Agency: Department of Defense | Branch: Army | Program: STTR | Phase: Phase I | Award Amount: 150.00K | Year: 2015
Numerous applications of THz systems have been demonstrated including imaging, nondestructive inspection and security screening. A major potential application of THz systems is in the spectroscopic analysis and detection of molecules through their fundamental absorption bands. Various polar molecules exhibit characteristic absorption lines arising from pure rotational transitions in the THz frequency region. Chemical substances such as illegal drugs or explosives show their characteristic absorption spectra at THz frequencies. Therefore, many gases, gas mixtures and chemical substances can be monitored by sensing and identifying their absorption spectra via THz spectroscopy. Here we propose a new method for efficient generation of broadly tunable THz waves, based on a comb of differential frequencies generation in a nonlinear crystal. Solid state lasers in doped photosensitive glasses will emit multiple equidistant frequencies controlled by volume Bragg gratings. Employing high intracavity intensities within a low-loss high Q resonator produced by extremely efficient VBGs will allow generating multi-mW powers in a wide range (1-5 THz) of THz frequencies.
Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase II | Award Amount: 750.00K | Year: 2015
ABSTRACT:The wavelength region covering short to long infrared diapasons is used for environmental sensing, metrology and clinical diagnosis, and LADAR applications. All these applications require good optical isolation to prevent laser destabilization and possible damage. The main objective of this project is creation of the suitable material for optical isolation, which includes development of a glass which shows high magnetooptical properties (large Verdet constant), low losses and high optical homogeneity, and demonstration of bulk and fiber prototypes of optical isolators in the visible, near and mid-IR spectral regions (0.4-5 um). In order to make new glass isolator material available for fiber systems, we are going to continue exploration of an efficient fabrication of optical fibers from rare earth doped germanate glasses. Our efforts will be concentrated on fabrication of a single mode magnetooptical fiber and with further design and fabrication of polarization maintaining single mode fiber.BENEFIT:Based on our studies of magneto-optical glasses doped with rare earth ions we selected several perspective candidates for an effective optical isolation in Mid-IR region. Moreover we showed the possibility of rare earth doped PTR and Ge glass fibers, which is the first step on the way of all-fiber Mid-IR optical isolators. In the framework of the Phase II we will concentrate our research on the development of the fully operated high power (up to 500 W) actively cooled optical isolator working in 3-5 um region with 30-40 dB of returning loss at all power levels. Anticipated benefits of a proposed optical isolator include reduction of weight and dimensions of the final prototype, wide transparency in mid-IR region and low loss. Potential Commercial Application are the laser systems operating in mid-IR spectral region represent a fast growing market for medical, environmental and industrial applications. Commercial applications include optical isolators for solid state and fiber lasers rare earth and transition ions doped crystals and glasses, quantum and interband cascade semiconductor lasers, etc. Mid-IR optical isolators can also be used as intracavity elements providing unidirectional lasing (for example ring-cavity single frequency lasers).
Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase I | Award Amount: 150.00K | Year: 2014
The laser sources emitting from short to long infrared wavelengths are used for environmental sensing, metrology and clinical diagnosis, LADAR applications. The second atmospheric window between 3-5 um is crucial where a large number of gases, e.g. methane, nitric oxide, carbon mono-dioxide or formaldehyde, can be detected. Due to the presence of very strong fundamental stretching modes of O-H, C-H and N-H bonds that are up to orders of magnitude stronger than the overtones in the near-IR, detection limits down to sub-ppb concentrations can be obtained. One of the necessary components for such measurements is optical isolator. However, there are no commercially available devices for this spectral range. The main objective of the current proposal is to create an optical isolator for 3-5 um that could be used in laser applications. The technical approach is to develop a vitreous material that is transparent in mid IR spectral region and can accept high concentration of ions that increase magnetooptical constant. Dependence of magnetooptical sensitivity on different dopants will be studied, a technology of fabrication of mid IR transparent magnetooptical glass will be developed and optical isolation in 3-5 um region will be demonstrated in bulk and fiber geometries.
Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase I | Award Amount: 150.00K | Year: 2012
ABSTRACT: The objective of the proposed research is to develop a new type of volume holographic elements that can operate in mid IR spectral region. To achieve this goal, research will be directed to a photo-thermo-refractive (PTR) glass which provides a photo-thermo-induced refractive index change while being transparent in the spectral range from 3 to 5 um, and to demonstration of the feasibility of fabrication of volume Bragg gratings from such glass for laser beam control and fine filtering in receivers. As a risk mitigation effort, a research will be extended to direct writing of volume gratings in several optical glasses that are transparent in mid IR spectral region. BENEFIT: Creation of holographic optical elements with low losses and high tolerance to laser radiation would be extremely beneficial for military application in the mid-IR spectral region because it would enable a dramatic increase in brightness of mid IR laser sources without an increase in weight, size, and energy consumption. Such diffraction gratings will provide unprecedented fine spectral and angular selection for both transmitters and receivers. This will enable development of high power, compact and robust lasers operating in the mid-IR window of transparency which should find wide applications for both DoD (effective missile sensor counter measures, night vision, and remote sensing) and commercial (micromachining and medical) needs.
Agency: Department of Defense | Branch: Defense Advanced Research Projects Agency | Program: STTR | Phase: Phase I | Award Amount: 100.00K | Year: 2012
The general objective of this proposal is to design a self-stabilized monolithic single frequency solid state laser. The main advantage of the approach is based on the integration of a laser cavity within active laser material - Nd-doped photo-thermo-refractive (PTR) glass, which allows constructing narrow line unidirectional, environmental insensitive laser. This glass possesses both properties of high efficiency gain medium and phase photosensitive medium for volume hologram recording. Therefore, it is possible to record a resonator consisting from two (or several) Bragg mirrors inside of a laser glass slab. Such a resonator cannot be misaligned. Thick Bragg mirrors will enable single frequency and single transverse mode regime. This slab will be pumped by a low noise narrow band semiconductor laser with emission wavelength stabilized by an external Bragg resonator. Such a Nd-doped PTR Bragg laser would be completely monolithic as semiconductor or fiber laser. However, it will possess compactness of semiconductor emitter combined with emission properties of solid state or fiber lasers. Development of PTR glass modification with decreased sensitivity to the thermal fluctuations inducing the change of the light pass length will allow reaching high frequency stability already at room temperature.
Agency: National Aeronautics and Space Administration | Branch: | Program: SBIR | Phase: Phase II | Award Amount: 600.00K | Year: 2011
The main goal of the project is to demonstrate the feasibility of a monolithic solid state laser on the basis of PTR glass co-doped with luminescent rare earth ions. The main feature of this new complex material is its ability to be simultaneously an active laser medium and a phase photosensitive medium. That way the same piece of material can be used as laser gain element and a monolithic laser resonator produced by the recorded in that volume Bragg gratings (VBGs). A series of PTR glasses co-doped with rare-earth ions (Nd, Yb and Er) was fabricated. It was shown that those glasses possess both high efficiency of luminescence and photosensitivity (photo-thermo-induced change of refractive index). A technology of the recording of volume Bragg gratings in each of these new PTR glasses was developed and controllable diffraction efficiency between 10 and 99% was demonstrated. A laser was demonstrated in Nd-doped PTR glass plate using an external Fabry-Perot resonator based on two plane dielectric mirrors with longitudinal pumping by laser diodes at 808 nm. Lasing and narrowing of spectrum down to ~20 pm is demonstrated when one of the mirrors was replaced by a high efficiency VBG.
OptiGrate Corporation and University of Central Florida | Date: 2012-02-10
A method for two-dimensional spatial (transverse) mode selection in waveguide and free-space laser resonators and associated laser systems employing said resonators. The invention is based on the cylindrical symmetry of the angular selectivity of reflecting volume Bragg gratings (R-VBGs) that are used as spectrally selective minors in resonators. Matching the divergence of a laser beam and the angular selectivity a reflecting volume Bragg grating can establish different losses for transverse modes of different orders, while not restricting the aperture of the laser resonator, and enables single mode operation for resonators that support a plurality of transverse modes. The invention provides a laser having increased brightness without a decrease of efficiency.
