Oxide crystals for electro-optic Q-switching of lasers

Abstract

A new generation of oxide crystals is emerging for electro-optic Q -switching or control of highpower pulsed lasers. Unlike the acousto-optic Q -switches in which the total turn-off time is limited by the duration of sound wave propagation (110-220 ns/mm) across the beam diameter, the electro-optic devices provide a short (<10 ns) response needed for minimum losses. Extinction ratios of better than 100 : 1 for electro-optic crystals ensure their reliable hold-off. By contrast, acousto-optic devices are characterized by single-pass dynamic losses of approximately 40%, which hinders their use in high-gain lasers. The basic principles of electro-optic Pockels cells are discussed. The performance characteristics of Q -switching for traditional electrooptic materials [deuterated potassium dihydrogen phosphate (DKDP), lithium niobate (LNB)] and other new electro-optic crystals, such as barium metaborate (BBO) and crystals belonging to the langasite (LGS) and potassium titanyl phosphate (KTP) families, are reviewed comparatively. Particular emphasis is placed on KTPtype electro-optic crystals, primarily on rubidium titanyl phosphate RbTiOPO 4 (RTP), which stand out in their ability to provide Q -switching at extremely high frequencies or repetition rates up to 200 kHz. The use of both X -and Y -oriented double crystals as Q -switches in order to combine large electro-optic coefficients and low quarter-wave hold-off voltages with excellent thermal stability of the device is considered.

Growth of large size high optical quality KTP-type crystals

“…large EO coefficients, high electrical resistivity and lack of piezoelectric ringing, and they are becoming the most promising material for high repetition rate electro-optic amplitude and phase modulation, Q-switching, filtering, etc. [11][12][13][14]. Growth of large and high optical quality KTP family crystals is, therefore, of high technological significance.…”

Ultra-high contrast retinal display system for single photoreceptor psychophysics

“…model EO-AM-NR-C4, Thorlabs GmbH, Dachau, Germany) or pockels cells (e.g. model EO-PC-550, Thorlabs), but both options have lower contrast ratios when compared to AOMs (EO-AM: 1:10 1 , EO-PC: 1:10 2.4 ) [26]. As exemplified in the current study, an SLO-based display with AOM cascading can produce spatially resolved stimuli with visual contrast ratios up to 1:10 10 .…”

Growth of high resistivity RbTiOPO4 crystals

“…The overall result is that very low conductivity RTP crystals can be grown from the modified self-flux. This implies that high voltages can be applied to such RTP crystals at low leakage currents, which is extremely essential for the development of large aperture RTP electro-optic Q-switches [3,12].…”

“…Tangibly higher Curie temperatures, implying better rubidium stoichiometry, are obtained with rubidium phosphate solvents of larger [Rb]/[P] ratios, such as Rb 4 P 2 O 7 , especially for growth on [1 0 0]-oriented seeds [7]. Accidentally, [0 0 1]-cut RTP crystals are known as the best choice for fabrication of large aperture electro-optic devices [3,12].…”