Photoconductivity and photovoltaic behaviour of LiNbO3 and LiNbO3 waveguides at high optical intensities

<title>Stability problems of LiNbO<formula><inf><roman>3</roman></inf></formula> waveguide components for interferometric applications in the visible and near-infrared regions</title>

“…objectives (6). The introduction of a prismatic glass plate (5) in front of the input objective ensures the simultaneous excitation of two neighbouring channel waveguides. The output beams of the two waveguides are collimated by a second microscope objective and, after passing the second prismatic glass plate (5), are brought to interference.…”

“…The introduction of a prismatic glass plate (5) in front of the input objective ensures the simultaneous excitation of two neighbouring channel waveguides. The output beams of the two waveguides are collimated by a second microscope objective and, after passing the second prismatic glass plate (5), are brought to interference. Thus, any optical phase change of one of the channel waveguides leads to a shift of the interference pattern, which we registered by a CCD line (4).…”

Photorefractive Waveguides

“…In strongly exchanged waveguides, no light-induced refractive index changes are found [58], and this effect has been attributed to both a large increase of dark and photoconductivity [54], and a strong degradation of the electro-optic properties [43]. Here a conversion of Fe 2þ to Fe 3þ has been found for the proton exchange process [59], which can explain the observed decrease in holographic sensitivity, too.…”

“…Annealing treatment of PE layers with a higher exchange ratio leads to a recovery of the electro-optic coefficients [19,47], while at the same time photoconductivity only slightly decreases [54]. Although the holographic sensitivity of APE samples is thus increased with annealing time, it is still two orders of magnitude lower than for titanium in-diffused samples.…”

“…What is even more difficult is the influence of different light intensities and wavelengths when probing optical damage. In general, steady-state refractive index changes, holographic sensitivity, and photoconductivity depend on light intensity [54,55]. For certain fabrication methods, both dark and photoconductivity of the waveguiding layer are considerably enlarged, and particularly at higher light intensities more than one photorefractive center can be involved in the charge transport [56], thus making the above quantities intensity dependent.…”