We propose and demonstrate a simple and reliable method for fabricating high-quality whispering-gallery mode (WGM) optical microresonators in "mid-IR relevant" low-loss ZrF(4)-BaF(2)-LaF(3)-AlF(3)-NaF (ZBLAN) glasses. Intrinsic quality factors of 10(7) have been demonstrated, providing great promise for WGM-based mid-IR (MIR) devices. Absorption-limited Q-factors of over 3×10(8) are anticipated over the 2.0 to 3.2 μm MIR wavelength range in ZBLAN microcavities in the foreseeable future.

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Channeled spectropolarimeters measure the polarization state of light as a function of wavelength. Typically, a channeled spectropolarimeter uses high-order retarders made of uniaxial crystal to amplitude modulate the measured spectrum with the Stokes polarization information. A primary limitation of these instruments is the thermal variability of the retarders, which necessitates frequent system recalibration. Past work has addressed this issue by implementing an athermalized retarder produced from two uniaxial crystals. However, reducing the complexity of an athermalized retarder is advantageous for minimizing size and weight requirements. In this Letter, a technique for producing a thermally stable channeled spectropolarimeter using biaxial retarders is presented. This technique preserves a constant phase over an appreciable temperature range. Proof-of-concept results from a KTP-based athermal partial channeled spectropolarimeter are presented from 500 to 750 nm for temperature changes up to 26°C. Spectropolarimetric reconstructions produced from this system vary by <=2.6% RMS when the retarder experiences a 13°C increase in temperature above 21°C ambient, <=5.2% for a 20°C increase, and <=6.7% for a 26°C increase.

Channeled spectropolarimetry can measure the complete polarization state of light as a function of wavelength. Typically, a channeled spectropolarimeter uses high order retarders made of uniaxial crystal to amplitude modulate the measured spectrum with the spectrally-dependent Stokes polarization information. A primary limitation of conventional channeled spectropolarimeters is related to the thermal variability of the retarders. Thermal variation often forces frequent system recalibration, particularly for field deployed systems. However, implementing thermally stable retarders, made of biaxial crystal, results in an athermal channeled spectropolarimeter that relieves the need for frequent recalibration. This report presents experimental results for an anthermalized channeled spectropolarimeter prototype produced using potassium titanyl phosphate. The results of this prototype are compared to the current thermal stabilization state of the art. Finally, the application of the technique to the thermal infrared is studied, and the athermalization concept is applied to an infrared imaging spectropolarimeter design.4