D. Liu, Z. Kuang, W. Perrie, P.J. Scully, A. Baum, S. Liang, A. Taranu,
S.P. Edwardson, E. Fearon, G. Dearden, K.G. Watkins
Spatial light modulator addressed with computer generated holograms is used to diffract femtosecond laser pulses into > 15 parallel beams and focused simultaneously inside poly(methyl methacrylate) (PMMA) for high throughput 3D refractive index modification. Uniform modification throughout the structure is demonstrated and used to create a 19 μm pitch, 5 × 5 × 3.5 mm3thick volume grating in < 50 minutes with first order Bragg diffraction efficiency > 65%. Thick volume phase gratings are created by carefully stitching filamentary modifications. PMMA shows a remarkable time dependent Δn, related to the photochemistry during and after exposure.