Fig. 1. Time-stretch principle diagram. (a) Time-frequency mapping relationship of fs pulse; (b) Time-frequency mapping relationship of time-stretched pulse

Fig. 2. Frequency gating schematic diagram. (a) Time-stretched ns pulse; (b) Spectral scan achieved after time domain gating; (c) Gas absorption line; (d) Gas absorption spectra scanned by dispersion gate technique

Fig. 3. Optical path diagram of dispersion gate experiment

Fig. 4. Single and multiple time-domain and frequency-domain pulse signals. (a) A single ps pulse in the time domain; (b) A single ps pulse in the frequency domain; (c) Picosecond pulse delay accumulation in the time domain after oscilloscope selection; (d) Picosecond pulse delay accumulation in the frequency domain after spectrometer selection

Fig. 5. Schematic diagram of time-frequency mapping equation

Fig. 6. Time domain dispersion gated pulse result graph. (a) Time-domain scanning signal after passing through the gas cavity; (b) Frequency-domain signal after time-frequency conversion, the black line is the spectrum by spectrometer of HCN gas; (c) Residual error between the inverted HCN spectrum and the HCN spectrum by spectrometer after time-frequency conversion