Agency: Department of Defense | Branch: Missile Defense Agency | Program: SBIR | Phase: Phase I | Award Amount: 100.00K | Year: 2012
The overall goal of the proposed project is to develop a Volume Bragg Grating (VBG) controlled surface emitting laser for pumping of low pressure Rb vapor laser. This approach will provide dramatic decrease of specific volume of a pumping lase system and, therefore, will dramatically decrease the size of the whole system enabling 100+ kW operating range. The goal of the Phase I project is to demonstrate an opportunity to lock GCSEL at maximum pumping current to 10 GHz wide line with spectral contrast up to 30 dB.
Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase II | Award Amount: 748.22K | Year: 2013
ABSTRACT: The purpose of this proposal is to develop a new photosensitive optical material with working range from 3 to 5 um, which enables recording of high efficiency volume holograms with tolerance to high power laser radiation, and to demonstrate the use of those holograms for beam control of mid IR lasers. Three directions will be pursued in the material part of the project. The first one is to develop optical glass transparent up to 5 um that would possess ability for photo-thermo-induced crystallization and, therefore, for refractive index change in the exposed areas. The second approach is to find proper compositions and conditions of irradiation of chalcogenide glasses that would enable direct writing of holograms by laser radiation. Chalcogenide glasses are transparent up to 12 um. This technology is well known for chalcogenide films but it is a challenging approach for recording of bulk holograms. The third direction will be the study of iron doped lithium niobate which is transparent up to 5 um and shows refractive index change resulted from electro-optical phenomenon caused by spatial separation of charges. We will use revealed photoinduced phenomena tor record holographic gratings for spectral beam combining and spectral locking of MIR lasers. BENEFIT: One of the hot topics in military photonics development is a robust emitter in 3 to 5 um spectral region for countermeasures against IR self-guided missiles. The most portable and efficient light sources are semiconductor lasers. However, semiconductor lasers operating in mid IR spectral region have not enough power and brightness for efficient countermeasures. A possible solution of this problem is to develop a method for spectral or coherent combining of NIR semiconductor lasers. This combining is routinely produced for near IR region by volume Bragg gratings recorded in a photo-thermo-refractive glass. However, this glass is not transparent in mid IR. The proposed research is directed to development of a phase photosensitive material that would be transparent up to 5 um. This material would enable fabrication of volume Bragg gratings that will be used for spectral and coherent locking of mid IR lasers and for spectral combining of multiple laser sources. Such approach with robust passive elements will provide dramatic increase of brightness of mid IR laser sources and will be used in a great number of military laser systems. Additionally these gratings could be used for narrow band spectral filtering in multiple night vision systems.
Agency: Department of Defense | Branch: Navy | Program: SBIR | Phase: Phase II | Award Amount: 749.99K | Year: 2012
The objective of this proposal is to extend the technology of chirped pulse amplification in ultrashort pulse lasers based on chirped volume Bragg gratings (CBGs) to higher stretching/ compression ratio and make the device more robust. In Phase I OptiGrate demonstrated high quality stretching and compression by CBGs fabricated in photo-thermo-refractive (PTR) glass. Phase II research and development enabled reliable manufacturing of CBGs designed for ultrashort pulse laser systems and extended the stretching time to the unprecedented level of 1 ns while this pulse could be compressed to the level of 200 fs. Record average power of 200 W has been demonstrated. The benefits of usage of such gratings are based on a compact geometry, unprecedented stability to optical radiation, high diffraction efficiency, absence of polarization dependence and durability to environmental conditions. However the most strategic importance of this technology is its scalability to large apertures and thickness which enable scaling to higher power and longer stretching. The specific target set for Phase II.5 of this project is a demonstration of multipass CBGs where 2-ns stretching time which is combined with large aperture up to 1010 mm capable of compressing pulses with energies more than 20 mJ.