A nonlinear theory is presented for the formation of hexagonal optical structures in a photorefractive medium equipped with a feedback mirror. Oppositely directed beams in photorefractive crystals are unstable against the excitation of sideband waves. It is shown here that as this instability evolves to its nonlinear stage, the three-wave interaction between weak sideband beams does not stabili...

The connection between noncentrosymmetric materials’ structure, electronic structure, and bulk photovoltaic performance remains not well understood. In particular, it is still unclear which photovoltaic (PV) mechanisms are relevant for the recently demonstrated visible-light ferroelectric photovoltaic (K,Ba)(Ni,Nb)O3−δ . In this paper, we study the bulk photovoltaic effect (BPVE) of (K,Ba)(Ni,N...

Hybrid semiconductor pixel detectors are being investigated as imaging devices for radiography and synchrotron radiation beam applications. Based on previous work in the CERN RD19 and the UK IMPACT collaborations, a photon counting GaAs pixel detector (PCD) has been used in an X-ray powder diffraction experiment. The device consists of a 200 mm thick SI-LEC GaAs detector patterned in a 64 64 ar...

We report measurements of thermal self-locking of a Fabry–Perot cavity containing a potassium niobate (KNbO3) crystal. We develop a method to determine linear and nonlinear optical absorption coefficients in intracavity crystals by detailed analysis of the transmission line shapes. These line shapes are typical of optical bistability in thermally loaded cavities. For our crystal we determine th...

We report theoretical and experimental evidence for transverse modulational instability of two counterpropagating beams in a photorefractive medium with no external feedback. A frequency detuning is applied to one of the beams in order to drive the system to instability. We perform a linear-stability analysis that allows for detuning of the counterpropagating pump beams in addition to an additi...

We describe a near-IR two-stage noncollinear optical parametric amplifier (NOPA) pumped at 800 nm that employs bulk congruent lithium niobate [LiNbO3 (c-LNB)] and bulk potassium niobate [KNbO3 (KNB)] crystals. Noncollinear phase matching in these materials allows for generation of pulses as broad as 2900 cm−1 (∼78 THz) centered in the near-IR at ∼1300 nm. In the particular geometry described he...

BACKGROUND Harmonic Nanoparticles are a new family of exogenous markers for multiphoton imaging exerting optical contrast by second harmonic (SH) generation. In this tutorial, we present the application of Hyper-Rayleigh Scattering (HRS) for a quantitative assessment of the nonlinear optical properties of these particles and discuss the underlying theory and some crucial experimental aspects. ...