The building blocks available to the laser source designer for various applications such as LIDAR are continuing to progress, especially with regard to the availability of significantly improved nonlinear optical (NLO) crystals and their coatings. These crystals enhance the performance of laser systems, providing wavelength shifting and tunability with ever increasing output power across the spectral range extending from ultraviolet through the terahertz region. Progress in the development of NLO crystal growth and processing techniques at the Air Force Research Laboratory, comprising both in-house and contractual components, will be presented. The optical characteristics of many of the 'workhorse' crystals continue to improve. For example, zinc germanium phosphide (ZGP), which became the material of choice for 2-micron pumped wavelength-tunable laser sources with average powers greater than 1 watt, continues to improve in terms of transparency and laser damage threshold. In addition, the search continues for NLO crystals that may be pumped by Nd:YAG lasers and generate longer-wavelength laser output through 5 microns. Several compounds are presently being investigated including AgGaGeS₄ and AgGaGe₅Se₁₂. Related to these bulk-crystal developments, surface preparation techniques and motheye surface structures continue to be developed. Since future laser trends are toward all-fiber systems, a new effort began earlier this year on nonlinear optical fiber for super continuum generation. Finally, NLO crystals are being studied for the generation and detection of terahertz radiation. In the presentation, recent advances in the materials development will be reviewed, and the direction of future efforts in this area will be forecast.

We carried out studies to identify, synthesize, purify and grow crystals of a novel class of halides for nonlinear optical applications. Tl₃PbBr₅, Tl₄PbI₆, Tl₄HgI₆ and Tl₃PbI₅, were synthesized by reacting binary halides and crystals were grown. Optical quality was evaluated by fabricating cm size crystals. The homogeneity of bulk crystal was evaluated by studying transparency, etchpit and X-ray rocking curve and 2θ-ω scans. These halides have transparency from visible to far-IR wavelength region. The material of the compounds of Tl₃PbBr₅ composition showed self-poling during the growth.

Piezoelectric single crystals of lead magnesium niobate-lead titanate Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT) show superior properties as compared to piezoelectric ceramics and piezoelectric films in device applications. However, the applications of PMN-PT single crystals are limited due to the lack of a simple and reproducible fabrication technique. By using the flux method, we have successfully obtained PMN-PT single crystals. The size of the obtained crystals varied from 2 to 5 mm³, mostly showing regular cubic shape. The microstructure and the growth mechanism of the as-grown single crystals are investigated by scanning electron microscopy. From simultaneous differential calorimetry and thermogravimetric analysis (SDT) measurements, we have found that PMN-PT melts at 1264.12°C. The long wave-length optical modes in PMN-PT single crystals have been investigated using Raman scattering measurements.

Potassium dihydrogen phosphate KDP; (KH₂PO₄) and triglycine sulfate TGS; (CH₂NH₂COOH.H₂SO₄), are extensively studied ferroelectric materials, and find wide applications in electrooptic and infrared detecting devices respectively. L-arginine phosphate monohydrate (C₆H₁₄N₄O₂H₃PO₄.H₂O), abbreviated as LAP, is a highly transparent monoclinic crystal with attractive properties for efficient frequency conversion of infrared lasers. Effects of doping KDP and TGS crystals with LAP are investigated. It was found in both cases that LAP affects the growth morphology and other properties. The properties of resulting crystals in terms of growth morphology, optical and mechanical properties are presented and discussed.

We discuss phenomena of the optical photons and charged particle channeling in the periodic structures. While particle (as protons) channeling is widely used for the characterization of defects in crystals, channeling of photons is less known. We have demonstrated feasibility of optical channeling method for copying of phase radial grating on the chalcogenide semiconductor glass film and photo-thermoplastic films (PTPF). Chalcogenide glassy semiconductors (CGS) as a medium for recording of optical information have some advantages such as the possibility of achieving a higher resolution power, stability, and a high photosensitivity. We report about recording of the radial phase grating in the doped As-S-Se (CGS). Radial grating was recorded by making copy from the master phase grating placed in the near-field zone and exposure to the CW green (λ=532 nm) low power (P=100 mW) solid-state laser or incoherent UV source. The exposure time has been varied from 15 to 30 min. The recording process could be explained by optical channeling. This phenomenon gives us an opportunity to create phase radial grating using coherent and incoherent illumination.

