DARPA and MIRTHE

For those new to the subject, I would suggest reading the following:

http://www.azooptics.com/Details.asp?NewsID=4162

and

http://www.laserfocusworld.com/display_article/365454/12/none/none/INDUS/DARPA-selects-Pranalytica-as-one-of-three-to-continue-development-of-high-efficiency-mid-IR-QCL

Last April, the Defense Advanced Research Projects Agency, or DARPA, selected Pranalytica for a grant of $3.3 million to develop high power, efficient continuous-wave room temperature operational QCLs for use in directional infrared countermeasures. Such a device works by locking on to a heat-seeking missile, and then using the laser to guide the missile off course thereby protecting the aircraft. Such a device could be used for helicopters and military aircraft, as well as private aircraft which need to fly in dangerous areas. The program to develop the lasers used in the countermeasure is titled “EMIL,” or the “Efficent Mid-Infrared Laser” program.

There are several challenges to developing such a device, but the major challenge at this phase is to develop high-power QCLs to redirect the missiles. However, on the topic of high-powered laser development, Pranalytica issued the following statement: “Pranalytica has already developed a 3 Watt continuous wave room temperature laser running at over 10% WPE,” which approaches the goals of the DARPA project, to create lasers generating over 3W of output at 50% wall plug efficiency. The lasers being developed lie between the 3.8-4.8 micron range.

So the question is, what does this funding and technological progress mean for MIRTHE?

The MIRTHE Center is concerned with QCL based spectroscopy for applications in health and the environment. At this point in time, this means developing QCL based sensing devices for breath analysis, and developing QCL based sensors which can be networked to cover large areas.

The breakthroughs to develop high power QCLs will not significantly transform the work being done with environmental and medical sensors. In the case of environmental sensor networks, the sensing is generally done in the 1-10mW range with success. Using systems with higher wattage output would be an unwarranted drain on the batteries, meaning the devices would need more upkeep which no one wants. In the case of using medical sensors (or environmental sensors in urban environments, where the devices can be plugged in), the increase in power output could be beneficial, but not radically so.**

However, high power output of lasers could allow for new kinds of sensing to take place. While aqueous sensing is still a very challenging application, a QCL based LIDAR system could become a reality, opening the possibility for new kinds of atmospheric research. Essentially, a high power system allows for a range of uncooperative sensing applications beyond MIRTHE’s primary goals, generating a range of potential devices for chemical, biological, or explosive detection.

The breakthroughs in high efficiency, room temperature operable QCLs is very beneficial to MIRTHE’s program in environmental sensing. The success Pranalytica has been having with its 4.6 micron QCLs will be useful in making higher efficiency QCLs at many different wavenumbers. Higher efficiency lasers means less energy consumption for the laser, and less energy needing to feed the cooling systems supporting the laser. The progress in the efficiency of lasers means environmental sensor networks stationed in remote locations are becoming a greater possibility- the lower the power consumption of these devices, the longer they can last in the field and the more data they can collect. On the topic of breath analysis, greater efficiency of the devices means handheld breath analyzers could be used more frequently in areas where access to electricity is limited.

The final benefit to MIRHTE that is worth discussing is what would happen if the project succeeds and QCL based infrared countermeasures become a reality. If this is the case, developments would need to occur to allow for the mass production of QCLs. This would allow QCL manufacturers to invest in devices for automated laser testing and develop the facilities for greater laser production. This would bring down the costs of QCLs, making the devices MIRTHE wants to be commercialized cheaper.

It should be noted the DARPA project is not overcoming all the challenges facing QCL based sensors. Developing widely tunable, single mode QCLs is necessary to spectroscopic sensing, and MIRTHE will continue working on the challenges these traits hold. Also, much of what MIRTHE does is develop its sensor systems, which will not be carried out by the DARPA project.

Overall, the DARPA funding is very good news for QCL development, and good news for MIRTHE.

**This is if we are using a traditional detector for environmental sensing. With developments in QEPAS technology, higher power may be more necessary to achieve the sensing.