The spatially heterodyned spectrometer (SHS) is one of a class of interesting Static Fourier Transform Spectrometers (FSTS) which offers particular advantages when high spectral resolution is required over a relatively narrow design wavelength range, and high light throughput is needed. The technique was invented by Harlander and Roesler in 1990, and have been under development in various embodiments since; the original applications were astronomical but other application areas are continually appearing. We have investigated a field-widened SHS in terms of its fundamental spectral resolution and its sensitivity. The light grasp of the SHS is very large compared to “standard” dispersive spectrometer hoverer one must be careful to distinguish between light grasp and sensitivity; our prototype device used a 3mm liquid light guide as the input optic, operating at f/1.4, and was constructed with off-the-shelf optical components, apart from the field widening prisms which were custom made. It demonstrated a S/N ratio of unity with an input power of tens of femto-Watts in a sub-resolution spectral feature, and a spectral resolution of 2.9 wave numbers, operating between 790nm and 940nm. The exposure time was of the order of 60 seconds or greater. We conclude that this arrangement would be an excellent tool for analysis of Raman spectra.

In recent years, laser-induced breakdown spectroscopy (LIBS) has been established as a promising analytical tool for online chemical analysis. The emitted light spectrum is analyzed for instantaneous determination of the elemental composition of the sample, enabling on-line classification of materials. Two major strengths of the technique are the possibilities to perform both fast and remote chemical analysis to determine the elemental composition of the samples under test. In order to reduce the size of LIBS systems, the use of a compact Q-switched diode-pumped solid-state laser (DPSSL) in a LIBS system is evaluated for the industrial sorting of aluminium alloys. The DPSSL, which delivers 150μJ pulses of high beam quality at more than 7KHz repetition rate, provides irradiance on the target that is appropriate for LIBS measurements. The experimental results indicate that alloy classification and quantitative analysis are possible on scrap aluminium samples placed 50 cm apart from the focusing and collecting lenses, without sample preparation. Similar calibration curves and limits of detection are obtained for traditional high-energy low-frequency flashlamp-pumped and low-energy high-frequency diode-pumped lasers, showing the applicability of compact diode-pumped lasers for industrial LIBS applications.

In this paper we consider two approaches widely used in optical testing: Shack-Hartmann wavefront sensor and Fizeau interferometer technique. Fizeau interferometer that is widely used in optical testing can be easily transformed to a device using Shack-Hartmann wavefront sensor, the alternative technique to check optical components. We call this device Hartmannometer, and compare its features to those of Fizeau interferometer.

We describe an acousto-optic tunable filter (AOTF) based hyper-spectral imaging microscope system that allows real time unmixing of the combination of cellular morphology staining and multiple biomarker staining on a single microscope slide. We describe several advances in AOTF technology such as novel acoustic apodization schemes in the longitudinal and transverse directions that have greatly improved image quality. In addition we demonstrate construction leading to improved broadband matching which in turn allows in lower power operation allowing up to 16 simultaneous arbitrary-wavelength optical channels to be processed if necessary. We discuss optical schemes and other factors that allow low stray light and rejection of out-of-band light. A hyper-spectral imaging bright field microscope using these advances demonstrates pathology results that have great potential for clinical use.

We demonstrate the fabrication of a mechanically robust planarised fibre-FHD optical composite. Fabrication is achieved through deposition and consolidation of optical grade silica soot on to both an optical fibre and planar substrate. The consolidated silica acts in joining the fibre and planar substrate both mechanically and optically. The concept lends itself to applications where long interaction lengths (order of tens of centimetres) and optical interaction via a planar waveguide are required, such as pump schemes, precision layup of fibre optics and hybrid fibre-planar devices. This paper considers the developments in fabrication process that enable component development.

The interaction between surface plasmon polariton (SPP) and acousto-optic tunable filter was studied. Acoustic wave was used to induce core mode to cladding mode coupling and eventually resulted in SPP generation at the fiber cladding surface. The interaction between optical fiber core mode, cladding mode and SPP mode is formulated by using mode coupling theory. The dielectric constant of SPP and light reflection coefficient on fiber surface was calculated using Nlayer model. Experimental studies were also carried out to verify the theory and simulation results. The existence of SPP at fiber surface boosted the acoustic assisted optical energy coupling from fiber core mode to TM and HE cladding mode but not to TE cladding mode, which agrees with the theoretical and simulation results. It provides a motion-free, high speed and full-electronic solution for generation and control of SPP with high flexibility and tunability.

