Planar waveguide chemical sensor

Details Planar waveguide chemical sensor Planar waveguide chemical sensor

1999-02-24

2002-01-01

Turner, Samuel A. (Department: 2877)

Optics: measuring and testing

By light interference

Using fiber or waveguide interferometer

C356S481000

Reexamination Certificate

active

06335793

ABSTRACT:

This invention relates to a system for sensing chemicals in order to identify chemicals present in a test material, and in order to determine the concentration of the identified chemicals in the test material.
The invention particularly relates to a system in which chemicals are sensed using the optical properties of a specialised architecture of wave guides providing either an individual chemical or physical sensor, or alternatively a number of such sensors which may be included in an array based device.
Further, the present invention relates to a system for the abstraction of data and control of interferometric chemical sensor devices.
Measuring chemical species using conventional chemical sensor technologies does not provide the level of sensitivity and robustness required and does not provide a required performance for any important applications.
Current chemical sensors incorporating transducers do not offer the sensitivity displayed, for example, by the human nose.
Known optical chemical sensors, work on the principles of interferometry.
It is known to make use of optical waveguides in which the evanescent field (that is, the field which extends outside the guiding region) is used to sense discrete changes in optical properties. This known method relies on “leakage” of optical signals from a conventional wave guide structure into a sensing layer which is typically formed from an absorbent polymer.
The evanescent component of the optical signal being guided by the wave guide is typically small leading to limited interrogation of the sensing layer.
Another disadvantage of known waveguides used as chemical sensors is that the wave guides are very sensitive to changes in temperature. As a consequence, the sensitivity of these known devices is significantly attenuated.
According to a first aspect of the present invention there is provided a sensor system having a laminate structure comprising means for providing electromagnetic radiation; two or more wave guides; propagating means for simultaneously propagating electromagnetic radiation into the two or more wave guides, each of the wave guides comprising a planar wave guide layer formed in a substrate.
In known sensors incorporating optical waveguides, a sensing layer is modified by the chemical to be tested, and evanescent excitation radiation which interrogates the sensing layer is a small fraction of the total radiation contained in the waveguide layer. As a consequence, the sensitivity of such known devices is significantly attenuated.
In contrast, the present invention incorporates a sensor in which the sensing layer is used as the wave guide for the electro-magnetic radiation, thus ensuring the majority of excitation radiation interrogates the material.
The system of the present invention therefore benefits from significant improvements in efficiency when compared to known sensors using evanescent wave strategies.
The present invention further comprises a reference wave guide in addition to a sensing wave guide, which reference wave guide is provided internally within the sensor.
The leads to a simplified structure.
The present invention provides a chemical sensor with improved reliability. The range and applicability of a chemical sensor according to the present invention is thus greatly enhanced.
The present invention provides a chemical sensor system with a novel architecture of wave guide structure which leads to a robust device with significantly enhanced signal to noise ratios (sensitivity) and discrimination.
In addition, the present invention may be used to make physical measurements relating to pressure, position or vibration or test environment or material.
The device of the present invention is suitable for detecting changes in an ambient chemical environment without being excessively stressed by other environmental factors such as temperature.
The device according to the present invention comprises an optical quantum well sensor (OQWS) which comprises two or more wave guides one of which wave guides is modified in response to chemical species present in the environment.
Preferably, the means for providing electro-magnetic radiation provides electro-magnetic radiation having a wavelength falling within the optical range.
However, it is to be understood that the invention is applicable to devices adapted for use with electro-magnetic radiation of any wavelength, for example, infra-red and ultra-violet.
Advantageously, the means for providing electro-magnetic radiation is adapted to provide plane polarised electro-magnetic radiation.
Conveniently, the system further comprises propagating means for substantially simultaneously propagating electro-magnetic radiation into the two or more wave guides.
The device may further comprise excitation means for exciting substantially simultaneously a dual or multiple symmetric wave guide system.
Preferably, the device further comprises measuring means for measuring phase changes in the electro-magnetic radiation in each of the two or more wave guides.
According to a second aspect of the present invention there is provided an apparatus comprising a plurality of sensor systems according to the first aspect of the invention, each of which devices is arranged into an array.
The sensing wave guide may be formed from silicon. Alternatively, the sensing wave guide is formed from polymeric material such as polymethyl methacrylate.
The reference wave guide may be formed from silicon oxynitride. Alternatively, the reference wave guide is formed from a polymeric material such as poly-4-vinyl pyridine P4VP. Conveniently, electrodes positioned in contact with a surface of the sensing layer enables simultaneous capacitance and optical changes to be measured as a consequence of absorption on a single device.
Conveniently, the device comprises an integrated optical device.
Conveniently, the device comprises a plurality of optical quantum well sensors.
Advantageously, the device comprises a plurality of sensing wave guide layers each of which is laid down in a laminar fashion.
Using electro-magnetic radiation of different frequencies varies the contributions of the various laminations and may further enhance the utility of the device. Preferably, both excitation modes may be used to interrogate the sensor. In other words, both the TE (transverse electric) and the TM (transverse magnetic) modes are used.
In known devices the TE mode only would be used. However, the inventors have realised that by using the TM mode as well further information may be provided.
The device according to the present invention may be a passive device, or alternatively through use of appropriate materials it may be an active optical device.
Substrates such as quartz may be used to provide an active optical device. In such a situation active feedback mechanisms may be used to compensate for temperature changes thus negating the need for a photo detector array.
The use of a plurality of wave guides leads to a highly optimised wave guide device and allows simple optical arrangements to be used.
The device according to the invention thus has fast response characteristics. The path length of each of the plurality of wave guides is long which provides greater sensitivity.
In a preferred embodiment, the wave guides are built onto a substrate through lamination processes. Such processes are highly repeatable and lead to accurate manufacture.
Due to the laminate structure of the device, the sensing wave guide and the reference wave guide are in close proximity to one another. This minimises the effects of temperature and other environmental factors.
A mixed mode device may be utilised where fundamental physical concepts such as birefringence are also used to provide additional information concerning the test chemicals.
An interference pattern is obtained when the electro-magnetic radiation from both wave guide layers is coupled into free space and is recorded.
The interference pattern is used to determine the relative phase change which has occurred in the sensing wave guide with respect to the reference wave guide during

Affiliated with

Also associated with

Rating

Planar waveguide chemical sensor does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Planar waveguide chemical sensor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Planar waveguide chemical sensor will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2857733