Abstract: A broadband fiber optic sensor array is formed along a length of single mode optical fiber, with the individual sensing elements formed by introducing local perturbations (e.g., changes in diameter) along the length of the optical fiber. The sensor array requires only a single light source input and a single (conventional) optical spectrum analyzer output and is capable of providing individual measurements (such as local temperature or pressure) for each sensing element disposed along the length of fiber. The individual transmission spectra of the sensing elements forming the array are smooth and strongly overlap, and a method has been developed for determining the characteristics of the individual elements from the variations in the total (combined) transmission spectrum.

Abstract: A surface nanoscale axial photonic (SNAP) device in the form of an optical bottle resonator is configured to exhibit a semi-parabolic profile (in terms of a change in radius along the longitudinal direction of the fiber). It has been found that this semi-parabolic profile provides the ability to create the dispersionless delay of optical pulses, where “dispersionless” in this case is considered to mean that the pulse retains its same shape with minimal distortions as it passes back and forth within the bottle resonator (i.e., minimal pulse-broadening). Delays on the order of several nanoseconds have been created within these semi-parabolic-shaped SNAP bottle resonators of about 3 mm in length (as compared with prior art microresonator devices' ability to create delays no greater that 1 ns, at best).

Abstract: A method of characterizing and correcting effective radius variations in a surface nanoscale axial photonic (SNAP) device that comprises a plurality of separate optical microdevices includes the steps of characterizing an as-fabricated SNAP device to determine local effective radius values of the plurality of separate optical microdevices, calibrating the as-fabricated SNAP device to determine a correction factor defined as a change in effective radius associated with a predetermined corrective treatment and then correcting individual microdevices by the application of a number of refractive index-changing treatments, the number of treatments applied to individual microdevices determined by the amount of correction required and the correction factor determined in the calibrating step. A number of iterations of the characterizing and correcting operations can be performed, achieving less than an Angstrom variation in effective radius variation. An apparatus for performing the method is also disclosed.

Abstract: A conically tapered optical fiber with a small half-angle ? (e.g., less than 10?2) has been found able to support whispering gallery mode (WGM) resonances and can therefore be used to form a high-Q cavity. This finding has led to the ability to measure angstrom-level variations in the radius of an optical fiber by viewing the resonance spectrum at various locations where a sensor contacts an optical fiber being measured. An evaluation process is proposed where a microfiber sensor is brought into contact with a target fiber and the created WGM resonance is measured so that location radius variation can be characterized. The sensor is then removed from the target fiber and re-positioned to contact the fiber to another location to repeat the evaluation.

Abstract: A broadband fiber optic sensor array is formed along a length of single mode optical fiber, with the individual sensing elements formed by introducing local perturbations (e.g., changes in diameter) along the length of the optical fiber. The sensor array requires only a single light source input and a single (conventional) optical spectrum analyzer output and is capable of providing individual measurements (such as local temperature or pressure) for each sensing element disposed along the length of fiber. The individual transmission spectra of the sensing elements forming the array are smooth and strongly overlap, and a method has been developed for determining the characteristics of the individual elements from the variations in the total (combined) transmission spectrum.

Abstract: An optical microresonator is configured as an optical microbubble formed along a section of an optical microcapillary. The curvature of the outer surface of the microbubble creates an optical resonator with a geometry that encourages the circulating WGMs to remain confined in the central region of the bubble, creating a high Q optical resonator. The resonator may be tuned by modifying the physical properties of the microbubble, allowing the resonator to be used as an optical filter. The resonator may also be used as a sensor or laser by introducing the material to be sensed (or the active laser material) into the microcapillary along which the microbubble is formed.

Abstract: A method of characterizing and correcting effective radius variations in a surface nanoscale axial photonic (SNAP) device that comprises a plurality of separate optical microdevices includes the steps of characterizing an as-fabricated SNAP device to determine local effective radius values of the plurality of separate optical microdevices, calibrating the as-fabricated SNAP device to determine a correction factor defined as a change in effective radius associated with a predetermined corrective treatment and then correcting individual microdevices by the application of a number of refractive index-changing treatments, the number of treatments applied to individual microdevices determined by the amount of correction required and the correction factor determined in the calibrating step. A number of iterations of the characterizing and correcting operations can be performed, achieving less than an Angstrom variation in effective radius variation. An apparatus for performing the method is also disclosed.

Abstract: Complex, coupled photonic microdevices are formed to include sub-wavelength-sized radial perturbations sufficient to create resonant cavities, where these devices may be formed along the length of a single optical fiber and coupled together to form relatively complex photonic devices. By carefully selecting the placement and separation of these local radius variations, and using microfibers (or other suitable arrangements) to couple optical signals into and out of the device fiber, resonances in the form of whispering gallery modes (WGMs) are created in the device fiber such that a number of coupled microstructures (such as ring resonators) may be formed.

Abstract: An optical microresonator is configured as an optical microbubble formed along a section of an optical microcapillary. The curvature of the outer surface of the microbubble creates an optical resonator with a geometry that encourages the circulating WGMs to remain confined in the central region of the bubble, creating a high Q optical resonator. The resonator may be tuned by modifying the physical properties of the microbubble, allowing the resonator to be used as an optical filter. The resonator may also be used as a sensor or laser by introducing the material to be sensed (or the active laser material) into the microcapillary along which the microbubble is formed.

Abstract: An optical microresonator is configured as an optical microbubble formed along a section of an optical microcapillary. The curvature of the outer surface of the microbubble creates an optical resonator with a geometry that encourages the circulating WGMs to remain confined in the central region of the bubble, creating a high Q optical resonator. The resonator may be tuned by modifying the physical properties of the microbubble, allowing the resonator to be used as an optical filter. The resonator may also be used as a sensor or laser by introducing the material to be sensed (or the active laser material) into the microcapillary along which the microbubble is formed.

