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Development of Infrared 'Optical Nose'

Sergey Mirov  -  University of Alabama at Birmingham


Background:  Imagine being able to detect if an area is good for oil drilling without having to dig.  Or detect low-level explosives, drugs or biological weapons in a bag at an airport without searching it.  Or catch the early stages of a disease such as diabetes or cancer just by smelling the breath of a human.  NSF-funded researchers at the University of Alabama at Birmingham (UAB) are aiming to accomplish all of these things and more by creating an “Optical Nose” - - laser-based instrument combining novel narrow-line-width, rapidly and ultra-broadly tunable middle-infrared (mid-IR) laser in conjunction with compatible sensing, signal enhancing and molecule identification techniques.  The system is called “Optical Nose” because it simulates functions of biological olfaction and effectively mimics a magnified sense of smell and displays it in optical domain in a form of absorption patterns specific for each detected molecule.  Optical detection will be performed in the molecular fingerprint region, located in the (mid-IR) wavelength range between 2 and 10 microns.  The laser-based Optical Nose will allow for rapid identification and quantification of organic trace-gases in multi-compound gas mixtures with full biochemical specificity and high sensitivity.

Methodology:  Novel mid-IR laser sources with very challenging properties are required for successful realization of the “Optical Nose” sensor.  Suitable laser sources must generate laser radiation with maximum spectral coverage of the molecular fingerprint spectral region (2-10 microns), excellent wavelength agility (hundreds of thousands of distinct wavelengths per second), watt-level output power, and low noise.  The Optical Nose is comprised of three different lasers:
(1) a Fiber-bulk Pump Laser,
(2) a Seed Laser, and
(3) an Optical Parametric Generator.
Combined in one system, the lasers, acting as the heart of the Optical Nose, provide a high-power, narrow linewidth, ultra-broad and rapidly tunable radiation capable of resonantly exciting the strongest absorption lines of any organic molecule.  This laser system, in conjunction with compatible sensing, signal enhancing and molecule identification techniques, provides real-time analysis and quantification of a measured sample.

The laser source being developed has a modular structure and consists of the following three major components:
(1) Narrow-linewidth, widely tunable (2-3 microns) chromium-doped zinc selenide (Cr2+:ZnSe) continuous-wave seed laser;
(2) Single-frequency, fixed-wavelength (2.09 microns) high energy, pulsed holmium-doped garnet (Ho:YAG) laser;
(3) Optical Parametric Generator based on zinc germanium phosphate (ZnGeP2) non-linear crystal.

Narrow-linewidth laser radiation over the entire molecular fingerprint region is produced by mixing the rapidly tunable laser light from the Cr2+:ZnSe seed laser and fixed-wavelength pulsed radiation from the Ho:YAG pump laser source in the ZnGeP2 non-linear crystal.  The rapid analysis of the gas sample’s chemical composition is performed in a ultra-high sensitivity photo-acoustic optical cell.  Due to high output power and narrow linewidth of the mid-IR laser radiation, very low trace gas content can be detected.  The envisioned sensitivity of the Optical Nose detector could reach a sub-parts-per-trillion level, thus enabling reliable detection of even ultra-low concentrations of biomarkers.  There are devices available that can measure light absorption in a gas sample, but they are very slow, or the spectral coverage of these systems is very limited, or the linewidth is not sufficient to provide necessary selectivity.  That is what makes the Optical Nose superior.  The range of tunability, narrow linewidth and wavelength agility are such that the system will provide a complete, total profile of the trace gas contents in complex gas mixtures in real-time.

Results:  The following core components of the Optical Nose laser system have been prototyped during the first stage of the project:
(1) The first Er-fiber-laser-pumped, single-frequency Cr2+:ZnSe laser with ultrafast tuning speed of 4 microns/s, the output power of 150 mW, and the laser linewidth of 120 MHz has been developed and tested;
(2) Power-scaling of the Cr2+:ZnSe laser was performed, resulting in the first room temperature, multi-watt (2.7 W), pure CW Cr2+:ZnSe laser source.
(3) A high-energy (20 mJ), compact Ho:YAG pulsed laser was built as a prototype for the Ho:YAG single-frequency pulsed laser pump source for the Optical Parametric Generator of the Optical Nose system.


