Polarization beam combining by fused silica subwavelength grating

Abstract

The fused silica subwavelength grating is applied to the combination of orthogonally polarized beams, of which wavelength tunability and robustness of geometric deviation is numerically investigated by combining efficiency based on the modal method. The experimental beam combining efficiencies of fabricated fused silica subwavelength gratings applied at 532 nm, 832 nm, and 1064 nm, respectively, are 82.9%, 80.3% and 86.6% for continuous-wave lasers without anti-reflection coatings. The experimental output combined from two 6J, 10ns, 1064 nm pulse lasers is 9.67J by fabricated 4-inch-wafer fused silica subwavelength grating with laser-induced damage threshold measured up to 26.4J/cm2. The polarization beam combining method by the subwavelength grating is applicable not only in the combination of diode laser arrays as pumping source but also in the power enhancement of bulky laser systems in fields such as laser cleaning, laser cutting and laser shock peening.