Advanced liquid crystalline electrooptical transducers for low-loss laser beam modulation

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Wiktor Piecek, Zbigniew Raszewski and Przemysław Kula
Military University of Technology, Warsaw, Poland

Abstract:

Two nematic liquid crystalline mixtures IRN1 and IRN2, dedicated to advanced electro-optical transducers were developed at the MUT. The IRN1 is an innovative, highly birefringent LC mixture working at VIS and NIR bands. The second LC mixture IRN2 is prepared for working at MWIR range. To obtain IRN2 with low absorption at the edge of MWIR one replaced hydrogen atoms in molecules of IRN1 with heavier ones, preferably with deuterium. To satisfy the requirement for low reflection the components of IRN1 were further selected to reduce the formation of light scattering smectic-like agglomerates.    

Ordinary and extraordinary refractive indices of IRN1 and IRN2 in full spectrum range were measured by custom-developed interference method using special “IR cells” with dielectric mirrors. To increase the transmission T of index-matched LC to the level above 97.5% all interfaces of electrooptical transducers were designed as a stack of functional, optically matched layers. The final parameters of prepared electrooptical transducers (reaching an edge of LC technology) and selected applications of developed technology will be presented and discussed. LC mixture IRN1 was used for fabrication of electro-optical transducers dedicated to laser rangefinders for 3D or 5D laser metrology, dense plasma diagnostics and spaceborne laser rangefinder of a landing unit. The second LC mixture IRN2 is prepared for the human breath analyzer where LC shutter works at MWIR range.