Research / 2020 / Article / Fig 2

Research Article

Spatial Wavefunction Characterization of Femtosecond Pulses at Single-Photon Level

Figure 2

Spatial wavefunction characterization of single photons from an ultrafast light source with quadratic wavefront shape. The 4-bin phase shifting induced by translation of BSC (see Video 1) is applied to the interferograms with shearing amount of , , , and to retrieve the phases. The phases are manipulated numerically to extract the wavefront shape (see Materials and Methods for details of the data acquisition and wavefront extraction). (a–h) Interferograms produced by a focusing beam with a focal length of  mm that passed through the CDSI. The shearing amount are (a–d) and (e–h) . The shearing direction are (a, b, e, f) and (c, d, g, h) . The phase shift pairs are (a, c, e, g) 0 and π and (b, d, f, h) and . (i) Probability distribution of the single photon measured by translating the BSC to fully contain the beam. (j) Extracted wavefront based on the interferograms (a–h). Each interferogram is made up of accumulation of 15000 frames at the rate of 0.72 photons per frame. (See Video 2 for the accumulation of frames.)