Optical manipulation of guided mode resonance in azo-copolyme waveguide gratings

Optical tuning of guided mode resonance (GMR) is demonstrated in an azo-copolymer waveguide grating structure (WGS), comprised of a one-dimensional holographic surface relief grating inscribed on top of an azo-copolymer planar waveguide layer. The resonance wavelength of GMR is blue-shifted by pumping the WGS with a linear polarized laser beam at 514 nm as a result of the photoinduced refractive index change in the waveguide layer. The GMR cannot return to its original resonance wavelength just by turning off the pumping beam. To make a full-recovery, the WGS has to be illuminated by the same pumping beam but with an orthogonal polarization.