A vertical cavity surface emitting laser with adjustable junction temperature

Abstract

The application discloses a junction temperature adjustable vertical cavity surface emitting laser, which comprises a substrate composed of an N-type electrode (10) and a substrate layer (11), a VCSEL composed of an N-type DBR (31), an active region (32), a SiO2 layer (33), an oxidation confinement layer (34), a P-type DBR (35) and a positive electrode (36), and a series thermocouple pair composed of a P-type electrode end (21), a plurality of thermocouple pairs and a grounding end (26). The laser disclosed by the application can also be composed of a two-dimensional array structure of a plurality of junction temperature adjustable vertical cavity surface emitting lasers, wherein the junction temperature of each junction temperature adjustable vertical cavity surface emitting laser can be adjusted by setting the current injected by the corresponding P-type electrode end (21). Compared with a conventional vertical cavity surface emitting laser, the application can realize accurate regulation and control of the junction temperature of a single laser and a laser with a two-dimensional array structure, thereby effectively improving the thermal reliability of the laser.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor lasers, and particularly relates to a junction temperature adjustable vertical cavity surface emitting laser. BACKGROUND

[0002] The vertical cavity surface emitting laser (VCSEL) has the advantages of small size, low power consumption, high efficiency, large modulation bandwidth, long service life, circular beam, on-chip testing, and easy two-dimensional array arrangement, and is widely used in the fields of data communication, sensing, laser radar, material processing, etc.

[0003] Figures 1(a) and (b) respectively illustrate the top view and longitudinal section view of a conventional VCSEL, which mainly consists of an N-type electrode (1), a substrate (2), an N-type DBR (3), an active region (4), a SiO2 layer (5), an oxidation confinement layer (6), a P-type DBR (7), and a positive electrode (8). When the VCSEL works under direct current bias, the thermal effect caused by the linear dissipation power of the active region (4) and the quadratic dissipation power of the P-type DBR (7) will cause the junction temperature of the active region of the VCSEL to rise rapidly. Further considering the influence of the negative temperature coefficient of internal quantum efficiency, the output optical power of the VCSEL will tend to be saturated and rapidly decrease. At the same time, the decrease of the above output optical power will be fully converted into heat energy in the form of dissipation power, which will further increase the junction temperature of the VCSEL. The continuously rising junction temperature will also affect the beam quality and modulation speed of the VCSEL, such as increasing the threshold current, causing thermal lens effect, affecting wavelength stability (resonant cavity and peak gain wavelength detuning), causing laser transverse mode change, limiting the optical gain of the active region, limiting the modulation speed due to saturation of the photon density of the active region, etc. It can be seen that how to effectively regulate and control the junction temperature of the VCSEL has important practical significance.

[0004] In addition, in order to effectively improve the output optical power level of the vertical cavity surface emitting laser, a two-dimensional array structure composed of multiple VCSELs in parallel is usually adopted. At this time, considering the difference in heat dissipation capacity of each VCSEL and the influence of the thermal coupling effect between the VCSELs, the junction temperature of the VCSELs located in the central region with poor heat dissipation capacity will be much higher than that of the VCSELs on the outside, and the non-uniformity of the junction temperature distribution of each VCSEL will be more prominent under the influence of the thermal photoelectric feedback effect. Therefore, how to design a junction temperature adjustable vertical cavity surface emitting laser has important theoretical and practical significance for improving the thermal reliability of the VCSEL. SUMMARY

[0005] The application discloses a junction temperature adjustable vertical cavity surface emitting laser, which is characterized in that the vertical cavity surface emitting laser comprises, from bottom to top, a substrate, a vertical cavity surface emitting laser (VCSEL) and a series thermocouple pair.

[0006] The junction temperature adjustable vertical cavity surface emitting laser is characterized in that the substrate is composed of an N-type electrode (10) and a substrate layer (11), wherein the substrate (11) is a GaAs or GaN substrate.

[0007] The junction temperature adjustable vertical cavity surface emitting laser is characterized in that the VCSEL comprises, from bottom to top, an N-type DBR (31), an active region (32), a SiO2 layer (33), an oxidation confinement layer (34), a P-type DBR (35) and a positive electrode (36).

[0008] The junction temperature adjustable vertical cavity surface emitting laser is characterized in that the series thermocouple pair comprises a P-type electrode end (21), a plurality of thermocouple pairs and a grounding end (26), wherein each thermocouple pair comprises a P-type thermocouple (23), a cold end (22), an N-type thermocouple (25) and a hot end (24).

