Optical fiber whispering gallery modes resonances: Applications
23 Jun 2013-pp 1-4
TL;DR: In this article, a tuning of the whispering gallery modes (WGM) resonances of an optical fiber can be exploited in a number of different applications, e.g., tuning a microresonator with an auxiliary diode laser, enabling all-optical fine tuning of WGM resonances.
Abstract: The properties of whispering gallery modes (WGM) resonances of an optical fiber can be exploited in a number of different applications. Making these resonances tunable is essential for many applications. Using erbiumdoped fibers to prepare the microresonator (MR), WGM resonances can be tuned by pumping the MR with an auxiliary diode laser, enabling an all-optical fine tuning of the resonances. The same idea can be exploited the other way round, an accurate measurement of pump-induced temperature variations in doped fibers can be achieved by monitoring the WGM resonances of a doped fiber when being used. In addition, a tunable narrow linewidth fiber lasers is demonstrated using a tunable MR prepared with a slightly tapered fiber.
Citations
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TL;DR: By taking advantage of axial symmetry of the planar whispering gallery microresonators, the three-dimensional problem of the resonator is reduced to a two-dimensional (2D) one; thus, only the cross section of the Resonator needs to be analyzed.
Abstract: By taking advantage of axial symmetry of the planar whispering gallery microresonators, the three-dimensional (3D) problem of the resonator is reduced to a two-dimensional (2D) one; thus, only the cross section of the resonator needs to be analyzed. Then, the proposed formulation, which works based on a combination of the finite-elements method (FEM) and Fourier expansion of the fields, can be applied to the 2D problem. First, the axial field variation is expressed in terms of a Fourier series. Then, a FEM method is applied to the radial field variation. This formulation yields an eigenvalue problem with sparse matrices and can be solved using a well-known numerical technique. This method takes into account both the radiation loss and the dielectric loss; hence, it works efficiently either for high number or low number modes. Efficiency of the method was investigated by comparison of the results with those of commercial software.
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References
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06 Jun 2003TL;DR: This work demonstrates a process for producing silica toroid-shaped microresonators-on-a-chip with Q factors in excess of 100 million using a combination of lithography, dry etching and a selective reflow process, representing an improvement of nearly four orders of magnitude over previous chip-based resonators.
Abstract: We demonstrate microfabrication of ultra-high-Q microcavities on a chip, exhibiting a novel toroid-shaped geometry. The cavities possess Q-factors in excess of 100 million which constitutes an improvement close to 4 orders-of-magnitude in Q compared to previous work [B. Gayral, et al., 1999].
2,177 citations
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TL;DR: This work reports a substantially different approach to comb generation, in which equally spaced frequency markers are produced by the interaction between a continuous-wave pump laser of a known frequency with the modes of a monolithic ultra-high-Q microresonator via the Kerr nonlinearity.
Abstract: Optical frequency combs provide equidistant frequency markers in the infrared, visible and ultraviolet, and can be used to link an unknown optical frequency to a radio or microwave frequency reference. Since their inception, frequency combs have triggered substantial advances in optical frequency metrology and precision measurements and in applications such as broadband laser-based gas sensing and molecular fingerprinting. Early work generated frequency combs by intra-cavity phase modulation; subsequently, frequency combs have been generated using the comb-like mode structure of mode-locked lasers, whose repetition rate and carrier envelope phase can be stabilized. Here we report a substantially different approach to comb generation, in which equally spaced frequency markers are produced by the interaction between a continuous-wave pump laser of a known frequency with the modes of a monolithic ultra-high-Q microresonator via the Kerr nonlinearity. The intrinsically broadband nature of parametric gain makes it possible to generate discrete comb modes over a 500-nm-wide span (approximately 70 THz) around 1,550 nm without relying on any external spectral broadening. Optical-heterodyne-based measurements reveal that cascaded parametric interactions give rise to an optical frequency comb, overcoming passive cavity dispersion. The uniformity of the mode spacing has been verified to within a relative experimental precision of 7.3 x 10(-18). In contrast to femtosecond mode-locked lasers, this work represents a step towards a monolithic optical frequency comb generator, allowing considerable reduction in size, complexity and power consumption. Moreover, the approach can operate at previously unattainable repetition rates, exceeding 100 GHz, which are useful in applications where access to individual comb modes is required, such as optical waveform synthesis, high capacity telecommunications or astrophysical spectrometer calibration.
1,950 citations
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TL;DR: It is demonstrated that quality factor Q - (0.8 +/- 0.1) x 10(10) of whispering-gallery modes in fused-silica microspheres at 633 nm, close to the ultimate level determined by fundamental material attenuation as measured in optical fibers, is demonstrated.
Abstract: We demonstrate the quality factor Q - (0.8 +/- 0.1) x 10(10) of whispering-gallery modes in fused-silica microspheres at 633 nm, close to the ultimate level determined by fundamental material attenuation as measured in optical fibers. The lifetime of ultimate Q is limited by adsorption of atmospheric water. Monitoring of adsorption kinetics with submonolayer sensitivity by Q factors and frequencies of whispering-gallery modes is demonstrated. The possibility of supermaterial Q's owing to intrinsic suppression of scattering losses in micropheres is discussed.
986 citations
"Optical fiber whispering gallery mo..." refers background in this paper
...Optical microresonators (MR) based on whispering gallery modes (WGM) resonances are remarkable devices that exhibit a unique combination of high quality factor, small mode volume, and good mechanical stability [1,2]....
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TL;DR: It is shown that high-Q whispering-gallery modes in fused-silica microspheres can be efficiently excited by an optical fiber taper and is believed to be the most efficient excitation of a high- Q microcavity resonance by a monomode optical fiber yet demonstrated.
Abstract: We show that high-Q whispering-gallery modes in fused-silica microspheres can be efficiently excited by an optical fiber taper. By adjusting the taper diameter to match the ropagation constant of the mode in the taper with that of the resonant mode of interest, one can couple more than 90% of the light into the sphere. This represents a significant improvement in excitation efficiency compared with other methods and is, we believe, the most efficient excitation of a high- Q microcavity resonance by a monomode optical fiber yet demonstrated.
937 citations
"Optical fiber whispering gallery mo..." refers methods in this paper
...The excitation of the WGM resonances is performed using a thin tapered fiber (TTF) [15]....
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TL;DR: In this paper, the spectral position of the whispering gallery mode (WGM) of a sphere shifts in response to the refractive index change in the surrounding medium, resulting in a sensitivity of approximately 30nm∕RIU (refractive index units).
Abstract: We have developed a highly sensitive refractometric sensor based on fused silica microsphere resonators. The spectral position of the whispering gallery mode (WGM) of a sphere shifts in response to the refractive index change in the surrounding medium. The strong light-matter interaction due to the extremely high Q factor associated with the WGM results in a sensitivity of approximately 30nm∕RIU (refractive index units). This, together with the high spectral resolution of our sensor system (∼0.01pm), yields a detection limit of refractive index change on the order of 10−7RIU. Theoretical calculation is also performed and agrees well with the experimental data.
361 citations