T-phase-shifted fiber Bragg gratings in optical waveguides, and methods of formation thereof. Sensing apparatus comprising such gratings using femtosecond pulse duration lasers and specialized transmission diffraction elements or phase masks.

Described are optical fibers, e.g., for use in stress-sensing or shape-sensing applications, that use overlapping grating configurations with chirped gratings to facilitate strain delay registration. In accordance with various embodiments, a fiber core may, for instance, have two overlapping sets of chirped gratings that differ in the direction of the chirp between the first and second sets, or a set of chirped gratings overlapping with a single-frequency grating. Also described are strain sensing systems and associated computational methods employing optical fibers with overlapping gratings.

Described are optical fibers, e.g., for use in stress-sensing or shape-sensing applications, that use overlapping grating configurations with chirped gratings to facilitate strain delay registration. In accordance with various embodiments, a fiber core may, for instance, have two overlapping sets of chirped gratings that differ in the direction of the chirp between the first and second sets, or a set of chirped gratings overlapping with a single-frequency grating. Also described are strain sensing systems and associated computational methods employing optical fibers with overlapping gratings.

T-phase-shifted fiber Bragg gratings in optical waveguides, and methods of formation thereof. Sensing apparatus comprising such gratings using femtosecond pulse duration lasers and specialized transmission diffraction elements or phase masks.

Described are optical fibers, e.g., for use in stress-sensing or shape-sensing applications, that use overlapping grating configurations with chirped gratings to facilitate strain delay registration. In accordance with various embodiments, a fiber core may, for instance, have two overlapping sets of chirped gratings that differ in the direction of the chirp between the first and second sets, or a set of chirped gratings overlapping with a single-frequency grating. Also described are strain sensing systems and associated computational methods employing optical fibers with overlapping gratings.

A manufacturing device of an optical fiber grating to write a grating in a core of an optical fiber by irradiating the optical fiber with laser light includes: a fixing device that fixes the optical fiber to at least one of a first position located more on an upstream side and a second position located more on a downstream side in a conveyance direction of the optical fiber than a laser light irradiating position of the optical fiber in a case of writing the grating; and a feeder having a structure capable of linearly reciprocating in the conveyance direction and adapted to feed a predetermined length of the optical fiber in the conveyance direction in a case where a fixed state of the optical fiber by the fixing device is released.

Fiber Bragg grating interrogation and sensing used for strain and temperature measurements. A simple, broadband light source is used to interrogate one or more fiber Bragg grating (FBG). Specifically, a packaged LED is coupled to fiber, the light therefrom is reflected off a uniform FBG. The reflected light is subsequently analyzed using a filter and a plurality of Si photodetectors. In particular, the filter is a chirped FBG or an optically coated filter, in accordance with some embodiments. Measurement analysis is performed by ratio of intensities at the plurality of detectors, at least in part.

Methods of producing gratings with trenches having variable height are provided. In one example, a method of forming a diffracted optical element may include providing an optical grating layer over a substrate, patterning a hardmask over the optical grating layer, and forming a sacrificial layer over the hardmask, the sacrificial layer having a non-uniform height measured from a top surface of the optical grating layer. The method may further include etching a plurality of angled trenches into the optical grating layer to form an optical grating, wherein a first depth of a first trench of the plurality of trenches is different than a second depth of a second trench of the plurality of trenches.

Provided is an optical waveguide with an inscribed Bragg grating, where the Bragg grating is stable at high temperature, has low scattering loss and high reflectivity. Also provided is a method for inscribing a Bragg grating in an optical waveguide, the method comprising irradiating the optical waveguide with electromagnetic radiation from an ultrashort pulse duration laser of sufficient intensity to cause a permanent change in an index of refraction within a core of the optical waveguide, where the irradiating step is terminated prior to erasure of a Bragg resonance, and heating the optical waveguide to a temperature and for a duration sufficient to substantially remove a non-permanent grating formed in the optical waveguide by the irradiating step.

A structured film for forming a pattern on a substrate includes a polymeric support layer, an adhesive layer, an etch resist layer disposed between the polymeric support layer and the adhesive layer, a structured resin layer disposed between the polymeric support layer and the etch resist layer, and one or more unstructured layers disposed between the etch resist layer and the adhesive layer. The structured resin layer has a structured major surface including a plurality of engineered structures. The etch resist layer at least partially fills spaces between adjacent engineered structures to substantially planarize the structured major surface. Methods of using the structured film to form a pattern on a substrate are described.