Polarization-based, transmissive-reflective beam scanner operating around 1550 nm using off-the-shelf components

Abstract

A novel transmissive-reflective beam scanner operating around 1550 nm wavelength has been demonstrated using two commercial wire grid polarizers (WGPs) with transmission axes offset by 45°, surrounding a latching garnet 45° Faraday rotator. Light in the system undergoes three 45° polarization rotations, resulting in two reflections inside the cavity between the two WGPs before being transmitted by the rear WGP. The two reflections inside the device facilitate beam steering in a transmissive layout (output beam emerging from the opposite side of the input beam). Polarization-resolved individual-component characterizations were performed for several WGPs and for the Faraday rotator to determine optical properties such as transmission efficiency and the polarization purity of the transmitted or reflected beams as a function of incidence angle to the optic, for multiple incident linear polarization states. This allowed us to both select the WGPs best suited to act as polarizing beam splitters in the system and to use the angle-resolved component data to predict the total transmission efficiency of the beam scanner as a function of front polarizer tilt angle (which in our geometry is half of the beam deflection angle). We then compared the predicted scanner efficiency with the measured transmission efficiency of the prototype beam scanner. The scanner maintained a transmission efficiency over 70% for beam deflection angles between ±45° (a 90° symmetric beam scan area) for a vertically oriented incident linear polarization state.