Joseph M. Fukumoto

Efficient Angle Tunable Output from a Monolithic Serial KTA Optical Parametric Oscillator

An arrangement (10) for efficiently shifting energy received at a first wavelength and outputting the shifted energy at a second wavelength. The arrangement (10) includes a laser (12) and an optical parametric oscillator (14) of unique design. The oscillator (14) is constructed with an energy shifting crystal (20) and first and second reflective elements (16) and (18) disposed on either side thereof. Light from the laser (12) at a fundamental frequency is shifted by the crystal and output at a second wavelength. The second wavelength is a secondary emission of energy induced by a primary emission generated by the first wavelength in the crystal. A novel feature of the invention is a coating applied on the reflective elements (16 and/or 18) for containing the primary emission and enhancing the secondary emission. This constrains the energy to be output by the arrangement (10) at the wavelength of the desired secondary emission.

Laser remote chemical sensors at Raytheon

Raytheon and the U.S. Army have been developing laser remote chemical sensors for the last decade. This has included advanced transmitter and sensor development, field testing, and concepts for spacecraft, aircraft, unmanned aerial vehicles, ground-mobile transports, and fixed sites. The WILDCAT sensor utilizes a wavelength agile CO2 laser with output energy of 1 J/pulse at a repetition rate of 100 Hz for ranges of 40 km. The receiver is composed of a 60 cm dia. telescope and HgCdTe detector, integrated into a gimbal system with full hemispherical scan. Algorithms allow for real-time data processing and concentration map display. An all solid state sensor breadboard has also been developed that is capable of 300 (mu) J output at 8-12 micrometers and 300 Hz repetition rate. The system is based on a Nd:YAG pump slab laser and two-stage, angle-tuned, optical parametric oscillator wavelength shifter. The system provides for power efficiency, compactness, and light weight that are consistent with manportability. Anticipated horizontal range is 3 km on the ground and 5 km vertically. Analysis of a space-based, low earth orbit system shows that chemical and biological species detection can be performed effectively by sensors derived from the laser components developed under these programs.

Compact DIAL sensor: SHREWD

The US Army Chemical Biological Center and Raytheon Electronic Systems are developing a lightweight, compact sensor, known as the Standoff Handheld Real-time Early Warning Detector (SHREWD), for detection of airborne chemicals at ranges of 3-5 km by differential absorption lidar for manportable applications and for vehicles where sensor size and weight are restricted. Engineering analysis shows that the final deployable sensor size and weight would be 0.9 cu gt and 35 lb, respectively. The fieldable breadboard sensor now under development in phase 1 of the program is composed of independent transmitter and receiver sections mounted on either side of a single, 20 in. By 24 in. Optical table held vertically on a tripod. The transmitter is composed of an air-cooled Nd:YAG pump laser and a robust, two-stage OPO that shifts the pump laser output to the 8-12 micrometers band. The pump laser emits 20 mJ pulses at a repetition rate of 300 Hz in a 1.2 time diffraction limited beam; and the OPO overall conversion efficiency is 1.2% resulting in an output pulse energy of 240 (mu) J. The sensor receiver is based on a 12 cm diameter, off-axis paraboloid mirror and cryo-engine-cooled HgCdTe detector. Data acquisition is performed by 8 bit, analog- digital converters with 0.5 ns resolution and data processing/display are performed in real time.

Efficient 1-μm to 8-12-μm OPO converter

Development of an OPO wavelength conversion scheme is currently in progress that converts the 1 micrometers output from a diode-pumped laser, to the 8 - 12 micrometers spectral region for remote chemical sensing applications. Preliminary results from the non-optimized first stage OPO, which uses an x-cut KTA crystal, show a 21% energy conversion efficiency from 1 micrometers to 2.59 micrometers . The 2.59 micrometers output will then be used to pump a CdSe OPO to generate tunable 8 - 12 micrometers idler wave output.

All solid-state, 8-12 ¼m continuously tunable DIAL laser transmitter with pattern-controllable, rapid wavelength switching

The first demonstration of a fieldable, 8-12 μm continuously tunable, all solid-state DIAL laser transmitter is reported. The 24˝ x 24˝ x 8˝ unit generates 10 kW pulses and can switch between two wavelengths in any pattern at 120 Hz.

Standoff handheld real-time early warning detector (SHREWD)

A lightweight, compact sensor breadboard demonstrator is being developed that will be capable of detecting chemical agents in the 8 - 12 micrometers band by DIAL for ranges on the order of 4 km. Engineering analysis shows that the overall sensor size and weight would be approximately 1 cu. ft. and 35 lbs., respectively. The sensor is composed of a 12.5 cm diameter, off-axis paraboloid receive telescope and a 300 Hz repetition rate solid-state laser transmitter. The transmitter is based on a diode-pumped, 1.06 micrometers laser with an output energy of 20 mJ and two cascaded OPO stages that shift the laser wavelength to the far IR bands. The first stage OPO is configured in an arrangement that shifts the laser output to beyond 2 micrometers . The second stage OPO completes the shift to the 8 - 12 micrometers band, giving an overall 1.06 (mu)

Dual cavity multifunction laser system

m yields 8 - 12 micrometers conversion efficiency of 2% and a sensor output power of 0.1 W.