The quantum cascade laser is a special kind of semiconductor laser, usually emitting in the mid- and long-wave infrared bands. Such a laser operates on laser transitions not between different electronic bands but on intersubband transitions of a semiconductor structure. Their wide tuning range and fast response time allow for faster and more precise compact trace element detectors and gas analyzers that are replacing slower and larger FTIR, mass spectroscopy, and photothermal microspectroscopy systems.
Applications include detecting chemical warfare agents and toxic industrial chemicals, monitoring building air quality, measuring greenhouse gases for atmospheric research, monitoring and controlling industrial processes, analyzing chemicals in exhaled breath for medical diagnostics, and many more. Compact, portable trace gas sensors enable operation in a wide range of platforms, including handheld units for use by first responders, fixed installations for monitoring air quality, and lightweight sensors for deployment in unmanned aerial vehicles (UAVs).
Most quantum cascade lasers emit mid-infrared light. However, quantum cascade lasers can also be made for generating terahertz waves. Such devices constitute very compact and simple sources of terahertz radiation. Recently, even room temperature terahertz generation has been achieved via internal difference frequency generation.
Improvised Explosive Devices (IEDs) are often made of compounds that absorb in the terahertz range; ruggedized and portable THz QCL-based detectors could be continuously scanned ahead of a moving convoy or used to search a public gathering space for threats.
QCLs are increasingly being used to detect, identify, and measure levels of trace gases in the air e.g. for detecting very small concentrations of pollutants in air. Such systems measure the unique infrared absorption “fingerprints” of chemicals to provide high detection sensitivity and identification confidence, and are particularly useful for field-portable sensing. This property is also useful to intelligence agencies for detecting chemical warfare agents.
QCL-based systems are also finding application in the growing field of medical diagnostics. Trace gases present on a patient’s breath can indicate diabetes, asthma and other respiratory issues, kidney and liver dysfunction, and other indicators are being discovered regularly. Such an application requires extremely fast sampling times, relatively small size, and accurate results in order to avoid misdiagnosis.
QCL enables standoff detection in battlefield as well as many civilian applications where it is not possible to locate the sensor in the near vicinity of the dangerous source. “Standoff detection of trace chemicals, such as explosive residues, chemical warfare agents and toxic industrial materials, is a critical unmet need within the Intelligence Community, Department of Defense, and Department of Homeland Security,” commented Dr. Anish Goyal, Block’s VP of Technology.
Quantum cascade laser (QCL) systems also support military applications such as Infrared Countermeasures (IRCM) and targeting. The demanding product requirements for aircraft platforms that include reduced size, weight, power consumption and cost (SWaP-C) extends to portable, battery powered handheld products.
Military and Security Applications
The spectral region from ~2 μm to >12 μm has been extensively explored for a broad range of laser sources because of the importance of the MWIR and the LWIR regions for spectroscopy, air pollution detection, detection of chemical warfare agents (CWAs), toxic industrial chemicals (TICs) and explosives, protection of aircraft from shoulder-fired missiles (MANPADS), target illuminators and designators and IFF beacons.
QCL technology operates throughout the mid-wave (MWIR) and long-wave (LWIR) infrared to provide new capabilities that leverage existing thermal imaging cameras. In addition to their suitability for aircraft platforms, QCL products are a natural fit to meet operator demands for small, lightweight pointer and beacon capabilities. Field-testing of high power, lightweight, battery operated devices has demonstrated their utility across a range of air and ground applications.
A key application for QCLs is stand-off explosives detection. In this developing field researchers have set the ambitious goal of detecting and discriminating nanogram quantities of various explosives at distances up to 50 m with eye-safe lasers.
There are a number of tactics being employed, one approach being Thermal Imaging. When a compound absorbs infrared light, it re-emits most of the absorbed light isotropically as heat which can be imaged by infrared cameras. Since each analyte has a unique absorption spectrum, each will heat selectively as the IR source is tuned through these absorptions and may be identified unambiguously by analysis of the multi-spectral or hyperspectral data cube produced.
While QCLs serve as the engines for new techniques in spectroscopy in the mid-IR, they also can provide raw power at new performance levels. Powers exceeding 5 W have been demonstrated from single room-temperature devices. Combining performance such as this with ruggedized packaging has enabled a new generation of Infrared Countermeasure (IRCM) devices. For IRCM applications, one needs a multiple wavelength illumination source to disable the tracking sensor in MANPADS.
