This pdf file contains the front matter associated with SPIE Proceedings Volume 7795, including Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Laser ignition of energetic materials is an attractive technology for replacement of low energy electro-explosive devices which pose a safety hazard. The development of this technology has historically been based on go/no-go threshold testing using off-the-shelf laser diodes and solid state lasers. Here we seek to build a more fundamental understanding of the laser ignition process by analyzing the interactions and response of the energetic material to the incident laser beam. We begin with a radiative heat transfer model of the laser-beam-assisted heating of a homogeneous energetic material with given optical properties. An analytical solution of the 2-flux model equations is developed and this expression for the volumetric absorption of laser energy in an absorbing and isotropically scattering medium is coupled to the conservation of energy equation. Two limiting cases-minimum power and minimum energy thresholds for ignition - are discussed, and the minimum energy threshold is calculated directly from the energy equation in the limit of zero dissipative losses. The effects of power density and beam shape are of particular interest and two common configurations are analyzed. Although the applicability of thermal models is limited by large uncertainties in the optical properties of energetic materials, the analysis provides a qualitative understanding of the ignition process and a correlation between ignition thresholds and the various material properties and design parameters.

The Indian Head Division, Naval Surface Warfare Center (IHD NSWC) CAD Engineering Division is conducting a program to evaluate the laser and energetic components which comprise the Canopy Fracturing Initiation System (CFIS). This system is currently installed on the T-6A Texan II or JPATS (Joint Primary Aircraft Training System) aircraft. The T-6A Texan II is the first aircraft used by the military to train future pilots. The CFIS is an element of the pilot emergency escape system which weakens the canopy in the path of the ejection seat. The CFIS is comprised of three differing laser configurations (Internal, External, and Seat Motion) which generate a pulse that is distributed through a fiber optic energy transmission system. This pulse, in turn, initiates one of the system's explosive components, a detonator (specifically, the CCU-158/A Laser Initiated Detonator). This detonator transfers the signal to the remaining energetic components that, in turn, function to weaken their respective canopies. All of the CFIS laser types are flashlamp-pumped, neodymium glass lasers which are located at various positions in the aircraft cockpit area. This paper builds on the previous SPIE papers (2008 - Conference 7070 and 2009 - Conference 7434, respectively) and presents the initial functional test results for the CFIS Laser Detonator. These functional test results provide the technical support to justify the useful lifetime of this energetic component while being installed in the T-6A Texan II aircraft under operational conditions.

Nanoporous silicon, commonly recognized for its photoluminescent properties, has gained attention as a new energetic material capable of energy density more than twice that of TNT. The addition of an oxidizer solution to inert nanoporous silicon results in an exothermic reaction when heat, friction, or focused light is supplied to the system. The energetic material can be integrated alongside microelectronics and micro-electro-mechanical systems (MEMS) for on-chip applications. This integration capability, along with the potential for large energetic yield, makes nanoporous energetic silicon a viable material for developing novel MEMS Safing and Arming (S&A) technologies. While ignition of nanoporous energetic silicon has been demonstrated for the purpose of propagation velocity measurements using a YAG laser, in this paper we show optical ignition for potential integration of the energetic with a miniaturized S&A device. Ignition is demonstrated using a 514nm laser at 37.7mW and a power density of 2.7kW/cm² at a stand-off distance of 23cm. Raman spectroscopy verifies that significant stress in porous silicon is produced by a laser operating near the power density observed to ignite porous silicon. Lastly, we integrate the nanoporous energetic silicon with a MEMS S&A, and demonstrate transfer to a firetrain consisting of one primary and one secondary explosive using a thermal initiator to ignite the nanoporous energetic silicon.

Laser initiation of the various explosive materials requires a wide variety of energy densities. With funding from DARPA, Alfalight has developed a Surface-Emitting Distributed Feedback (SE-DFB) lasers. The technology allows a single laser diode to replace many of today's more complex solid state lasers in LIO applications. The highest-recorded continuous output power from a single emitter - 73 watts - is detailed along with peak pulsed powers exceeding 300 watts. Other beneficial properties such as wafer-level processing, surface output coupling and on-chip beam-shaping are among the attributes of this type of laser.

We present an analysis of a reliability assessment tailored specifically to fuzes based on laser diode assemblies. Fuzes are required to deliver high energy in a single short pulse (micro- to milliseconds) after prolonged storage (tens of years) in thermally non-stabilized environments. The temperature variation could easily exceed 100 degrees, and the transition from one extreme to the other could be slow or rapid, depending on a particular application. The operating requirements for diode laser fuzes are dramatically different from the majority of other diode laser applications and thus a reliability assurance program for laser fuzes should reflect these differences in usage. In this paper we demonstrate that it is possible to build accelerated aging conditions based on thermal cycling. As parameters in the accelerated thermal aging, we used the total temperature difference between the lowest and the highest points in the cycle, and the average rate of temperature change between the extreme points. This accelerated aging technique based on thermal cycling can predict the performance deterioration over time after storage in thermally non-stabilized environments. The basis of this approach can be extended to the analysis of reliability in environments with high vibration and radiation levels.

