Enhancement of nonlinear Raman-Nath diffraction in two-dimensional optical superlattice.
We study second harmonic generation via nonlinear Raman-Nath diffraction in an optical superlattice that maintains a periodic modulation of the second-order nonlinear coefficient χ((2)) in transverse direction but undergoes random modulation in longitudinal direction. We show that the random χ((2)) modulation offers a continuous set of reciprocal lattice vectors to compensate for the phase mismatch of nonlinear Raman-Nath diffraction in the longitudinal direction, leading to more efficient harmonic generation for a wide range of wavelengths. We also characterize the intensity dependence of nonlinear Raman-Nath diffraction on the degree of randomness of the optical supperlattice.
Key Lab of Advanced Transducers and Intelligent Control System of Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, China. joywwj@gmail.com
Wenjie
W
Wang
Yan
Y
Sheng
Vito
V
Roppo
Zhihui
Z
Chen
Xiaoying
X
Niu
Wieslaw
W
Krolikowski