High-power, solid-state lasers that operate in mid-infrared “atmospheric windows” can be used by pointer-trackers to disable the heat seeking mechanism employed on surface-to-air missiles, thus safeguarding soldiers in battlefield situations. Multiple “socket” QCL-based laser systems have been militarily hardened and have completed helicopter flight testing.
Indra and Elettronica to develop quantum cascade laser DIRCM system
Indra has collaborated with Elettronica Group for the development of the first European advanced self-protection solution that would help defend any type of aircraft from heat-guided missiles.Under the partnership, the two companies will work together to deliver the advanced Quantum Cascade Laser (QCL) based Direct Infrared Countermeasure (DIRCM) system that can be used to protect rotary and fixed wing aircraft.
DIRCM is a self-protection airborne system used to safeguard aircraft from the impact of heat-seeking missiles, particularly from Man Portable Air Defence Systems (MANPADS) missile attacks.The system helps detect incoming threats during the missile launch and countermeasure missile guidance using a directed laser beam that deviates its trajectory. Being quick and automatic, the DIRCM system can react against attacks of any imaging infrared (IR) seeker with a jamming sequence that facilitates successful countermeasure.
EuroDIRQM is designed as an ‘all-in-one’ piece of equipment for different platforms and a range of missions that will offer self-protection capabilities to all kinds of aircraft, including helicopters, transport, tankers, and jets. As the latest development in laser technology, quantum cascade laser energy helps optimise power consumption at the same time as output beam
IARPA’s Standoff Illuminator for Measuring Absorbance and Reflectance Infrared Light Signatures (SILMARILS)
In April 2015, the Inteligence Advanced Research Projects Activity (IARPA), Office of Smart Collection released a broad agency announcement for Standoff ILluminator for Measuring Absorbance and Reflectance Infrared Light Signatures (SILMARILS).
Block MEMS, the Massachusetts company specializing in photonics-based threat detection technologies, was awarded $10.7 million under the US Intelligence Advanced Research Programs Activity (IARPA) developmental funding scheme. The Marlborough-based firm, which has been nominated for a Prism Award at the forthcoming SPIE Photonics West event, says that the “Phase II” backing follows its successful stand-off detection of trace quantities of explosives using a benchtop system based around quantum cascade lasers (QCLs).
Under this contract, Block will develop a new class of widely tunable, high-pulse energy Quantum Cascade Lasers and also next-generation detection algorithms to detect and identify hundreds of chemicals on a wide range of surfaces. In addition to the suitable wavelength range, QCLs usually feature a relatively narrow linewidth and good wavelength tunability, making them very suitable sensor to detect a broad range of CWAs, TICs and explosives.
“Under Phase I, Block successfully demonstrated the ability to detect trace quantities of explosives and other threats on multiple surfaces at 1 and 5 meter standoff distances in a few seconds,” it stated, adding that the Phase II selection was made in a competitive down-selection process. That Phase I award was made in July 2016.
It has won the funding under IARPA’s “Standoff Illuminator for Measuring Absorbance and Reflectance Infrared Light Signatures” (SILMARILS) program, which is managed by Kristy DeWitt and the US Air Force Research Laboratory at Wright-Patterson Air Force Base in Ohio.
30 meter stand-off target
The ultimate aim of the SILMARILS program is to develop a portable system for real-time stand-off detection and identification of trace chemical residues on surfaces using active infrared spectroscopy, at a range of 30 meters.
In combination with what Block MEMS calls its “innovative chemical detection algorithm”, the QCL is able to probe for tell-tale spectroscopic transitions in the mid-infrared part of the spectrum that are characteristic of specific molecules. “The algorithm combines powerful data processing techniques, simulations of light/material interactions, and modeling of anticipated detected signatures in order to eliminate the effect of clutter, reduce false alarm rates, and improve limits of detection,” says the firm.
Specific applications envisaged for the developed technology include airport scanning of hands and clothes for signs of narcotics or explosives, or forensic analysis of the pavement around the area of a chemical release. Other contractors to have been involved in the program include Leidos, LGS Innovations, Physical Sciences, Inc., and Spectrum Photon
Standoff chemical detection is a ubiquitous need across the Intelligence Community (IC) for applications ranging from forensic crime scene analysis to border and facility protection to stockpile and production monitoring. However, current systems do not provide the sensitivity, specificity, and low false-alarm rates that are needed to enable effective use in a cluttered, realworld environment.