Quantum and statistical mechanical calculations have been used to guide the improvement of the macroscopic electro-optic activity of organic thin film materials to values greater than 300 pm/V at telecommunication wavelengths. Various quantum mechanical methods (Hartree-Fock, INDO, and density functional theory) have been benchmarked and shown to be reliable for estimating trends in molecular first hyperpolarizability, β, for simple variation of donor, bridge, and acceptor structures of charge-transfer (dipolar) chromophores. β values have been increased significantly over the past five years and quantum mechanical calculations suggest that they can be further significantly improved. Statistical mechanical calculations, including pseudo-atomistic Monte Carlo calculations, have guided the design of the super/supramolecular structures of chromophores so that they assemble, under the influence of electric field poling, into macroscopic lattices with high degrees of acentric order. Indeed, during the past year, chromophores doped into single- and multi-chromophore-containing dendrimer materials to form binary glasses have yielded thin films that exhibit electro-optic activities at telecommunication wavelengths of greater than 300 pm/V. Such materials may be viewed as intermediate between chromophore/polymer composites and crystalline organic chromophore materials. Theory suggests that further improvements of electro-optic activity are possible. Auxiliary properties of these materials, including optical loss, thermal and photochemical stability, and processability are discussed. Such organic electro-optic materials have been incorporated into silicon photonic circuitry for active wavelength division multiplexing, reconfigurable optical add/drop multiplexing, and high bandwidth optical rectification. A variety of all-organic devices, including stripline, cascaded prism, Fabry-Perot etalon, and ring microresonator devices, have been fabricated and evaluated.

Optical spectra of Pr³⁺ doped fiber was recorded under dye laser and Ar⁺ laser excitation. Fluorescence was observed from ¹D₂ and ³P₀ levels. In addition to that emission was also observed at 280 to 300 nm due to cooperative emission.

A real-time phase reversal speckle photography system using BaTiO₃ crystal as a recording medium is developed for phase step calibration. A pi-phase shift on the random speckle pattern is accomplished by varying pressure within an air-filled quartz cell inserted in the pump beam in a two-beam coupling arrangement It is shown that phase reversal can be achieved when a pi-shifted speckle pattern overlaps on an un-shifted speckle pattern at the observation plane in real-time, results in, destructive interference between the two speckle patterns. This phenomenon is exploited for calibration of the phase shifter. A four frame phase shifting technique is used, and the experimental whole field speckle fringe analysis carried out on a diffuse surface subjected to rotation in its own plane is presented.

Cesium hydrogen L-malate monohydrate, CsH(C₄H₄O₅).H₂O, is a new non-linear optical semi-organic crystalline material with a second harmonic generation efficiency roughly 2.5 times greater than KDP. Its crystal structure, space group P2₁, shows that the malate anions, are interconnected through directional O-H•••O hydrogen bonding, in a head-to-tail arrangement, creating extended anionic layers. The water molecules provide a cross-link, through hydrogen bonding, between adjacent layers. Especially noteworthy is that the Cesium cations and the COO- group from the malate anions, form a sequence of nearly perfectly aligned dipoles oriented along the b crystallographic axis giving a permanent dipole moment of 38 Debye per unit cell. As the crystals are non hygroscopic and easy to grow, they are potential new material for nonlinear optical and pyroelectric applications.

The growth of high-quality InN and indium rich group III-nitride alloys are of crucial importance for the development of high-efficient energy conversion systems, THz emitters and detectors structures, as well as for high-speed linear/nonlinear optoelectronic elements. However, the fabrication of such device structures requires the development of growth systems with overlapping processing windows in order to construct high-quality monolithic integrated device structures. While gallium and aluminum rich group III-nitrides are being successfully grown by organometallic chemical vapor deposition (OMCVD), the growth of indium rich group III-nitrides presents a challenge due to the high volatility of atomic nitrogen compared to indium. In order to suppress the thermal decomposition at optimum processing temperatures, a new, unique high-pressure chemical vapor deposition (HPCVD) system has been developed, allowing the growth of InN at temperatures close to those used for gallium/aluminum-nitride alloys. The properties of InN layers grown in the laminar flow regime with reactor pressures up to 15 bar, are reported. Real-time optical characterization techniques have been applied to analyze gas phase species and are highly sensitive the InN nucleation and steady state growth, allowing the characterization of surface chemistry at a sub-monolayer level. The ex-situ analysis of the InN layers shows that the absorption edge in the InN shifts below 0.7 eV as the ammonia to TMI precursor flow ratio is lowered below 200. The results indicate that the absorption edge shift in InN is closely related to the In:N stoichiometry.

A numerical model was developed to simulate vapor deposition in high-pressure chemical vapor-deposition reactors, under different conditions of pressure, temperature, and flow rates. The model solved for steady-state gas-phase and heterogeneous chemical kinetic equations coupled with fluid dynamic equations within a three-dimensional grid simulating the actual reactor. The study was applied to indium nitride (InN) epitaxial growth. The steady-state model showed that at 1050-1290 K average substrate temperatures and 10 atm of total pressure, atomic indium (In) and monomethylindium [In(CH₃)] were the main group III gaseous species, and undissociated ammonia (NH₃) and amidogen (NH₂) the main group V gaseous species. The results from numerical models with an inlet mixture of 0.73:0.04:0.23 mass fraction ratios for nitrogen gas (N₂), NH₃ and trimethylindium [In(CH₃)₃], respectively, and an initial flow rate of 0.17 m s^-1, were compared with experimental values. Using a simple four-path surface reaction scheme, the numerical models yielded a growth rate of InN film of 0.027 μm per hour when the average substrate temperature was 1050 K and 0.094 μm per hour when the average substrate temperature was 1290 K. The experimental growth rate under similar flow ratios and reactor pressure, with a reactor temperature between 800 and 1150 K yielded an average growth rate of 0.081 μm per hour, comparing very well with the computed values.

