THERMAL FIXING OF HOLOGRAPHIC GRATINGS IN PLANAR LINBO3-TI-FE WAVE-GUIDES

Refractive index gratings in planar LiNbO3:Ti:Fe waveguides are therma lly fixed during hologram recording at elevated temperatures. Differen t guides are fabricated by titanium indiffusion using iron-doped and n ominally pure y-cut LiNbO3 substrates and characterization is performe d by dark-mode spectroscopy. The refractive index modulation of gratin gs written and simultaneously fixed at 180 degrees C is investigated a s a function of propagation depth, titanium and iron concentration. Th e experimental results are compared with those obtained for unfixed ho lograms recorded at room temperature.