Yury Dulashko

Super free spectral range tunable optical microbubble resonator

An optical resonator is often called fully tunable if its tunable range exceeds the spectral interval that contains the resonances at all the characteristic modes of this resonator. For high-Q-factor spheroidal and toroidal microresonators, this interval coincides with the azimuthal free spectral range (FSR). In this Letter, we demonstrate what we believe to be the first mechanically fully tunable spheroidal microresonator created of a silica microbubble having a 100microm order radius and 1microm order wall thickness. The tunable bandwidth of this resonator is more than two times greater than its azimuthal FSR.

Surface nanoscale axial photonics:robust fabrication of high-quality-factor microresonators

Recently introduced surface nanoscale axial photonics (SNAP) makes it possible to fabricate high-Q-factor microresonators and other photonic microdevices by dramatically small deformation of the optical fiber surface. To become a practical and robust technology, the SNAP platform requires methods enabling reproducible modification of the optical fiber radius at nanoscale. In this Letter, we demonstrate superaccurate fabrication of high-Q-factor microresonators by nanoscale modification of the optical fiber radius and refractive index using CO2 laser and UV excimer laser beam exposures. The achieved fabrication accuracy is better than 2 Å in variation of the effective fiber radius.

Probing optical microfiber nonuniformities at nanoscale

We demonstrate a novel, simple, and comprehensive method for probing optical microfiber surface and bulk distortions with subnanometer accuracy. The method employs a regular optical fiber as a probe that slides along a microfiber transmitting the fundamental mode. The fraction of radiation power absorbed in the probe depends on the local distribution of the mode propagating in the microfiber. From the measured variation of the absorbed power, we determine the variation of the effective microfiber radius, which takes into account both the microfiber radius and refractive index variations. Furthermore, we verify the cylindrical symmetry of the microfiber nonuniformities by probing the microfiber from different sides. These results explain observed transmission losses in silica microfibers and open broad opportunities for microfiber investigation.

Coupled high Q-factor surface nanoscale axial photonics (SNAP) microresonators

We report the first experimental demonstration of coupled identical super-high Q-factor bottle microresonators formed by periodic nanoscale variation of the optical fiber radius. The Q-factor of the fabricated microresonator series exceeds 107.

Sensing an optical fiber surface by a microfiber with angstrom accuracy

By monitoring the whispering gallery mode resonances, which are excited in an optical fiber by a moving microfiber, we determine the optical fiber effective diameter variation with angstrom accuracy and sensor the residuals and defects on the fiber surface

Demonstration of a microfiber loop optical resonator

We demonstrate a microfiber loop optical resonator. At telecommunication wavelengths, it achieves loaded and intrinsic Q-factors of 95000 and 630000, respectively. As an example, the resonator performs as an ultrafast gas contact temperature sensor.

Interferometric characterization of phase masks

We demonstrate a novel interferometric technique for highly accurate characterization of phase masks used in optical fiber grating fabrication. The principle of the measurement scheme is based on the analysis of the interference pattern formed between the first- and zero-order beams transmitted through or reflected from the grating under test. For spatial resolution of a few millimeters, our methods allow the determination of local variations of the order of 1-microm grating period with an accuracy of a few picometers. These methods are applicable to a broad class of diffractive grating structures.

Temperature and pressure compensated microfluidic optical sensor

We demonstrate a robust double-capillary microfluidic ring resonator optical sensor imbedded into a solid polymer matrix. The device is capable of compensating the temperature and pressure variations and can be generalized to a multi-capillary lab-on-a-chip.

Demonstration of coupled high Q-factor surface nanoscale axial photonics (SNAP) microresonators

We report the first experimental demonstration of coupled identical super-high Q-factor bottle microresonators formed by periodic nanoscale variation of the optical fiber radius. The Q-factor of the fabricated microresonator series exceeds 107.

Fabrication of Ultra-Low-Loss Photonic Circuits with Angstrom Precision

Researchers have achieved much progress in fabricating complex photonic circuits, laying the groundwork for revolutionary applications in optical computing, communications and fundamental science. Yet attenuation of light primarily caused by surface roughness and insufficient fabrication precision remains a major bottleneck.