[Review of Scientific Instruments]Resonant absorption induced fast melting studied with mid-IR QCLs
Prof. Li and Dr. Lu et al. develop a pump-probe setup based on two mid-infrared QCLs for the study of melting and crystallization of materials through resonant absorption.The related work is published in Review of Scientific Instruments (88, no. 2 (2017): 023108).
In this paper we demonstrate the use of a pump-probe setup based on two mid-infrared quantum cascade lasers (QCLs) to investigate the melting and crystallization of materials through resonant absorption. A combination of pump and probe beams fulfills the two-color synchronous detection. Furthermore, narrow linewidth advances the accuracy of measurements and the character of broad tuning range of QCLs enables wide applications in various sample and multiple structures. 1-Eicosene was selected as a simple model system to verify the feasibility of this method. A pulsed QCL was tuned to the absorption peak of CH2 bending vibration at 1467 cm1 to resonantly heat the sample. The other QCL in continuous mode was tuned to 1643 cm1 corresponding the C==C stretching vibration to follow the fast melting dynamics. By monitoring the transmission intensity variation of pump and probe beams during pump-probe experiments, the resonant absorption induced fast melting and re-crystallization of 1-Eicosene can be studied. Results show that the thermal effect and melting behaviors strongly depend on the pump wavelength (resonant or non-resonant) and energy, as well as the pump time. The realization and detection of melting and recrystallization can be performed in tens of milliseconds, which improves the time resolution of melting process study based on general mid-infrared spectrum by orders of magnitude. The availability of resonant heating and detections based on mid-infrared QCLs is expected to enable new applications in melting study.
This work is supported by the National Natural Science Foundation of China (Nos. 51325301, 51227801, and 51633009).
Schematic of mid-infrared pump-probe setup. ND: neutral density.
Yellow dotted line represents a sealed box