[0009] The P-type electrode end (21) is connected to the P-type thermocouple (23) via the SiO2 layer (33), the active region (32) and the N-type DBR (31) to the inside of the substrate layer (11) from top to bottom, and the P-type electrode end (21) is not connected to the positive electrode (36).

[0010] The number of the plurality of thermocouple pairs is an even number greater than or equal to 4, and the plurality of thermocouple pairs are symmetrically distributed on the outside of the P-type DBR (35) and are in a regular polygon distribution form.

[0011] The cold end (22) and the hot end (24) are located in the inside of the SiO2 layer (33) and the substrate layer (11) respectively.

[0012] The grounding end (26) is located in the inside of the substrate layer (11) and is connected to the hot end (24) and the N-type electrode (10) respectively.

[0013] The materials of the P-type electrode end (21), the cold end (22), the hot end (24) and the grounding end (26) are all aluminum; the material of the P-type thermocouple (23) is Bi 0.4 Te 3.0 Sb 1.6 The material of the N-type thermocouple (25) is Bi 2.0 Te 2.7 Se 0.3 .

[0014] The junction temperature adjustable vertical cavity surface emitting laser of the present application is characterized in that the peak junction temperature of the junction temperature adjustable vertical cavity surface emitting laser and the number of series thermocouple pairs and the current injected by the P-type electrode end (21) satisfy the following relationship:

[0015] T = -0.8n - 19.7I + 343.9

[0016] Wherein, T is the peak junction temperature of the junction temperature adjustable vertical cavity surface emitting laser, n is the number of series thermocouple pairs, and I is the current injected by the P-type electrode end (21).

[0017] The junction temperature adjustable vertical cavity surface emitting laser of the present application is characterized in that the laser can also be composed of a two-dimensional array structure of a plurality of junction temperature adjustable vertical cavity surface emitting lasers, wherein the peak junction temperature of each junction temperature adjustable vertical cavity surface emitting laser can be adjusted by setting the current injected by the corresponding P-type electrode end (21).

[0018] Compared with the conventional vertical cavity surface emitting laser, the junction temperature adjustable vertical cavity surface emitting laser of the present application can realize accurate regulation and control of the junction temperature of a single laser and a laser with a two-dimensional array structure, thereby effectively improving the thermal reliability of the VCSEL. BRIEF DESCRIPTION OF DRAWINGS

[0019] The following description in conjunction with the accompanying drawings can further understand the purposes and advantages of the present application. In these drawings:

[0020] Figure 1(a) illustrates a top view of a conventional vertical cavity surface emitting laser;

[0021] Figure 1(b) illustrates a cross-sectional structure schematic diagram of the conventional vertical cavity surface emitting laser along the dividing line L1 in Figure 1(a);

[0022] Figure 2(a) illustrates a top view of the embodiment 1 of the present application;

[0023] Figure 2(b) illustrates a cross-sectional structure schematic diagram of the embodiment 1 of the present application along the dividing line L2 in Figure 2(a);

[0024] Figure 2(c) illustrates a cross-sectional structure schematic diagram of the embodiment 1 of the present application along the dividing line L3 in Figure 2(a);

[0025] Figure 3(a) illustrates a temperature distribution of the embodiment 1 of the present application;

[0026] Figure 3(b) illustrates a temperature distribution of a conventional vertical cavity surface emitting laser;

[0027] Figure 4Fig. 4 shows the peak junction temperature of the embodiment 1 of the present application versus the number of series thermocouple pairs and the current injected into the P-type electrode end (21);

[0028] Figure 5 Fig. 5 shows a top view of the embodiment 2 of the present application;

[0029] Fig. 6(a) shows the temperature distribution of the embodiment 2 of the present application;

[0030] Fig. 6(b) shows the temperature distribution of a conventional vertical cavity surface emitting laser with a 3x3 array structure;

[0031] Figure 7 Fig. 6(c) shows the improvement of the embodiment 2 of the present application on the peak junction temperature distribution of each VCSEL in a 3x3 array structure laser. DETAILED DESCRIPTION

[0032] The embodiments of the present application are described in detail below with single laser and laser with 3x3 array structure as examples. The present application is not limited to these examples.

