This Small Business Technology Transfer (STTR) Phase II project addresses an urgent law enforcement need for a sensitive, portable, low-cost, laser remote sensor to detect illicit methamphetamine (meth) production labs from a distance. The research objectives are to: 1. Refine, optimize, and package laser subsystem, 2. Design, construct, and optimize receiver subsystem, 3. Integrate laser and receiver subsystems onto compact breadboard and test, 4. Design and construct first-revision prototype. To accomplish these objectives, the team and Montana State University will optimize the performance of the critical high-energy, narrowband, mid-infrared pulsed laser system that was developed under the Phase I effort. The laser subsystem will be miniaturized and packaged for use in the sensor and for direct sales to bootstrap the sensor commercialization. The receiver subsystem will be designed, constructed, and optimized for performance, size, weight, and cost. The laser and receiver subsystems will be integrated and the unit will be field-tested. The first revision prototype will then be designed and constructed, incorporating identified improvements and modifications, and law enforcement customer input.
Meth use in our country has reached epidemic levels. It is considered the most addictive illicit drug, can be easily produced with widely available and inexpensive ingredients, and is rapidly becoming more popular with young adults. Almost 1/5 of 2003 federal sentences were meth related and the state of Illinois estimates a $2B/yr meth-related burden. In 2005, 65% of Montana?s young adults reported that meth is ?very or somewhat easy? to obtain. Meth?s abundance is often attributed to the fact that it is alarmingly easy to produce in makeshift clandestine labs (in homes, apartments, motels, storage facilities, etc). These labs also pose lethal hazards to law enforcement, first responders, and children inhabitants. Washington State reported that children are or have been at 35% of the lab sites. Although 2005 legislation restricting the sale of a key meth ingredient reduced the number of labs, there is now resurgence. Moreover, the labs are becoming increasingly difficult for drug enforcement to uncover as the producers become more sophisticated and mobile. Drug enforcement personnel on local, national, and international levels require the ability to detect meth labs rapidly and in widely varying locations and circumstances. If successful law the outcome of the project will enable enforcement personnel to have a higher success rate in detecting these meth manufacturing laboratories.
Over the course of Bridger Photonics, Inc.’s (Bridger) NSF STTR award, the company achieved its primary goals of conducting the research and development required to commercialize a compact and powerful mid-infrared pulsed laser source (1.5 to 4 micron wavelength) and demonstrating the utility of this laser source for gas concentration measurements that can be used for uncovering illicit methamphetamine labs. After the preliminary laser source was developed under the NSF STTR award, Bridger also uncovered an unexpected but important entry market; laser ablation of water-rich substances. Through a commercial partnership with Protea Biosciences (Protea), Bridger demonstrated that their compact laser source was ideally suited to serve as the ablation source for Protea’s proprietary new method of mass spectrometry. Figure 1 (left) shows Bridger’s commercial laser source, which they now supply on an OEM basis for Protea’s LAESI DP-1000 mass spectrometry system. There were a number of laser emission characteristics developed under the NSF STTR award that made Bridger’s laser source ideal for both tissue ablation and gas concentration measurements via remote sensing. First, Bridger developed a proprietary laser design for high output pulse energy combined with an excellent spatial mode. As shown in Figure 2 (left), Bridger’s laser can reach nearly 1.7 mJ at a wavelength of 3 microns and can exceed 3 mJ for wavelengths near 1.5 microns in ~5 ns pulse durations. The laser utilizes diode pumping and exhibits nearly quantum-limited nonlinear conversion efficiency to the mid-infrared, which mitigates thermal problems and allows for excellent beam quality, as evidenced by the M-squared parameter at a wavelength of 3 microns approaching M2 = 2 as shown in Figure 2 (right). High pulse energy and excellent beam quality are critical emission characteristics for both tissue ablation and gas concentration measurements. In addition to the output energy and beam quality features, Bridger’s proprietary design also enables single-longitudinal mode operation, which results in outstanding pulse-to-pulse energy and pointing stability. Figure 3 (left) shows a time record of the laser’s pulse energy while operating at a repetition rate of 10 Hz for one hour. The pulse energy stability is as low as 0.2% at the 3 micron wavelength. Moreover, Figure 3 (right) shows that the pointing stability is better than 10 microradians for hours on end. These stability features are critical for achieving repeatable ablation and gas concentration results. Bridger demonstrated that they could seed the laser to narrow its emission linewidth and perform range-resolved gas concentration measurements. By seeding with DFB diode lasers, Figure 4 shows Bridger’s model and experimental result for range-resolved atmospheric carbon dioxide concentration measurements near a 2 micron wavelength with no topographical scatterer. The measurements shows that Bridger could achieve measurement precisions at or near 100 ppmv out to about 50 meters range relying only on atmospheric backscattering. The systematic errors for longer ranges were due to beam overlap issues and have been since resolved after this award ended. To put these measurements into perspective, the carbon dioxide concentration of human breath is around 5,000 ppmv and typical industrial emissions can often exceed 100,000 ppm. Bridger is currently further reducing the size, and improving the ruggedness and repetition rate of this laser source in order to appeal to a broader range of applications.
