Research On Optical Filter Based On Compact Traveling Wave-like Fabry-perot Resonator

High density integration and wavelength division multiplexing(WDM)have the advantages of low cost and high efficiency.Optical filters are key components of WDM,they are the basic components for optical switches,optical modulators,and photodetectors.The optical resonators based on the multi-mode photonic crystal nanobeam cavities have the characteristics of small size and low loss,and is suitable for optical filters with compact structure and high Quality factor(high-Q).In this thesis,a compact and high-Q add-drop filter and an all-pass filter based on traveling wave-like Fabry–Pérot resonators are designed and fabricated by optimizing the grating strength of the multimode photonic crystal nanobeam.The main research contents include the following aspects:(1)Aiming at the shortcomings of multi-mode photonic crystal nanobeams with many periods to achieve high efficiency conversion,a rectangular hole structured photonic crystal nanobeam is designed and optimized to obtain a high grating coupling coefficient,a mode conversion efficiency from the fundamental mode to the second-order mode of 99%is achieved with only 20 periods.The size of the device is effectively reduced,and it is conducive to reducing the intra-cavity loss of the Fabry-Perot cavity and improving the quality factor.(2)The response of the traveling wave resonance filter was obtained by optimizing multimode photonic crystal nanobeam cavity.The cavity size of the fabricated add-drop filter is only 23.5×1.1?m~2.Experimental results show the drop port yields a quality-factor(Q-factor)of 3233,3-d B line width is 0.48 nm and an insertion loss is less than 1 d B at 1552 nm.In addition,it shows an extinction ratio of 13.2 d B at through port,and the suppression of 20.2 d B.According to the fitting result,The reflectivity of the multimode photonic crystal nanobeam is about 99.1%.(3)An all-pass filter based on the traveling wave-like Fabry–Pérot resonator is fabricated.The footprint of the cavity is only 22.7×1.1?m~2.Experiment results show a Q-factor up to 10424 and an extinction ratio of 14.6 d B.According to the fitting result,the reflectivity of the multimode photonic crystal nanobeam is about 99.3%.The Fabry–Pérot cavity with compact structure and high Q-factor has a good application prospect in the fields of modulators,optical switches,sensors and other fields.