Multiple nonlinear Bragg diffraction of femtosecond laser pulses in a ${\chi^{(2)}}$ photonic lattice with hexagonal domains

Abstract

Frequency doubling of femtosecond laser pulses in a two-dimensional rectangular nonlinear photonic lattice with hexagonal domains is studied experimentally and theoretically. The broad fundamental spectrum enables frequency conversion under nonlinear Bragg diffraction for a series of transverse orders at a fixed longitudinal quasi-phase-matching order. The consistent nonstationary theory of frequency doubling of femtosecond laser pulses is developed using the representation based on the reciprocal lattice of the structure. The calculated spatial distribution of the second-harmonic spectral intensity agrees well with the experimental data. Condition for multiple nonlinear Bragg diffraction in 2D nonlinear photonic lattice is offered. The hexagonal shape of domains contributes to multibeam second harmonic excitation. The maximum conversion efficiency for a series of transverse orders in the range from 0.01% to 0.03% is obtained.

Frequency doubling of femtosecond laser pulses in three dimensional nonlinear photonic crystals

“…Theoretical model proposed in [3] is shown to be universal and appropriate for describing second harmonic generation (SHG) of ultrashort radiation in periodic 1D NPC under RNND [8] and CND in random 1D NPCs [9,11]. Then later, theoretical model has been generalized to nonlinear frequency conversion of femtosecond radiation in 2D NPCs [12]. In the work [4], similar model was applied for describing frequency conversion of monochromatic radiation in 2D NPCs, and, then this approach was adopted to utilize third spatial direction [10].…”