This PDF file contains the front matter associated with SPIE Proceedings Volume 8187, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

The US Army is investing in Solid State Laser (SSL) technology to assess counter rocket, artillery, and mortar (C-RAM) and counter unmanned aerial vehicle (C-UAV) capabilities of solid state based HEL systems, as well as other potential applications for HELs of interest to the Army. The Army HEL program thrust areas are systematically moving the technology forward toward weaponization, including solid state laser technologies, advances in beam control technology, and conducting major demonstrations. The High Energy Laser Mobile Demonstrator (HELMD) will be a major step toward demonstrating HEL weapon capability to the soldier. The US Army will continue to pursue technologies that enable more compact systems compatible with, for example, a Stryker tactical vehicle as a crucial part of our strategy to provide a capability to the warfighter that can maneuver with the force.

At cryogenic temperatures, Yb:YAG behaves as a 4-level laser. Its absorption and emission cross-sections increase, and its thermal conductivity improves. Yb:YAG thin disk laser performance at room and cryogenic (80°K) temperatures will be presented. The Yb:YAG gain media is cooled using either a pressurized R134A refrigerant system or by a two-phase liquid nitrogen spray boiler. Interchangeable mounting caps allow the same Yb:YAG media to be switched between the two systems. This allows direct comparison of lasing, amplified spontaneous emission, and temperature performance between 20°C and -200°C.

Diode pumped alkali lasers attract growing attention during the past several years because they have demonstrated potential to compete and, possibly, replace the best existing high power laser systems. In spite of the fact that an optically pumped alkali (potassium) vapor laser was first proposed by A.L. Schawlow and C.H. Townes in 1958, the intensive research and development of alkali vapor started only in 2003, when really efficient lasing in Rb and Cs vapors was demonstrated. The interest to this research was stimulated by the possibility of using efficient diode lasers for optical pumping of the alkali gain medium that promises high overall efficiency of the device. A variety of experiments on alkali lasers, including the demonstration of efficient Rb, Cs and K vapor lasers, power scaling experiments with multiple diode laser pumping sources and experiments on diode pumped alkali vapor amplifiers were performed during the past several years. In this paper we present a review of the most important achievements in high power alkali lasers research and development, discuss some problems existing in this field and future perspectives in DPAL development.

Numerical simulations and analysis of a very efficient and stable non-collinear Optical Parametric Chirped Pulse Amplification (OPCPA) femtosecond system are presented. The system is optimized for a long (nanosecond), rectangular temporal profile and a flat-top spatial profile of the pump laser pulse. We show that a two stage system consisting of a multipass preamplifier and a time-sheared power amplifier operating around 850 nm and pumped by a 532 nm pulse can amplify pulses directly from a femtosecond oscillator up to multi-terawat levels with quantum efficiencies as high as 0.9. We also discuss practical schemes of the few-cycle multi-terawatt OPCPA systems employing different nonlinear crystals. The results of the Monte-Carlo simulations are used to balance the stability and efficiency of the parametric amplifier system.

An external cavity with a binary phase grating has been developed to achieve the coherent beam addition of five quantum-cascade lasers emitting at 4.65 μm. The combining of these five emitters is achieved by a binary phase grating or Dammann grating able to separate an incident beam into five beams of equal intensities with a 75% efficiency. A CW output power of ~ 0.5 W corresponding to a combining efficiency of 66% with a good beam quality is obtained. More results concerning output power, combining, efficiency stability and beam quality and spectrum are exposed.

There has been considerable progress on development of technological solutions for high power and high energy mid-IR generation for directed optical countermeasure applications using optical parametric generators. Here we give a summary of what we believe are the important considerations to be made in the design of such sources based on our research over the last years and the general progress in the field. We also give a short review on our latest results in this area, and some thoughts on possibilities for further progress.

Ceramic laser materials have come a long way since the first demonstration of lasing in 1964. Improvements in powder synthesis and ceramic sintering as well as novel ideas have led to notable achievements. These include the first Nd:YAG ceramic laser in 1995, breaking the 1 KW mark in 2002 and then the remarkable demonstration of more than 100 KW output power from a YAG ceramic laser system in 2009. Additional developments have included highly doped microchip lasers, ultrashort pulse lasers, novel materials such as sesquioxides, fluoride ceramic lasers, selenide ceramic lasers in the 2 to 3 μm region, composite ceramic lasers for better thermal management, and single crystal lasers derived from polycrystalline ceramics. This paper highlights some of these notable achievements.

