We have demonstrated experimentally beam amplification by coupling between the signal beam and the photorefractive surfaces wave in Bi12TiO20 crystal. A gain of 16,000 has been measured, with an output signal-to-noise ratio of >20 for weak input signals.

Amplification of optical signals in Bi(12)TiO(20) crystal by photorefractive surface waves.

An optical amplification system directs a diffraction-limited signal beam through a series of approximately 90° crossings with a number of non-diffraction-limited pump beams in a photorefractive medium All of the beams are s-polarized, resulting in an energy transfer from the pumps to the signal beam while leaving the signal beam diffraction-limited The photorefractive medium is preferably a series of BaTiO 3 :Rh crystals that receive the pump and signal beams through orthogonal faces, with their C-axes at approximately 45° to both beams A binary tree optical distribution network is used to minimize waveguide splits in forming a large number of pump beams The outputs of several amplification modules are combined into a single output beam using adaptive optics, with the outputs from the different modules phase matched to each other by diverting two minor portions of the combined beam, partially overlapping the diverted beams and adjusting the amplification module phases to cancel phase differentials between the overlapped portions Similarly, sets of combined and phase-matched beams can be combined with each other (again using adaptive optics) to generate still higher powers using a super module approach

Hybrid laser power combining and beam cleanup system using nonlinear and adaptive optical wavefront compensation

In this paper we investigate the intrinsic optical bistability (IOB) in a 
ferroelectric (FE) single layer using an alternative analysis. The FE 
material is considered to have an intensity-dependent refractive index where 
the third order nonlinear susceptibility χ(3) acts like Kerr 
coefficient. The nonlinear response of the FE medium is modeled using the 
Landau-Khalatnikov (LK) dynamical equation with the nonlinear anharmonic 
potential obtained from the Landau-Devonshire free energy expressed in terms 
of polarization. Within a single frequency approximation, the 
electromagnetic wave equation is written in terms of the polarization P 
rather than the electric field E as the dependent variable. With the 
application of the nonlinear boundary conditions we have derived expressions 
for both reflectance and transmittance as a function of the electric field 
incident amplitude, polarization and other material parameters. The 
formalism proves to be more suitable for FE materials since most of these 
materials have highly linear and nonlinear coefficients especially when the 
operating frequency is in the resonance region. The effects of thickness, 
operating frequency and temperature on BaTiO3 single film are 
investigated theoretically. The results presented here agree in principle 
with the recent experimental observations of intrinsic OB in BaTiO3 
monocrystal and other FE photorefractive materials.

Intrinsic optical bistability in Kerr ferroelectric materials

Optical bistability in BaTiO3

Influence of substrate temperature and oxygen pressure on the structural and optical properties of polycrystalline BaTiO3 thin films grown by PLD

We propose a two-wave mixing interaction between a self-bent pump beam and a signal beam in a BaTiO3 crystal. This new configuration exhibits two-wave mixing gain values as high as Gsat = 1.5 × 105, corresponding to an enhancement of 40× in comparison with a conventional two-wave mixing geometry. Application to coherent image amplification with such a high gain combined with a very good signal-to-noise ratio is demonstrated.

J.-P. Huignard

Papers

Very high-gain two-wave mixing in BaTiO 3 with a self-bent pump beam