Browsing by Author "Khan, Zuhaib"

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Effect of Thermal Management on the Performance of VCSELs
(2020-09-01)
Pan, Po-Chou
;
Nag, Dhiman
;
Khan, Zuhaib
;
Chen, Ching-Jung
;
Shi, Jin-Wei
This study investigated the effect of thermal management on the performance of vertical-cavity surface-emitting lasers (VCSELs). It was found that the thickness of silicon substrate, which can serve as the submount for VCSEL packages, has a strong influence on the thermal dissipation of on-chip laser sources, and eventually impacts on their output characteristics. Moreover, the improvements in optical characteristics of the on-chip VCSELs were the best heat dissipation through thinning silicon substrates to 50-mu m thickness combined with electroplated Cu with 100-mu m thickness. In addition, this study also performed COMSOL simulations. The simulation results were consistent with experimental results.
High-brightness and high-speed vertical cavity surface-emitting laser arrays
(2020-04-20)
Khan, Zuhaib
;
Shih, Jie-Chen
;
Chao, Rui-Lin
;
Tsai, Tzong-Liang
;
Wang, Hsin-Chuan
High-power vertical-cavity surface-emitting laser (VCSEL) arrays, which can serve as the light source in modem lidar and three-dimensional optical sensing systems, have recently attracted a lot of attention. In these types of systems, the time-of-flight (ToF) technique, based on the round-trip time of short optical pulses is usually adopted. Further enhancement of the ranging distance and depth resolution in these ToF driven systems by the incorporation of a VCSEL array with a high available power, high brightness (narrow divergence angle), and fast response time is highly deskable. However, a large number of light emission apertures (several hundreds) in the VCSEL array is usually necessary to raise the output power level to several watts. This leads to a large parasitic capacitance and the RC-limited bandwidth may become the dominant limiting factor of the speed of the high-power VCSEL array. In this work, Zn-diffusion and oxide-relief apertures are used to manipulate the optical modes and reduce the parasitic capacitance, respectively, in a unit device for a 940 nm VCSEL array. The demonstrated VCSEL array has a quasi-single-mode output, high available power (4 W; 1% duty cycle), narrow divergence angle (similar to 14 degrees at 1/e(2)) under maximum output power, and a fast rise time (<100 ps). These results open up new possibilities for further enhancing the performance of ToF sensing systems at the 940 nm wavelength. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
High-power and single-mode VCSEL arrays with single-polarized outputs by using package-induced tensile strain
(2020-09-01)
Shi, Jin-Wei
;
Khan, Zuhaib
;
Horng, Ray-Hua
;
Yeh, Hsiao-Yun
;
Huang, Chun-Kai
In this work, we demonstrate a novel high-power vertical-cavity surface-emitting laser (VCSEL) array with highly single-mode (SM) and single-polarized output performance without significantly increasing the intra-cavity loss and threshold current (Ith). By combining a low-loss zinc-diffusion aperture with an electroplated copper substrate, we can obtain a highly SM output (side mode suppression ratio >50 dB) with a wry narrow divergence angle (1 / e(2) : similar to 10 degrees) under high output power (3.1 W; 1% duty cycle) and sustain a single polarization state, with a polarization suppression ratio of around 9 dB, under the full range of bias currents. Compared to the reference device without the copper substrate, the demonstrated array can not only switch the output optical spectra from quasi-SM to highly SM but also maintain a close threshold current value (Ith: 0.8 versus 0.7 mA per unit device) and slope efficiency. The enhancement in fundamental mode selectivity of our VCSEL structure can be attributed to the single-polarized lasing mode induced by tensile strain, which is caused by the electroplated copper substrate, as verified by the double-crystal x-ray measurement results. (C) 2020 Optical Society of America