[0033] Embodiment 1:

[0034] The vertical cavity surface emitting laser with adjustable junction temperature disclosed by the embodiment of the present application, figures 2(a), (b), (c) show the structural schematic diagram of the embodiment 1 of the present application, and sequentially include substrate, vertical cavity surface emitting laser (VCSEL) and series thermocouple pair from bottom to top; the substrate is composed of N-type electrode (10) and substrate layer (11), wherein the substrate (11) is GaAs or GaN substrate. The VCSEL sequentially includes N-type DBR (31), active region (32), SiO2 layer (33), oxidation confinement layer (34), P-type DBR (35), positive electrode (36) from bottom to top; the series thermocouple pair includes P-type electrode end (21), multiple groups of thermocouple pairs and ground end (26), wherein each group of thermocouple pairs includes P-type thermocouple (23), cold end (22), N-type thermocouple (25) and hot end (24). The P-type electrode end (21) reaches the inside of the substrate layer (11) via SiO2 layer (33), active region (32) and N-type DBR (31) from top to bottom and is connected with the P-type thermocouple (23), and the P-type electrode end (21) is not connected with the positive electrode (36); the number of groups of the multiple groups of thermocouple pairs is an even number greater than or equal to 4, and the multiple groups of thermocouple pairs are symmetrically distributed on the outside of the P-type DBR (35) and are in the form of regular polygon distribution; the cold end (22) and the hot end (24) are located in the inside of the SiO2 layer (33) and the substrate layer (11) respectively; the ground end (26) is located in the inside of the substrate layer (11) and is connected with the hot end (24) and the N-type electrode (10) respectively; the materials of the P-type electrode end (21), the cold end (22), the hot end (24) and the ground end (26) are all aluminum; the material of the P-type thermocouple (23) is Bi 0.4 Te 3.0 Sb 1.6 , the material of the N-type thermocouple (25) is Bi 2.0 Te 2.7 Se 0.3 .

[0035] The mesa radius of the embodiment 1 of the present application is 13.5 μm, and there are 6 groups of thermocouple pairs (C1, C2, C3, C4, C5 and C6), the length and width of the cold end in each group of thermocouple pairs are 18 μm and 3 μm respectively, and the spacing between the cold end in each group of thermocouple pairs and the mesa on the side close to the mesa is 17.5 μm.

[0036] In the embodiment 1 of the present application, the positive electrode of the power supply is connected with the P-type electrode end (21), and the negative electrode of the power supply is connected with the N-type electrode (10). At this time, the current injected from the P-type electrode end (21) will flow through the multiple groups of thermocouple pairs composed of the P-type thermocouple (23), the cold end (22), the N-type thermocouple (25) and the hot end (24) in turn, and finally flows out through the ground end (26) and the N-type electrode (10), so as to realize the precise regulation and control of the junction temperature of the laser.

[0037] Considering that the linear dissipation power inside the active region (32) and the quadratic dissipation power of the P-type DBR (35) are the main factors causing the rapid rise of the junction temperature of the laser, the cold end (22) arranged near the active region (32) and the P-type DBR (35) will effectively reduce the peak junction temperature of the laser. At the same time, the heat will be transferred to the hot end (24) in the form of temperature difference through the multiple thermocouple pairs via the cold end (22), and will be quickly dissipated through the substrate side, thereby achieving precise temperature control of the embodiment 1 of the present application.

[0038] FIG. 3(a) illustrates the temperature distribution of the embodiment 1 of the present application, when the operating current of the laser is 16 mA and the current I injected at the P-type electrode end is 1 mA, the peak junction temperature of the laser is only 320.9 K.

[0039] FIG. 3(b) illustrates the temperature distribution of the conventional vertical cavity surface emitting laser, when the operating current of the laser is 16 mA, the peak junction temperature of the laser is as high as 345.8 K.

[0040] It can be seen that, under the same operating current, compared with the conventional vertical cavity surface emitting laser, the peak junction temperature of the embodiment 1 of the present application is improved by 24.9 K.

[0041] Figure 4 FIG. 4 illustrates the relationship between the peak junction temperature of the embodiment 1 of the present application and the number of series thermocouple pairs and the current injected at the P-type electrode end (21). It can be seen that, with the increase of the number of series thermocouple pairs and the increase of the current injected at the P-type electrode end, the peak junction temperature of the laser will be effectively improved. Further, it is concluded that the peak junction temperature of the embodiment 1 of the present application satisfies the following relationship with the number n of series thermocouple pairs and the current I injected at the P-type electrode end:

[0042] T = -0.8n - 19.7I + 343.9

[0043] Embodiment 2:

[0044] Figure 5 FIG. 5 illustrates a top view of the embodiment 2 of the present application with a 3x3 array structure. The embodiment 2 of the present application comprises 9 VCSELs (211, 212, 213, 221, 222, 223, 231, 232 and 233), each with a mesa radius of 13.5 μm, and a center distance of 42 μm. Each VCSEL has a separately controllable P-type electrode end and a ground end, and each VCSEL has 6 groups of thermocouple pairs, each with a cold end length of 18 μm and a width of 3 μm, and a distance between the cold end of each group of thermocouple pairs and the mesa of 17.5 μm.

