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.