High-Brightness VCSEL Arrays With Inter-Mesa Waveguides for the Enhancement of Efficiency and High-Speed Data Transmission

• Published in: IEEE journal of selected topics in quantum electronics 2022-01, Vol.28 (1: Semiconductor Lasers), p.1-11
• Main Authors: Shih, Jie-Chen, Khan, Zuhaib, Chang, Yung-Hao, Shi, Jin-Wei
• Format: Article
• Language: English
• Subjects: Arrays; Brightness; Data transmission; Dilution; Efficiency; Emitters; Free-space optical communication; High speed; High-speed optical techniques; Holes; Light sources; Optical arrays; Optical device fabrication; Optical refraction; Optical variables control; Optical waveguides; Photon density; semiconductor laser arrays; Semiconductor lasers; Vertical cavity surface emitting lasers; vertical-cavity surface emitting lasers (VCSEL)
• ISSN: 1077-260X; 1558-4542
• DOI: 10.1109/JSTQE.2021.3106910

A novel VCSEL array for high-efficiency, high-speed, and high-brightness performance is demonstrated. In contrast to the traditional VCSEL arrays, which have several independent VCSEL cavities in parallel, the novel array structure has additional passive optical waveguides connecting each cavity. In addition, Zn-diffusion and oxide-relief structures are adopted for each single element of the array to obtain the high-brightness (single-mode; SM) output and relax the RC-limited bandwidth. Comparison is made to the traditional reference array. Although the values of the oxide-relief apertures are close to each other, the novel demonstrated arrays exhibit a higher wall plug efficiency, larger maximum output power, and better eye-opening for high-speed data transmission, when both of their output optical spectra are quasi-(SM) with close narrow divergence angle values (FWHM: ∼6°). The superior performance of the demonstrated array for (quasi-) SM operation can be attributed to the dilution of the photon density in the SM output pattern from each VCSEL unit through the connections of passive waveguide. Furthermore, it also enhances the coherence between the neighboring VCSEL emitters, minimizing their interference noise which occurs under large signal modulation. This novel 940 nm VCSEL array has good potential to serve as a light source in free-space optical communication.