Diffraction efficiency increase by corona discharge in photoinduced surface-relief gratings on an azo polymer film

The diffraction efficiency of a surface;relief grating (SRG) was dramatical ly increased by corona discharge. We fabricated this SRG by applying surfac e modulation to azo polymer films, using laser interference fringes. The el ectric charge was deposited upon the SRG by a corona discharge in an oven. The first-order diffraction efficiency measured before and after corona dis charge above the glass-transition temperature increased from similar to2% t o similar to 40% in a SRG written with a circularly polarized beam. The rel ief depth of the SRG as measured with an atomic-force microscope also incre ased, from similar to 130 nm to similar to 450 nm. The increase in diffract ion efficiency was independent of the writing polarization. (C) 2001 Optica l Society of America OCIS codes: 050.1950, 050.7350; 090.2900, 210.4770, 23 0.1950, 250.2080.