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Technical Paper: High performance semiconductor optical amplifier and array for FMCW LiDAR in high-speed autonomous vehicles
Abstract
Semiconductor optical amplifier (SOA) has drawn much attention due to its critical need in coherent detection scheme such as FMCW (frequency-modulated continuous-wave) in automotive LiDAR (Light Detection and Ranging). Coherent detection provides more features than ToF (Time of Flight) such as speed and direction for autonomous vehicles. Instead of a bulky and expensive fiber laser, a coherent laser source with high gain SOA can achieve small form factor with Si PIC (Photonic Integrated Circuit). Here we present a proprietary SOA structure based on AlInGaAs material system with multiple quantum wells on InP substrate. The SOAs with curved and tilted straight waveguides were developed and tested. The saturated output power of such SOA at 1550nm and 1310nm can reach higher than 350mW and 450mW with high wallplug efficiency. The small signal gain exceeds 40dB for both 1310nm and 1550nm. The low anti-reflection (AR) coating can achieve 0.01% reflectivity, and the noise figure and near-field mode fields of various SOA configurations are presented and compared. An array of four SOA waveguides at 127um or 500um pitch can deliver total output power over 2 Watts with proper heat sinking. SOA arrays can also be processed as individually addressable with electrical and optical isolations. Such high-performance SOA array offers the design freedom to LiDAR systems with various scanning strategies such that long range detection can be realized. Gain chip, RSOA (Reflective SOA) based on the curved waveguide for external cavity laser configurations is tested and discussed. Self-alignment features can be built onto the SOA chipset to achieve integration of Si PIC for minimal footprint and low-cost mass production.
Technical Paper: Eye-safe high-reliability triple junction laser diode for long-range rangefinder and LiDAR
Abstract
We have developed a proprietary Triple Junction laser diode at eye-safe 1550nm based on AlInGaAs/InP material systems for LiDAR and laser range finding applications. Three monolithic laser structures with tunnel junction layers are designed to reduce mechanical stress with superior heat dissipation. It achieves 3x output power and 2x wall plug efficiency of a single junction with low operating voltage and high slope efficiency at 1W/A. A 1550nmTriple Junction laser diode allows a LiDAR or laser rangefinder to achieve the longest detection range compared to a single junction or 905nm laser diode. Here we demonstrate the high reliability of Triple Junction high power laser diodes at 1550nm for adoption in various applications. The life test was performed on Triple Junction samples with 95μm aperture and 2.5mm cavity length in a TO9 package. They were driven at average power of 700mW in pulse width of 100 μsec and 10% duty cycle at 60°C. Such stressed electrical and thermal condition is almost 20 times higher than standard operation for automotive LiDAR. We have accumulated over 1000 hours of life test on 17 devices. Based on Arrhenius conditions the estimated MTTF (mean time to failure) is 75k hours at 20°C and 17k hours at 50°C operating temperature, which is respectively 9.3x and 2.5x more than the required 8k hours in automotive applications. We also tested Triple Junction laser diodes up to 100°C and it shows no sign of COD (catastrophic optical damage). Under a high stress CW operating condition at 5W, Triple Junction laser diodes exhibit thermal rollover but return to normal performance under pulsed operation.
SemiNex is more than happy to work with you on the design-in effort or custom design requests to meet the requirements in your integrated LiDAR systems. For inquiries regarding product offerings, custom designs and future projects with SemiNex, as well as scheduling a meeting with us, contact sales@seminex.com or +1-978-326-7703. Details on the Triple Junction laser diodes and SOAs are available at seminex.com/lidar/.
