University of Southampton

Gregory Daniel Emmerson

Peter George Robin Smith

Corin Barry Edmund Gawith

Richard Williams

Vassilios Albanis

Samuel Paul Watts

Andriy Heorhiyovych Dyadyusha

Ian James Grayston Sparrow

Malgorzata Kaczmarek

An optical sensor comprises at least two planar Bragg gratings defined on a single substrate and arranged to receive light from a light source, each grating having a wavelength filtering response that varies with an effective modal index experienced by light propagating in the Bragg grating and a Bragg wavelength different to those of the other gratings, and at least one sample window overlying one or more of the gratings that can receive a sample of fluid that affects the effective modal index and response of the grating, the gratings filtering the light and outputting the filtered light for spectral analysis, from which the refractive index and related properties of the fluid can be determined. One or more of the gratings can be a reference grating used to compensate for temperature and other disturbances to the sensors. Gratings may have individual sample windows for testing separate fluid samples, or may share a common window so that a single fluid can be tested using several gratings.

Multiwavelength optical sensors

An optical sensor comprises a sensing element comprising a waveguide grating with a response that varies with an effective modal index experienced by light propagating in the grating and a sample window for receiving fluid which affects the effective modal index to modify the response, the sensing element arranged to receive light from a light source and to output the light after filtering; and an analyzing element comprising a second waveguide grating having a second response, and arranged to receive light output by the sensing element and to output the light after filtering for detection by an optical power detector. The combination of the two gratings converts changes in the wavelength of light output by the sensing element in response to the sample of fluid to changes in the amount of light, allowing the fluid index to be deduced from a measurement of optical power. The two elements may be fabricated on a single substrate to reduce errors from environmental disturbances such as temperature changes.

Optical sensors for sensing the refractive index of fluid samples

A method of simultaneously defining a waveguide and grating in a sample of photosensitive material comprises providing a sample of material () having a region which is photosensitive to light of a specific wavelength, generating a spot of light () at the specific wavelength, the spot having a periodic intensity pattern of high and low intensity fringes, and a width which is related to the width of the channel, positioning the spot within the photosensitive region and causing relative movement between the sample and the light spot along the desired path of the waveguide/grating define a channel of altered refractive index by exposing parts of the photosensitive region to the light spot. Modulation of the light spot to produce multiple exposures produces a grating, while continuous exposure results in a uniform waveguide. These structures can be written in straight lines or around curves, and can be accurately overwritten, so that complex optical devices can be produced in a single fabrication step.

Fabrication of waveguides and Bragg gratings with UV-irradiation

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Highfield, United Kingdom

Gregory Daniel Emmerson