High-resolution Interferometric Diagnostics for Ultrashort Pulses

4. EXPERIMENTAL IMPLEMENTATIONS OF MULTIPLE SPECTRAL SHEARINGINTERFEROMETRYCLTPBS1DL1βbλ/2BS2GrL1br rbDL2χ (2)SFL2ImagingspectrometerFigure 4.7: SEA-CAR-SPIDER setup. The symbols are defined in the text.filter SF the sum-frequency beams are re-imaged onto an imaging spectrometer by lens L2 withfocal length f 2 = 300mm. The spectrometer’s entrance slit is oriented in the dispersion planeof the ancillae and the signal is internally dispersed perpendicular to this plane. The signal isrecorded with a 1280 × 1024pixel CMOS detector with 8 bit analog-to-digital conversion. Singleshotdata is recorded at a rate of 30 Hz limited by memory and data-transfer capacities.4.2.2 ExperimentFigure 4.8 shows the experimental setup. To demonstrate recovery of the spectral phase acrossa null, I characterized a bichromatic double pulse, synthesized using a 4f pulse shaper with a19.4mrad/fs wide stop (≈ 25% of the full-width at half-maximum (FWHM) bandwidth) in theFourier plane. To one side of the stop, a glass slide delayed frequencies above 2.378rad/fs by 380fs.The temporal intensity, spectrum and spectrogram of the resulting pulse is shown in Fig. 4.9. Figure4.11(c) shows the measured SEA-CAR-SPIDER interferogram, consisting of the coherent sumof the two single-arm spectra shown in Figures 4.11(a) and (b). The large fringe-covered areas atlower and higher frequencies in Fig. 4.11(c) represent self-overlap of the near transform-limited100