The SILMARILS program aims to develop a portable system for realtime standoff detection and identification of trace chemical residues on surfaces using active infrared spectroscopy at a 30 meter range. Program goals include: high chemical sensitivity and specificity across a broad range of target classes; effective operation in a real-world environment accounting for issues such as gas phase and surface-adsorbed clutter, varying substrates, temperature, humidity, indoor/outdoor background light; a system that is eye-safe and has a visually unobservable illumination beam; human-portable size and power draw commensurate with limited-duration battery operation; and a rapid scan rate.
Primary chemical classes and specific representative examples that are of interest in the SILMARILS program include, but are not limited to:
- Explosives: Nitro-based compounds such as TNT and RDX, newer formulations such as acetone peroxide, and home-made explosives such as fertilizer bombs.
- Chemical weapons and poisonous or toxic chemicals: Chemical weapons such as sarin or tabun, newer non-traditional agents, and toxic chemicals that may be intentionally or unintentionally released such as hydrogen cyanide or ammonia gas.
- Narcotics: Illicit drugs such as cocaine, heroin, or methamphetamine, or legal but abused· drugs such as Vicodin or hydrocodone.
“This machine would use infrared lasers to measure the signature of chemical agents and different molecules so that it’s much safer, practical way of interrogating a surface, like the bottom of someone’s shoe, footprints and those kinds of things,” said Kevin Kelly, chief executive officer of LGS Innovations, which could earn as much as $11 million over four years through SILMARILS.
Key goals for SILMARILS indicate the device must produce a steerable “eye-safe, visually unobservable illumination beam,” and must be of “human-portable size,” while drawing power at low enough levels to be battery operated. “There are also many commercial applications for sensitive, standoff chemical detection. Block’s QCL technology combined with advanced data analytics makes it possible to meet the challenging performance goals of the SILMARILS Program.
Quantum Cascade Lasers Market Growth
The global quantum cascade laser market size is expected to grow from USD 335 million in 2019 to USD 422 million by 2025, at a CAGR of 3.9% during the forecast period. Increasing use of quantum cascade lasers in gas sensing and chemical detection applications and growing demand for quantum cascade lasers in healthcare applications are the key factors driving the growth of the quantum cascade laser market. The high cost of QCLs is the main restraining factor for the QCL market.
The market for continuous wave (CW) operation mode is expected to grow at a higher CAGR during the forecast period. This high growth is due to its use in most of the QCL devices, as it provides continuous waves without any delay in time. In continuous wave mode, QCLs emit an uninterrupted laser beam. This is achieved through the constant pumping of the QCL. In this mode, the amplitude and the frequency of the wave are constant. A QCL operating in continuous wave mode requires stable output power.
The telecommunication segment is expected to be the major adopter of QCL technology during the forecast period. The deployment of quantum cascade lasers in the telecommunication sector is likely to further fuel the demand for QCL-based devices in free-space optical communication applications. Free-space optical communication is a promising solution that has an advantage of unlimited bandwidth, high security, and low cost. QCLs, being the most optimum light source in infrared wavelength, can be used in free-space optical communication.
The market for HHL & VHL packaged QCLs is expected witness the highest growth during the forecast period because of the high-power applications in the military and defense sector. HHL & VHL packaged QCLs are used in high-power applications in the military and defense sector for infrared countermeasures (IRCM).
The industrial sector held the largest share of the QCL market among industries such as medical, telecommunication, and military and defense. Gas sensing and chemical detection is the main application of QCLs. These techniques are adopted in various industries to detect hazardous gases such as CO, CO2, and NH3.
Key Market Players are Thorlabs (US), Hamamatsu Photonics K.K. (Japan), mirSense (France), Emerson Electric Co. (US), Block MEMS (US), Wavelength Electronics Inc (US), Pranalytica (US), DRS Daylight Solutions (US), PNNL (US), nanoplus Nanosystems Technologies GmbH (Germany), Lasermax Inc. (US), Picarro Inc (US), Akela Laser Corporation (US), Aerodyne Research Inc. (US), Alpes Laser (Switzerland), Power Technology Inc. (US), Boston Electronics Corporation (US), MG Optical (Germany), SacherLaser Technik (Germany), AdTech Optics (US), Longwave Photonics (US), and Eluxi Ltd. (UK) are some of the major companies in the quantum cascade laser market.