Photoacoustic absorption spectrometer for highly transparent dielectrics with parts-per-million sensitivity.

A sensitive photoacoustic absorption spectrometer for highly transparent solids has been built and tested. As the light source an optical parametrical oscillator pumped by a nanosecond pulse laser with 10 Hz repetition rate is employed, covering the complete wavelength range from 407 to 2600 nm. A second-harmonic-generation unit extends the range of accessible wavelengths down to 212 nm.

Highly tunable low-threshold optical parametric oscillation in radially poled whispering gallery resonators.

Whispering-gallery resonators (WGR's), based on total internal reflection, possess high quality factors in a broad spectral range. Thus, nonlinear-optical processes in such cavities are ideally suited for the generation of broadband or tunable electromagnetic radiation. Experimentally and theoretically, we investigate the tunability of optical parametric oscillation in a radially structured WGR made of lithium niobate.

Kinetics of photorefractive recording for circular light beams.

We show, theoretically and experimentally, that the buildup of the space-charge field in photorefractive crystals is far from monoexponential for circular light beams. This is a general property of the two-dimensional (2D) case, in contrast to the one-dimensional case. The results form a basis for determination of the photoelectric parameters of photorefractive crystals within a wide intensity range, which is important, e.

Fabrication and characterization of whispering-gallery-mode resonators made of polymers.

High-quality whispering-gallery-mode resonators made of polymethylmethacrylate (PMMA) are fabricated by simple mechanical turning and polishing according to a technique used by Ilchenko et al. to produce crystalline whispering-gallery-mode resonators with high quality factors (Q-factors). The high-Q PMMA resonators are investigated in two wavelength regimes: in the near infrared between the wavelengths 1470 and 1580 nm and at the wavelength 635 nm.

Ultraslow shock waves of electron density in LiNbO3 crystals.

We show, experimentally and theoretically, that the application of modest voltages, U0=(0.1-1) kV, to LiNbO3ratioFe crystals at sufficiently high temperatures, T approximately (550-700) degrees C, leads to the formation of ultraslow shock waves (moving discontinuities) of the electron density owing to the removal of electrons from Fe2+ centers. Behind the sharp wave front, almost all iron centers are in the Fe3+ state, the sample is optically transparent, and its transport properties are strongly modified.