Her Majesty the Queen in Right of Canada As Represented by the Minister of Industry Through the Communications Research Centre Canada

Her Majesty the Queen in Right of Canada, As Represented by the Minister

National Research Council of Canada

Her Majesty the Queen in Right of Canada, As Represented by the Minister of Industry Through the Communications Research Centre

Her Majesty in Right of Canada As Represented by the Minister of Industry

Xiaoli Dai

Huimin Ding

Stephen J. Mihailov

Dan Grobnic

Christopher W. Smelser

Gino Cuglietta

Ping Lu

Robert B. Walker

Her Majesty in Right of Canada As Represented by the Minister of Industr

Christopher W Smelser

Stephen J Mihailov

Robert Walker

Robert B Walker

George Henderson

Claire Callender

Chantal Blanchetiere

Haimin Ding

A method of producing a thermally stable grating allows the grating to be placed in environments where temperatures reach 1000&#xb0; C. These gratings may be concatenated so as to form a sensor array. The method requires a step of lowering the characteristic intensity threshold of a waveguide by at least 25%, followed by irradiating the waveguide with femtosecond pulses of light having a sufficient intensity and for a sufficient duration to write the grating so that at least 60% of the grating remains after exposures of at least 10 hours at a temperature of at least 1000&#xb0; C. Pre-writing a Type I grating before writing a minimal damage Type II grating lowers the characteristic threshold of the waveguide so that a stable low damage type II grating can be written; alternatively providing a hydrogen or deuterium loaded waveguide before writing the grating lowers the characteristic threshold of the waveguide.

High temperature stable fiber grating sensor and method for producing same

A method of producing a thermally stable grating allows the grating to be placed in environments where temperatures reach 1000&#xb0; C. and where the grating is relatively stable and has very low loss from scatter. These gratings have spectral characteristics that allow them to be concatenated so as to form a sensor array. The method requires a step of lowering the characteristic intensity threshold of a waveguide by at least 25%, followed by irradiating the waveguide with femtosecond pulses of light having a sufficient intensity and for a sufficient duration to write the grating so that at least 60% of the grating remains after exposures of at least 10 hours at a temperature of at least 1000&#xb0; C. Pre-writing a Type I grating before writing a minimal damage Type II grating lowers the characteristic threshold of the waveguide so that a stable low damage type II grating can be written; alternatively providing a hydrogen or deuterium loaded waveguide before writing the grating lowers the characteristic threshold of the waveguide.

A method of inducing birefringence in an optical waveguide is disclosed wherein the waveguide cladding is irradiated with energy of a sufficient intensity so as to induce a stress in the optical waveguide so as to cause a multitude of spaced stress induced regions within the cladding of the optical waveguide such that there are 10 to 5000 spaced regions per mm and wherein the stress induced regions are proximate the core greater than 2 microns distance from the core-cladding interface. This waveguide has numerous uses, for example a fiber sensor.

Method of changing the birefringence of an optical waveguide by laser modification of the cladding

An optical sensor for sensing information relating to an analyte liquid or gas, has a a planar substrate having a refractive index n. The planar substrate supports a ridge waveguide having an unclad top portion having a refractive index n. The substrate serves as cladding layer for the ridge waveguide at a location where the ridge waveguide contacts the substrate. A Bragg grating inscribed in the ridge waveguide has two modes for providing information relating to both temperature and refractive index of the surrounding analyte liquid or gas. A cladding mode has a different response to the analyte when compared to a Bragg resonance response. Both modes have a same reaction to temperature, wherein said Bragg grating is formed within the unclad region of ridge waveguide, wherein n&#x3c;n. Advantageously multiple parameters can be sensed using only a single Bragg grating.

Ridge waveguide optical sensor incorporating a Bragg grating

A method of increasing the refractive index in a photosensitive glass is disclosed so as to induce an refractive index change of at least 10within a region of the glass. The method includes the step of providing a hydrogen or deuterium loaded doped glass material wherein a dopant within the glass is photosensitive to infrared radiation in the presence of hydrogen or deuterium. The hydrogen or deuterium loaded doped glass is subsequently irradiated with femtosecond pulses of infrared light having an intensity of at least 10W/cmand less than 5&#xd7;10W/cm.

Method of increasing photosensitivity of glasses to ultrafast infrared laser radiation using hydrogen or deuterium

Fiber Bragg gratings were written in pure silica photonic crystal fibers and photonic crystal fiber tapers with 125 fs, 800 nm IR radiation. High reflectivites were achieved with short exposure times in the tapers. Both multimode and single mode grating reflections were achieved in the fiber tapers. By tapering the photonic crystal fibers scattering that would otherwise have occurred was lessened and light external to the fiber could reach the core effectively to write a grating.

Method of changing the refractive index in a region of a core of a photonic crystal fiber using a laser

A retro-reflective sensor for sensing mechanical, chemical or temperature related information, is disclosed. The sensor is formed of an optical waveguide suitable for use in-situ in a high temperature environment having a Bragg grating written into a core region thereof with short-pulsed electromagnetic radiation, said optical waveguide having a glass transition temperature substantially higher than that of silica. Preferably the sensor is written into a length of sapphire fiber or within a zirconium waveguide. Preferably the pulse duration of the short pulsed electromagnetic radiation is less than 500 picoseconds.

Optical fiber sensor based on retro-reflective fiber Bragg gratings

The invention relates to an optical waveguide device for monitoring a characteristics of light, e.g. a wavelength. The device incorporates a waveguide, such as an optical fiber, with an embedded tilted Bragg grating operating in a regime of wavelength detuning. The grating is designed to disperse light azimuthally in two or more different directions about the fiber axis, said directions changing with wavelength. A photodetector array is provided for detecting the azimuthal distribution of light. A processor coupled to the photodetector array determines wavelength information from the detected azimuthal distribution of the out-coupled light.

Optical device incorporating a tilted bragg grating

A novel Bragg grating filter in optical waveguiding fiber with suppressed cladding mode coupling and method of producing same is disclosed. The novel grating structure is induced in both the core and the cladding of the optical fiber irrespective of the photosensitivity of the core or cladding to actinic radiation. Such core and cladding of the optical fiber need not be chemically doped to support the grating. The method incorporates an ultra short duration pulse laser source. Electromagnetic radiation provided from the laser propagates to a diffractive element positioned a specific distance to the target material such that the diffracted electromagnetic radiation forms a 2-beam interference pattern, the peaks of which are sufficiently intense to cause a change in index of refraction.

Bragg grating and method of producing a Bragg grating using an ultrafast laser

A novel method and apparatus for varying the index of refraction of a material using an interference pattern is disclosed. The method and apparatus incorporate an ultra short duration pulse laser source. Electromagnetic radiation provided from the laser propagates to a diffractive element positioned in close proximity to the target material. The diffracted electromagnetic radiation forms an interference pattern, the peaks of which are sufficiently intense to cause a change in index of refraction.

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Ottawa, Canada

Christopher W Smelser