This PDF file contains the front matter associated with SPIE Proceedings Volume 8032, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

Waveguide grating couplers (WGC) are used for input and output coupling in many planar waveguide based sensors. By using a chirped grating, guided light can be decoupled and focused to a desired location. The location and spot size of focused beam depends upon the size and chirp of the grating as well as the wavelength of the light. The locus of the focused beams for different wavelengths lies along a curve. In many applications a planar detector array is used to capture spectral data. Wherever the planar detector array does not intersect this focal curve, images of a point source will be defocused. We develop a theoretical model to calculate the image location and geometric spot size for a given set of grating parameters. In order to experimentally verify the model, chirped waveguide grating couplers were fabricated on HfO2/Quartz planar waveguides using e-beam lithography. The spot size, intensity, and location of diffracted beam was measured at several wavelengths and compared with the theoretical results.

We present a miniature tunable Fabry-Perot (FP) filter development effort based on using MEMS technology to fabricate and package it. The tunable filter development is intended to cover spectral regions from the visible to the longwave infrared by developing a number of different filters each operating over a different wavelength region. The main objective of developing such miniature tunable filters is to use each in a miniature hyperspectral imager by placing it in front of a commercial focal plane array with a suitable optical train. Such a miniature tunable device has many more applications, i.e., in developing tunable sources. Recently, we succeeded in fabricating some operational FP filters operating in the visible/near infrared (VIS/NIR) wavelength region from 400 to 800 nm. The filter design uses one fixed mirror and the second mirror moves using an electrostatic force. The device with a dimension of 18x24 mm² is composed of two parts: one fixed Ag mirror and one electrostatically moveable Ag mirror. Commercially available thin quartz wafer with low total thickness variation (TTV) was used as the substrate for each of these two parts. Au bumps were deposited in both parts in order to control the initial air gap distance and Au-Au bonding was used to bond two parts together. This paper will describe the device design considerations, the fabrication process, the effect of electrostatic force, the optical spectral measurements, and present test results.

We present our results on efficient coupling of Quantum Cascade Lasers (QCLs) into Whispering Gallery Resonators, Hollow Waveguide. We also present results of micro sensors using the unique properties of QCLs, e.g. online sensors for Gas Chromatography (GC). We show that because of the unique brightness properties of QCLs, we could improve GC-Infrared sensors' sensitivity to the same level as Mass Spectrometry, and with different dimension of chemical information.

This work presents our recent progress in development of a field-deployable isotopic N₂O analyzer based on mid-infrared cavity ring-down spectroscopy technique. This instrument operates using thermoelectrically cooled technology, enabling the system to be run unattended for extended periods of time without the use of liquid nitrogen. Ambient atmospheric gas samples are introduced directly into the instrument which will be capable of measuring N₂O concentration with precision of 0.1 ppb in less than a minute of data acquisition time, while isotopic ratio of ¹⁵N/¹⁴N of N₂O is analyzed at < 1 ‰ precision within a few minutes.

Block Engineering has developed an absorption spectroscopy system based on widely tunable Quantum Cascade Lasers (QCL). The QCL spectrometer rapidly cycles through a user-selected range in the mid-infrared spectrum, between 6 to 12 μm (1667 to 833 cm^-1), to detect and identify substances on surfaces based on their absorption characteristics from a standoff distance of up to 2 feet with an eye-safe laser. It can also analyze vapors and liquids in a single device. For military applications, the QCL spectrometer has demonstrated trace explosive, chemical warfare agent (CWA), and toxic industrial chemical (TIC) detection and analysis. The QCL's higher power density enables measurements from diffuse and highly absorbing materials and substrates. Other advantages over Fourier Transform Infrared (FTIR) spectroscopy include portability, ruggedness, rapid analysis, and the ability to function from a distance through free space or a fiber optic probe. This paper will discuss the basic technology behind the system and the empirical data on various safety and security applications.

