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Burlington, MA, United States

Hobbs D.S.,Telaztec, Llc
Proceedings of SPIE - The International Society for Optical Engineering

Surface relief textures fabricated in optical components can provide high performance optical functionality such as antireflection (AR), wavelength selective high reflection, and polarization filtering. At the Boulder Damage XXXIX symposium in 2007, exceptional pulsed laser damage threshold values were presented for AR microstructures (ARMs) in fused silica measured at five wavelengths ranging from the near ultraviolet (NUV) to the near infrared. For this 2010 symposium, NUV pulsed laser damage measurements were made for ARMs built in fused silica windows in comparison to untreated fused silica windows. NUV threshold values are found to be comparable for both ARMs-treated and untreated windows, however the threshold level was found to be strongly dependent on the material and surface preparation method. Additional infrared wavelength damage testing was conducted for ARMs built in four types of mid-infrared transmitting materials. Infrared laser damage threshold values for the ARMs treated windows, was found to be up to two times higher than untreated and thin-film AR coated windows. © 2010 Copyright SPIE - The International Society for Optical Engineering. Source

Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase I | Award Amount: 100.00K | Year: 2011

Multiple strategic military missions depend on the advancement of high power lasers that operate within the IR spectral region. For maximum effectiveness, laser systems under development for the CIRCM, ABL, and next generation UAV programs, require increased power and broad wavelength agility. Promising tunable mid-IR solid state laser sources depend on conventional thin-film coating technology to achieve critical optical functions such as anti-reflection (AR), high reflection (HR), and spectral or polarization filtering. Thin-film coatings are easily damaged within high power laser systems, and the threshold for coating damage decreases as the demand for higher performance or wider bandwidth increases. As a primary example of this performance/reliability tradeoff, developers scaling the power output and tuning range of metal-ion doped semiconductor lasers opt for more complex, less stable laser cavity configurations with reduced efficiency in order to avoid the use of thin-film AR and HR coatings directly on the laser gain material facets. Dramatic increases in the power output and tuning range of these laser sources could be attained by development of a more robust AR treatment applied to the gain material facets alone. An innovative AR treatment based on surface relief microstructures has been shown to have great potential for increasing the reliability and power handling capacity of optical components. AR microstructures (ARMs) etched directly in the surface of relevant IR transmitting materials have consistently exhibited damage thresholds 2 times higher than untreated surfaces, a value that equates to a 4-5 time increase over any equivalent performance broad-band thin-film AR coated surface. This Phase I project proposes to demonstrate robust, wide bandwidth, high performance ARMs textures built in the end facets of chromium ion (Cr2+) doped zinc selenide (ZnSe) and zinc sulfide (ZnS) laser gain material. Multiple ARMs design variants will be fabricated in ZnSe, ZnS, and Cr2+:ZnSe coupons and subjected to standardized pulsed and continuous wave laser damage testing. Additional ARMs treated coupons of the most promising designs will be delivered to the Government for further damage testing. In collaboration with IR laser manufacturer IPG Photonics, the new robust AR treatment will be integrated into critical AFRL systems during Phase II and Phase III commercialization projects. BENEFIT: It is anticipated that a dramatic increase in laser power handling capacity combined with enhanced operational lifetime will be achieved through the integration of anti-reflecting microstructures in solid state laser systems. In particular, the broad-band performance of ARMs will benefit tunable metal-ion doped ZnSe and ZnS lasers that find a wide range of applications throughout the mid-IR spectral region. Air Force applications requiring more reliable, higher power, wavelength agile mid-IR laser sources include laser communications, countermeasures, target designators, weapons, rangefinders, remote chemical sensors, and infrared scene projectors. Commercial applications include environmental chemical monitoring, industrial welding and cutting systems, and food processing. Significant advances in medical devices for surgery, noninvasive treatments, breath diagnostics, and imaging await higher power laser sources, as do astronomical instruments for spectroscopy, planetary exploration, earth and solar observations, and optical telecommunications. Although the proposed effort will immediately benefit metal ion doped ZnSe and ZnS laser materials, the robust nature of ARMs can be extended to any current or emerging laser technology such as quantum cascade lasers, zinc germanium phosphide lasers, and semiconductor microchip lasers, as well as silica and chalcogenide glass optical fiber laser delivery systems.

