A Study of Radiation-Induced Effects in Photonic Devices: Acoustooptic Modulators and Deflectors

In a preliminary report acoustooptic devices (AODs) were exposed to flash x-ray, linearly accelerated electrons, and gamma ray irradiations to determine their sensitivity to radiation and applicability to space and enhanced radiation environments. This final report is a continuation and finalization of those initial studies and details the findings of a comprehensive investigation of radiation induced effects in Lead Molybdate (PbMoO4), Gallium Phosphide (GaP) , Indium Phosphide (InP), Tellurium Dioxide (TeO2), and Lithium Niobate (LiNbO3) acoustooptic Bragg cell deflectors and modulators. Gamma ray, X-ray, electrons, proton and neutron irradiations were conducted to bound, delineate and differentiate radiation induced changes to operational AO Bragg Cells. The majority of the irradiations were performed in situ, wherein the Bragg cells were fully operational during the radiation exposures. Using this approach, instantaneous changes to Bragg cell parameters such as spatial intensities, deflection angles, bandwidth, material absorption, diffraction efficiency and polarization states were determined. A majority of the radiation induced effects observed were determined to evolve from the heating associated with the interaction of radiation with matter, thus resulting in observable thermooptic effects. The effects of heating in AO Bragg crystals were investigated and confirmed using three independent approaches: traditional broad area source irradiations, ion microbeam irradiations, and irradiation by a CO2 laser. It was concluded that AO Bragg deflectors and modulators are quite insensitive to the long term low dose radiation environments that would be encountered in the natural space environment. However, under pulsed high dose (or high fluence) irradiations, Bragg cell transient responses could result in disruption of normal operations. Providing that adequate thermal control is imAir Force Research Lab Kirtland Afb Nmspace Vehicles Directorate is the author of 'A Study of Radiation-Induced Effects in Photonic Devices: Acoustooptic Modulators and Deflectors' with ISBN 9781423559054 and ISBN 1423559053.