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Depolarization of the fluorescence excited at 1492, 1526, and 1568nm in EDF with concentrations 600-5600ppm proved to be in good qualitative agreement with earlier reported reduction in population gratings recorded via saturation of absorption.

Amplitudes of dynamic phase gratings in rare-earth (Er, Yb) doped fibers are compared with spatially uniform photo-induced refractive index change and are found to demonstrate similar disagreement with theoretical estimate as the amplitude population gratings.

Application of two waves mixing via dynamic population gratings in Yb-doped fibers with saturable absorption at 1064 nm for detecting laser induced ultrasonic signals in the linear configuration of an adaptive interferometric vibrometer is reported.

High sensitivity recording of population gratings in Yb-doped fiber at typical pumping wavelength ??976nm is reported. Effective mixed (amplitude and phase) dynamic gratings with formation times below 1ms were recorded at sub-mW CW power level.

We report a controllable delay of the probe light pulse sequence by a master, saturating pulses of significantly different wavelength (at 1526 and 1568 nm respectively) observed in erbium-doped single-mode fiber with saturable absorption.

Dynamic gratings in rare-earth-doped fibers are recorded via local saturation of optical absorption/gain in bright fringes of the interference pattern. Their principal properties and applications in tunable filters, fiber lasers, and adaptive interferometry are discussed.

Transient two-wave mixing in Er-doped optical fibers with saturable absorption was shown to be nearly two times more efficient in linear interferometric configuration with significantly different powers of recording waves than in symmetric recording arrangement.

Dynamic Bragg gratings can be recorded in Er-doped fibers via spatial hole burning in optical absorption or gain. We present results on optimization of the grating formation taking into account both incoherent optical saturation of the fiber by two recording beams and their coherent two-wave coupling at the recorded grating.

Earlier we investigated the non-steady-state photo-EMF effect in PVK-based photorefractive polymer films in the conventional transmittance tilted configuration [1]. Here we apply this effect and dynamic TWM for the characterization of reflectance gratings in similar polymer films. Note that both experimental configurations utilize periodically phase-modulated recording beams and allow us to probe shifted and unshifted components of the space charge grating (by detecting fundamental and second harmonics (SH) in the output signals).

Green region of spectrum is one of most promising for interferometric applications since the sensitivity grows with reduction of wavelength, and powerful CW lasers are commercially available now. Photorefractive Bi12SiO20 (BSO) crystal is the most sensitive one in this spectral region, which makes it attractive for adaptive detection of laser ultrasonic via two-wave mixing (TWM). We report basic dependencies of TWM of phase modulated beams in this PRC in its conventional holographic (110) cut (in particular on external dc field, input light polarization etc.). Since the amplitude noise of laser is usually dominating, the sensitivity of the whole system can be essentially increased using anisotropic (i.e. with polarization plane rotation) light diffraction in BSO.

The relatively high (typically several MΩ) resistance of conventional GaAs photo-EMF detectors is one of the most important disadvantages of these devices, especially for laser ultrasonic detection. Indeed, to ensure the 10-30 MHz frequency band necessary for this application, one has to use feedback resistors in the input transimpedance amplifier of values less than 10 kΩ. This is clearly very far from optimal matching conditions, and the input noise of the bipolar-input operational amplifier (≈ 1 pA/Hz) proves to be dominating. Improving the current responsivity of the photodetector is of a vital importance in this situation. This can be done, in particular, in longitudinal configuration of the photodetector, or by using planar asymmetric interdigitated system of electrodes.