Agency: Department of Defense | Branch: Missile Defense Agency | Program: SBIR | Phase: Phase II | Award Amount: 997.89K | Year: 2014

Compact, efficient, mega-watt power level lasers are being developed by the MDA for the mission of destroying targets over a range of many hundreds of kilometers. A candidate laser technology with the promise of meeting this mission goal is based on alkali gas that is optically pumped by multiple, electrically driven diode lasers. One current problem limiting the potential operational lifetime of these Diode Pumped Alkali Lasers, or DPALs is that the windows of the cell containing the alkali vapor, become fouled with deposits or fogged by damage from chemical reactions with the gas, reactions that increase as the laser optical power is scaled up. In addition, DPALs cannot operate efficiently in the presence of laser cavity losses such as reflections from the gas cell windows, and therefore some form of anti-reflection (AR) treatment must be applied. Conventional thin-film material coatings designed to suppress reflections are typically less resistant to chemical attack from alkali compounds than the cell window material, and thin-film AR coatings suffer optical damage at laser power levels well below the mission requirements. A roadblock to major increases in the power output and reliability of DPALs can be removed by development of a more robust AR treatment for the windows of the gas cell. The innovative solution proposed is to eliminate thin-film coatings completely, creating the critical AR function by fabricating microstructures directly in sapphire windows that have been shown to be naturally resistant to alkali chemical attack. AR microstructures (ARMs) etched in sapphire windows have exhibited higher transmission and pulsed laser damage thresholds 2-5 times higher than thin-film AR coatings. This Phase I project proposes to demonstrate high transparency ARMs textures built in sapphire and other chemically resistant window materials suitable for DPAL vapor cells. Multiple ARMs design variants will be fabricated in sapphire coupons and subjected to standardized pulsed laser damage testing and alkali vapor exposure testing using the flowing DPAL system at Kirtland AFB. Additional ARMs treated vapor cell windows will be delivered to the Government for further evaluation. As part of a Phase I Option, a design for a microstructure-based, all sapphire output coupler will be investigated and prototyped as a means for eliminating other DPAL cavity thin-film coatings. Potential DPAL manufacturers such as General Atomics, Northrup Grumman, and Boeing will be engaged to enable the new robust AR treatment to be integrated into MDA test platforms during Phase II and Phase III commercialization projects.

Agency: Department of Energy | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 150.00K | Year: 2010

This Small Business Innovation Research Phase I project proposes research into the feasibility of scaling the fabrication of efficiency-enhancing nanostructures used for organic light emitting diodes, or OLEDs, to enable low-cost solid-state lighting (SSL). Of specific interest in this DOE-ITP Nanomanufacturing Initiative opportunity is the potential for OLED-based SSLs to be inexpensively produced in large area formats compatible with the US industrial base. In addition, such low-cost, large format SSL would not only realize dramatic energy savings for US manufacturers, but would play a significant role in reducing worldwide energy consumption, and lead to a healthy commercial market. Today the incorporation of a wide variety of surface relief textures as part of the OLED structure has been shown in numerous laboratory demonstrations to increase the light extraction efficiency many times over. Much of this work has focused on micro-scale structures such as microlenses and diffraction gratings that reduce light losses generated by only part of the OLED structure. One recent study showed that a micro-scale grid pattern within the organic emitter materials could produce dramatic increases in light extraction efficiency. This study showed that further increases in extraction efficiency might be obtained by decreasing the size of the grid to the nano-scale where the grid structures were all smaller than the wavelengths of visible light. TelAztec has been developing large-scale, low-cost origination and replication methods for such sub-wavelength surface relief textures for numerous applications in sensors, displays, and high energy lasers. For this Phase I effort, TelAztec will design and fabricate sub-wavelength sized nano-structures within the organics layer of existing OLED structures using established scalable manufacturing processes. In collaboration with Pacific Northwest National Laboratory (PNNL), and ARKEMA Corporation, OLED prototypes incorporating several nano-structure variants will be produced and evaluated for light extraction efficiency. In a Phase II effort, several SSL manufacturers will be engaged to produce large scale nano-structured OLED light panels that are further combined with other light extraction enhancement methods such as TelAztec

Agency: Department of Defense | Branch: Army | Program: SBIR | Phase: Phase I | Award Amount: 100.00K | Year: 2015

Infrared imaging has revolutionized the Armys approach to warfare, providing the capability to see day or night through smoke, fog, and dust. Imaging in all battlefield conditions enables 24-hour covert targeting and tracking, threat warning, hostile fire identification; thereby increasing mission capability while providing protection for the troops. For high-resolution imaging in all conditions, the Army utilizes electro-optic/infrared (EO/IR) focal plane arrays that cover the VISIBLE to LWIR spectral range. For suppression of problematic reflections from the high index sensor surfaces, thin film antireflection coatings are employed. The Army has identified that these coatings do not adequately suppress reflections to mission specifications and often have environmental durability issues related to stress and thermal fluctuations. An innovative and rugged and solution to the AR problem is based on surface relief AntiReflective Microstructures (ARMs) imparted directly in the sensor substrate material through a simple plasma deposition, etch, and cleaning process. With no dissimilar materials as a component of the AR treatment, stress and environmental durability issues are eliminated. The optical performance of microstructures has been shown to be far superior to thin film coatings with respect to reflection suppression, transmission bandwidth, and off-axis performance. The combination of large batch processing, short cycle times, and in-situ process controls result in an ARMs manufacturing process that will produce the low unit costs required to equip the warfighter in the field.

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