An in-line fiber-optic sensing element, a system, and methods for detecting strain using a fiber optic sensor are described that include using at least two chirped grating structures. In an implementation, an in-line fiber-optic sensing element that employs example techniques in accordance with the present disclosure includes an optically transmissive fiber including a core and an outer layer; a Fabry-Perot cavity defined by a portion of the optically transmissive fiber and two chirped fiber-Bragg grating structures, where the two chirped grating structures are separated and are configured to reflect light.

This invention relates to methods of generating NP gallium nitride (GaN) across large areas (>1 cm.sup.2) with controlled pore diameters, pore density, and porosity. Also disclosed are methods of generating novel optoelectronic devices based on porous GaN. Additionally a layer transfer scheme to separate and create free-standing crystalline GaN thin layers is disclosed that enables a new device manufacturing paradigm involving substrate recycling. Other disclosed embodiments of this invention relate to fabrication of GaN based nanocrystals and the use of NP GaN electrodes for electrolysis, water splitting, or photosynthetic process applications.

A grating based optical transmitter includes a light source region coupled to an interference region, two reflective regions on both sides of the interference region, and one or several gratings interacting with the interference light wave in the interference region causing a vertical emission. Two electrodes are used to inject electrical carriers, and a third electrode can be added to modulate the electrical carrier density recombined in the light source region. Compared to conventional edge-emitting laser with two electrodes, the grating-based optical transmitter in this invention largely reduces the packaging cost and complexity due to the vertical emission, and largely enhances the modulation bandwidth due to the three-terminal configuration.

Provided are a Bragg grating and a spectroscopy device including the same. The Bragg grating is disposed at each of opposite ends of a resonator for reflecting light of a certain wavelength band and includes a core member extending from a waveguide of the resonator in a lengthwise direction of the waveguide; a plurality of first refractive members protruding from the core member and spaced apart from each other along the lengthwise direction; and a second refractive member filling spaces between the first refractive members and having a refractive index different from a refractive index of the first refractive members.

A method of manufacturing an optical fiber sensing device includes steps of moving an optical fiber having a core linearly along a first direction, during the moving, directly writing a number of nanograting structures into the core using a laser beam generated by an ultrafast laser system, wherein the number of nanograting structures form a number of scattering points; and forming an energy transducing element on an outer surface of the optical fiber, wherein the number of scattering points is/are structured and configured to scatter light out of fiber core and into the transducing element to provide local power for the optical fiber sensing device. A system for performing the method is also provided.

A method for non-intrusive pipeline testing involves constructing the pipeline at a construction location that is above ground, affixing an optical fiber along a surface of a length of the pipeline that is at the construction location, measuring dynamic strain experienced by the length of the pipeline by performing optical interferometry using the optical fiber, and moving the length of the pipeline from the construction location to a different installation location. The optical fiber includes at least one pair of fiber Bragg gratings (FBGs) tuned to reflect substantially identical wavelengths with a segment of the optical fiber extending between the FBGs.

Provided are a Bragg grating and a spectroscopy device including the same. The Bragg grating is disposed at each of opposite ends of a resonator for reflecting light of a certain wavelength band and includes a core member extending from a waveguide of the resonator in a lengthwise direction of the waveguide; a plurality of first refractive members protruding from the core member and spaced apart from each other along the lengthwise direction; and a second refractive member filling spaces between the first refractive members and having a refractive index different from a refractive index of the first refractive members.

In some embodiments, a system includes a laser that generates an optical signal and a resonator that receives the optical signal. The resonator includes an optical resonator cavity comprising a first and second end, wherein the optical signal propagates at a resonant frequency; a first optical anti-resonator terminating the first end and having a first stopband; and a second optical anti-resonator terminating the second end and having a second stopband. The system includes a detector that generates an electrical signal from a modified resonator output of the resonator; and Pound-Drever-Hall servo circuitry configured to generate control signals for controlling a frequency of the optical signal generated by the laser or phase modulation devices attached to the optical resonator cavity or the first or second optical anti-resonator, wherein each phase modulation changes a length of at least one of the optical resonator cavity or the first or second optical anti-resonator.

Provided are a Bragg grating and a spectroscopy device including the same. The Bragg grating is disposed at each of opposite ends of a resonator for reflecting light of a certain wavelength band and includes a core member extending from a waveguide of the resonator in a lengthwise direction of the waveguide; a plurality of first refractive members protruding from the core member and spaced apart from each other along the lengthwise direction; and a second refractive member filling spaces between the first refractive members and having a refractive index different from a refractive index of the first refractive members.

An in-line fiber-optic sensing element, a system, and methods for detecting strain using a fiber optic sensor are described that include using at least two chirped grating structures. In an implementation, an in-line fiber-optic sensing element that employs example techniques in accordance with the present disclosure includes an optically transmissive fiber including a core and an outer layer; a Fabry-Perot cavity defined by a portion of the optically transmissive fiber and two chirped fiber-Bragg grating structures, where the two chirped grating structures are separated and are configured to reflect light.