Design and fabrication of highly efficient electrooptic modulators using bragg grating reflectors

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Title: Design and fabrication of highly efficient electrooptic modulators using bragg grating reflectors
Author: Kim, Ryoung-Han
Abstract: Bragg grating reflectors etched in amorphous silicon overlay films have been integrated with Ti :LiNbO3 optical waveguides . With a 12 .5 mm long grating segment and an etch depth of ~ 93 nm in a 105 nm -thick silicon film , a narrow (0 .05 nm ) spectral bandwidth with a record high transmission dip ( > 20 dB ) was achieved at a wavelength of ~1542 nm for TE polarization on an x -cut , y -propagating substrate . The reflectance in the channel waveguides is found to be strongly dependent on the depth of the etched grating . The 3 -dB bandwidth of 0 .05 nm obtained for all tested samples is the smallest reported for waveguides in LiNbO3 . The effect of the Bragg waveguide loss factor on the transmittance and reflectance spectra is investigated using a model for contra -directional coupling that includes an attenuation coefficient . The Bragg grating spectral characteristics are exploited to fabricate distributed Bragg feedback modulators (DBFM ) and Bragg reflector Fabry -Perot modulators (BFPM ) . The sharp cut -off in transmission and reflection spectra , which is an inherent characteristic of Bragg grating , was tuned by applying voltage via the linear electrooptic effect , to produce intensity modulation . The Bragg grating based modulators consume less electric power compared to polarization intensity modulators (PIMs ) . The DBFM demonstrates 1 /1 .6 times the modulating voltage of a PIM with identical waveguide and electrode structure . The BFPM shows 1 /3 .3 times the modulating voltage of the PIM . No difference in the frequency response is observed among the three modulators . Comparison of the modulation sensitivity in the linear region indicates that the Bragg grating based modulators provide better sensitivity than that of the PIM with identical waveguide and electrode structure . These results indicate the potential advantage of the Bragg grating based modulators for enhanced modulation efficiency over conventional modulators . Further improvements can be expected from the optimization of the electrode design .
URI: http : / /hdl .handle .net /1969 .1 /3325
Date: 2006-04-12

Citation

Design and fabrication of highly efficient electrooptic modulators using bragg grating reflectors. Available electronically from http : / /hdl .handle .net /1969 .1 /3325 .

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