser emitter provided in the prior art; a vertical external cavity surface emitting laser (VECSEL) can be divided into two types according to the driving mode, an optical pumped vertical external cavity surface emitting laser (OP-VECSEL) and an electrical pumped vertical external cavity surface emitting laser (EP-VECSEL), compared with the OP-VECSEL, the electrical pumped VECSEL has a more compact and small size; on the other hand, the EP-VECSEL can directly convert electrical energy into laser output through electrical injection, and has a higher electro-optical conversion efficiency. Figure 2 As shown in FIG. 1, the external cavity mirror of the EP-VECSEL is integrated outside the VCSEL chip. From top to bottom, it includes an external cavity mirror, an N-type ohmic contact electrode, a substrate, an N-type doped distributed Bragg reflector (DBR), a multi-quantum well active region, a protective material layer, a P-type doped DBR, and an N-type ohmic contact electrode. The quantum well active region is located between the n-type doped and p-type doped DBRs. The DBR mirror has a reflectivity of more than 99%, and is formed by alternately epitaxially growing high and low refractive index media or semiconductor materials, and the optical thickness of each layer of material is 1 / 4 of the laser wavelength. The optical thickness of the active region is an integer multiple of 1 / 2 of the laser wavelength, and the injection of current into the active region through the P-contact generates stimulated radiation photons which are reflected and resonantly amplified in the DBR, thereby forming a laser. As shown in FIG. 2, the external cavity mirror of the EP-VECSEL is integrated outside the VCSEL chip, which is not conducive to the further integration and miniaturization of the light source. Figure 2 As shown in FIG. 2, the external cavity mirror of the EP-VECSEL is integrated outside the VCSEL chip, which is not conducive to the further integration and miniaturization of the light source.

[0029] Figure 3 A structure diagram of a laser emitter provided in the embodiment of the present application, and Figure 2 The functions and materials of each layer are similar to those in the prior art and will not be repeated here. The improvement of the present application is that the first DBR layer 301 is further connected to the substrate layer 306, and the transparent conductive layer 304 and the external cavity mirror 305 jointly form a resonant part. The resonant part penetrates through the entire 306 substrate layer, and the light output hole size of the resonant part is 20-160um. The thickness of the transparent conductive layer is 80-160um, and the material of the transparent conductive layer includes transparent electrodes such as indium tin oxide (ITO) or indium zinc oxide (IZO). The thickness of the 305 external cavity mirror layer is 10-50um, and the external cavity mirror layer has a certain curvature with a curvature radius of 20-160um. The 305 external cavity mirror layer forms a resonant cavity with R1, and the number of N-DBR pairs can be reduced from the original 22-26pairs to 8-10pairs, which can effectively reduce the resistance of the N-DBR and the Joule heat generated during operation.

[0030] Figures 4-11 A process implementation schematic diagram is provided for the embodiment of the present application. Figure 4 It is an epitaxial growth step, and a few pairs of N-DBR are epitaxially grown, and the number of pairs of N-DBR is 8-12. Figure 5 It is mesa etching, and a series of circular mesas are etched on the P-type doped surface (P surface) of the epitaxial wafer by inductively coupled plasma dry etching, and the etching depth exceeds the oxidation limiting layer. Figure 6 It is to evaporate ohmic contact electrodes, and a Ti / Pt / Au layer is grown to form electrode contact. Figure 7 It is to prepare an oxidation limiting layer by side oxidation, and the oxidation limiting layer is formed by side oxidation. Figure 8 It is a filling protective layer diagram; 9 is a substrate etched light hole, and a light window is made on the substrate by double-sided alignment, and the substrate is etched to the N-DBR area, and the light hole size is 20-160um. Figure 10 It is to deposit ITO and dielectric layer, and transparent conductive material is deposited on the light window by chemical vapor deposition technology, and the deposition thickness is 80-160um; the transparent conductive material includes transparent electrode, indium tin oxide (ITO) or indium made. Zinc oxide (IZO) and the like; the dielectric layer is deposited on the transparent conductive material in the light window by chemical vapor deposition technology, including silicon oxide, silicon nitride and the like, and the dielectric layer thickness is 10-50um, and the dielectric layer has a certain curvature, and the curvature radius is 20-160um. The deposited dielectric layer is an external cavity mirror; Figure 11 It is to flip and bond the laser chip on the base.

[0031] The technical scheme of the present application realizes the following technical advantages:

[0032] 1) The electrically pumped emission laser with integrated vertical external cavity surface adopts an external cavity surface (deposited dielectric layer), and the number of pairs of N-DBR can be reduced from the original 22-26 pairs to 8-10 pairs, which can effectively reduce the N-DBR resistance and the Joule heat generated during operation.

[0033] 2) The back light emitting area is completely penetrated by etching technology, and is filled with ITO material;

[0034] 3) Good ohmic contact ensures efficient injection of carriers;

[0035] 4) ITO has higher light transmittance than GaAS substrate.

[0036] It has to be noted that, in the present document, relational terms are intended only to convey a possible relationship between elements or items or

[0037] The foregoing is merely illustrative of the principles of this application and various modifications can be made by those skilled in the art without departing from the scope and spirit of the application. Accordingly, the disclosure of the present application is intended to be illustrative, but not limiting, of the scope of the application, which is set forth in the following claims. It is noted that, as used in the specification and the appended claims, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a component" can include mixtures of two or more such components, and the like. It is further noted that the claims can be drafted to exclude any element or step considered to be unnecessary for the practice of the application and this application can be defined solely by the appended claims and equivalents thereof.

Claims

1. A semiconductor laser emitter, characterized in that, include: A first DBR layer, a second DBR layer, a resonant portion located above the first DBR layer, and a quantum well active region disposed between the first DBR layer and the second DBR layer, wherein the first DBR layer is also connected to a substrate layer. The resonant section includes an external cavity mirror and a transparent conductive layer, and the resonant section extends through the entire substrate layer; The external cavity mirror and the first DBR layer form a resonant cavity; A transparent conductive material is deposited in the light-emitting window using chemical vapor deposition (CVD) to form the transparent conductive layer. A dielectric layer is then deposited on top of the transparent conductive material filling the light-emitting window using CVD. The deposited dielectric layer is an external cavity reflector.

2. The semiconductor laser emitter according to claim 1, characterized in that, The first DBR layer is N-type doped, and the second DBR layer is P-type doped.

3. The semiconductor laser emitter according to claim 1, characterized in that, The transparent conductive layer is indium tin oxide.

4. The semiconductor laser emitter according to claim 1, characterized in that, The thickness of the transparent conductive layer is 80-160 μm.

5. The semiconductor laser emitter according to claim 1, characterized in that, The external cavity reflector layer is curved.

6. The semiconductor laser emitter according to claim 1, characterized in that, The radius of curvature of the external cavity reflective mirror layer is 20-160 μm.

7. The semiconductor laser emitter according to claim 1, characterized in that, The light emission size of the resonant part is 20-160 μm.

8. The semiconductor laser emitter according to claim 1, characterized in that, The thickness of the external cavity reflector layer is 10-50 μm.

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