Strong guided mode resonant local field enhanced visible harmonic generation in an azo-polymer resonant waveguide grating

• Published in: Optics express Vol. 22; no. 3; pp. 2790 - 2797
• Main Authors: Lin, Jian Hung, Tseng, Chun-Yen, Lee, Ching-Ting, Young, Jeff F, Kan, Hung-Chih, Hsu, Chia Chen
• Format: Journal Article
• Language: English
• Published: United States 10.02.2014
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.22.002790

Guided mode resonance (GMR) enhanced second- and third-harmonic generation (SHG and THG) is demonstrated in an azo-polymer resonant waveguide grating (RWG), comprised of a poled azo-polymer layer on top of a textured SU8 substrate with a thin intervening layer of TiO2. Strong SHG and THG outputs are observed by matching either in-coming fundamental- or out-going harmonic-wavelength to the GMR wavelengths of the azo-polymer RWG. Without the azo-polymer coating, pure TiO2 RWGs, do not generate any detectable SHG using a fundamental beam peak intensity of 2 MW/cm(2). Without the textured TiO2 layer, a planar poled azo-polymer layer results in 3650 times less SHG than the full nonlinear RWG structure under identical excitation conditions. Rigorous coupled-wave analysis calculations confirm that this enhancement of the nonlinear conversion is due to strong local electric fields that are generated at the interfaces of the TiO2 and azo-polymer layers when the RWG is excited at resonant wavelengths associated with both SHG and THG conversion processes.