Quantum Cascade Lasers: Where They Are and Where They're Going
QCLs are carving a clearer niche in photonics applications, namely in defense and security, medical diagnostics, atmospheric gas sensing and mid-infrared imaging.
Since its first demonstration more than two decades ago, the quantum cascade laser (QCL) has proved a versatile, powerful tool in the lab and in the field. It is smaller and faster, and requires less power than earlier Fourier transform infrared (FTIR) and mass spectroscopy systems. And its continued evolution is anticipated across the board.
Some challenges exist, however, such as changing customer needs, and costs associated with broadening the scope of QCL-based systems. QCL system users are working to overcome such hurdles, looking at how QCLs could be used with new technologies and discovering potential new applications.
Photonics Spectra spoke with representatives of several companies about their thoughts on the state of the industry’s QCL sector.
• Daylight Solutions Inc. in San Diego, a developer of mid-wave infrared (MWIR) detection and imaging systems: Tim Day, CEO and chief technology
officer; Paul Larson, president and chief operating officer; Eric Takeuchi, senior director of business development; and Matthew Barre, business development manager.
• Mary Johnson, CEO of Wavelength Electronics Inc. in Bozeman, Mont., developer of quantum cascade lasers and diode laser drivers.
• Dr. Anish K. Goyal, vice president of technology at Block Engineering/MEMS LLC in Marlborough, Mass., a manufacturer of QCL and FTIR spectrometers for chemical imaging and detection.
• Kenneth Puzey, founder of Quanta-Spec Inc. in Burlington, Vt., developer of quantum cascade laser diode and imaging detector systems.
• Antoine Müller, CEO of Alpes Lasers SA in Neuchâtel, Switzerland, a developer of QCLs and other advanced light sources used in tunable diode laser spectroscopy, gas detection and other such applications.
• Patrick Gale, product marketing manager at ILX Lightwave Corp., a division of Newport Corp. that supplies laser diode instrumentation and control equipment for photonics research and development.
Q: Your company develops and manufactures QCLs. Where is your technology currently?
Larson: For all of our business units, we continue to work closely with our broad portfolio of QCL chip suppliers to advance the technology in key areas such as wavelength coverage, power and efficiency. We have accumulated over 1.25 million hours of component-level run-time testing, and over 6000 hours of laser system testing. We have also accumulated over 8000 hours of laser testing while integrated into military system hardware. Daylight Solutions’ laser systems have been flight tested on seven different military airborne platforms.
Goyal: Our QCL module is called the Mini-QCL. The Mini-QCL leverages telecom-style packaging methods and is an extremely compact, rapidly tunable and very widely tuning QCL. It is based on an external-cavity design. In addition to the laser, we have developed sophisticated electronics to control the Mini-QCL to perform high-speed spectroscopy.
Johnson: Our drivers deliver current to QCLs using extremely low-noise circuitry. Our drivers use patented technology licensed from Battelle Memorial Institute. We offer both the QCL Lab instruments for benchtop research and the QCL OEM for integration into complete sensor systems. These drivers redefine “state of the art” with noise an order of magnitude lower than competitor units, higher bandwidth (2 to 3 MHz), and better stability and temperature coefficient.
Müller: We are now deploying our XT or extended tuning technology to most of our inventory and want to further improve this technology. Presently, we are at 0.4 percent and shoot for over 1 percent. Similarly, we now deploy devices with extremely low dissipation below 1 W. Regarding the gain media for external cavity, our coverage goes from 5 to 12 µm with high performances. Regarding high power, presently we are around 1 W to 1.5 W on Peltiers.
Q: What applications do your company’s QCL technology and products focus on, and why?
Gale: ILX Lightwave makes precision current sources (CW and pulsed), temperature controllers and a laser mount for quantum cascade lasers. Our products are used in R&D at university labs, government labs and commercial companies that are using QCLs. Also, our products are used in production testing of QCLs.
Johnson: Our drivers are frequently used by trace-gas sensor developers. [There are] specific field-deployed systems in applications that analyze atmospheric gas content, detect nitric oxide in breath and blood to diagnose diseases, or sense the presence of ammonia or ethylene. Our drivers have also been used in cavity-ringdown spectroscopy, with photoacoustic sensing systems and in detection systems for liquids and solids (pharmaceutical process control).
Puzey: We are developing defense, homeland security and medical applications because they are high-margin applications.
Barre: Our commercial business unit is focused on molecular detection and imaging solutions for a variety of markets. We see life sciences as a particularly strong sector as they continue to leverage the recent advances in biophotonic and spectroscopic technologies.
Takeuchi: Our defense and security business unit is poised to provide MWIR and LWIR QCL-based systems to this industry. This business unit has successfully established Directional Infrared Countermeasures (DIRCM) and combat identification applications initially, based on the natural marriage of market need and technical capabilities.