Sergey Mirov Image 1   Sergey Mirov Image 2

The “heart” of the Optical Nose: single-frequency, high-power, widely-tunable Cr2+:ZnSe laser.
 
 
Fiber-bulk “hybrid” Tm-fiber-Ho:YAG infra-Red pulsed laser, burning a hole in a 10c coin.
 
Credit, both images:  Sergey B. Mirov, University of Alabama at Birmingham

 
Scientific Uniqueness:  Even after decades of laser and nonlinear optical research, ideal versatile sources capable of generating the mid-IR radiation required for the envisioned applications do not exist.  Previous attempts to utilize mid-IR laser sources, such as lead salt diode lasers, quantum cascade lasers, and free-electron lasers, suffered from their insufficient output power, limited spectral coverage, or spectral controllability, resulting in an unacceptably low detection sensitivity, selectivity and speed.  So far, the most promising sources of coherent radiation for mid-IR optical nose are optical parametric oscillators capable of generating coherent radiation in the molecular fingerprint spectral region, where conventional lasers perform poorly or are unavailable.  The Optical Nose system combines existing and novel laser technologies in a single, high-performance integrated system capable of generating narrow-linewidth high power laser radiation tunable over the entire organic molecular fingerprint region spanning 2-10 microns.  The uniqueness of this instrument is that it will be capable of identifying a large variety of molecular organic trace-gases in multi-compound gas-mixtures and to quantify them at ultra-low concentration levels (parts per trillion and lower).

Impact on Industry and/or Society:  UAB’s Optical Nose is unique in that it is narrow-linewidth, broadly tunable, and ultrasensitive in the mid-IR range.  As a result, this Optical Nose opens a new pathway for using ultrasensitive mid-IR sensors in environmental monitoring (oil prospecting, hazardous waste, atmospheric), counter-terrorism applications (detection of explosives and landmines, airport safety, applications with aircraft, ships, satellite/aircraft-based countermeasures, detection of explosives, chemical and biological warfare agents), and industrial process control.  This technology also will enable new discoveries in the fundamental understanding of life processes including physiological and pathological processes in the human body.

This work is notable because it will satisfy the challenging demands of highly-sensitive and fast detection of molecules in the molecular fingerprint mid-IR spectral region by applying optical detection methods based on high-power, ultra-broad and rapidly tunable mid-IR sources, compatible sensing and signal enhancing techniques along with advanced packaging, miniaturization, and automation of the instrument.

This work is multidisciplinary.  The development project will bring together laser scientists, optical sensor and spectroscopy experts, environmental scientists, molecular biologists, chemists, biochemists, and biomedical research communities in an exciting environment of interdisciplinary research and education, and will provide the opportunity for understanding life processes and important new discoveries in biomedicine, environmental monitoring, and Counter-Terrorism related detection of toxic and explosive materials.

This project addresses the NSF Strategic Goals of:
(1) Discovery.  This work is at the forefront of discovering new techniques and mechanisms for generation of the narrow-linewidth laser radiation in the organic molecular fingerprint mid-IR spectral region and identifying the biomarkers suitable for early diagnosis of mutations in the human body.
(2) Learning.  The multidisciplinary approach fostered by the research team will equip the graduate students with the tools and skills to work collaboratively with physicists, chemists, and bioengineers.  Results from this project will be used to enhance graduate and undergraduate curricula to ensure that the most current up-to-date material is presented to the future workforce.

This Nugget represents transformative research.  The outcome of this development project will be offered as a "technology opportunity" for U.S. laser and photonics companies, in order to maximize the societal impact of the project.



     
Program Officer:   Leon Esterowitz
     
NSF Award Number:   0521036
     
Award Title:   MRI: Development of Middle Infrared 'Optical Nose'
     
PI Name:   Sergey Mirov
     
Institution Name:   University of Alabama at Birmingham
     
Program Elements:
 
  1189 - Major Research Instrumentation
7236 - Biophotonics, Advanced Imaging, & Sensing for Human Health
     
CBET Nugget:   FY 2007
     

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This Nugget was Updated on 26 September 2008.