Abstract
We report on fabrication of high-Q lithium niobate (LN) whispering-gallery-mode (WGM) microresonators suspended on silica pedestals by femtosecond laser direct writing followed by focused ion beam (FIB) milling. The micrometer-scale (diameter ~82 μm) LN resonator possesses a Q factor of ~2.5 × 105 around 1550 nm wavelength. The combination of femtosecond laser direct writing with FIB enables high-efficiency, high-precision nanofabrication of high-Q crystalline microresonators.
Highlights
We report on fabrication of high-Q lithium niobate (LN) whispering-gallery-mode (WGM) microresonators suspended on silica pedestals by femtosecond laser direct writing followed by focused ion beam (FIB) milling
A variety of semiconductor and silica WGM microresonators have been fabricated based on semiconductor lithography approach, in which either second (x(2)) or third order (x(3)) nonlinear optical process have been demonstrated with pronounced conversion efficiency[7,8,9,10]
Owing to the technical difficulties related to the material growth and the lithographic fabrication on LN substrate, high-Q LN resonators are typically realized using mechanical polishing whose sizes are limited to millimeter-scale[15]
Summary
It should be noted that the FIB process frequently induces the creation of lattice defects (i.e., vacancies and atomic nuclei), leading to the formation of amorphous material due to keV ion beam side dose or lateral ion straggle at the periphery of the microresonator. The transmitted spectrum measured from the output end of the fiber taper showed a series of sharp dips at the WGM resonant wavelengths We envisage that our technique can be extended for fabricating highQ on-chip microresonators on various types of dielectric materials
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