Yin Jiaze, Pfluegl Christian, Teng Chu C, Bolarinho Rylie, Chen Guo, Gong Xinrui, Dong Dashan, Vakhshoori Daryoosh, Cheng Ji-Xin
Boston University, Department of Electrical and Computer Engineering, Boston, Massachusetts 02215, USA.
Boston University, Photonics Center, Boston, Massachusetts 02215, USA.
Phys Rev Lett. 2025 Mar 7;134(9):093804. doi: 10.1103/PhysRevLett.134.093804.
It is generally assumed that the spectral acquisition speed in photothermal spectroscopy is fundamentally limited by the thermal diffusion process. Here, we demonstrate midinfrared energy deposition (MIRED) spectroscopy that offers both microsecond-scale temporal resolution and submicron spatial resolution. In this approach, the photothermal process is optically probed while the infrared pulses from a quantum cascade laser array are rapidly tuned. Based on Newton's law of heating and cooling, the energy deposition is the first derivative of local temperature rise over time and gives the instantaneous absorption. By employing time-resolved measurement of transient energy deposition, the upper limit for spectrum encoding shifts to the vibrational relaxation level, which occurs on the picosecond scale. This method significantly increases the detection bandwidth while retaining the sensitivity and resolution benefits of photothermal detection.
一般认为，光热光谱中的光谱采集速度从根本上受到热扩散过程的限制。在此，我们展示了中红外能量沉积（MIRED）光谱，它兼具微秒级的时间分辨率和亚微米级的空间分辨率。在这种方法中，当来自量子级联激光器阵列的红外脉冲快速调谐时，对光热过程进行光学探测。基于牛顿加热和冷却定律，能量沉积是局部温度随时间上升的一阶导数，并给出瞬时吸收。通过采用瞬态能量沉积的时间分辨测量，光谱编码的上限转移到皮秒级发生的振动弛豫水平。这种方法在保持光热检测的灵敏度和分辨率优势的同时，显著增加了检测带宽。