The rapid growth of global data traffic demands the continuous search for new technologies and systems that could increase transmission capacity in optical links and recent experiments show that to do so, it is advantageous to explore new degrees of freedom such as polarization, wavelength or optical modes.

Mode division multiplexing (MDM) appears in this context as a promising and viable solution for such capacity increase, since it utilizes multiple spatial modes of an optical fiber as individual communication channels for data transmission. In order to evaluate its performance, a MDM system requires advanced characterization methods with regard to the modal content of its photonics components and in particular of the fibers involved for data transmission.

In this contribution we present a time-domain interferometric technique for a full modal characterization of few mode fibers (FMF), commonly used in a MDM scenario. This experimental technique requires the use of a Mach-Zehnder interferometer, where the reference’s path length is controlled by an optical delay line. The interference between the output beams of reference and fiber under test (FUT) is recorded on a CCD camera and a careful evaluation of the resulting interferograms allows us to have full access to key parameters such as number of modes, modal weight, differential time delay between propagating modes and intensity profiles.

In this work, we apply this simple and complete characterization method to the case of a short link with two optical modes propagating in a FMF, which illustrates its potential as a diagnostic tool for MDM systems.

Thin films continue to show great promise for improving a wide variety of devices in applications such as medical instrumentation, material processing, and astronomical instrumentation. While ellipsometry and reflectometry are standard characterization techniques for determining thickness and refractive index, these techniques tend to require highly reflective or polished films and rely on empirical equations. We have created Quantum Tunneling Photoacoustic Spectroscopy (QTPAS) that uses light induced ultrasound to obtain thickness and refractive index estimates of transparent films. We present QTPAS to be used for the estimation of properties of single layer films as an alternative to ellipsometry and give qualitative sample measurements of the technique's estimated parameters.

Surface plasmon resonance (SPR) sensor has been studied for high sensitivity optical biosensor as a single molecule detection, virus detection, DNA sequencing etc. SPR sensor requires an ultra-small signal detection system that measures very small intensity variation of reflected light along with the change of a refractive index near the sensor surface. In this reason, lock-in detection method which is able to detect small signal buried in noise has been applied to SPR sensor. In general lock-in detection method using multiplier and low pass filter measures DC value of output, and its sensitivity is determined by 1/f noise at DC. Unlike the DC measurement we have proposed 2ω harmonic lock-in detection method using multiplier and band pass filter. Sensitivity of the proposed lock-in detection method is much lower than 1/f noise at DC. In this paper we will show that 2ω harmonic lock-in detection method for SPR sensor system providing the sensitivity enhanced.

A novel fuel level sensor for aeronautical applications is developed. The sensor is based on an array of total internal reflection (TIR) point sensors. Respect to conventional TIR sensors the new design permits to be sensitive to common jet fuels (JetA, JP4,JP7) but also to operate with new alternative fuels. The sensor doesn’t require aircraft calibration, temperature compensation and furthermore is able to operate correctly when partially or totally exposed to presence of condensed water on its surface. The point sensors are multiplexed on a single fiber by optical couplers and interrogated simultaneously by Optical Time Domain Reflectometry (OTDR) at a wavelength of 1550nm. Experimental results show a resolution of ±1.5mm could be achieved. The sensors is also able to measure the free water level in the fuel.

The distributed optical fiber magnetic field sensors have a capability of spatially resolving the magnetic field along the entire sensing fiber that is distinguishes from other sensing methods. We present a distributed optical fiber magnetic field sensor based on magnetostriction using Rayleigh backscattering spectra shift in OFDR (optical frequency-domain reflectometry). As the spectral shift of Rayleigh backscattering can be used to achieve a distributed strain measurements with high sensitivity and high spatial resolution using OFDR. In the proposed sensor, the magnetostrictive Fe-Co-V alloy thin films as sensing materials are attached to a 51 m standard single mode fiber (SMF). We detect the strain coupled to SMF caused by variation of magnetic field by measuring Rayleigh Backscattering spectra shift in OFDR. In our experiment, we measure the range of the magnetic field is from 12.9 mT~143.3 mT using proposed method. The minimal measurable magnetic field variation is 12.9 mT when the spatial resolution is 4 cm. The minimal measurable magnetic field variation can be improved to 5.3 mT by increasing the spatial resolution to 14 cm. Moreover, we present the simulation result of two dimension (2D) distribution for the static magnetic field using the Maxwell software program.

Partially coherent light provides attractive benefits for different applications in microscopy, astronomy, telecommunications, optical lithography, etc. However, design and generation of partially coherent beams with desirable properties is challenging. Moreover, the experimental characterization of the spatial coherence is a difficult problem involving second-order statistics represented by four-dimensional functions that cannot be directly measured and analyzed. We discuss the techniques for design and generation of partially coherent structurally stable beams and the recently developed phase-space tomography methods supported by simple experimental setups for practical quantitative characterization of partially coherent light spatial structure, including its local coherence properties.

