Time-resolved, high-accuracy and high-resolution spectroscopy of frequency-agile cw lasers is critical to realizing their full potential for sensing, but is not possible with conventional spectroscopy methods. We demonstrate a dual comb-based spectrometer capable of measuring cw optical waveforms at 30-300 υs update times over optical bandwidths of many THz. For narrowband sources, the spectrometer measures the electric field at kHz resolution/accuracy, while for broadband sources, the spectrometer measures the intensity spectrum at 100-MHz resolution (set by the comb repetition rate). To demonstrate the techniques broad applicability, we measure a laser during a perturbation, a tunable laser step-scanned over 45 nm, two tunable lasers, and an incoherent source. Unlike etalon-based techniques, each measurement is independent, calibrated in absolute frequency, and puts no restrictions on the source tuning, enabling the use of highly optimized waveforms in sensing applications including multi-species gas detection [1-3], coherent laser radar [4-6], and telecom diagnostics [7-9].
Citation: Nature Photonics
Pub Type: Journals
frequency comb, laser metrology, LIDAR, spectroscopy