Published in: SPIE LASE 2021
Authors: K. Nechay, R. Ulkuniemi, A. Filipchuk, T. Hartikainen, V. Kaivosoja, R. Hietikko, J. Nikkinen, J. Sillanpaa, P. Melanen, V. Vilokkinen, S. Talmila, P. Uusimaa
Vertical-cavity surface-emitting lasers (VCSELs) have just recently started generating a lot of interest as the illumination source in the multitude of commercial applications. VCSELs capability to provide narrow spectrum emission with low temperature sensitivity and high beam quality, coupled with the possibility of nanosecond pulses generation, makes VCSELs an excellent laser platform for the outdoors, high-precision time-of-flight (ToF) and structured light applications. These advantageous features of VCSELs emission arise from their vertical cavity geometry, which also enables possible VCSELs direct integration onto circuitry and allows power scaling by arranging single-emitting VCSELs into compact high-power 2D arrays. These benefits have made VCSEL the current most popular illumination source for the 3D sensing applications both in the consumer market (e.g. proximity sensors for face and gesture recognition) as well as in the industrial sector (e.g. automotive short- to middle-range LiDAR and in-cabin monitoring). We present development results of both high-efficiency VCSEL single-emitters and multi-Watt VCSEL arrays emitting at the 940 nm purposed for 3D sensing applications. The VCSEL development involved optimization of epitaxial design in terms of DBR doping concentrations and the material content of the bottom DBR and oxide layer. While, on the other hand, optimization of the device parameters and processes targeted oxide aperture and mesa diameters, as well as etching depth. Wet thermal oxidation process has been specifically developed to facilitate precise oxidation depth control, run-torun reproducibility, and uniformity on the wafer scale. Successful VCSEL development is attributed to the Modulight’s full-cycle in-house semiconductor fabrication capabilities.