Due to a wide transparency range (0.9-17 μm), a low absorption loss (~ 0.01 cm^-1), and a laser damage threshold comparable to ZGP crystals (~ 2 J/cm²), combined with excellent nonlinear, thermal and mechanical properties, quasi-phase-matched orientation-patterned gallium arsenide (OP-GaAs) crystals are well adapted for efficient mid-infrared optical parametric oscillators (OPOs). The paper discusses the best results obtained, to our knowledge, with an OP-GaAs OPO pumped by a Qswitched 2.09 μm Ho³⁺:YAG laser. The compact (33 × 48 cm) high-repetition rate source developed allows to achieve 4.0 W of average output power in the 3-5 μm range at 40 kHz repetition rate with a 45 % slope efficiency and a very good beam quality (M² < 1.8). 6.4 W were obtained at 70 kHz with a 51 % slope efficiency, and 7.7 W at 100 kHz with a 46 % slope efficiency. At 40 kHz and 70 kHz, an optical damage occurred at a fluence of 1.9 J/cm² and 1.5 J/cm² respectively. The power is limited by the OP-GaAs crystal thickness and is expected to be scaled in thicker samples recently fabricated.

Optical photoluminescence spectroscopic method for detection of impurities, hazardous materials, pesticides, and pollutants in water resources, both qualitatively and quantitatively, is presented. The method is based on synchronous fluorescence spectroscopy (SFS) of organic aromatic compounds, or poly-aromatic hydrocarbons (PAH), and is carried out by following simultaneously their excitation and emission spectra. The full excitation emission matrix (EEM) generated in this way provides a 2-D and 3-D fluorescence map of the tested sample and the diagonals through the axes origin provide the synchronous fluorescence spectra at a constant wavelengths differences between the emission and excitation wavelengths, thus enabling multitude components identification. This map contains all the relevant spectroscopic information of the tested sample, and serves as a unique "fingerprint" with a very specific and accurate identification. When compared with pre-determined spectra and calibration curves from a "databank", there is a one-toone correspondence between the image and the specific compound, and it can be identified accurately both qualitatively and quantitatively. This method offers several significant advantages, and it provides a sensitive (ppm detection level), accurate and simple spectroscopic tool to monitor impurities and pollutants in water. The design and performance of the spectrofluorimeter prototype, as well as the software development and analysis of chemical organic compounds and mixtures in water will be discussed in this paper.

We are reporting on research, development, and operational results of the photon counting detectors that are being developed in our lab for ground laser ranging and space missions related to laser ranging, optical navigation or precise time transfer by laser pulses. The detector is based on silicon avalanche photodiode operated in a special mode with single photon detection capability in optical wavelength region. Routinely used wavelength is 532 nm, but any below 1.2 microns can be used. The detection chip is controlled by a dedicated circuit. The circuit allows biasing and active quenching of detection structure. The bias is controlled by optional external gate. The ground version of detector is optimized for an precision time tagging of an incoming laser pulse in order of several picoseconds and for high dynamical range of incoming optical signal. The space versions of detectors are optimized for an on-board detection and precision time tagging of an incoming laser pulse. The photon counting approach advantages will be discussed for several time of flight application mainly in order to reduce the systematic biases as much as possible. The optical receiver concept and experiment results in satellite laser ranging and laser time transfer will be presented focused on result overlapping to other optical techniques. Some new application and instrumentation to provide one-way ranging over planetary distances will be discussed.

A comprehensive approach to quantify more accurately the physical phenomena leading to blooming effects on infrared sensors is proposed. Laser dazzling effects on mid-infrared HgCdTe focal-plane-array are investigated thanks to the use of an experimental breadboard. This dedicated breadboard is capable of delivering intense laser spots on focal-planearrays with accurate control of laser spot diameter, position, power and pulse time sequence. The main subsystems of this experimental bench are described, laser sources, focusing optics, power control device and opto-electronic synchronization. HgCdTe focal-plane-array dazzling experiments are then analyzed. The main parameters affecting blooming are varied and the impact of spatial, time and energy characteristics on the resulting dazzled image are assessed.

