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We fabricated nanometer- and micrometer-order diameter optical fibers (NMOFs) by drawing them in a microfurnace comprising a sapphire tube heated with a CO(2) laser. Using very short - a few mm long - fiber biconical tapers having a submicron waist, which can be bent locally in a free space by translation of the taper ends, we studied the effect of bending and looping on the transmission characteristics of a free NMOF. In particular, we have demonstrated an optical interferometer built of a coiled self-coupling NMOF.

We develop a method for fabricating very small silica microbubbles having a micrometer-order wall thickness and demonstrate the first optical microbubble resonator. Our method is based on blowing a microbubble using stable radiative CO 2 laser heating rather than unstable convective heating in a flame or furnace. Microbubbles are created along a microcapillary and are naturally opened to the input and output microfluidic or gas channels. The demonstrated microbubble resonator has 370 m diameter, 2 m wall thickness, and a Q factor exceeding 10 6 .

We demonstrate a robust and highly responsive optical microsensor, which probes the refractive index of liquids flowing along a ~ 100 mum radius channel formed in a polymer matrix. Sensing is based on measurement of the transmission spectrum of the whispering gallery modes, which are excited across the liquid channel by an optical microfiber imbedded into the polymer. The achieved sensitivity is 800 nm/RIU. Potentially, it is straightforward to assemble the sensing elements of this type into a lab-on-the-chip imbedded in a solidified optical material.

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.