[0045] Figure 6(a) illustrates the temperature distribution of the embodiment 2 of the present application. When the working current of the laser is 144 mA and the total injection current of the P-type electrode end of the 9 VCSELs is 9 mA, the peak junction temperature of the laser is only 320.4 K.

[0046] Figure 6(b) illustrates the temperature distribution of the conventional vertical cavity surface emitting laser with 3x3 array structure. When the working current of the laser is 144 mA, the peak junction temperature of the laser is 369.0 K.

[0047] It can be seen that, under the same working current, the peak junction temperature of the embodiment 2 of the present application is improved by 48.6 K compared with the conventional vertical cavity surface emitting laser.

[0048] Figure 7 The improvement of the embodiment 2 of the present application on the peak junction temperature distribution of each VCSEL in the 3x3 array structure laser is illustrated. Under the same working current, the maximum peak junction temperature difference of each VCSEL in the embodiment 2 of the present application is only 3.9 K, which is improved by 16.7% compared with the conventional vertical cavity surface emitting laser.

[0049] The above results all show the superiority of the embodiment of the present application, and the present application has important theoretical and practical significance for designing and manufacturing a vertical cavity surface emitting laser with adjustable junction temperature and improving the thermal reliability of the vertical cavity surface emitting laser.

Claims

1. A vertical cavity surface emitting laser with adjustable junction temperature, characterized in that The substrate, a vertical cavity surface emitting laser (VCSEL) and a series of thermocouples from bottom to top; The VCSEL comprises, from bottom to top, an N-type DBR (31), an active region (32), a SiO2 layer (33), an oxidation confinement layer (34), a P-type DBR (35), and a positive electrode (36); The series of thermocouples comprises a P-type electrode end (21), a plurality of groups of thermocouples, and a ground end (26), wherein each group of thermocouples comprises a P-type thermocouple (23), a cold end (22), an N-type thermocouple (25), and a hot end (24); The P-type electrode end (21) is connected to the P-type thermocouple (23) via the SiO2 layer (33), the active region (32), and the N-type DBR (31) from top to bottom and reaches the inside of the substrate layer (11), and the P-type electrode end (21) is not connected to the positive electrode (36); The number of groups of the plurality of groups of thermocouples is an even number greater than or equal to 4, and the plurality of groups of thermocouples are symmetrically distributed on the outside of the P-type DBR (35) and in the form of a regular polygon; The cold end (22) and the hot end (24) are located inside the SiO2 layer (33) and the substrate layer (11), respectively; The ground end (26) is located inside the substrate layer (11) and is connected to the hot end (24) and the N-type electrode (10), respectively.

2. The junction temperature adjustable vertical cavity surface emitting laser of claim 1, wherein, The substrate comprises an N-type electrode (10) and a substrate layer (11), wherein the substrate (11) is a GaAs or GaN substrate.

3. The junction temperature adjustable vertical cavity surface emitting laser of claim 1, wherein, The P-type electrode end (21), cold end (22), hot end (24) and ground end (26) are all made of aluminum; the P-type thermocouple (23) is made of Bi 0.4 Te 3.0 Sb 1.6 The N-type thermocouple (25) is made of Bi 2.0 Te 2.7 Se 0.3 .

4. The junction temperature adjustable vertical cavity surface emitting laser of claim 1, wherein, The peak junction temperature of the junction temperature adjustable vertical cavity surface emitting laser satisfies the following relationship with the number of groups of the series of thermocouples and the current injected by the P-type electrode end (21): T = -0.8n - 19.7I + 343.9 wherein T is the peak junction temperature of the junction temperature adjustable vertical cavity surface emitting laser, n is the number of groups of the series of thermocouples, and I is the current injected by the P-type electrode end (21).

5. The junction temperature adjustable vertical cavity surface emitting laser of claim 1, wherein, The laser can also be composed of a two-dimensional array structure of a plurality of junction temperature adjustable vertical cavity surface emitting lasers, wherein the peak junction temperature of each junction temperature adjustable vertical cavity surface emitting laser is adjusted by setting the current injected by the corresponding P-type electrode end (21).

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