Ultra-High-Q Microresonator
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The ultra-high-Q silica microsphere has enabled many scientific experiments in such fields as CQED and biosensing.  However, it is difficult to fabricate.  By planarizing this stucture on a silicon wafer, this problem has been solved.  In addition, the ultra-high-Q microtoroid confines the degenerate azimuthal modes present in the ultra high Q microsphere. This creates a more regular free spectral range, enabling many new devices.

Using special techniques, free portable UHQ  microtoroids with Q-factors in excess of 10 million have been fabricated.  The toroids can be controllably placed in linear chains, allowing arrays of ultra-high-Q devices to be realized.

By testing in the visible (680nm), the UHQ microtoroid has achieved Qs greater than 100 million in water.  Additionally, detection of concentrations as low as 1ppmv  of D2O in H2O has been demonstrated.

One recently understood feature of the ultra-high-Q microtoroid resonator is the ability to controllably drive mechanical oscillations of the silica toroid using radiation pressure.

Using replica molding, High-Q polymer microtoroid resonator arrays were fabricated from several different polymers.  Because the UHQ silica microtoroid master has ultra-smooth surfaces, this fabrication method results in material-loss limited polymer resonators. Using this technique, the material loss of previously uncharacterized polymers was determined.

In addition, by integrating a metallic contact into the pillar of the ultra high Q microtoroid, a tunable microtoroid can be fabricated.  This is important for biosensing and for telecommunications applications.

Also, when light is absorbed into an ultra-high Q cavity, the resonance wavelength is shifted primarily through two competing mechanisms: thermal expansion coefficient and refractive index dependence on temperature (dn/dT). Using silica UHQ cavities, this resonance shift and its subsequent hysteretic behavior around the pump wavelength can be explored.

By doping the microtoroid resonator with rare earth dopants, such as erbium, microlasers have been fabricated.  Other dopants, such as CdSe/ZnS nanocrystals, have also been used.

Caltech optics microcavity microtoroid microresonator array optical micro-cavity photonics optical fiber taper nanowire tapered optical fiber laser microlaser XeF2 xenon difloride BOE thermo-optic effect near-IR visible laser silica silicon microelectronic fluidics microfluidics biosensing chemical sensing optofluidics biological sensing single molecule sensing optical polymer composite high Q quality factor ultra high Q photolithography microoptics micro-optics H2O D2O water heavy water Vicast PDMS polydimethylsiloxane trichloromethylsilane replica molding silane embossing stamping silicone dopant