Maintaining a stable and high quality laser wavefront is pivotal for efficient laser communications in deep space networks. In this presentation, we describe the design and expected optical and structural performance of the afocal beam expanding telescope for the NASA DSOC mission. This 22 cm aperture, 11x magnification telescope must survive the stresses of launch and maintain alignment through solar illumination, laser irradiance, thermal transients, and temperature extremes during the DSOC mission life from Earth to Mars. Structural-Thermal-OPtical (STOP) analysis predict very stable downlink wavefront error (< 122 nm RMS) and beam divergence (< 14.5 microradians). Furthermore, we present additional telescope link loss contributions that will be minimized through particulate contamination control, high spectral throughput, and polarization purity. Successful performance of this telescope will support NASA’s ongoing efforts to extended high data rate communications into deep space.
Optical refrigeration is currently the only completely solid state cooling method capable of reaching cryogenic temperatures from room temperature. Optical cooling utilizing Yb:YLF as the refrigerant crystal has resulted in temperatures lower than 123K measured via a fluorescence thermometry technique. However, to be useful as a refrigerator this cooling crystal must be attached to a sensor or other payload. The phenomenology behind laser cooling, known as anti-Stokes fluorescence, has a relatively low efficiency which makes the system level optimization and limitation of parasitic losses imperative. We propose a variety of potential designs for a final optical refrigerator, enclosure and thermal link; calculate conductive and radiative losses, and estimate direct fluorescence reabsorption. Our simulated designs show losses between 60 and 255 mW, depending on geometry and enclosure choice, with a lower bound as low as 23 mW.
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