研究目的
Investigating the tunability of the free-spectral range (FSR) of quantum cascade lasers (QCLs) emitting at 4.7 μm through direct microwave modulation and analyzing the effects of radio frequency (RF) injection on the lasing spectrum.
研究成果
The study demonstrates the tunability of the FSR of QCLs through direct microwave modulation, with a significant broadening and flattening of the lasing spectrum observed under RF injection. High-resolution spectroscopy revealed a comb-like regime for both free-running and RF modulated QCLs, with no observable dispersion beyond 10 MHz over the entire spectra. The ability to tune the FSR and operate QCLs in a comb-like regime opens new possibilities for applications in heterodyne, dual comb spectroscopy, and free-space communications.
研究不足
The study is limited by the resolution of the FTIR and the bandwidth of the RF generator. The packaging designed for high-speed transmission is not ideal in environments with strong vibrations.
1：Experimental Design and Method Selection:
The study involves direct microwave modulation of QCLs to tune the FSR, with high-resolution spectroscopy used to analyze the effects on the lasing spectrum.
2：Sample Selection and Data Sources:
QCLs emitting at
3：7 μm were used, with spectra recorded at various pumping currents. List of Experimental Equipment and Materials:
Equipment includes a source meter (KEITHLEY 2400), a signal generator (Anritsu MG3693B), a spectrum analyzer (Agilent E4407B), and a Bruker IFS 125 HR Fourier transform infrared spectrometer (FTIR).
4：Experimental Procedures and Operational Workflow:
The QCLs were modulated at frequencies close to the round-trip cavity frequency, and high-resolution spectra were recorded to analyze the FSR and mode spacing.
5：Data Analysis Methods:
The evolution of the FSR as a function of the mode number or frequency was analyzed, with averaging applied to smooth oscillations due to the resolution.
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