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Characterization of laser-optical systems packaged for use in harsh environments

The characterization of laser-optical subsystems packaged for survivability in harsh environments is crucial for the development of robust laser-optical firing systems. Previously, custom mounts and bonded optical assemblies were environmentally tested to ensure their survivability1. The results verified the sub-assemblies would enable the design of a laser-optical initiation system that could be fielded for use in extreme conditions. A design package, which utilized the proven opto-mechanical sub-assemblies, was selected. This design was based on past experience and desired performance criteria. The packaged laser-optical assembly was tested to the same environmental levels as the sub-assemblies. This test regiment encompassed the harshest environments currently utilized. Temperature tests were performed ranging from a maximum of +75 degrees C to a minimum of -55 degrees C, allowing for a two hour soak at each temperature set point. Vibration tests were performed to a maximum level of 15.5 grms for forty seconds in each of three critical axes. Shock tests were performed until failure which was an impulse level of 5700 G's with a 1.1 millisecond long pulse. The laser-optical assembly was visually inspected and functionally tested before and after each test to verify survival. As designed, the system was intended to be hermetically sealed via laser welding. Therefore the visual inspection of the interior was performed post mortem. Experimental results obtained from the environmental tests will be discussed as will their impact on future packaging strategies.