“Interband Cascade Lasers, namely Interband Cascade Lasers, referred to as ICL lasers, is an important innovative product after near-infrared DFB lasers and mid-infrared QCL lasers, especially in the 3-6 μm wavelength field to fill the shortcomings of DFB lasers and QCLs .
Interband Cascade Lasers, namely Interband Cascade Lasers, referred to as ICL lasers, is an important innovative product after near-infrared DFB lasers and mid-infrared QCL lasers, especially in the 3-6 μm wavelength field to fill the shortcomings of DFB lasers and QCLs .
Currently, nanoplus is the only manufacturer that can provide inter-band cascaded ICL lasers with arbitrary center wavelengths between 3000nm and 6000nm. In this wavelength range, most gases have their strongest absorption lines, which are orders of magnitude higher than other infrared regions, such as CH4, HCl, CH2O, HBr, CO, CO2, NO, and H2O. The innovation of ICL lasers opens up TDLAS ultra-high sensitivity gas sensing applications in the mid-infrared field.
The development history of ICL laser:
In 1994, Rui. Q. Yang first proposed the concept of the second type of interband cascaded laser (ICL). The interstitial InAs/AlSb/GaSb superlattice has a large conduction band discontinuity, which can provide very good free carrier confinement, and the lattice constants of GaSb, InAs and AlSb are very close, which is conducive to the growth of high quality material, so it is very suitable for the second type of ICL material.
After the concept of the second type of ICL was proposed, it was theoretically predicted that it could be lasing in continuous wave (CW) mode at room temperature with high output power and low threshold current density. The Type II ICL has been extensively studied by a number of research institutions, including the University of Houston’s Vacuum Epitaxy Center, the U.S. Naval Laboratory, the U.S. Army Laboratory, and the California Institute of Technology’s Jet Propulsion Laboratory. Until 2012, the first commercialized ICL laser was successful. It was successfully developed by the German nanoplus company in conjunction with the University of Wurzburg and other research institutions. ICL lasers with a wavelength range of 3 to 6 μm have been successfully launched. Many highly sensitive gas absorption lines, such as CH4, HCl, CH2O, HBr, CO, CO2, NO and H2O, etc., will bring new applications to laser gas analysis applications.
The nanoplusICL laser won the 2012 Prism Award:
The nanoplus ICL interband cascade laser won the Prism Award in 2012 jointly selected by the International Society for Optical Engineering (SPIE) and Photonice Media, and held an award ceremony in San Francisco at the end of January 2012 to recognize nanoplus has launched an innovative product ICL laser, which covers the entire wavelength range from 3000nm to 6000nm, opening up the research and application of tunable diode laser spectroscopy in this band.
Main features of ICL lasers:
At present, the parameter characteristics of ICL lasers are very similar to those of near-infrared DFB lasers, with lower threshold current, room temperature operating temperature, higher output power, and relatively low heat dissipation. As shown in the figure below are the typical characteristic parameters of the device in the wavelength range of 46xx nm and 52xx nm. It can be seen that the ICL laser has very similar characteristics to ordinary near-infrared DFBs at an operating temperature of 20°C and a typical output power of 5mW. parameter characteristics, and the circuit power consumption threshold is only 150mW, with very low power consumption.
In addition, take the 5262.9nm ICL laser as an example:
Comparison of radiation principles between ICL lasers and DFB lasers and QCL lasers:
1) DFB, ICL, and QCL radiate light in different wavelength ranges from different substances.
Different emission wavelengths are based on different material radiation, as shown in the figure below, blue represents the chip material for VCSEL, DFB structure, red represents the chip material for ICL structure, and green represents the chip material for QCL structure.
2) Basic composite scheme from visible light to infrared light radiation.
3) The relationship between the emission wavelength of DFB, ICL and QCL lasers and the threshold power density.
figure 1.Relationship between laser emission wavelength and threshold power density
Threshold power density is an index to measure the amount of energy required to excite the laser. The higher the threshold power density, the higher the input current, the higher the energy consumption, and the more heat generated for the same optical output power. As shown in the figure above, black represents the DFB laser, the threshold power density is getting higher and higher at 2-3.5μm, green and blue represent the ICL laser, the threshold power density is getting higher and higher at 3-7μm, red represents the QCL laser, the threshold value The power density is higher than that of DFB and ICL, especially within 4μm. It can be seen from the above figure that the DFB laser has a lower threshold power density within 3 μm, the ICL laser has a lower threshold power density at 3-6 μm, and QCL has a higher threshold power density.
Innovative applications of ICL lasers:
TDLAS has many advantages in using mid-infrared ICL laser as the emission light source. First, it selects the strongest absorption line of a large number of trace gases as the detection object, which helps to improve the detection speed and detection limit, and can reduce the noise of the whole system, and Portable and miniaturized devices are made by reducing the optical path length.
For example, ICL lasers are used in vehicle exhaust telemetry:
Through the horizontal fixed or vertical fixed all-laser vehicle exhaust remote sensing monitoring system, the components of CO, CO2, HC (especially C3H8), NO, NO2, N2O and other gases emitted by the exhaust gas emitted by the vehicle can be monitored in real time. The light transmittance can effectively and automatically identify vehicles and smoky vehicles whose exhaust emissions do not meet the standards.
Another example is the use of ICL lasers for medical breath analysis:
It is the most popular method of breath analysis today to detect what disease you have. Medical breath analysis requires detection methods with very high sensitivity and a very low detection limit. The emergence of ICL lasers just solves the problem of low sensitivity of conventional methods. Conventional exhaled gases such as CO2, CO, and NO have the strongest detection in the mid-infrared region. The absorption line can be accurately detected, for example, by detecting the content of exhaled 13CO2 to diagnose whether Helicobacter pylori is carried, and by detecting NO in exhaled air to diagnose whether or not asthma, etc.
Future development of ICL lasers:
At present, lasers have basically covered the wavelength range from 760nm to 20μm, which can detect most gases, especially the gas detection with high sensitivity in the mid-infrared. However, the cost of lasers is still high, which restricts the wide application of laser absorption spectroscopy. In the future, with the continuous breakthrough of laser technology and the maturity of process technology, the cost will be greatly reduced after mass production of lasers, and miniaturized, highly integrated, low-cost lasers and gas sensors will become an inevitable trend.
With the advent of the Internet of Things, the application of laser absorption spectroscopy technology will be widely promoted. In addition to industry and environmental protection, it will also enter the consumer field and become household and personal consumer goods. Laser absorption spectroscopy technology will move from analytical instruments and meters to the field of sensors, and the scale should be greatly improved.
One example is an ongoing European project, MIRPHAB: Fabrication of Infrared Optoelectronics for Chemical Sensing and Spectroscopy.
The MIRPHAB project brings together major manufacturers of mid-infrared lasers and detectors and will build a new pilot line to meet the growing European demand for mid-infrared devices. The EU hopes to provide end-to-end production capabilities from design to manufacturing packaging for a wide range of mid-infrared devices for a wide range of infrared sensing applications.
By introducing a large number of integrated circuit/MEMS device technologies and developing integrated process models for silicon and III-V materials, the pilot line will bring technologies that have never been realized before for sensors, opening up many applications that existing technologies and devices cannot bring. , meet the needs of next-generation chemical sensing and spectroscopy, and significantly reduce cost, power consumption and size.
The maturity and stability of the ICL laser will be a huge contributor to the success of MIRPHAB.
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