3D integrated 45 W peak power 2D addressable VCSEL array and laser driver for true solid-state LiDAR

Abstract

We fabricated a high output power large-scale 2D addressable VCSEL array and demonstrated a small footprint transmitter (Tx) module for true solid-state LiDAR. The module integrated VCSEL array and laser diode driver built-in circuit board in three dimensions. Each used VCSEL had five junctions, large optical aperture, and bump for individual driving. The wavelength of light output through a substrate was 940 nm. VCSELs were arranged in 48×48 matrix wherein 2,304 emitters can be individually driven. The array chip was assembled on the circuit board by flip-chip bonding via bump. All VCSELs were connected to the driver with very short current path caused by the three-dimensional integration. Short current path and small current loop resulted in small resistance and inductance, which facilitated driving of VCSELs with short current pulse. The transmitter module can generate high peak power with short pulse duration for time-of-flight measurement without RF input. Each VCSEL can be sequentially driven by trigger pulse input. The footprint of the module was 17.3 mm square. We confirmed that all VCSELs emit with sequential driving mode; the peak output power was over 45 W and pulse width was approximately 4 ns. The pulse shapes and widths were nearly identical at the center and edge of the array, which is generally unusual for a Tx module with two-dimensional integration where VCSEL and laser driver are integrated side by side. The divergence of output was less than 10 °.

3D integrated 2D addressable VCSEL array with highly uniform short pulse characteristics

“…Compared to other donors generally used for GaAs, tellurium can be added to GaAs while maintaining the activation rate up to a high concentration, which enables the reduction of the voltage drop in the TJ. For comparison, we have also included the measurement results of the device from the generation we reported last year 5 . The measurements were conducted at 25 degrees.…”

“…Please note that the shape of the temperature dependence is slightly different because last year's report was based on measurements with a fixed current, while this report presents results from measurements with a fixed voltage. Figure 6 summarizes the changes from Photonics West 2023 paper 5 for the Tx module we are reporting this time. Although improvements have been made in many items, the changes will be described below.…”

“…Fig.5(b) displays the result of the VL evaluation. For comparison, we have also included the measurement results of the device from the generation we reported last year5 . The measurements were conducted at 25 degrees.…”