Ultra-Fast Wavemeter for CW Laser Based on Wavelength-to-Time Mapping

An ultra-fast continuous wave (CW) wavemeter with the 51 MHz update rate is proposed and demonstrated based on wavelength-to-time mapping and optical heterodyne. The system consists of a mode-locked laser (MLL) as the probe source and a reference tunable laser. The mode-locked pulses emitted from the MLL are first stretched in a dispersive element and its spectrum is mapped into time-domain. Then, the stretched pulses beat with reference beam and the beam under test in two arms, respectively. By measuring the time delay between the beating results in two arms, the wavelength information can be obtained. In the meantime, we introduce cross correlation to our data processing to improve the measurement resolution. A resolution of about 0.03 nm is achieved. The spectral range of the ultra-fast wavelength meter is about 10 nm. Using the proposed scheme, we successfully trace the wavelength variation of a linearly chirped laser source with the 125 kHz repetition rate.