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2024

Novel on-chip integrated waveguide antimonide semiconductor mid-infrared laser

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Mid-infrared high power semiconductor lasers have broad application prospects in gas detection, manufacturing, space communications and other fields. Although the traditional wide-area (BA) structure antimonide semiconductor laser is relatively mature in manufacturing process and high in output power, it is restricted by thermal effect and lateral carrier accumulation effect, and the laser power is prompted to increase the lateral divergence angle under high injection current, facing the bottleneck problem of beam quality degradation, which seriously limits its application scenarios. Solving the problem of large laser beam divergence angle under high power has become a research hotspot.

On-Chip Integration of a Novel Sawtooth Waveguide Structure Antimonide Semiconductor Laser

Niu Zhichuan, a researcher from the National Key Laboratory of Optoelectronic Materials and Devices, Institute of Semiconductors, Chinese Academy of Sciences, has proposed a new type of sawtooth waveguide (ASW) structure. By effectively increasing the loss difference between the higher-order mode and the fundamental mode, the lateral divergence angle of the beam is reduced to 11.39 compared with the 19.61 of the traditional BA structure laser at high output power. The dependence of the divergence angle on current is significantly improved, showing stable and effective beam mode control effect. The research results are published in "Precise Mode Control of mid-infrared high-power laser diodes using on-chip advanced sawtooth waveguide designs". High Power Laser Science and EngineeringJournal, and was selected as Editors 'Pick.

The structure of the antimonide semiconductor ASW laser is shown in Figure 1. The structure design is based on the near-field distribution characteristics of the wide-area waveguide, using two-dimensional time domain finite differential (FDTD) simulation, and setting a series of sawtooth structures along the cavity length direction accurately improves the loss of high-order modes, and also improves the carrier accumulation on both sides of the waveguide.

The intracavity optical field distribution of the antimonide semiconductor ASW laser is shown in Figure 2. The sawtooth structure on both sides hardly affects the fundamental mode, and the scattering of higher-order modes increases significantly. The optical field distribution of each order mode of the laser in the cavity surface is shown in fig. 3: its microstructure size ratio (L-d)/L is 0.5, and the residual energy of the fundamental mode is about 1.4 times that of the high order mode. it can be seen that most of the energy of the fundamental mode is retained, while the intensity distribution of the high order mode is significantly reduced on both sides of the waveguide, while the carrier profile and the mode profile of the device are more matched.

In this study, ASW and BA lasers with the same output aperture are compared. ASW has higher photoelectric efficiency under the equivalent output power of 1.1W. The lateral far-field distribution of the two devices and the relationship between the lateral far-field divergence angle and the injection current are shown in Figure 4: Obviously, the traditional BA laser is a typical multi-lobe far-field, while the ASW laser far-field distribution is more concentrated. In the whole dynamic current range, in addition to the smaller lateral divergence, the dependence of the lateral divergence on the current is reduced from 2.19 °/A to 1.35 °/A, revealing a more stable mode regulation.

Summary and Prospect

The research results successfully developed a new type of on-chip integrated waveguide structure mid-infrared semiconductor laser with innovative design, which effectively reduced the laser lateral divergence angle based on the selective control mode loss mechanism, and achieved higher power and narrow divergence angle stable power output without increasing the complexity and cost of process preparation. The structure and preparation technology can be compatible with other semiconductor materials different band lasers, is one of the ideal technical routes for the application of high integration and high brightness laser technology.

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