In this paper, pulsed operation of the 980 nm diode-pumped Yb:Er:glass solid-state-laser operating at 1543 nm using Co:Spinel saturable absorber is described. The Yb:Er:glass gain medium was end-pumped using a 10 W fiber-coupled 980 nm laser diode. Passively q-switched laser operation was accomplished for both CW and quasi-CW operations. Up to 2 mm thick uncoated Co:Spinel samples were used for our tests. With quasi-CW pumping, pulsewidths greater than 20 ns, pulse energies of greater than 250 μJ and free-running PRFs up to 1.2 kHz have been demonstrated. So far, up to 3 % optical-to-optical efficiency has been achieved with uncoated q-switch materials. Currently, this laser is being developed for pumping a long-wave IR (8-12 μm) optical parametric oscillator for use in spectrapolarimetric applications.
The NetFires program is poised to redefine extended range precision engagements for tactical ground forces. This system is designed to support light and mechanized near term and objective U.S. Army and U.S. Marine Corps forces. The system uses a combination of advanced propulsion, navigation and seeker technology, and networked data links to enable a new class of weapons enabling precision dominance on future battlefields. In addition the program is clearly focused on reducing the logistical footprint of future ground forces.
A comprehensive hyperspectral system simulation with applications to space and airborne sensors has been developed. A companion paper presents results for the hyperspectral payload simulation and the end-to-end testing of the system. In this paper we discuss current and planned work in the development of a new, integrated scene modeling capability which combines the detailed simulation capabilities of the DIRSIG model with the wide area capabilities of the GENESSIS model. In addition, the overall integration architecture, which is based upon the System Simulation Toolkit (SST), and the associated simulation components including space and aircraft platform models, ground control elements and interfaces to exploitation elements is described.
Planar metal-semiconductor-metal (MSM) devices fabricated on gallium arsenide (GaAs) are promising candidates for use as photodetectors in coherent optical communications and millimeter-wave phased-array applications. Their primary features are broad bandwidth, large responsivity, high power-handling capability, and compatibility with monolithic optoelectronic integrated circuits. We have characterized the performance of an interdigitated GaAs MSM photodetector grown by molecular beam epitaxy at 350 degree(s)C using a fast sampling technique in the time domain. A key factor for undoped GaAs material grown at this temperature is the optimal combination of both low dark current and high photocurrent. Experimental measurements are made of the temporal response of the MSM detector to optical impulses generated by a mode-locked titanium-sapphire (Ti:Al2O3) laser. Speed and responsivity are characterized over a range of optical powers and DC bias voltages. Results demonstrate that this device can switch up to 69% of the applied DC bias voltage under high optical pulsed power. Results also indicate responsivities exceeding 80 mV/pJ and bandwidths approaching 20 GHz. This high-efficiency, broad-bandwidth photodetector may find critical applications in the optical production of millimeter-wave signals by frequency conversion (mixing) and harmonic generation.
In meeting the growing demand for graduates who have background in optical engineering,the Department of Electrical Engineering and Computer Science and the Photonics Research Center at the U.S. Military Academy have jointly developed an instructional program that familiarizes every student with principles of laser operation and provides undergraduate research opportunities in optics for electrical engineering majors and others. The program includes a series of laboratory demonstrations in the Photonics Research Center for students in all majors during their sophomore year. For electrical engineering majors, the program also offers a senior level photonics engineering course, advanced individual study in laser applications, and a variety of capstone design projects. Advanced individual study may include up to three semesters of experimental research similar to masters degree thesis work in a graduate program, while the capstone project is accomplished in one semester by design teams based on the design-build- test methodology. Both types of projects address real-world requirements specified by faculty advisors or external mentors. Our integrated approach to optics education supports ongoing state-of-the-art research in the Photonics Research Center and provides technically qualified graduates to meet the demands of the field Army of the 21st century.
We report systematic studies of the femtosecond transient reflectivity and transmission in low- temperature-grown III-V semiconductors. By using a 2-eV-pump/white-light-probe system as well as a tunable infrared laser we are able to investigate different materials and shed new light on the processes governing the photoexcited carrier dynamics in these compounds.