【摘 要】
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We use the nonlinear coupled-mode theory to theoretically investigate second-harmonic generation[SHG]in subwave-length x-cut and z-cut lithium niobate[LN]thin-film waveguides and derive the analytical formula to calculate SHG efficiency in x-cut and z-cut
【机 构】
：
School of Physics and Optoelectronics,South China University of Technology,Guangzhou 510641,China;Gu
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We use the nonlinear coupled-mode theory to theoretically investigate second-harmonic generation[SHG]in subwave-length x-cut and z-cut lithium niobate[LN]thin-film waveguides and derive the analytical formula to calculate SHG efficiency in x-cut and z-cut LN thin-film waveguides explicitly.Under the scheme of optimal modal phase matching[MPM],two types of LN thin films can achieve highly efficient frequency doubling of a 1064 nm laser with a comparable conversion efficiency due to very consistent modal field distribution of the fundamental wave and second-harmonic wave with efficient overlap between them.Such a robust MPM for high-efficiency SHG in both the subwavelength x-cut and z-cut LN thin-film wave-guides is further confirmed in a broad wavelength range,which might facilitate design and application of micro-nano non-linear optical devices based on the subwavelength LN thin film.
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