Influence of the Brangg angle on the optimal energy exchange in the course of two-wave mixing in a Bi_12SiO_20 piezoelectric crystal

摘要

The problem of maximising the relative intensity of the signal optical wave in the course of two-wave mixing was solved taking into account the self-diffraction in a Bi~12Sio_20 piezoelectric crystal. The maximisation was carriedout simulaneously with respect to four parameters: the polarisation (Ψ) and orientation (0) angles, the crystal thickness d, and the Bragg angleρ. It was established that there are tow sets of optimal parameters for a Bi~12SiO_20 crystal at the wavelength of 632.8 nm and for a Bi~12SiO_20 crystal at the wavelength of 632.8 nm and for a typical acceptor concentration of 10~22 m~-3:ρ≈11deg,0≈39.1deg, Ψ≈98,85deg, d≈7.11 mm (for the first maximum) and ρ≈11deg, 0≈320.9,Ψ≈54.15deg, d≈7.11 (for the second maximum). The dependences of these optimal parameters on the acceptor concentration in the range 10~21-4 x 10~22 m~-3 were found. The mdoel proposed for two-wave mixing in the special case of a fixed Bragg angle and the constant visibility approximation improved the agreement between the theoretical results and the known experimental data.