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Schematic diagram illustrating the fabrication of microspheres from lead-silicate fiber. (a) A lead-silicate glass fiber with a microscope image of its cross section (, , core diameter: , cladding OD: ); (b) the lead-silicate fiber is tapered to a waist diameter over a length of by using a microheater at a temperature of ; (c) the tapered lead-silicate fiber is cut in the middle; (d) a microsphere is formed at the taper tip when the tip approaches the microheater maintained at about , which is significantly higher than the softening point of SF6 lead-silicate glass (approximately ).
Experimental apparatus used for microsphere resonance characterization. Light from a narrow-line tunable laser source (Agilent 81600B, Agilent, Santa Clara, CA, USA) emitting 1 mW over the wavelength range 1554–1556 nm was launched into a tapered fiber and coupled to the microsphere. The throughput signal was collected using an InGaAs detector. The separation between the microsphere and the tapered fiber was controlled with a precision nanotranslation stage equipped with piezoelectric actuators and stepper motors and monitored using a microscope equipped with a CCD camera.
Microscope images of lead-silicate microspheres with diameters (a) and (b) showing their fiber stems and the tapered coupling fibers. (c) and (d) show the infrared images of the microsphere when the input laser light is turned off and on, respectively.
(a) Experimental resonance spectra for wavelengths between 1554 and 1555 nm for the microsphere with diameter (b) Close-up spectrum in the region 1554.78–1554.80 nm clearly showing the high- resonances and (c) a Lorentzian fit to one of the measured tuning-resolution limited resonance dips used to accurately determine the bandwidth.
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