Atmospheric turbulence effects close to ground may affect the performance of laser based systems severely. The variations in the refractive index along the propagation path cause effects such as beam wander, intensity fluctuations (scintillations) and beam broadening. Typical geometries of interest for optics detection include nearly horizontal propagation paths close to the ground and up to kilometre distance to the target. The scintillations and beam wander affect the performance in terms of detection probability and false alarm rate. Of interest is to study the influence of turbulence in optics detection applications. In a field trial atmospheric turbulence effects along a 1 kilometre horizontal propagation path were studied using a diode laser with a rectangular beam profile operating at 0.8 micrometer wavelength. Single-path beam characteristics were registered and analysed using photodetectors arranged in horizontal and vertical directions. The turbulence strength along the path was determined using a scintillometer and single-point ultrasonic anemometers. Strong scintillation effects were observed as a function of the turbulence strength and amplitude characteristics were fitted to model distributions. In addition to the single-path analysis double-path measurements were carried out on different targets. Experimental results are compared with existing theoretical turbulence laser beam propagation models. The results show that influence from scintillations needs to be considered when predicting performance in optics detection applications.

A time-correlated single-photon counting (TCSPC) laser radar system can be used for range profiling of objects with high time resolution and dynamic range. A system setup is described and daytime outdoor measurements over distances up to 1 km are presented. The system has 114 ps full width half maximum system response, indicating a Rayleigh criterion resolution of two surfaces separated by 17 mm and much better with more advanced signal processing methods. The high dynamic range and time resolution allows measurement of distances between different optical surfaces in objects such as optical sights. The system thus has a potential use to classify objects and remove false alarms in an optics detection system. Effects of atmospheric turbulence and background radiation in daytime conditions are analyzed. A method for determining the scintillation index in noisy data using the temporal autocorrelation is described. System performance calculations based on measured data indicate that the performance necessary to detect characteristic features of optical sights and other retroreflecting objects may be found in reasonable dwell times well below 100 ms.

To locate actively geodesic satellites stationed on the low Earth orbits lasers are often used via illumination of the satellites and detection of the laser reflected radiation. But, the lasers can strongly affect electronic devices of the satellites because of scattering of the laser radiation inside its optical systems. To exclude the influence of laser radiation on operating capabilities of the satellites, the characteristic properties of scattered laser radiation in a plane of receiver optical systems are studied in the paper. It is known that scattered laser radiation fields have a speckled character and registered speckles depend on both the laser and photo detector array spectral and power characteristics. In the paper, the laser radiation recorded experimentally in a focal plane of optical system by using photo detector array is investigated at various conditions of the array illumination. Theoretical analysis of the speckles is carried out to determine such characteristics of speckled images as dispersion and covariance and its dependence on the illumination conditions.

The preventive application of automated latent fingerprint acquisition devices can enhance the Homeland Defence, e.g. by improving the border security. Here, contact-less optical acquisition techniques for the capture of traces are subject to research; chromatic white light sensors allow for multi-mode operation using coarse or detailed scans. The presence of potential fingerprints could be detected using fast coarse scans. Those Regions-of- Interest can be acquired afterwards with high-resolution detailed scans to allow for a verification or identification of individuals. An acquisition and analysis of fingerprint traces on different objects that are imported or pass borders might be a great enhancement for security. Additionally, if suspicious objects require a further investigation, an initial securing of potential fingerprints could be very useful. In this paper we show current research results for the coarse detection of fingerprints to prepare the detailed acquisition from various surface materials that are relevant for preventive applications.

Imaging seekers used in modern Anti Ship Missiles (ASMs) use a variety of counter countermeasure (CCM) techniques including guard gates and aspect ratio assessment in order to counter the use of IR decoys. In order to improve the performance of EO/IR countermeasures it is necessary to accurately configure and place the decoys using a launcher that is trainable in azimuth and elevation. Control of the launcher, decoy firing times and burst sequences requires the development of algorithms based on multi-dimensional solvers. The modelling and simulation used to derive the launcher algorithms is described including the countermeasure, threat, launcher and ship models. The launcher model incorporates realistic azimuth and elevation rates with limits on azimuth and elevation arcs of fire. A Navier Stokes based model of the IR decoy includes thermal buoyancy, cooling of the IR smoke and its extinction properties. All of these factors affect the developing size, shape and radiance of the decoy. The hot smoke also influences the performance of any co-located chaff or other obscurant material. Typical simulations are described against generic imaging ASM seekers using shape discrimination or a guard gate.

