Nonlinear Raman–Nath diffraction of femtosecond laser pulses

Abstract

We study the nonlinear Raman-Nath diffraction (NRND) of femtosecond laser pulses in a 1D periodic nonlinear photonic structure. The calculated second-harmonic spectra represent frequency combs for different orders of transverse phase matching. These frequency combs are in close analogy with the well-known spectral Maker fringes observed in single crystals. The spectral intensity of the second harmonic experiences a redshift with a propagation angle, which is opposite the case of Čerenkov nonlinear diffraction. We analyze how NRND is affected by the group-velocity mismatch between fundamental and second-harmonic pulses and by the parameters of the structure. Our experimental results prove the theoretical predictions.

Multiple quasi-phase-matching in nonlinear Raman–Nath diffraction

“…Nonlinear Raman-Nath diffraction (NRND) is the most exciting nonlinear optical phenomenon to occur in periodic nonlinear photonic lattices [1][2][3][4][5][6]. This phenomenon appears as multiple second harmonic beams generated at small angles with respect to the incoming fundamental frequency (FF) beam, which is defined by the lattice periodicity [2].…”

Infrared supercontinuum frequency doubling via nonlinear Raman-Nath and Cerenkov scattering processes

“…4 shows also a far more interestingly SH diffraction patterns obtained due to the one-dimensional quadratic square grating, along the x coordinate. The diffraction patterns can be explained by the Raman-Nath [23][24][25][26] and the Cerenkov [27,28] phase matching conditions. In the Raman-Nath case, also known as transverse QPM, the phase matching condition for the m-th diffraction order is defined by the relation…”

Theory of second-harmonic generation in a chirped 2D nonlinear optical superlattice under nonlinear Raman-Nath diffraction

“…The most promising phenomenon, which can be used for these proposes, is nonlinear Raman-Nath diffraction (NRND) in onedimensional nonlinear optical superlattices (NLOSs) [1][2][3][4][5][6]. The main advantage of this phenomenon is the ability to emit multiple second harmonic (SH) beams at characteristic angles relative to the incoming fundamental frequency (FF) beam.…”