Abstract
The total outgoing longwave radiation emitted from the earth-atmosphere system to the outer space is in 3 - 100 µm wavelength band. Development of satellite instrumentations for the outgoing longwave radiation depends on material study, sensor research, and instrument tests in the wavelength region of interest. Beyond 20 µm, the availability of a laser source with the average output power > several mW is a challenge in the commercial market. In the presentation, we report the results of testing and assessing a quantum cascade laser (QCL) at 23 µm (430 cm-1) with average power < 1 mW. It operates in a pulsed multimode around LN2 temperature in a cryostat. The QCL at 23 µm has been installed successfully, and was tested using a LiNbO3 pyroelectric detector with some preliminary results. To further stabilize the output of the laser in the cryogenic temperature, a recommended transfer line and a vertical withdrawal container are equipped to the laser cryostat. And a more sensitive and efficient detection is required to measure the output power using a focusing optics for the beam divergence of 60° and 40° in vertical and horizontal directions, respectively. To improve detection, a blocked impurity band (BIB) detector is planning to be applied in the next test, as well as a Deuterium Triglycine Sulfate (DTGS) pyroelectric detector that is recommended by the manufacturer. The test results of the QCL at 23 μm will be compared with that of the power output at the same wavelength from a synchrotron radiation facility. Eventually, it will be integrated with the Complete Hemispherical Infrared Laser-based Reflectometer (CHILR) and the Infrared Laser-based Gonio-reflectometer (ILGR) at NIST to support measurement in the longwave infrared region.
Test and Assessment of a New Quantum Cascade Laser at 23 μm for Applications in the Longwave Infrared Region
The total outgoing longwave radiation emitted from the earth-atmosphere system to the outer space is in 3 - 100 µm wavelength band. Development of satellite instrumentations for the outgoing longwave radiation depends on material study, sensor research, and instrument tests in the wavelength region of interest. Beyond 20 µm, the availability of a laser source with the average output power > several mW is a challenge in the commercial market. In the presentation, we report the results of testing and assessing a quantum cascade laser (QCL) at 23 µm (430 cm-1) with average power < 1 mW. It operates in a pulsed multimode around LN2 temperature in a cryostat. The QCL at 23 µm has been installed successfully, and was tested using a LiNbO3 pyroelectric detector with some preliminary results. To further stabilize the output of the laser in the cryogenic temperature, a recommended transfer line and a vertical withdrawal container are equipped to the laser cryostat. And a more sensitive and efficient detection is required to measure the output power using a focusing optics for the beam divergence of 60° and 40° in vertical and horizontal directions, respectively. To improve detection, a blocked impurity band (BIB) detector is planning to be applied in the next test, as well as a Deuterium Triglycine Sulfate (DTGS) pyroelectric detector that is recommended by the manufacturer. The test results of the QCL at 23 μm will be compared with that of the power output at the same wavelength from a synchrotron radiation facility. Eventually, it will be integrated with the Complete Hemispherical Infrared Laser-based Reflectometer (CHILR) and the Infrared Laser-based Gonio-reflectometer (ILGR) at NIST to support measurement in the longwave infrared region.