James Andrew Hutchinson

2-μm-pumped 8-12-μm OPO source for remote chemical sensing

A 100 Hz, optical parametric oscillator (OPO) lidar breadboard is designed, built and tested for remote chemical sensing in the 8 - 12 micrometers range. Continuous tuning is achieved by angle tuning a type II, silver gallium selenide (AgGaSe2) OPO crystal pumped in a single step by a 2.088-micrometers pump laser. The pump source for the OPO consists of a temperature stabilized, continuously pulsed, resonantly pumped Ho:YAG (2.088-micrometers ) laser, end-pumped by a diode- end-pumped Tm:YLF (1.9-micrometers ) laser. The 9 mm X 5 mm X 25 mm-long OPO crystal was mounted on a computer-controlled galvanometer scanner for rapid wavelength tuning (1.5 micrometers between shots). Continuous tunability was demonstrated from 7.9 to 12.6 micrometers with energies in the 50 - 400 (mu) J range. Quantum slope conversion efficiencies up to 40% were obtained. Far-field beam divergence measurement showed the output of the OPO to be 2.6 times diffraction limit. The improved OPO beam quality over previous studied tandem OPO systems is attributed to the reduced Fresnel number of the OPO cavity (idler resonating) and the better beam quality of the pump source. A LabWindows based data collection and analysis system is implemented. The effectiveness of the OPO as a source for chemical sensing is demonstrated by the collection of the absorption spectrum of ammonia.

Diode-array side-pumped Er,Yb:phosphate glass eyesafe laser

Pumped with two 970nm, InGaAs strained-layer diode arrays, a side-pumped Er,Yb:phospha te glass laser has been const ructed. The long pulse slope eff iciency was 14%, and threshold occurred wit h 60mJ input. The maximum output pulse energy was 20.5mJ, wit h output wavelengt hs at 1545 ± 12nm. When Q-switched, the laser prod uced 0.3mJ, 46ns FWHM pulses at an output wa velengt h of 1533 ± 1nm and wit h a repetition rate of 7Hz.

Nonconfocal unstable resonator for solid-state dye lasers based on a gradient-reflectivity mirror

A compact high-brightness solid-state dye laser, consisting of a nonconfocal unstable resonator formed of a planar mirror and a gradient-reflectivity mirror, is modeled by use of ray-tracing analysis. Collimated 80-mJ output was obtained in a 10-mm mrad beam.

Advances in optical parametric oscillators with application to remote chemical sensing

In this paper, we review some recent advances in optical parametric oscillator (OPO) technology, discuss major coherent source issues and then propose possible solutions that have relevance to remote chemical sensing. The authors discuss their latest result on two OPO schemes. 1) Energies up to 1.2 mJ/pulse and continuously tunable OPO output from 6.7 to 9.8 micrometers was obtained using a 5 X 5 X 25 mm3 type II AgGaS2 crystal, pumped a second OPO using NCPM ZnGeP2 to generate output near 8 micrometers . The tandem OPO produced pulse energies of > 1.5 mJ at 7.8 micrometers with an energy conversion efficiency of 6.8 percent. Finally, we describe schemes for generating multiple photons in the 8-12 micrometers band from one initial 1 micrometers pump photon, and thereby increase the quantum efficiency when OPOs are pumped by Nd:YAG lasers.

Co2+:MgAl2O4 crystal passive Q-switch performance at 1.34, 1.44, and 1.54 μm

Passive Q-Switch characteristics of Co2+:MgAl2O3 sample were evaluated in a diode pumped QX/Er Erbium glass laser at 1535 nm, a flashlamp pumped Nd:YAG laser at 1.44 micrometers and Nd3+:KGd(WO4)2 laser at 1.34 micrometers .

Multifunction laser radar II

Laser radar systems are required for various military applications including obstacle detection, target recognition, and terrain mapping. Each application requires different system parameters such as pulse energy, repetition rate, and field of view. This paper is the second in a series of papers describing the progress toward a multifunction laser radar system under construction for the Cooperative Eyesafe Laser Radar Program (CELRAP) of the U.S. Army CECOM Night Vision and Electronic Sensors Directorate.

Multifunction laser radar

Laser radar systems are required for various military applications including obstacle detection, target recognition, and terrain mapping. Each application requires different system parameters such as pulse energy, repetition rate, and field of view. This paper presents a review of a multifunction laser radar system under construction for the Cooperative Eyesafe Laser Radar Program (CELRAP) of the U.S. Army CECOM Night Vision and Electronic Sensors Directorate.

Digital imaging and remote sensing image generator (DIRSIG) as applied to NVESD sensor performance modeling

The US Army’s Communications Electronics Research, Development and Engineering Center (CERDEC) Night Vision and Electronic Sensors Directorate (referred to as NVESD) is developing a virtual detection, recognition, and identification (DRI) testing methodology using simulated imagery as a means of augmenting the field testing component of sensor performance evaluation, which is expensive, resource intensive, time consuming, and limited to the available target(s) and existing atmospheric visibility and environmental conditions at the time of testing. Existing simulation capabilities such as the Digital Imaging Remote Sensing Image Generator (DIRSIG) and NVESD’s Integrated Performance Model Image Generator (NVIPM-IG) can be combined with existing detection algorithms to reduce cost/time, minimize testing risk, and allow virtual/simulated testing using full spectral and thermal object signatures, as well as those collected in the field. NVESD has developed an end-to-end capability to demonstrate the feasibility of this approach. Simple detection algorithms have been used on the degraded images generated by NVIPM-IG to determine the relative performance of the algorithms on both DIRSIG-simulated and collected images. Evaluating the degree to which the algorithm performance agrees between simulated versus field collected imagery is the first step in validating the simulated imagery procedure.

Characteristics of diode-pumping erbium ytterbium-doped glass laser

The various aspects of erbium glass laser characteristics were carefully examined, including the influences of pumping pulsewidth, dopant concentration, output wavelength, relaxation oscillation and energy transfer processing between Yb3+ and Er3+.

Co 2+ :MgAl 2 O 4 crystal passive Q-switch performance at 1.34,1.44 and 1.54 micron

Cobalt doped materials, such as Co2+:ZnSe[1,2], Co2+:YSGG, and Co2+:MgAl2O4[3,4], have shown promise for use as high performance saturable absorber Q-switches for near infrared lasers.