1：Experimental Design and Method Selection:

The experiment involved pulse beam emission and measurements of electron holograms in the SP-TEM with an ultrashort-laser. The cathode used was a semiconductor pulse photocathode with a GaAs-GaAsP-strained superlattice structure to control the spin polarization and the temporal structure of the emitted electron beam.

2：Sample Selection and Data Sources:

The photocathode had a maximum polarization of about 90% at a wavelength of 780 nm. A drive laser with a diameter of 1.8 μm was focused on the photocathode surface.

3：8 μm was focused on the photocathode surface. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: The setup included an electron biprism with a positive bias voltage of the filament, a pulsed laser with a central wavelength of 780 nm, a repetition frequency of 80 MHz, and a 16-ps pulse duration, and a combination of ultrafast electric detectors and an imaging sensor.

4：Experimental Procedures and Operational Workflow:

The pulsed electron beam emitted from the photocathode surface was accelerated to a voltage of 30 kV over a traveled distance of 8 mm. The pulse duration of the laser was measured by optical interferometric autocorrelation with a non-linear crystal.

5：Data Analysis Methods:

The electron holograms of the electron pulse beams were measured by an electron biprism. The intensity of the pulse laser was tuned continuously by a polarized beam splitter and a half-wave plate.