Single‐Mode, High‐Brightness, and High‐Speed VCSEL Arrays

Abstract

AbstractOptical sources such as high‐brightness and high‐speed vertical‐cavity surface‐emitting laser (VCSEL) arrays are preferred for a variety of applications such as, LiDAR, 3‐D sensing, and free‐space optical communication (FSC). However, further improvement in depth of resolution and ranging distance for these time‐of‐flight (ToF)‐driven systems can be accomplished by using VCSEL arrays having high brightness (large output power and narrow divergence angle) and faster response time. However, to increase the output power of these VCSEL arrays to watt level, several light emission apertures (several hundreds) need to be connected in parallel, which results in large parasitic capacitance. Hence, RC‐limited bandwidth becomes an influential aspect that restricts the speed of these high‐power VCSEL arrays. In this review article, we discuss recent progresses in high‐power VCSEL arrays and our own achievements in this field. By using tensile strain (induced by electroplated copper substrate) and Zn‐diffusion technique, we elaborate our previous work in which we successfully demonstrated a novel VCSEL array having high power (3 W), highly single mode (SM), high brightness (1 e−2divergence angle, ∼10°), and single‐polarized output performance without increasing threshold current (Ith) and intra‐cavity loss. Furthermore, thanks to the oxide‐relief process, which has tendency to decrease the parasitic capacitance that leads to rise time of demonstrated VCSEL array as short as around 100 ps. This number is around ten times shorter than that of commercially available VCSEL arrays with the same output power level (∼3 W) at the same wavelength (∼940 nm).