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(Color online) [(a) and (b)] Concept of the miniature cavity. The basic building block is an optical fiber functionalized with a concave dielectric mirror. Two such fibers, brought sufficiently close to each other, result in a stable Fabry-Pérot cavity which can be interrogated remotely, either in transmission or in reflection, through the two fibers [2FFP configuration (a)]. Alternatively, a single fiber can be brought close to a reflecting planar surface [1FFP configuration (b)]. The 1FFP configuration is suitable for use with nanofabricated structures such as quantum dots. (c) A single-mode optical fiber, total diameter of processed with a concave mirror. The mirror has radius of with a stop band centered at . (d) A miniature cavity, realizing the configuration (a), mounted on an atom chip used in the detection of cold atoms.
(Color online) White light transmission spectra of a 1FFP cavity recorded at three different cavity lengths . The mirrors have a stop band centered at . is the effective cavity length, determined by , where is the change in wave number from one fundamental longitudinal mode to the next. The modes are labeled with the sum of the two lateral mode indices, and . The widths of the transmission peaks are limited by the spectrometer and therefore do not reflect the true finesse. (b) Separation in wavelength of the higher lateral modes from the fundamental mode as a function of at . The two curves for each mode represent the analytical results for a spherical-planar FP cavity with radius (black) and (blue online).
Transmission of a 2FFP cavity vs cavity length. A piezo is used to vary the cavity length. The absolute length is determined by using up to three lasers with known wavelengths. The mirrors have radius of with a stop band centered at . The cavity has an effective cavity length of with a finesse of 1050; equivalently, free spectral range of and mode width (full width at half maximum) of . The inset shows the line shape of the fundamental (0,0) mode.
(Color online) Atom detection with an on-chip fiber resonator. (a) At , a magnetically trapped atom cloud is released into a very elongated Ioffe-Pritchard potential, created using the wire shown in gray. This potential guides the atoms through the center of the resonator mode. (b) Transmission signal of the fiber resonator for a single experimental run (solid line), along with an empty cavity transmission signal (dashed line). The transmission drops to 35% of the empty-resonator value.
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