Abstract
Lithium niobate (LN) microdisk resonators on a LN-silica-LN chip were fabricated using only conventional semiconductor fabrication processes. The quality factor of the LN resonator with a 39.6-μm radius and a 0.5-μm thickness is up to 1.19 × 10(6), which doubles the record of the quality factor 4.84 × 10(5) of LN resonators produced by microfabrication methods allowing batch production. Electro-optic modulation with an effective resonance-frequency tuning rate of 3.0 GHz/V was demonstrated in the fabricated LN microdisk resonator.
Highlights
Lithium niobate (LN) is referred to as photonic silicon for its extraordinary electro-optic (r33 = 30.9 pm/V), nonlinear optical (d33 =41.7 pm/V), and acousto-optic effects in a wide wavelength band ranging from 0.35 μm to 5 μm [1]
Tunable nonlinear optical devices that operate with remarkably low turn-on powers down to mW were successfully demonstrated in millimeter-size LN whispering gallery mode (WGM) resonators with Q factor on the order of 107 fabricated by traditional optical fabrication techniques such as cutting and polishing [2,3,4,5,6,7]
The ordinary and extraordinary refractive indices of LN crystal were set as no = 2.2113 and ne = 2.1377, respectively, and no dispersion was considered because we focused on a narrow wavelength band near 1550 nm
Summary
Lithium niobate (LN) is referred to as photonic silicon for its extraordinary electro-optic (r33 = 30.9 pm/V), nonlinear optical (d33 =41.7 pm/V), and acousto-optic effects in a wide wavelength band ranging from 0.35 μm to 5 μm [1] It is widely used in optical, electro-optic and acoustooptic devices such as electro-optic modulator, wavelength convertor, and surface acoustic wave filter. Tunable filter with wavelength tuning rate of 0.14 GHz/V was realized in a micrometer-size LN ring resonator based on the electro-optic effect of LN crystal [12]. LN WGM resonators on LNOI wafer with micrometer size and Q factor of 105 were made using femtosecond laser micromachining [11], followed by focused ion beam polishing and high temperature annealing, which does not allow batch production. Thanks to extraordinary electrooptic effect of LN crystal, we observed a 3.0-GHz/V tuning rate of the resonance frequency of LN WGM resonators
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