Abstract
We fabricate a long-period grating band-rejection filter with a lithium niobate channel waveguide, where the grating is formed on the waveguide surface by plasma reactive ion etching. The filter shows three distinct thermal tuning regimes. Below , the center wavelength of the rejection band decreases linearly with an increase in the temperature at a high sensitivity . The temperature sensitivity drops abruptly to a negligible value at and stays low up to , above which it jumps abruptly to a large positive value . We attribute these peculiar tuning characteristics to the formation of different crystal phases in the core and cladding areas of the waveguide and the abrupt transitions of the thermo-optic coefficients of some crystal phases. The grating could be developed into various kinds of integrated-optic filters and switches for application in optical signal processing.
© 2010 Optical Society of America
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