Tunable Diode Laser Absorption Spectroscopy (TDLAS) is finding ever increasing utility for industrial process measurement and control. The technique's sensitivity and selectivity benefit continuous concentration measurement of selected analytes in complex gas mixtures. Tradeoff options among optical path length, absorption linestrength, linewidth, cross-interferences, and sampling methodology enable sensor designers to optimize detection for specific applications. This paper describes TDLAS measurement precision and accuracy limitations in emerging applications that demand increasing volumes of distributed miniaturized sensors at diminishing costs. In these situations, the TDLAS specificity is a key attribute, while high sensitivity enables novel sampling package designs with short optical pathlengths. Under these circumstances, the traditional approaches to optimizing accuracy and precision may fail if analyzer control features are sacrificed to reduce cost. We describe here a relatively simple TDLAS sensor designed to meet the needs for acceptable cost, and discuss its theory of operation along with the implications on measurement accuracy and precision.

A consortium of researchers at University of New South Wales (UNSW@ADFA), and Loyola University New Orleans (LU NO), together with Australian government security agencies (e.g., Australian Federal Police), are working to develop highly sensitive laser-based forensic sensing strategies applicable to characteristic substances that pose chemical, biological and explosives (CBE) threats. We aim to optimise the potential of these strategies as high-throughput screening tools to detect prohibited and potentially hazardous substances such as those associated with explosives, narcotics and bio-agents.

In this presentation we report on our progress in developing a small, lightweight and low power consumption carbon monoxide sensor for detection and post-fire cleanup aboard manned spacecraft. The sensor is a laser-based absorption spectrometer that uses a Quantum Cascade Laser (QCL) operating at 4.61 microns. The target sensitivity for post-fire cleanup applications is 1 to 500 ppmv. The presentation will detail the laser design and performance and the bench-top performance of the TDLAS sensor including sensitivity and Allan variance measurements. The status of the prototype sensor including size, weight and power consumption estimates and measurements will be presented.

Intracavity Laser Absorption Spectroscopy (ICLAS) at IR wavelengths offers an opportunity for spectral sensing with sufficient sensitivity to detect vapors of low vapor pressure compounds such as explosives. Reported here are key enabling technologies for this approach, including multi-mode external-cavity quantum cascade lasers and a scanning Fabry-Perot spectrometer to analyze the laser mode spectrum in the presence of a molecular intracavity absorber. Reported also is the design of a compact integrated data acquisition and control system. Applications include military and commercial sensing for threat compounds, chemical gases, biological aerosols, drugs, and banned or invasive plants or animals, bio-medical breath analysis, and terrestrial or planetary atmosphere science.

Cavity ringdown spectroscopy (CRDS) measures the decay time, of a resonant optical cavity containing a measurand, as a function of optical frequency. The measurand is identified and quantified by the cavity decay time, which is modified by the measurand within. As coupling light into a high-finesse optical cavity is difficult, the throughput of the cavity is small. A recent variant, swept-cavity heterodyne CRDS, interferes backward escaping cavity light, with light reflected from the cavity input mirror, providing better signal sensitivity due to the heterodyne advantage. The measured interference signal is demodulated and log-amplified to produce a signal whose slope is representative of the cavity decay time. This paper, for the first time, examines the conditions required for high-fidelity measurements of the cavity decay time using swept-cavity heterodyne CRDS and log-amplification technique. We demonstrate that, due to the very large bandwidth and dynamic range of the log-amplifier, for realistic measurement conditions, the log-amplifier does not impose any significant restrictions on the measurement accuracy. We also demonstrate, however, the measurement accuracy is limited by two factors, the detector bandwidth, and segment of acquired data used to measure the slope.

Pathogen detection using Raman spectroscopy is achieved through the use of a sandwich immunoassay. Antibody-modified magnetic beads are used to capture and concentrate target analytes in solution and surface-enhanced Raman spectroscopy (SERS) tags are conjugated with antibodies and act as labels to enable specific detection of biological pathogens. The rapid detection of biological pathogens is critical to first responders, thus assays to detect E.Coli and Anthrax have been developed and will be reported. The problems associated with pathogen detection resulting from the spectral complexity and variability of microorganisms are overcome through the use of SERS tags, which provide an intense, easily recognizable, and spectrally consistent Raman signal. The developed E. coli assay has been tested with 5 strains of E. coli and shows a low limit of detection, on the order of 10 and 100 c.f.u. per assay. Additionally, the SERS assay utilizes magnetic beads to collect the labeled pathogens into the focal point of the detection laser beam, making the assay robust to commonly encountered white powder interferants such as flour, baking powder, and corn starch. The reagents were also found to be stable at room temperature over extended periods of time with testing conducted over a one year period. Finally, through a specialized software algorithm, the assays are interfaced to the Raman instrument, StreetLab Mobile, for rapid-field-deployable biological identification.

