P.M. Jeffrey

BaTiO3 waveguide self-pumped phase conjugator

For the first time to our knowledge, self-pumped phase conjugation is reported in a planar waveguide structure in a BaTiO3 single crystal. The waveguide was fabricated by the technique of ion implantation, with 1.5-MeV H+ ions at a dose of 1016 ions/cm2. Phase-conjugate reflectivities >20% have been measured for waveguide self-pumped phase conjugation, and, for a given input power, an order-of-magnitude reduction in the response time is observed in the waveguide compared with the bulk. The fidelity of phase conjugation in the guide is also discussed.

Theoretical analysis of mechanism of photorefractive enhancement of photochromic gratings in BSO

We present the results of theoretical modelling of the increase in diffraction efficiency in photorefractive BSO under conditions of photorefractive enhancement via permanent photochromic gratings. The results are modelled using coupled wave theory, including the anisotropic nature of the secondary refractive index grating, optical activity and electric field induced birefringence. The dependence of the enhancement of the diffraction efficiency as a function of the input polarisation of the diffracted beam. and of the applied electric field is presented for two different crystal geometries.

Mechanism of photorefractive enhancement of photochromic gratings in BSO : experimental results and phenomenological modelling

We report an increase of more than a factor of 100 in the diffraction efficiency from photochromic gratings written in BSO by uniformly illuminating these gratings with 488 nm light to induce secondary photorefractive gratings. Upon application of an electric field, the phase shift between the two gratings can he varied and under appropriate conditions the diffraction efficiency can increase. The dependence of the enhanced diffraction efficiency as a function of the applied electric field and readout beam polarisation was experimentally investigated for two different crystal orientations. Phenomenological modelling is presented requiring modifications to the phase angle between the photochromic and induced photorefractive gratings in order to reproduce the experimentally observed asymmetry in the increase in the diffraction efficiency. This suggests a periodic modulation of the photorefractive donor/acceptor density, due to the presence of the photochromic grating.

Waveguide mutually pumped phase conjugators

The operation of the bridge mutually pumped phase conjugator is reported in a planar waveguide structure in photorefractive BaTiO(3). The waveguide was fabricated by the technique of ion implantation, using 1.5-MeVH(+) ions at a dose of 10(16) ions/cm(2). An order of magnitude decrease in response time is observed in the waveguide as compared with typical values obtained in bulk crystals, probably as a result of a combination of the optical confinement within the waveguide and possible modification of the charge-transport properties induced by the implantation process.