The development and optimisation of modern infrared systems necessitates the use of simulation systems to create radiometrically realistic representations (e.g. images) of infrared scenes. Such simulation systems are used in signature prediction, the development of surveillance and missile sensors, signal/image processing algorithm development and aircraft self-protection countermeasure system development and evaluation. Even the most cursory investigation reveals a multitude of factors affecting the infrared signatures of realworld objects. Factors such as spectral emissivity, spatial/volumetric radiance distribution, specular reflection, reflected direct sunlight, reflected ambient light, atmospheric degradation and more, all affect the presentation of an object's instantaneous signature. The signature is furthermore dynamically varying as a result of internal and external influences on the object, resulting from the heat balance comprising insolation, internal heat sources, aerodynamic heating (airborne objects), conduction, convection and radiation. In order to accurately render the object's signature in a computer simulation, the rendering equations must therefore account for all the elements of the signature. In this overview paper, the signature models, rendering equations and application frameworks of three infrared simulation systems are reviewed and compared. The paper first considers the problem of infrared scene simulation in a framework for simulation validation. This approach provides concise definitions and a convenient context for considering signature models and subsequent computer implementation. The primary radiometric requirements for an infrared scene simulator are presented next. The signature models and rendering equations implemented in OSMOSIS (Belgian Royal Military Academy), DIRSIG (Rochester Institute of Technology) and OSSIM (CSIR & Denel Dynamics) are reviewed. In spite of these three simulation systems' different application focus areas, their underlying physics-based approach is similar. The commonalities and differences between the different systems are investigated, in the context of their somewhat different application areas. The application of an infrared scene simulation system towards the development of imaging missiles and missile countermeasures are briefly described. Flowing from the review of the available models and equations, recommendations are made to further enhance and improve the signature models and rendering equations in infrared scene simulators.

The use of flares of flares against 1st and 2nd generation man-portable air-defence (MANPAD) systems proved to be very effective. This naturally led to the development of counter-countermeasures (CCM) that could be incorporated into the MANPADs infrared (IR) seeker. One possible CCM is two-colour where the seeker detects in two separate IR bands. It is designed to exploit the different spectral characteristics of the target and flare. In this paper we describe the modelling process of a two-colour conical scan (conscan) IR seeker using CounterSim, a missile engagement and countermeasure simulation software tool developed by Chemring Countermeasures Ltd. It starts by explaining the signal processing needed to be able to reject the flare and track the target. The MANPAD model is then used in an engagement with a fast jet model and a transport aircraft model. Flares are first deployed reactively then released throughout an engagement to investigate the effect of flare release time and the viability of pre-emptive countermeasures.

This paper investigates feature based tracking algorithms that could be used within models of imaging infrared anti-ship missile seekers in a simulation environment. The algorithms use global shape based object features such as Fourier Descriptors or Hu Moments to track a target in rendered sensor images. A template of the desired target is saved during acquisition, and matching is performed between the template and the features of unknown objects extracted from subsequent sensor images. The centroid of the object that matches the best becomes the seeker aim-point. A seeker using local features, generated by the Scale Invariant Feature Transform, to track objects will also be examined. It discriminates between objects within the sensor images by clustering SIFT features that have neighbouring regions of similar intensity. The cluster of features whose average neighbouring intensity is the closest to a desired target template is chosen as the highest priority cluster. A variable radius distance metric is used to reject features in this cluster that are too far from the seeker's previous aim-point. The new aim-point is calculated as the centroid of the cluster of remaining features. Comparisons of the three algorithms' ability to track a naval vessel deploying countermeasures will be also presented.

The aim of work is to develop efficient theoretical model enabling analysis and optimization of Q-switched quasi-threelevel lasers. The model consists of two parts: pumping part and Q-switched part, which can be separated in a case of active Q-switching regime. For the pumping of quasi-three-level gain medium the semi-analytical model was developed, enabling the calculations for average occupation of upper laser level for given pump power and pump duration, spatial pump beam profile, length and dopant level of gain medium. Moreover, ground-state-depletion, up-conversion parasitic relaxation and temperature effects were considered in the model. The new approach for optimization of CW regime of quasi-three-level lasers was developed for Q-switched lasers operating with high repetition rates. Moreover, for long pump durations comparable to laser upper level lifetimes, the optimization procedure based on Lagrange multiplier technique was developed. The simple analytical formulae for effective pump duration needed to achieve the quasistationary inversion for given pump power density and up-conversion parameter were derived. The model enables the optimization of gain medium length and absorbance, average pump area and out-coupling losses for wide class of quasithree- level lasers.