Room Temperature Terahertz Frequency Comb Using Quantum Cascade Lasers

Researchers at Northwestern University, Illinois have designed a terahertz (THz) frequency comb using a Quantum Cascade Laser (QCL) with a Distributed Feedback (DFB) grating inside the cavity. The DFB grating addition allows for dual wavelength emission from the QCL. A single-mode state and a harmonic comb state combine inside the cavity for a THz frequency comb. The device generates THz frequencies at room temperature without any external optical setup. This allows for a harmonic frequency comb at 3.0 THz with a range of 2.2 to 3.3 THz. With the single QCL dual wavelength emission, the THz comb is more stable than multiple sources. This devices enables a greater current dynamic range for harmonic comb operation, especially useful in spectroscopy applications. Two uses of QCL frequency combs demonstrated by researchers at Harvard University are also discussed.