Propagation invariant structured laser beams play an important role in several photonics applications. A majority of propagation invariant beams are usually produced in the form of laser modes emanating from stable laser cavities. This work shows that anamorphic optical systems can be effectively employed to transform input propagation invariant laser beams and produce a variety of alternative propagation invariant structured laser beam distributions with different shapes and phase structures. This work also presents several types of anamorphic lens systems suitable for transforming the input laser modes into a variety of structured propagation invariant beams. The transformations are applied to different laser mode types, including Hermite-Gaussian, Laguerre-Gaussian, and Ince-Gaussian field distributions. The influence of the relative azimuthal orientation between the input laser modes and the anamorphic optical systems on the resulting transformed propagation invariant beams is presented as well.

NASA GSFC’s Thermal Signature Identification System (TheSIS) 1) measures the high order dynamic responses of optoelectronic components to direct sequence spread-spectrum temperature cycling, 2) estimates the parameters of multiple autoregressive moving average (ARMA) or other models the of the responses, 3) and selects the most appropriate model using the Akaike Information Criterion (AIC). Using the AIC-tested model and parameter vectors from TheSIS, one can 1) select high-performing components on a multivariate basis, i.e., with multivariate Figures of Merit (FOMs), 2) detect subtle reversible shifts in performance, and 3) investigate irreversible changes in component or subsystem performance, e.g. aging. We show examples of the TheSIS methodology for passive and active components and systems, e.g. fiber Bragg gratings (FBGs) and DFB lasers with coupled temperature control loops, respectively.

We present here methodology and instrumentation for the precise measurement of retardance and optic axis orientation of retarder assemblies for the Daniel K. Inouye Solar Telescope. This solar telescope will perform broadband polarimetry of the sun. Each Meadowlark assembly is made up of three compound zero order retarders that must have a retardance variation of less than 6.33 nanometers across the greater than 110 millimeter clear aperture. The retardation of each component was measured using a combination of spectral transmission scans and ellipsometry, with test wavelengths of less than a 0.45 nanometer bandwidths and yielding a standard deviation in measurements of less than 0.001 waves. A technique for the measurement of the near zero window (Infrasil® and CaF₂) retardance is shown, in addition to retardance measurements of the component waveplates. An average retardance of 0.63 nm for CaF₂ and 0.28 nm for Infrasil® was found. Finally, a technique for determining the optic axis tilt of each crystal waveplate using laser ellipsometry is discussed.

We present a high performance Time-to-Digital Converter (TDC) card that provides 10 ps timing resolution and 20 ps (rms) timing precision with a programmable full-scale-range from 160 ns to 10 μs. Differential Non-Linearity (DNL) is better than 1.3% LSB (rms) and Integral Non-Linearity (INL) is 5 ps rms. Thanks to the low power consumption (400 mW) and the compact size (78 mm x 28 mm x 10 mm), this card is the building block for developing compact multichannel time-resolved instrumentation for Time-Correlated Single-Photon Counting (TCSPC). The TDC-card outputs the time measurement results together with the rates of START and STOP signals and the number of valid TDC conversions. These additional information are needed by many TCSPC-based applications, such as: Fluorescence Lifetime Imaging (FLIM), Time-of-Flight (TOF) ranging measurements, time-resolved Positron Emission Tomography (PET), single-molecule spectroscopy, Fluorescence Correlation Spectroscopy (FCS), Diffuse Optical Tomography (DOT), Optical Time-Domain Reflectometry (OTDR), quantum optics, etc.

A novel optical accelerometer based on laser self-mixing effect is presented and experimentally demonstrated, which consists of a mass-loaded elastic-beam assembly and laser self-mixing interferometer. Under external acceleration, an inertial force is applied to the mass, flexible beams deflect from their equilibrium position. The deflection can be read out by the self-mixing interferometer. In order to reduce the impact of higher harmonic, wavelet analysis is introduced to remove singular points. Preliminary results indicate that the resolution is 0.19μg/Hz^1/2 within a bandwidth of 100Hz. The optical accelerometer has the potential to achieve high-precision, compact accelerometers.

