Thermally induced multi-wavelength filtering in electro-optic long period Ti:LiNbO3 waveguide grating
We have studied thermal effect on filtering feature of electro-optic long period grating (LPG) in Ti-diffused LiNbO3 waveguide, and observed the phenomenon of thermally induced multi-wavelength filtering. At room temperature (20.8 °C), a rejection band due to LPG effect is observed at 1450 nm wavelength regime for a driving voltage of 115 V. As the temperature is increased, the band weakens gradually, and is no longer discernible at 27 °C. Meanwhile, three new dips with similar contrasts and wavelength intervals are resolved at shorter wavelengths 1190, 1265 and 1339 nm. Their contrasts increase with a rise in temperature and have a value of 20 dB at available temperature of 44.5 °C. The positions of these dips change little with the temperature, but red-shift with the increase of driving voltage. These dips are associated with thermally induced multi-mode interference.
This work was supported by the National Natural Science Foundation of China under Project nos. 61875148, 61628501, 51472240, 61377060, 61077039, 50872089, 60577012, and by the Tianjin Science and Technology Commission of China under Project no. 16JCZDJC37400.
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