NASA is striving to develop a scientific understanding of the universe, the Earth-Sun System and the Earth's response to natural or human-induced changes. Space lasers are vital tools for NASA's missions to advance our understanding of space research and improving our prediction capability for climate, and natural hazards. Unfortunately, several past spaceflight missions that utilized lasers proved to be short-lived and unreliable. In this paper, we are shedding more light on the contamination issue in the absence of gravity. We performed a set of relevant experiments on liquids and subsequently correlated the results to the spaceflight laser environment. We found that in the absence of gravity the contamination plays a major role in spaceflight laser failures. We also proposed a methodology using the adsorption mechanism to be adopted in future spaceflight lasers to minimize the presence of contaminants in the laser compartment.

We have synthesized large batches of GaSe reacted mixtures and grown centimeter size indium doped single crystals by the vertical Bridgman technique. Second harmonic measurements were made for high rep rates and data showed a "d" value of 51 pm/V for the GaSe crystals. SHG values were also theoretically calculated and appear to be in good agreement with the experimental data. These values were smaller compared to solid solution GaSe crystals, which showed a "d" value higher than 72 pm/V.

Nonlinear confined (optical and/or electrical) heterostructures based on III-IV-V2 chalcopyrite (CP) thin films and/or embedded CP materials offer unique advantages over group III-V and IV linear structures. These stem from the birefringent nature and the lower crystal symmetry of the CP semiconductors. As an example, this property is responsible three-wave nonlinear parametric processes (a second-order nonlinear effect) and very high values of the second-order hyperpolarizabilities. The recent discovery of room-temperature ferromagnetism in diluted magnetic CP semiconductors adds an additional functionality to this material system that makes possible the construction of novel magneto-optical device structures based on ferromagnetic nanocomposites and confined ferromagnetic heterostructures, which can be embedded in confined birefringent layers. Such structures are the basic elements for advanced "Solid-State Molecular Sensor" (SSMS) device structures. Rugged, miniaturized SSMS structures can be constructed which are based on a unique, optically confined birefringent, group II-IV-V2 CP heterostructure technology. This system identifies target chemicals and biological molecules in real-time under ambient conditions. It can detect and discriminate between numerous and varied molecular species by employing resonant phase- and/or amplitude sensitive detection over a large, tunable spectral range. The SSMS can be made sensitive to a specific group of molecules with appropriate phase matching conditions. Its response is unlike that of a linear waveguide sensor in two primary areas: change of frequency output, and intensity of the output light generated. Both signals are generated in a nonlinear second harmonic generation process sensitive to small changes in the phase matching conditions. Potential applications include compact ultra-sensitive sensors, nonlinear optical modulators, magnetic photonic crystals, magneto-optical switches, detectors, and spin electronic devices.

Cadmium germanium diarsenide (CdGeAs₂,) crystals are very promising for infrared second harmonic generation. However, their use has been limited by optical absorption in the 5 pm region. The role of composition and dopants has been extensively studied, and some point defects have been identified which do affect transparency. While some low absorption material has been produced, it has not been reproducible and variations within boules have been a serious problem. In this paper, which reviews some recent work on this problem, we describe a surprising and complex correlation between optical transparency, dislocations and point defects.

We show that the dynamics of photons in a ring laser gyro are adequately represented by the damped Rabi problem, and thus demonstrate a variety of photonic coherence phenomena analogous to those that occur in atoms. We discuss methods to circumvent the deleterious consequences and exploit the advantageous consequences of these effects. Specifically, we discuss the use of short pulses for the elimination of the gyro dead-band, the use of the dead-band locking frequency for the hypersensitive measurement of scattering and absorption, and the incorporation of fast and slow light media into the cavity for the enhancement of the gyro response.

In this paper the dependence of the radius of a Nd:YVO₄ cylindrical bar, grown in a low-gravity environment, on the pulling rate (v), melt temperature (T₀) at the meniscus basis, pressure in the furnace (p) and die radius (r_0e) is found. Those values of v, T0, p and r_0e are determined for which the crystal radius variation, due to small uncontrollable variations of v, T₀, p around some average values, cause minimal surface non-uniformity. Numerical results are given for a Nd:YVO₄ cylindrical bar grown in a furnace in which the vertical temperature gradient is k=33 K/mm. Finally, the results obtained in low-gravity environment are compared to those obtained in terrestrial conditions.