A new real-time nondestructive polarimetric method is suggested for the determination of the stressed state distribution in different objects. Light reflected from the object is polarized in a varying degree, and the distribution of the polarization state in the object image is related to the distribution of stresses in it. Method is based on the obtaining the distribution pattern of the polarization state of light in the object image, which is formed by an objective. The integral polarization-holographic diffraction element developed by us is used for real time complete analysis of the polarization state of light at each point of the image, formed by the element in the diffraction orders. The simultaneous measurement of the intensities in four diffracted beams by means of a matrix of photodetectors and the appropriate software enable the polarization state of an analyzable light and its change to be obtained in real time. The laboratory model is presented. The correlation relations between the polarization state of light reflected from the sample with the distribution of the dosated mechanical stresses is considered. The theoretical model is presented. The experimental results are shown for different samples with one- and two-axis stress distribution. The method is nondestructive, i.e. there is no need to drill holes or openings or sticking transparent photoelastic plates on the object to determine the stresses. This method will enable the distance monitoring and diagnosis of already existing constructions to be carried out. This method will differ by universality, simplicity, high speed and comparative cheapness.

Using a novel numerical method we show how to optimize the resolution enhancement of stimulated emission depletion (STED) by simulating the entire process including the absorption, overlapping multiple beams and stimulated emission. We provide calculations showing that for fixed donut pulse energy, a longer donut pulse length can result in greater resolution enhancement than a shorter donut pulse length. These results show how it is possible to use our simulations to design the best experimental conditions for STED resolution enhancement and illustrate the importance of having a software program that includes both multiple beams and stimulated emission.

Here, we present a triple illumination phase interferometer to have a more flexible unwrapping measurement range for single shot optical unwrapping. Three beams of this interferometer illuminate a sample at different incident angles, three phases of the different incident angles are simultaneously recorded using three spatial frequencies. The different direction phases can be used for dual illumination optical unwrapping; as a result, the phase can be unwrapped by more than one measurement range. The feasibility of this technique is demonstrated by measuring a stepped object with heights of 150 and 660 μm. The smaller stepped phase is unwrapped by two measurement range; however, the phase of larger step is wrapped for only one of the measurement range.

Quality control of different coatings (colorful, paint, marker, safety, etc.) that are applied to the surface of various objects (both metallic and non-metallic) is an important problem. Also, there is a problem of dealing with counterfeit products. So it’s necessary to distinguish the fake replicas of marking from the authentic marking of producer. To solve these problems, we propose an automated apparatus for analysis and control of spectral reflection characteristics, albedo and color parameters of extended (up to 150 mm × 150 mm) flat objects. It allows constructing the color image of the object surface as well as its multispectral images in different regions of the spectrum. Herewith the color of the object surface can be calculated for various standard light sources (A, B, C, D65, E, F2, F7, F11, GE), or to any light source with a predetermined emission spectrum. The paper presents the description of working principles of the proposed apparatus as well as the results of reflection and multispectral analysis of different flat objects.

The relevance of noninvasive method for determining the blood sugar is caused by necessity of regular monitoring of glucose levels in diabetic patients blood. Traditional invasive method is painful, because it requires a finger pricking. Despite the active studies in the field of non-invasive medical diagnostics, to date the painless and inexpensive instrument for blood sugar control for personal use doesn't exist. It's possible to measure the concentration of glucose in the blood with help of spectrophotometry method. It consists of registering and analyzing the spectral characteristics of the radiation which missed, reflected or absorbed by the object. The authors proposed a measuring scheme for studying the spectral characteristics of the radiation, missed by earlobe. Ultra-violet, visible and near infrared spectral ranges are considered. The paper presents the description of construction and working principles of the proposed special retaining clip and results of experiment with real patient.

Color is one of the most important metrics of foodstuffs quality. It gives an indication of freshness, ingredient composition as well as about the presence or absence of falsification. Most often, the color is estimated visually, and thus, the evaluation is subjective. By automating the color analysis a wide application for this method could be found. The aim of this research is to study the principles of color analysis as applied to the task of evaluating the freshness of meat products using modern machine vision systems. From a scientific point of view, the color of meat depends on the proportion of myoglobin and its derivatives. It's the main pigment that characterizes the freshness of meat. Further color of meat can change due to oxidation of myoglobin during storage. Myoglobin exists in three forms. There are oxygenated form, oxidized form and form without oxygen. The meat color changes not only due to the conversion of one form into another. The content of amino acids and ammonia are another characteristics and constant signs of meat products spoilage. The paper presents the results of meat color computer simulation based on data on the content of various forms of myoglobin in different proportions. The spectral characteristic of the light source used to illuminate the meat sample is taken into account. Also the experimental studies were conducted using samples of beef. As a result the correlations between said biochemical indicators of the quality and color of the meat obtained with the help of machine vision system were found.