Narrowband Bragg reflectors in Ti:LiNbO3 optical waveguides

Area of Science:

• Materials Science
• Optoelectronics
• Integrated Optics

Background:

• Titanium-indiffused lithium niobate (Ti:LiNbO3) waveguides are crucial for integrated optics.
• Bragg gratings are used for wavelength-selective optical filtering.
• Amorphous silicon is a viable material for fabricating optical components.

Purpose of the Study:

• To integrate amorphous silicon Bragg gratings with Ti:LiNbO3 waveguides.
• To achieve narrow reflectance spectra and significant transmittance dips.
• To investigate the impact of grating depth on optical performance.

Main Methods:

• Fabrication of Bragg gratings etched in amorphous silicon overlay films.
• Integration of gratings with Ti:LiNbO3 optical waveguides.
• Characterization of reflectance and transmittance spectra at 1542.7 nm for TE polarization.
• Modeling of contradirectional coupling including attenuation coefficients to determine grating parameters.

Main Results:

• Achieved a narrow reflectance spectrum of 0.05 nm.
• Obtained a > 20 dB dip in the transmittance spectrum.
• Demonstrated strong dependence of reflectance on etched grating depth (approx. 93 nm).
• Determined coupling constants and attenuation constants from spectral data.

Conclusions:

• The integrated amorphous silicon Bragg gratings effectively function as narrow-band reflectors.
• The corrugated silicon overlay increases insertion loss by ~2.7 dB, independent of grating depth.
• This integration offers a promising approach for advanced optical filtering in Ti:LiNbO3 devices.