Dr. Xiaolong Ma Profile

Dr. Xiaolong Ma

at Institute of Semiconductors

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Publications (3)

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Proceedings Article | 24 October 2017 Paper

High-efficiency fiber-coupled module based on multi-single emitter photonic-band-crystal laser diodes

Yang Chen, Hongwei Qu, Yufang Zhang, Yufei Wang, Xiaolong Ma, Wanhua Zheng

Proceedings Volume 10457, 104572J (2017) https://doi.org/10.1117/12.2284900

KEYWORDS: Semiconductor lasers, Fiber lasers

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High-efficiency, high-power and high-brightness, fiber-coupled modules based on semiconductor laser diodes have been important sources in many fields, such as fiber laser pumping, material processing and defense applications. The coupling efficiency of fiber-coupled module has been limited due to the large vertical divergent angle of conventional semiconductor laser diodes. We present a high coupling efficiency module by using photonic-band-crystal (PBC) laser diodes with narrow vertical divergent angle. Fourteen PBC single-emitter laser diodes are combined into a fiber with core diameter of 200 μm and numerical aperture (NA) of 0.22. A high and stability coupling efficiency of 88% and peak otuput power of 47W with the injection current of 5 A are obtained. A comparison with the coupling efficiency of conventional laser diodes module is also presented. And there is a 5% increase of fiber-coupled efficiency based on PBC laser diodes module compared to conventional semiconductor laser diodes module.

Proceedings Article | 24 October 2017 Paper

Improved power and efficiency for tapered lasers with optimized photonic crystal structures

Xiaolong Ma, Hongwei Qu, Shaoyu Zhao, Xuyan Zhou, Yuzhe Lin, Wanhua Zheng

Proceedings Volume 10457, 104571O (2017) https://doi.org/10.1117/12.2284461

KEYWORDS: Quantum efficiency, High power lasers, Quantum wells

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High power and high beam quality laser sources are required in numerous applications such as nonlinear frequency conversion, optical pumping of solid-state and fiber lasers, material processing and others. Tapered lasers can provide a high output power while keeping a high beam quality. However, the conventional tapered lasers suffer from a large vertical beam divergence. We have demonstrated 2-mm long tapered lasers with photonic crystal structures. A high beam quality and a narrow vertical divergence are achieved.

In this paper, we optimized the photonic crystal structure and fabricated a 4-mm long tapered laser to further increase the output power and the wall-plug efficiency. Compared with our precious wafer, the optimized structure has a lower doping level to reduce the internal loss. The period of the photonic crystal structure and the thickness of the upper cladding are also reduced. The device has a 1-mm long ridge-waveguide section and a 3-mm long tapered section. The taper angle is 4°. An output power of 7.3 W is achieved with a peak wall-plug efficiency of 46% in continuous-wave mode. The threshold current is around 500 mA and the slope efficiency is 0.93 W/A. In pulsed mode, the output power is 15.6 W and the maximum wall-plug efficiency is 48.1%. The far-field divergence with full width at half maximum is 6.3° for the lateral direction at 3 A. The vertical far-field beam divergence is around 11° at different injection levels. High beam qualities are demonstrated by beam quality factor M² of 1.52 for the lateral direction and 1.54 for the vertical direction.

Proceedings Article | 31 October 2016 Paper

980 nm tapered lasers with photonic crystal structure for low vertical divergence

Xiaolong Ma, Hongwei Qu, Pengchao Zhao, Yun Liu, Wanhua Zheng

Proceedings Volume 10019, 1001907 (2016) https://doi.org/10.1117/12.2246353

KEYWORDS: Photonic crystals, Crystals, Laser crystals, Laser applications, High power lasers, Semiconductor lasers, Continuous wave operation, Refractive index, Temperature metrology

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High power tapered lasers with nearly diffraction-limited beam quality have attracted much attention in numerous applications such as nonlinear frequency conversion, optical pumping of solid-state and fiber lasers, medical treatment and others. However, the large vertical divergence of conventional tapered lasers is a disadvantage, which makes beam shaping difficult and expensive in applications. Diode lasers with photonic crystal structure can achieve a large mode size and a narrow vertical divergence. In this paper, we present tapered lasers with photonic crystal structure emitting at 980 nm. The epitaxial layer is grown using metal organic chemical vapor deposition. The device has a total cavity length of 2 mm, which consists of a 400-um long ridge-waveguide section and a 1600-um long tapered section. The taper angle is 4°. An output power of 3.3 W is achieved with a peak conversion efficiency of 35% in pulsed mode. The threshold current is 240 mA and the slope efficiency is 0.78 W/A. In continuous wave mode, the output power is 2.87 W, which is limited by a suddenly failure resulting from catastrophic optical mirror damage. The far field divergences with full width at half maximum are 12.3° in the vertical direction and 2.9° in the lateral direction at 0.5 A. At high injection level the vertical divergence doesn’t exceed 16°. Beam quality factor M² is measured based on second moment definition in CW mode. High beam quality is demonstrated by M² value of less than 2 in both vertical and lateral directions.

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