Recycling of glass requires the removal of specialist glasses, such as fireproof and mineral glasses, and glass ceramics, which are regarded as contaminants. The sorting must take place before melting for efficient glass recycling. Here, we demonstrate the feasibility of a real-time Raman mapping system for detecting and discriminating a range of industrially relevant glass contaminants in recovered glass streams. The components used are suitable for industrial conditions and the chemometric model is robust against imaging geometry and excitation intensity. The proposed approach is a novel alternative to established glass sorting sensors.

Spatially offset Raman spectroscopy (SORS) is demonstrated for the non-contact detection of energetic materials concealed within non-transparent, diffusely scattering containers. A modified design of an inverse SORS probe has been developed and tested. The SORS probe has been successfully used for the detection of various energetic substances inside different types of plastic containers. The tests have been successfully conducted under incandescent and fluorescent background lights as well as under daylight conditions, using a non-contact working distance of 6 cm. The interrogation times for the detection of the substances were less than 1 minute in each case, highlighting the suitability of the device for near real-time detection of concealed hazards in the field. The device has potential applications in forensic analysis and homeland security investigations.

SPR based sensing techniques utilize a spectroscopy for transducing biomolecular binding events to variations in spectra. This label-free and real-time technique has widely applied for conducting biomedical research. In this study, we present a spectroscopy-based SPR system for monitoring binding between human serum albumin and nucleic acid library. Compared with conventional SPR technique, this novel system utilizes cost-effective nanostructured arrays and a portable UV-Vis spectrometer. These advantages enable a promising development of a portable analytical device for widespread applications. Meanwhile, multispectral analysis used here also helps increase the sensitivity, and thus transducing the binding event to optical signal efficiently. The result demonstrates that this cost-effective and portable system could be applied for a future application of selecting target aptamer. Moreover, we also present surface enhanced Raman spectroscopy (SERS) on the nanostructured arrays in a label-free approach. This integration of multiple spectroscopy technologies is utilized for conducting genome research efficiently.

Ion mobility spectrometry (IMS) is a well known technique; offering small size and a sensitivity in the ppb range makes it a typical technique for the detection of explosives or chemical warfare agents. Ordinary IMS devices use in general a continuously working radioactive ionization source. We use a pulsed non-radioactive electron source for ionization which offers the innovative possibility of introducing delay times in between ionization and ion detection. The application and benefits of such a pulsed ionization source in the detection of the chemical warfare agent simulant dimethyl methylphosphonate (DMMP) and the toxic toluene diisocyanate (TDI) will be demonstrated.

Surface-enhanced Raman spectroscopy (SERS) has repeatedly been shown to be capable of single molecule detection in laboratory controlled environments. However, superior detection of desired compounds in complex situations requires optimization of factors in addition to sensitivity. For example, SERS sensors are metals with surface roughness in the nm scale. This metallic roughness scale may not adsorb the analyte of interest but instead cause a catalytic reaction unless stabilization is designed into the sensor interface. In addition, the SERS sensor needs to be engineered sensitive only to the desired analyte(s) or a small subset of analytes; detection of every analyte would saturate the sensor and make data interpretation untenable. Finally, the SERS sensor has to be a preferable adsorption site in passive sampling applications, whether vapor or liquid. In this paper, EIC Laboratories will discuss modifications to SERS sensors that increase the likelihood of detection of the analyte of interest. We will then demonstrate data collected for TATP, a compound that rapidly decomposes and is undetected on standard silver SERS sensors. With the modified SERS sensor, ROC curves for room temperature TATP vapor detection, detection of TATP in a non equilibrium vapor environment in 30 s, detection of TATP on a sensor exposed to a ventilation duct, and detection of TATP in the presence of fuel components were all created and will be presented herein.

A static dual-channel polarization imaging spectrometer which can simultaneously acquire inphase and antiphase interference images by using a single CCD camera is presented theoretically. The increase of interference signal together with the extractions of the pure image and the pure fringes can be achieved from the summation and the difference of the two interference images respectively. The polarization interferometer is based on the combination of a linear polarizer, a Savart polariscope and a Wollaston prism. To get straight fringes over a relative large field of view, a combined Savart polariscope made of the positive and negative uniaxial crystals can be employed. The principle and the configuration of the system are described.

