Photorefractive planar waveguides in BaTiO₃ fabricated by ion-beam implantation

For the first time to our knowledge, photorefractive properties have been observed in planar waveguides fabricated by the technique of ion-beam implantation in BaTiO3 single crystals. The implantation was carried out by using 1.5 MeV H+ ions at a dose of 10-16 ions/cm2. For a given input power, a decrease in the effective photo-refractive two-beam coupling response time of ≥102 has been observed, owing to a combination of optical confinement within the waveguide and possible modification of charge-transport properties induced through implantation. Experiments carried out on the two-beam coupling gain show that the gain direction has been reversed in the waveguide compared with that of the bulk crystal

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

Investigation of photorefractive waveguides fabricated by excimer laser ablation and ion-implantation

The fabrication of thin films optical waveguides of photorefractive materials is particularly desirable for applications in integrated optics. It is also of interest because the guided-wave intensity-length product can be considerably larger than in bulk media because of the optical confinement within the waveguide. The increased intensity-length product may therefore allow much faster response times than in the bulk (typically by a factor of ~ 103 - 104. Thin crystalline films can be fabricated by a variety of techniques such as RF sputtering, flash evaporation, molecular beam epitaxy and liquid phase epitaxy. However, the films grown are often of the incorrect (or variable) composition and phase and are rarely of good optical quality. We discuss here two methods that we have investigated for producing optical waveguides in several different photorefractive materials

Pulsed-laser deposition of Ga-La-S chalcogenide glass films for optical waveguide applications

Thin films of Ga-La-S chalcogenide glass have been ablatively deposited onto a range of substrates, including CaF2, and microscope cover slips. The resultant films are deficient in their sulphur composition by approximately 25%, when compared to the bulk targets used, but the interesting chalcogenide photostructural effects are not compromised by this deficiency. Experiments so far have established that photorefractive effects, such as photodoping, photobleaching and grating formation. all occur readily in the thin films, and gratings have been written using laser and e-beam addressing, to create diffractive structures for optical waveguide applications

Optical phase conjugation in photorefractive waveguides

Self-pumped and mutually-pumped phase conjugator configurations have been demonstrated in a planar waveguide in BaTiO3, fabricated by the technique of ion implantation. For equal input powers a two order of magnitude decrease in response time is observed in the waveguide as compared to the bulk

Photorefractive properties of ion-implanted waveguides in BaTiO₃

Optical confinement within a planar waveguide structure in BaTiO3 produces significant decreases in the response times of two-wave mixing, self-pumped and mutually-pumped phase conjugation