Thermal dissipation is critical for any semiconductor lasers, because heat will lead to their performance degradation, such as wavelength shift, output power decrease, and even device damage. For InP-based InGaAsP semiconductor lasers, heat affection induced by their Auger recombination is so strong that thermal-electronic-controller must be adopted for these lasers operation. Therefore, heat dissipation from up (flip-chip method) and down (heat sink) of these InP-based InGaAsP semiconductor laser has been thoroughly investigated. cladded by the passivation material with high thermal resistance. In this paper, we built two-dimension heat dissipation model by finite-element-method for InP-based InGaAsP FP lasers and investigated the influence of lateral waveguide structure, passivation material, and filling material on the lateral heat dissipation. Our simulation results shows that both the passivation material with low thermal resistance and two-channel waveguide filled with high thermal conductivity material indeed benefit the lateral heat dissipation of these edge-emitting semiconductor lasers. The maximum temperature decrease of 6.8°C in this InP-based InGaAsP ridge waveguide laser with the output power of 18 mW has been achieved in the optimized waveguide structure, where, double-channel waveguide with channel radius of 17 μm and filled with graphene was adopted, the active region is cladded by 300 nm-thick AlN, and then the filling layer of graphene is designed near the InP ridge, and a layer of gold coating with 3.5 μm thickness is deposited on the ridge of the semiconductor laser. Such investigation shows that lateral heat dissipation is possible for these channel waveguide semiconductor lasers.
Fivefold photonic crystal (PC) structure is originally presented with theoretical investigation about its photonic band gap through transmission spectrum calculated by finite-difference time-domain methods. The existence of PC band gap makes it possible for defect structures with high-quality factor. Two types of fivefold PC microcavity are proposed of which the quality factor, normalized frequency, and electromagnetic field profile have been simulated. With some preliminary structural parameters optimization, monopole mode in one-defect fivefold PC microcavity with a high-Q factor (∼2212) and whispering gallery mode in six-defect fivefold PC microcavity with a high-Q factor (∼13,300) are obtained.
We designed two kinds of hybrid plasmonic annular resonators with different cross-sectional shapes, i.e., a square and circle called “square ring” and “circle ring” resonators, respectively. Both resonators feature an ultracompact mode volume of ∼10−4 μm3 and a relatively high-quality factor of ∼102 at a submicron footprint within our studied wavelength range from 400 to 900 nm. Their performance as defined by the Q/V ratio (quality factor over mode volume) is enhanced considerably with a reduction in their physical dimensions. There exists critical annular radii, which increase from 400 to 600 nm with an increase in the azimuthal numbers from m=7 to m=10, if the two types of rings are compared with the same mode numbers and same ring thickness of 120 nm. Below the critical radii, the circle ring resonator outperforms the square ring resonator in terms of the Q/V ratio, and the difference in Q/V of the two types of rings increases rapidly with the decrease of the radii. On the other hand, they have critical annular radii of ∼250 nm, below which the square ring resonator outperforms the circle ring resonator at the wavelengths of 490 and 595 nm; however, the difference in Q/V of the two types of rings remains small within the radii range we consider. It is suggested that, in practice, with the consideration of the wavelength of green emission for these two ring structures with radii from 100 to 500 nm and ring thickness ∼120 nm, they have a negligible difference in Q/V performance.
We report on our design and fabrication of 1470 nm high power InGaAlAs quantum well lasers. It is found that the 2-mm-long-cavity devices with aperture size of 96 μm can reach maximum power of around 4.2 W. The threshold is around 500 mA, and slope efficiency is about 0.42 W/A. Apart from the excellent external quantum efficiency and thermal performance, devices also show reduced beam divergence which is about 30°. Accelerated life-time test has also been performed to determine the reliability performance. Thus far more than 9000 life-test-hour has been accumulated, and there is no detectable sign of the power degradation, indicating our devices are extremely reliable.
We report on our design and fabrication of 830 nm high power semiconductor lasers with extremely low beam divergence. Here we propose a novel approach in which by combining asymmetric waveguide and a feature called “pins” together, we were able to design an optimized epi structure which not only produces a beam divergence of less than 16°, but also has very good growth tolerance as well. Tested devices show the beam divergence is as small as 13°, yet they still retain very high slope efficiency of around 1.15 W/A and low threshold current of 400 mA for the devices with cavity length being 2 mm long, and ridge width being 40 μm wide.
We report on our design and fabrication of very high power semiconductor lasers based on a core-aluminum-free (CAF) active structure. The optical power of as high as 45 W, limited by the thermal roll-over, has been obtained when the single emitter devices are tested under quasi-continuous wave (QCW) conditions, and more than 10 W has been acquired at the operation current of 10 A under continuous wave (CW) conditions. For 10 mm long bar chips, emitting power of up to 200 W is attainable for the operation current of 200 A. The lasers also exhibit excellent slope efficiency of about 1.3 W/A and beam divergence of only 25 °.