We experimentally demonstrate a 300μm long silicon photonic crystal slot waveguide for on-chip near-infrared absorption spectroscopy. Based on the Beer-Lambert absorption law, our device combines slow light in photonic crystal waveguide with high electric field intensity in low-index 75nm wide slot, which effectively increases the optical absorption path length of the analyte. We demonstrate near-infrared absorption spectroscopy of xylene in water, independent of near-infrared absorption signatures of water, with a hydrophobic PDMS sensing phase that extracts xylene from water. Xylene concentrations up to 100ppb (parts per billion) (86μg/L) in water were measured.

We show results on the progress in the development of MOEMS based FT spectrometers dedicated to operate in the mid-IR. Recent research is performed within an EC-FP7 project with the goal to show the feasibility of miniaturized high performance infrared spectroscopic chemical analyzers. Exploiting the high analyte selectivity of the mid-IR paired with the inherent sensitivity of an FT-IR spectrometer, such devices could be used in a wide range of applications, from air monitoring over in-line real-time process control to security monitoring. For practical applicability in these fields, appropriate detection limits and spectral quality standards have to be met. The presented system aims at a performance to measure in the range between 4000-700 cm^-1 at a spectral resolution better than 10 cm^-1, which would clearly outmatch previous MOEMS based spectrometer approaches. A further technological advantage is the rapid-scan capability. The MOEMS devices oscillate at 500 Hz. A spectrometer based on this device can acquire 1,000 scans per second in forward-backward mode. The interplay of all these components with the challenges in system integration will be described in detail and experimental results will be shown, presenting a significant step forward in smart spectroscopic sensors, microsystems technology and vibrational spectroscopy instrumentation.

We report on the development of a portable, battery-operated terahertz spectrometer designed for reflection-mode or transmission-mode studies of materials in a wide range of applications. We discuss the challenges overcome to achieving low cost and compact form-factor for the spectrometer instrument, by leveraging commercial fiber-optic packaging techniques for the lasers and photomixers. This approach also permits the THz source and sensor heads to be located remotely from the processing and control electronics. We also discuss novel optical THz phase-control and frequency calibration methods employed in the system.

At the University of Hawaii, we have developed a compact, portable remote Raman and Laser-Induced Breakdown Spectroscopy (LIBS) system with a 532 nm pulsed laser for planetary exploration under the Mars Instrument Development Program. The compact time-resolved remote Raman and LIBS system consists of (i) a regular 85 mm Nikon (F/1.8) camera lens with clear aperture of 50 mm as collection optics, (ii) a miniature spectrograph that occupies 1/14^th the volume of a comparable commercial spectrograph from Kaiser Optical Systems Inc., (iii) a custom mini-ICCD detector, and (iv) a small frequency-doubled 532 nm Nd:YAG pulsed laser (30 mJ/pulse, 20 Hz) with a 10x beam expander. In the standoff Raman mode the system is capable of measuring various minerals, water, ices, and atmospheric gases from a 50 meter range with a 10 s integration time. At shorter distances of 10 m or less, good quality Raman spectra can be obtained within 1 s. The time-gated system is capable of detecting both the target mineral as well as the atmospheric gases before the target using their Raman fingerprints. Various materials can easily be identified through glass, plastic, and water media. The time-gating capability makes the system insensitive to window material, which is highly desirable for future missions to Venus where instruments are expected to be within the lander. The standoff LIBS range is 10 m and LIBS spectra of various minerals can be obtained with single laser pulse excitation. The standoff LIBS capability provides additional elemental verification of the targeted material.

A novel compact LED array based light induced fluorescence (LIF) sensor has been developed for real-time in-line monitoring of intrinsic fluorophores in the solid and liquid state. The sensor is essential for on-the-spot, routine, and cost effective real-time analysis. The sensor is designed to provide real-time emission response along with various smart sensing parameters to ensure real-time measurement quality that is required for regulated GMP process monitoring applications. This work describes a LIF sensor tailored for solid-phase fluorometry. Fundamental figures of merit, excitation overexposure and smart sensing features required for modern process monitoring and control are discussed within the context of pharmaceutical solid-phase manufacturing and similar applications.