Larson: Our scientific business unit delivers tunable laser solutions into research markets for a large variety of applications with hundreds of systems in the field. This market provides an excellent opportunity to seed and investigate emerging and next-generation applications for potential commercialization.
Q: Where do you see your company’s technology taking you in the future?
Puzey: We see applications in standoff detection (telescopic sensor) and medical (microscopic sensor). Goals [are to] develop products in each sector.
Johnson: We have been asked to make the QCL OEM product even more compact, so that is one of our current projects.
Takeuchi: To provide mid-infrared-based protection for every soldier and every platform in the military. Within the commercial business unit, we plan to introduce a range of molecular-detection products that leverage the speed, precision and reliability of QCL-based systems.
Müller: We see a lot of potential with devices based on ideas such as vertical-emission and optical-bandgap type devices. They offer an additional level of freedom of design and very appealing performances for the system maker.
Goyal: We see our technology being adopted for use in a variety of applications which span a range of industries. As we proceed, the technology will likely need adjustment to meet application-specific needs.
Q: What are existing and potential challenges you are facing in efforts to advance your QCL technology?
Gale: One issue with QCLs is price and efficiency. For price to come down to levels that will allow more research using QCLs, it will require a large-volume application. The second is efficiency, and there has been good progress made every year on improving the electrical-to-optical efficiency.
Larson: The cost of individual QCL die continues to be the biggest challenge in advancing broader adoption of QCL technology.
Takeuchi: The biggest challenge in the defense and security industry is to manage the business through lengthy processes that are characteristic of government procurement. As a small business, it is a challenge to focus resources on a particular segment and application, and then await lengthy time-to-market schedules.
Johnson: The price of QCLs has dramatically dropped over the last few years (from $35,000 to $6,400). This opens up even more opportunity for material sensor development. We find that our biggest existing challenge is assisting customers in finding ground loops and other electronic noise sources that were masked by the competitors’ old technology.
Goyal: A major challenge is related to adoption of a new technology by an industry. The first step is finding the right applications for which there is a clear cost benefit for using QCLs. Then, the challenge is getting the industry to recognize these advantages so that they will move toward adoption of the technology. This requires working closely with customers to understand their requirements and then building systems that meet their needs and expectations.
Müller: Technically, for spectroscopic applications, mid-IR is a desired region for the cross sections of the chemicals under investigation but is much less desirable when it comes to the optical components and materials that are more expensive and less available than the cheap components available in the [near-infrared]. This means that the market grows where trace-gas detection is necessary and no other solutions are available. The recent development of QCLs with low dissipation, CW operation and longer wavelength available is a challenge to QCLs, as there is a misrepresentation of the QCL as a high-dissipation device.
Puzey: Capital. [We will] continue obtaining R&D funding from customers to develop products they want.
Q: What do you see for the future of the QCL sector?
Müller: We see a strong interest on broad accessibility to the spectrum, and we believe that large tuning sources, multiwavelength sources and detection integration will be hot topics in the years to come.
Takeuchi: QCLs have already been adopted by the [U.S.] Department of Defense for a variety of life-critical applications, and we expect this adoption trend to continue within the research and commercial markets. In particular, QCL technology has advanced to the point of being practical for compact and even handheld sensor and imaging applications. In addition, large commercial businesses are beginning to integrate QCL technology into their product portfolios, which will continue to drive adoption and price reduction.
Day: We are now approaching a turning point in QCL market penetration and will begin to see products and applications that can truly leverage the cost reductions and miniaturization taking place at the component level. We can expect to see the integration of QCL technology into mobile devices for personal health measurements and environmental monitoring. The molecular-detection capabilities of QCL-based systems are certainly poised to make a huge impact on areas such as cancer diagnostics, personalized medicine and in vivo spectral imaging.
Gale: QCL wavelengths are of great interest to customers developing spectroscopy applications and security/defense applications and, due to their size, will provide a more portable solution at these wavelengths.
Puzey: The QCL sector will see tremendous growth once an application is commercialized that drives volumes up and prices down.
Johnson: Growth. Discovery of new applications. For example, several companies are working to develop noninvasive glucose monitors – no more blood draws to determine sugar levels for diabetics. The data available to spectroscopy in the mid-IR region opens up many exciting new sensor possibilities.
Goyal: It will continue to grow. Of that I have no doubt.
- quantum cascade laser
- A Quantum Cascade Laser (QCL) is a type of semiconductor laser that emits light in the mid- to far-infrared portion of the electromagnetic spectrum. Quantum cascade lasers offer many benefits: They are tunable across the mid-infrared spectrum from 5.5 to 11.0 µm (900 cm-1 to 1800 cm-1); provide a rapid response time; and provide spectral brightness that is significantly brighter than even a synchrotron source.
Quantum cascade lasers comprise alternating layers of semiconductor...
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