High-power and single-mode VCSEL arrays with single-polarized outputs by using package-induced tensile strain

• Published in: Optics letters 2020-09, Vol.45 (17), p.4839-4842
• Main Authors: Shi, Jin-Wei, Khan, Zuhaib, Horng, Ray-Hua, Yeh, Hsiao-Yun, Huang, Chun-Kai, Liu, Cheng-Yi, Shih, Jie-Chen, Chang, Yung-Hao, Yen, Jia-Liang, Sheu, Jinn-Kong
• Format: Article
• Language: English
• Subjects: Apertures; Copper; Laser arrays; Polarization; Selectivity; Substrates; Tensile strain; Threshold currents; Vertical cavity surface emission lasers
• ISSN: 0146-9592; 1539-4794
• DOI: 10.1364/OL.398896

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 ( I th). 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 d B ) with a very narrow divergence angle ( 1 / e 2 : ∼ 10 ∘ ) 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 ( I th: 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.