POLY-SI SIO2 LAMINATED WALK-OFF POLARIZER HAVING A BEAM-SPLITTING ANGLE OF MORE THAN 20-DEGREES/

A spatial walk-off polarizer having a split angle of more than 20 degr ees in both the 1.3 and 1.5 mu m wavelength regions has been fabricate d for the first time, The polarizer consists of alternate laminated la yers of poly-Si and silica. The new polarizer makes the best use of th e characteristics of crystal Si, namely high refractive index, and low absorption coefficients in the longer wavelength regions. A rather si mplified fabrication process that utilizes the RF sputtering method is also proposed, in which only the oxygen-intake valve is used to contr ol the deposition of poly-Si and silica layers from a single-crystal S i target, The fabricated polarizer has beam splitting angles as large as 22 and 21 degrees at wavelengths of 1.30 and 1.55 mu m, respectivel y, being roughly four times larger than those of rutile or calcite.