We present test results from a compact, fast (F/1.4) imaging spectrometer system with a 33° field of view, operating in the 450-1650 nm wavelength region with an extended response InGaAs detector array. The system incorporates a simple two-mirror telescope and a steeply concave bilinear groove diffraction grating made with gray scale x-ray lithography techniques. High degree of spectral and spatial uniformity (97%) is achieved.

OPTRA is developing a high speed resonant Fourier transform infrared (HSR-FTIR) spectrometer for surface contaminant measurements via time resolved thermal luminescence. This system incorporates a multipass reciprocating interferometer and a resonant mirror structure to accomplish the scanning. The resonant scanning approach significantly reduces the mirror drive power requirement relative to a non-resonant system. Because the spectral range is limited only by the spectral transmission and reflection properties of the components and the detector responsivity, this system can be made as broadband as a typical FTIR spectrometer system. For this application, the system will operate over the 700 - 1400 cm^-1 spectral range with 8 cm^-1 spectral resolution. This paper presents a portion of the preliminary design of the HSR-FTIR prototype and includes the results from breadboard tests of the resonant mirror assembly.

Current hyperspectral imagers are either bulky with good performance, or compact with only moderate performance. This paper presents a new hyperspectral technology which overcomes this drawback, and makes it possible to integrate extremely compact and high performance push-broom hyperspectral imagers for Unmanned Aerial Vehicles (UAV) and other demanding applications. Hyperspectral imagers in VIS/NIR, SWIR, MWIR and LWIR spectral ranges have been implemented. This paper presents the measured performance attributes for a VIS/NIR imager which covers 350 to 1000 nm with spectral resolution of 3 nm. The key innovation is a new imaging spectrograph design which employs both transmissive and reflective optics in order to achieve high light throughput and large spatial image size in an extremely compact format. High light throughput is created by numerical aperture of F/2.4 and high diffraction efficiency. Image distortions are negligible, keystone being <2 um and smile 0.13 nm across the full focal plane image size of 24 mm (spatially) x 6 m (spectrally). The spectrograph is integrated with an advanced camera which provides 1300 spatial pixels and image rate of 160 Hz. A higher resolution version with 2000 spatial pixels will produce up to 100 images/s. The camera achieves, with spectral binning, an outstanding signal-to-noise ratio of 800:1, orders of magnitude higher than any current compact VIS/NIR imager. The imager weighs only 1.4 kg, including fore optics, imaging spectrograph with shutter and camera, in a format optimized for installation in small payload compartments and gimbals. In addition to laboratory characterization, results from a flight test mission are presented.

Two long-wave infrared (LWIR) hyperspectral imagers have been under extensive development. The first one utilizes a microbolometer focal plane array (FPA) and the second one is based on an Mercury Cadmium Telluride (MCT) FPA. Both imagers employ a pushbroom imaging spectrograph with a transmission grating and on-axis optics. The main target has been to develop high performance instruments with good image quality and compact size for various industrial and remote sensing application requirements. A big challenge in realizing these goals without considerable cooling of the whole instrument is to control the instrument radiation. The challenge is much bigger in a hyperspectral instrument than in a broadband camera, because the optical signal from the target is spread spectrally, but the instrument radiation is not dispersed. Without any suppression, the instrument radiation can overwhelm the radiation from the target even by 1000 times. The means to handle the instrument radiation in the MCT imager include precise instrument temperature stabilization (but not cooling), efficient optical background suppression and the use of background-monitoring-on-chip (BMC) method. This approach has made possible the implementation of a high performance, extremely compact spectral imager in the 7.7 to 12.4 μm spectral range. The imager performance with 84 spectral bands and 384 spatial pixels has been experimentally verified and an excellent NESR of 14 mW/(m²srμm) at 10 μm wavelength with a 300 K target has been achieved. This results in SNR of more than 700. The LWIR imager based on a microbolometer detector array, first time introduced in 2009, has been upgraded. The sensitivity of the imager has improved drastically by a factor of 3 and SNR by about 15 %. It provides a rugged hyperspectral camera for chemical imaging applications in reflection mode in laboratory and industry.

