Beam shaping in nonlinear volume holograms via optically engineered ferroelectric domain patterns

Abstract

Efficiency of optical frequency conversion in quadratic media critically depends on spatial modulation of the nonlinear optical response of the materials. This modulation ensures, via the quasi phase matching (QPM), an efficient energy exchange between optical waves at different frequencies. The QPM structures, also known as the nonlinear photonic crystals, offer a variety of novel properties and functionalities that cannot be obtained in uniform nonlinear crystals. In particular the 3-dimensional modulation of nonlinearity allows one to realize the so-called nonlinear volume holograms which extends the concept of volume holography to nonlinear optics. Nonlinear volume hologram represents the 3- dimensional distribution of the nonlinear polarization which arises from interaction between input fundamental beam and generated wave with complex wave front, in medium exhibiting quadratic nonlinearity (χ(2)). When illuminated by fundamental beam, the nonlinear hologram gives rise to a wave at different frequency (e.g. second harmonic of fundamental wave) having complex intensity distribution following the transverse structure of the hologram itself. In this way one can combine generation of waves at new frequencies with simultaneous shaping of their transverse and longitudinal intensity profiles. In this work we present formation of various types of nonlinear volume holograms in ferroelectric crystals by using unique all-optical domain inversion technique and demonstrate their application in optical wave-shaping.