Design and characterization of integrated-optic-based chemical sensors

Persistent Link:
http://hdl.handle.net/10150/285055
Title:
Design and characterization of integrated-optic-based chemical sensors
Author:
Beregovskii, Iouri
Issue Date:
1999
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
A novel line of integrated-optic-based chemical sensors was developed. The sensors are based on modification of the optical cavity of a single-mode semiconductor distributed Bragg reflector (DBR) laser. A sensitive layer changes its refractive index in presence of a specific chemical, thus changing the effective refractive index of the section and the optical length of the cavity. This results in laser frequency shift measured either directly or by heterodyne detection using a reference laser as the second source. It is shown that DBR-laser-based sensors can achieve in principle a much higher sensitivity than passive sensors, such as Mach-Zehnder interferometers, due to the narrow linewidth of DBR lasers. The theory of DBR-laser-based sensors is described. It allows optimizing the sensitive section length and field confinement in the sensitive layer for the lowest detection limit. The optimum parameters depend on cavity losses and absorption of the sensitive material. Numerical modeling shows a wide acceptable range of sensitive section parameters for low-loss materials, while for higher-loss materials this range becomes much narrower. Narrow-linewidth DBR lasers are required for high sensitivity. In this respect, sol-gel waveguides with and without Bragg grating were incorporated in the DBR laser scheme. Single-mode operation of DBR lasers with sol-gel waveguide gratings was demonstrated for the first time, with 34-dB side mode suppression and a short-term linewidth of 150 to 500 kHz. A 3-section configuration with sol-gel waveguides and fiber grating showed 28-dB side mode suppression and a short-term linewidth of 600 kHz. Chemical sensing was performed with fiber grating, sol-gel waveguide grating, and 3-section DBR lasers. The first two types showed frequency shift of over 130 MHz in the presence of acetone vapors, and reversibility within experimental errors. The 3-section scheme showed significant dispersion of response and lack of reversibility due to parasitic reflections and instability of the setup. The effect of reflections from facets on performance of this design was examined and found to reduce the maximum sensitivity.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Chemistry, Analytical.; Physics, Optics.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Optical Sciences
Degree Grantor:
University of Arizona
Advisor:
Fallahi, Mahmoud

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleDesign and characterization of integrated-optic-based chemical sensorsen_US
dc.creatorBeregovskii, Iourien_US
dc.contributor.authorBeregovskii, Iourien_US
dc.date.issued1999en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractA novel line of integrated-optic-based chemical sensors was developed. The sensors are based on modification of the optical cavity of a single-mode semiconductor distributed Bragg reflector (DBR) laser. A sensitive layer changes its refractive index in presence of a specific chemical, thus changing the effective refractive index of the section and the optical length of the cavity. This results in laser frequency shift measured either directly or by heterodyne detection using a reference laser as the second source. It is shown that DBR-laser-based sensors can achieve in principle a much higher sensitivity than passive sensors, such as Mach-Zehnder interferometers, due to the narrow linewidth of DBR lasers. The theory of DBR-laser-based sensors is described. It allows optimizing the sensitive section length and field confinement in the sensitive layer for the lowest detection limit. The optimum parameters depend on cavity losses and absorption of the sensitive material. Numerical modeling shows a wide acceptable range of sensitive section parameters for low-loss materials, while for higher-loss materials this range becomes much narrower. Narrow-linewidth DBR lasers are required for high sensitivity. In this respect, sol-gel waveguides with and without Bragg grating were incorporated in the DBR laser scheme. Single-mode operation of DBR lasers with sol-gel waveguide gratings was demonstrated for the first time, with 34-dB side mode suppression and a short-term linewidth of 150 to 500 kHz. A 3-section configuration with sol-gel waveguides and fiber grating showed 28-dB side mode suppression and a short-term linewidth of 600 kHz. Chemical sensing was performed with fiber grating, sol-gel waveguide grating, and 3-section DBR lasers. The first two types showed frequency shift of over 130 MHz in the presence of acetone vapors, and reversibility within experimental errors. The 3-section scheme showed significant dispersion of response and lack of reversibility due to parasitic reflections and instability of the setup. The effect of reflections from facets on performance of this design was examined and found to reduce the maximum sensitivity.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectChemistry, Analytical.en_US
dc.subjectPhysics, Optics.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineOptical Sciencesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorFallahi, Mahmouden_US
dc.identifier.proquest9946832en_US
dc.identifier.bibrecord.b39917009en_US
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