Optics: measuring and testing – By particle light scattering – With photocell detection
Patent
1997-07-17
1999-02-02
Kim, Robert
Optics: measuring and testing
By particle light scattering
With photocell detection
356361, 356352, G01B 902
Patent
active
058672672
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a device for detection of a characteristic of a medium by interferometry, manufactured in integrated optics technology and comprising, on a substrate, an input microguide connected by an input end to means for emitting a light beam, forming means to form at least one reference beam and one measurement beam from said light beam, means for making the reference beam and measurement beam interfere and supply interference signals, means for detection connected to an output end of an output microguide transmitting the interference signals, and an interaction zone between the measurement beam and the medium to be studied.
It is known to use an optic interferometer to detect the presence or concentration of a gas. A known device using an interferometer of the Mach-Zehnder type, achieved in integrated optics technology, is represented in FIG. 1. The interferometer comprises a substrate 1 on which an input microguide 2 is achieved. The input microguide 2 is divided into two arms by a first Y-junction, a reference arm 3 and a measurement arm 4. The two arms are joined, by means of a second Y-junction, in an output microguide 5. An interaction zone 6 with the gas to be studied covers a part of the measurement arm 4. This interaction zone is for example covered by a film able to absorb a predetermined gas and whose refraction coefficient changes according to the quantity of gas absorbed. An input light beam 7 applied to the input of the microguide 2 is therefore separated into two beams one of which is transmitted by the reference arm to the output microguide and the other of which, transmitted by the measurement arm, undergoes a variable phase displacement according to the variation of the coefficient of the absorbent film. The reference and measurement beams interfere in the second Y-junction and the interference signal thus formed detected at the output of the microguide 5 is representative of the gas to be studied.
The object of the invention is to achieve a device presenting an increased sensitivity while being easy to achieve in integrated optics.
According to the invention, this object is achieved by the fact that the forming means comprise a flat guide arranged between the input and output microguides in such a way as to achieve light coupling by optical tunnel effect between each microguide and the flat guide, and comprising at least a first zone, not sensitive to the medium, and a second zone constituting the interaction zone with the medium. The different zones can be of any shape.
The flat guide is bounded by two sides respectively parallel to the input and output microguides, each of said sides being arranged near to an intermediate part of an associated microguide.
According to a development of the invention, the interaction zone comprises a superstrate sensitive to the medium to be studied and deposited on the substrate.
According to a first alternative embodiment, the input and output microguides are parallel and the interaction zone has the shape of a parallelogram having two sides parallel to the microguides.
According to a second alternative embodiment, the interaction zone has the shape of a triangle having one side on the same side as the flat guide associated to the input microguide and an opposite peak on the same side as the flat guide associated to the output microguide.
Other advantages and features of the invention will become more clearly apparent from the following description of particular embodiments of the invention, given as non-restrictive examples only and represented in the accompanying drawings in which:
FIG. 1 represents a device of known type;
FIG. 2 represents an embodiment of the device according to the invention;
FIGS. 3 and 4 represent two particular embodiments of the flat guide of the device according to FIG. 2, in a double wave interferometer;
FIG. 5 illustrates the amplitude-phase displacement response curve of the devices according to FIGS. 3 and 4;
FIGS. 6, 7 and 9 represent three particular embodiments of the flat guide of the device according t
REFERENCES:
patent: 5692076 (1997-11-01), DeLisle
Applied Optics, "New integrated-Optics Interferometer in Planar Technology", Sep. 1994, by Duport et al., pp. 5954-5958.
Sensors and Actuators, "Integrated Optical Gas Sensors Using Organically Modified Silicates as Sensitive Films", 1993, by Brandenburg et al., pp. 361-374.
Chemical and Mezcal Sensors, "Gas Sensor Based on an Integrated Optical Interferometer", by Brandenburg et al., pp. 148, 149 & 155.
Benech Pierre
Helmers Hakon
Kim Robert
Schneider Electric SA
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