Fig. 3: Temporal magnification measurement.

Two CW lasers are combined to emulate large Doppler shifts and to calibrate the time lens. One of the lasers is set to 1541.47 nm and the other one is varied in the range 1540.70–1541.43 nm with a low −15dBm power to emulate weak return signals from a target. The first two columns show the idler time trace and the corresponding Fourier transform amplitudes for input wavelengths of 1541.20 nm, 1541.10 nm, 1541.00 nm and 1540.90 nm. The measured frequencies can be extracted from the peak position of the FFT amplitudes. The right panel shows the measured frequencies from these FFT maxima and the set frequencies calculated from the wavelength difference are plotted and show excellent agreement between the design and the measured temporal magnification. The yellow band shows  ± 2σ estimated from 199 pulses where σ is the standard deviation.