Pharmaceutical counterfeiting is a significant issue in the healthcare community as well as for the pharmaceutical industry worldwide. The use of counterfeit medicines can result in treatment failure or even death. A rapid screening technique such as near infrared (NIR) spectroscopy could aid in the search for and identification of counterfeit drugs. This work presents a comparison of two laboratory NIR imaging systems and the chemometric analysis of the acquired spectroscopic image data. The first imaging system utilizes a NIR liquid crystal tuneable filter and is designed for the investigation of stationary objects. The second imaging system utilizes a NIR imaging spectrograph and is designed for the fast analysis of moving objects on a conveyor belt. Several drugs in form of tablets and capsules were analyzed. Spectral unmixing techniques were applied to the mixed reflectance spectra to identify constituent parts of the investigated drugs. The results show that NIR spectroscopic imaging can be used for contact-less detection and identification of a variety of counterfeit drugs.

FT-IR spectroscopy is the technology of choice to identify solid and liquid phase unknown samples. Advances in instrument portability have made possible the use of FT-IR spectroscopy in emergency response and military field applications. The samples collected in those harsh environments are rarely pure and typically contain multiple chemical species in water, sand, or inorganic matrices. In such critical applications, it is also desired that in addition to broad chemical identification, the user is warned immediately if the sample contains a threat or target class material (i.e. biological, narcotic, explosive). The next generation HazMatID 360 combines the ruggedized design and functionality of the current HazMatID with advanced mixture analysis algorithms. The advanced FT-IR instrument allows effective chemical assessment of samples that may contain one or more interfering materials like water or dirt. The algorithm was the result of years of cumulative experience based on thousands of real-life spectra sent to our ReachBack spectral analysis service by customers in the field. The HazMatID 360 combines mixture analysis with threat detection and chemical hazard classification capabilities to provide, in record time, crucial information to the user. This paper will provide an overview of the software and algorithm enhancements, in addition to examples of improved performance in mixture identification.

Fourier transform infrared (FT-IR) spectra of seed and lint cottons were collected to explore the potential for the discrimination of immature cottons from mature ones and also for the determination of actual cotton maturity. Spectral features of immature and mature cottons revealed large differences in the 1200-900 cm^-1 region, and such spectral distinctions formed the basis on which to develop simple three-band ratio algorithm for classification analysis. Next, an additional formula was created to assess the degree of cotton fiber maturity by converting the three-band ratios into an appropriate FT-IR maturity (MIR) index. Furthermore, the MIR index was compared with parameters derived from traditional image analysis (IA) and advanced fiber information system (AFIS) measurements. Results indicated strong correlations (R² > 0.89) between M_IR and M_AFIS and between M_IR and M_IA among either International Cotton Calibration (ICC) standards or selected cotton maturity references. On the other hand, low correlations between the pairs were observed among regular cotton fibers, which likely resulted from the heterogeneous distribution of structural, physical, and chemical characteristics in cotton fibers and subsequent different sampling specimens for individual and independent measurement.

Peak wavelength and full-width-half-maximum (FWHM) are the two important parameters to characterize the spectra of monochromatic LED lights. In this work, a low-cost miniature filter-array spectrum sensor for accurate LED measurement is proposed. For mapping the data from the outputs of the filter-array spectrum sensor to the measurement parameters of peak wavelength and FWHM, Gaussian curves are used as the basis functions to facilitate the estimation. In addition, particle swarm optimization (PSO) is utilized for searching the optimal center locations and the widths of the Gaussian basis functions. The resulting measurement accuracy is competitive to a professional optical spectrometer.

Spectral imaging measures data that is spatially and spectrally resolved: that is at each point in the image the spectrum is measured. Classical spectral imaging requires that the sample is scanned either spatially or spectrally. The main drawback of the classical approaches is that they are sequential. This paper presents a computed tomographic imaging spectrometer (CTIS) that can image two spatial and one spectral dimension in one camera frame. Unlike hyper-spectral imaging techniques which provide full spatial and spectral resolution, with the proposed technique there is a tradeoff between spatial and spectral resolution. The proposed CTIS system uses two crossed glass gratings that project the spectral and spatial image information to a 2D CCD camera array. The current system is designed for microscopic applications in pathology and cell imaging as well as macroscopic material analysis.