Performance study of a GaAs based laser diode chip in a condensing environment

This paper presents a performance study done on semiconductor laser diodes in a moisture condensing environment. Devices with laser diodes are used in a wide variety of electronic applications and in various climatic conditions. The motivation behind this study is a common environmental exposure, where a device using a laser diode is brought into a relatively humid environment (a building) from a cold, outside environment. Under such conditions, condensation occurs on various components of the device, including the diode, and could affect the laser output power. Reliability of the device is a critical concern since the laser diode and the lens are susceptible to failure due to such repetitive condensation conditions. The test vehicle chosen for this study was a 980nm laser diode. These are used in products for a broad range of markets, including data communications, aerospace, material processing, scientific and defense industries [1-3]. These products may be used in environmental conditions that could result in condensation within the product. A hermetic package could address this concern, but it is an expensive option. Non-hermetic packaging for the laser component could help lower the cost of these devices; however reliability is a potential concern. Prior research on laser diodes consists of various reliability measurements on 980nm lasers using stress tests (e.g. accelerated aging tests; thermal cycling tests) [3-6]. Reliability analysis of laser diodes specifically addressing condensation measurements has not been previously reported. A Military Standard Specification [MIL-STD-883E Method 1004.7] titled, 'Moisture resistance test' was used to conduct this reliability study [10]. An experimental setup was designed and fabricated. A photonic package with a 980nm laser diode was subjected to repetitive condensing cycles and laser output power was recorded as a function of time, temperature and humidity. The variation in laser output power due to condensation was observed and quantified. The focus of this paper is on performance degradation of the laser diode. The possible mechanisms for this degradation are currently being investigated.