There are a number of attractive micro optical elements or combinations of elements that are currently used or could be employed in optically initiated ordnance systems. When taking a broad-spectrum examination of optically initiated devices, the required key parameters become obviously straightforward for micro optics. Plainly stated, micro optics need to be simple, inexpensive, reliable, robust and compatible within their operational environment. This presentation focuses on the variety of optical elements and components available in the market place today that could be used to realize micro-optical beam shaping and delivery systems for optically initiated devices. A number of micro optical elements will be presented with specific bulk, planar optical and thin film optical devices, such as diffractive optics, micro prisms, axicons, waveguides, micro lenses, beam splitters and gratings. Further descriptions will be presented on the subject of coupling light from a laser beam into a multimode optical fiber. The use of micro optics for collimation of the laser source and conditioning of the laser beam to achieve the highest efficiency and matching the optical fiber NA will be explained. An emphasis on making these optical assemblies compact and rugged will be highlighted.

Direct Optical Initiation (DOI), uses a moderate energy Q-switched Nd:YAG laser to shock initiate secondary explosives, via either a flyer plate or exploding metal foil. DOI offers significant performance and safety advantages over conventional electrical initiation. Optical fibers are used to transport the optical energy from the laser to the explosive device. Energy densities in the region of 35 J cm^-2 are required for initiation, significantly above the damage threshold of typical optical fibers. Laser-induced damage is typically caused by laser absorption at the input face due to imperfections in the surface polishing. To successfully transmit energy densities for DOI, a high quality fiber end face finish is required. Fiber assemblies were prepared by C Technologies Inc, NJ, USA, with Innovaquartz FG365UEC optical fiber, using a variety of polishing methods, with both steel and zirconia ferrules. The quality of the fiber end faces was assessed using non-contact optical profilometry. The damage threshold for each polishing method was then determined using a Q-switched Nd:YAG laser and the optimal polishing method determined for each ferrule material. Significant performance differences between zirconia and steel ferrules were observed, and a physical cause of this difference is proposed.

Planar polymer waveguides provide opportunities for small form factor distribution of laser light for communication, energy transfer and triggering devices used in the field of optically initiated arming, safing, fusing and firing. The two primary methods or classes of polymer waveguide technology use photolithographic processes both mask and maskless techniques. A waveguide is a device that controls the propagation of an electromagnetic wave so that the wave is forced to follow a path defined by the physical structure of the guide. Fabrication takes the form of both a ridge technology (ridge or trench formed by an embossing or etching method) and the second fabrication technique and the subject of this paper is termed Diffusion Technology [1]. This method includes the formation of a high refractive index waveguide by monomer diffusion into the light-exposed guide forming region with no mechanical or chemical etching contact. An essential process feature here is the photomask-defined light exposure of a mobile monomer waveguide forming region in a polymer matrix that converts the monomer to a polymer. The process of continued monomer diffusion into the surrounding guide imaged region increases the density. The addition of other laminated monomer/polymer diffusing layers with the typical three-plus layer configuration is completely photopolymerized after diffusion is complete. The essential steps include a light induced imaging reaction, a total polymerization light fixing for the entire film, and final cure, all using pre-coated dry materials without waveguide side wall contact. Light and molecular diffusion determine the guide walls [1]. This paper will provide testing results and information on the state of polymer waveguides, the methods of fabrication and the general conditions that these waveguides can operate under. The use of polymer waveguides for connectivity has sufficiently advanced, is practical and available for consideration in near term application development with the field of arming, safing, fusing and firing or laser/optically initiated ordnance.

The optical pulse generation system of SG-III laser facility is presented. The optical time division multiplexing (OTDM) technique, high speed electro-optic modulation technique, pulse single-selected based on polarization independently acousto-optic modulation technique and pulse polarization stabilization technique applied in low repetition rate mode are successfully employed in the system. And also the phase modulation unit is at the last stage of the system, which could avoid FM-AM effect induced in fiber system. The test experiment results showed that the demonstrated specification is better than the designed to a certain degree.

Large-aperture plasma Pockels cell is one of important components for inertial confinement fusion laser facility. We demonstrate a single-pulse driven PPC with 350mm×350mm aperture. It is different to the PPC of NIF and LMJ for its simple operation to perform Pockels effect. With optimized operation parameters, the PPC meets the optical switching requirement of SGII update laser facility. Only driven by one high voltage pulser, the simplified PPC system would be provided with less associated diagnostics, less the maintenance, and higher reliability.