Fig. 1. (a) The ordinary and extraordinary light refractive indexes and (b) the absorption of GaSe crystal in the mid-infrared range

Fig. 2. The response function of the EOS with different GaSe thicknesses (10 μm, 20 μm, 30 μm, and 50 μm) with two different probe laser wavelengths：(a) is with 800 nm and (b) is with 1 030 nm

Fig. 3. The pulse distortions of few-cycle laser pulse with a wavelength of 2 μm induced by the EOS with different thicknesses： (a) shows the time waveforms and (b) shows their frequency spectra, respectively

Fig. 4. The pulse distortions of few-cycle laser pulse with a wavelength of 3 μm induced by the EOS with different thicknesses： (a) shows the time waveforms and (b) shows their frequency spectra

Fig. 5. The changing of (a) the central frequency and (b) the bandwidth depending on the wavelength of the few-cycle laser pulse from 2 μm to 10 μm