High-brightness and high-speed vertical-cavity surface-emitting laser arrays

Abstract

High-power vertical-cavity surface-emitting laser (VCSEL) arrays, which can serve as the light source in modern 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 desirable. 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 ( ∼ 14 ∘ at 1 / e 2 ) under maximum output power, and a fast rise time ( < 100 p s ). These results open up new possibilities for further enhancing the performance of ToF sensing systems at the 940 nm wavelength.