Abstract: An optical fiber coupler is formed of a section of optical fiber that is positioned between a conventional input fiber (for example, a single mode fiber) or waveguide and a coiled optical fiber device. The adiabatic coupler is coiled (or, at least, curved) to assist in transforming a conventional fundamental mode optical signal propagating along the longitudinal axis of the input fiber to an optical signal that is shifted into a peripheral region of the coiled optical fiber. Moreover, the pitch of an inventive coiled optical fiber coupler can be controlled to assist in the adiabatic transformation process.

Abstract: A conically tapered optical fiber with a small half-angle ? (e.g., less than 10?2) has been found able to support whispering gallery mode (WGM) resonances and can therefore be used to form a high-Q cavity. This finding has led to the ability to measure angstrom-level variations in the radius of an optical fiber by viewing the resonance spectrum at various locations where a sensor contacts an optical fiber being measured. An evaluation process is proposed where a microfiber sensor is brought into contact with a target fiber and the created WGM resonance is measured so that location radius variation can be characterized. The sensor is then removed from the target fiber and re-positioned to contact the fiber to another location to repeat the evaluation.

Abstract: An evanescent optical sensor is formed as a coil of either optical fiber or microfiber. By coiling the fiber/microfiber, the overall size of the sensor is significantly reduced when compared to “straight path” fiber sensors, yet exhibits a similar degree of sensitivity. An optical signal is coupled into a fiber coil that has been immersed in an ambient to be analyzed. The use of a coil configuration results in creating a plurality of whispering gallery modes (WGMs) that will propagate along the coil by reflecting from the surface of the curved fiber/microfiber forming the coil. The interference between these modes will be modified as a function of the properties of the ambient environment. Environmental changes cause variations in the optical length of the coil as “seen” by the various modes, and the interference of the modes is analyzed by studying the transmission spectrum at the output of the coil.

Abstract: To date, the probes of scanning near-field optical microscopes were aimed at creating electromagnetic field characteristics that are maximally localized near a nano-sized point (miniature apertures and tips, fluorescent nano-particles and molecules, dielectric and metal corners). Alternatively, the probe field, which is distributed within a larger area, can ensure the super-resolution as well. For this purpose, the field spectrum should be enriched with high spatial frequencies corresponding to small sample dimensions. As examples of such near-field probes, we propose and theoretically study the models of optical fibers with end-faces containing sharp linear edges and randomly distributed nanoparticles. These probes are more robust than the conventional probes and their fabrication is not concerned with nanoscale precision. The probes enable waveguiding of light to and from the sample with marginal losses distributing and utilizing the incident light more completely.

Abstract: An optical fiber coupler is formed of a section of optical fiber that is positioned between a conventional input fiber (for example, a single mode fiber) or waveguide and a coiled optical fiber device. The adiabatic coupler is coiled (or, at least, curved) to assist in transforming a conventional fundamental mode optical signal propagating along the longitudinal axis of the input fiber to an optical signal that is shifted into a peripheral region of the coiled optical fiber. Moreover, the pitch of an inventive coiled optical fiber coupler can be controlled to assist in the adiabatic transformation process.

Abstract: An optical fiber coupler is formed of a section of optical fiber that is positioned between a conventional input fiber (for example, a single mode fiber) or waveguide and a coiled optical fiber device. The adiabatic coupler is coiled (or, at least, curved) to assist in transforming a conventional fundamental mode optical signal propagating along the longitudinal axis of the input fiber to an optical signal that is shifted into a peripheral region of the coiled optical fiber. Moreover, the pitch of an inventive coiled optical fiber coupler can be controlled to assist in the adiabatic transformation process.

Abstract: Complex, coupled photonic microdevices are formed to include sub-wavelength-sized radial perturbations sufficient to create resonant cavities, where these devices may be formed along the length of a single optical fiber and coupled together to form relatively complex photonic devices. By carefully selecting the placement and separation of these local radius variations, and using microfibers (or other suitable arrangements) to couple optical signals into and out of the device fiber, resonances in the form of whispering gallery modes (WGMs) are created in the device fiber such that a number of coupled microstructures (such as ring resonators) may be formed.

Abstract: An optical delay line is formed from a coil of optical fiber (in many cases microfiber), where the radius of the optical fiber is greater than the wavelength ? of the propagating signal and the radius R of the coil is selected, in consideration with the optical fiber radius, to limit propagation loss by minimizing coupling between adjacent turns of the coil. The difference in dimension between the fiber diameter and wavelength prevents the mode propagating along one turn from coupling into an adjacent turn. It has been discovered that the modal intensity at the interface between the central rod and the coil will be minimized when the radius of the fiber satisfies the following condition: r >> ( R ? 2 ) 1 / 3 , where ?=(2?n)/?, and n is the refractive index of the fiber.

Abstract: An evanescent optical sensor is formed as a coil of either optical fiber or microfiber. By coiling the fiber/microfiber, the overall size of the sensor is significantly reduced when compared to “straight path” prior art fiber sensors, yet exhibits a similar degree of sensitivity, in operation, an optical signal is coupled into a fiber coil that has been immersed in an ambient to be analyzed. The use of a coil configuration results in creating a plurality of whispering gallery modes (WGMs) that will propagate along the coil by reflecting from the surface of the curved fiber/microfiber forming the coil. The interference between these modes will be modified as a function of the properties of the ambient environment within which the coil is immersed. Environmental changes cause variations in the optical length of the coil as “seen” by the various modes, and the interference of the modes is analyzed by studying the transmission spectrum at the output of the coil.

Abstract: The specification describes optical devices and related methods wherein an input mode is converted by multiple LPG mode transformers to produce an output with multiple predetermined modes.