Laser spectroscopy is a technique used to measure concentration of molecules in various applications like pollution monitoring, process control or non-invasive medical monitoring. Indeed, most molecules absorb infrared light at specific wavelengths and therefore, by tuning our infrared laser at the right wavelength and shining it on a given gas, liquid or solid sample, our clients can determine the amount of molecules present in the sample with the right detection setup (using pyroelectric detectors or photoacoustics for example).
One core parameter of successful laser spectroscopy is the selected wavelength and mirSense offers its clients the unprecedented 10 to 17 microns wavelength spectrum. The production of QCL lasers in the 10-17 microns range is unique in the world as mirSense holds an exclusive license of this technology developed at the University of Montpellier, France. In this long wave wavelength region, customers can detect various molecules like BTEX or hydrogen cyanide (see below some examples). Furthermore at these long wavelengths, the intrapulse linewidth broadening is relatively smaller than in the mid-infrared region and therefore, pulsed operation can be more attractive for spectroscopy.
The uniMir lasers are mounted on a thermoelectric cooler (TEC) inside a sealed High Heat Load (HHL) package integrating a collimation lens and a thermistor to readout the laser chip temperature. By controlling the chip’s operating temperature through the TEC element inside the laser’s package, customers tune the emission wavelength without mode hopping while keeping a single-mode operation.
HHL-package diagram showing the built-in thermistor that monitors the laser chip temperature and the base plate that dissipates the heat generated by the laser and the TEC.
Example of emission spectra as a function of the chip temperature for a QCL emitting at the wavelength of 17.7 µm. These DFB lasers are single mode with a side mode suppression ratio larger than 25dB.
Typical output characteristics of a DFB QCL emitting at 13.5µm.
mirSense can manufacture any wavelength in the 10-17 µm range and below are examples of gases that can be measured by spectroscopy at specific wavelengths.
General datasheet presenting the 10-17 µm offer
| Wavelength | Measurable gases | QCL product datasheet when available | |
| In microns units | In cm-1 units | ||
| ~ 11.3 µm | ~ 885 cm-1 | CH3i Methyl Iodide | UN0885C010HNA |
| ~ 12.6 µm | ~ 795 cm-1 | p-Xylene | UN0746C005HNA |
| ~ 13 µm | ~ 769 cm-1 | m-Xylene | UN0746C005HNA |
| ~ 13.5 µm | ~ 741 cm-1 | o-Xylene | UN0746C005HNA |
| ~ 13.7 µm | ~ 729 cm-1 | Toluene | UN0746C005HNA |
| ~ 14 µm | ~ 713 cm-1 | HCn Hydrogen cyanide | UN0713C005HNA |
| ~ 14.3 µm | ~ 697 cm-1 | Ethylbenzene | |
| ~ 14.4 µm | ~ 694 cm-1 | Toluene | |
| ~ 14.8 µm | ~ 673 cm-1 | Benzene | UN0674C005HNA |
| ~ 15.9 µm | ~ 628 cm-1 | UF6 Uranium hexafluoride | UN0628C002HNA |
| ~ 16 µm | ~ 624 cm-1 | Neptunium NpF6 | |
| ~ 16.1 µm | ~ 619 cm-1 | Plutonium PuF6 | |
| ~ 17.2 µm | ~ 581 cm-1 | Nitrous oxide N2O | |
At the Photonics West 2021 laser show, mirSense was a finalist at the Prism Award in the category smart sensing for the uniMir quantum cascade lasers that allow new spectroscopy applications in the 10 to 17 microns wavelength spectrum like Benzene detection.
Ask Adrien Dequaire
Adrien is in charge of our laser solutions
