Role of a localized modulation of χ^(2) in Čerenkov second-harmonic generation in nonlinear bulk medium

Abstract

We study the second-harmonic generation in quadratic nonlinear media with localized spatial modulation of χ((2)) response. We demonstrate that the emission of Čerenkov second-harmonic takes place only when the fundamental beam illuminates the region of χ((2)) variation. This proves that the sharp modulation of the χ((2)) nonlinearity constitutes a sufficient condition for the emission of Čerenkov second harmonic in bulk materials. Our calculations are in excellent agreement with simple analytical approach utilizing the concept of reciprocal vectors representing the Fourier spectrum of the modulation of χ((2)).

Calcium barium niobate as a functional material for broadband optical frequency conversion

“…As a reference we used the same-sized Sr 0.61 Ba 0.39 Nb 2 O 6 (SBN-61) crystal. To visualize ferroelectric domain structures inside these crystals, we employed the so-called Čerenkov SH microscopy technique that is based on a strong emission of the Čerenkov SH signal only when the ferroelectric domain wall is illuminated by a tightly focused infrared fundamental beam [21,22]. Figure 1 shows a typical x-z scan of the antiparallel ferroelectric domains inside the CBN-28 and SBN-61 crystals, respectively.…”

Nonlinear Čerenkov radiation from a single ferroelectric domain wall

“…Here we resolve this issue by studying the Čerenkov second harmonic generation in an optical bulk medium consisting of two semi-infinite regions with different strengths and/or signs of the nonlinearity χ (2) . We reveal that the abrupt change of χ (2) in transverse direction constitutes a sufficient condition for the emission of Čerenkov second harmonic signal [5] as shown in Fig.1 (b). In fact, an individual spatially localized change of χ (2) can provide a continuous set of reciprocal vectors leading to efficient emission.…”

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…”