Fig. 4: 50 layers of 5D optical data storage by elliptical polarization writing.
From: Efficient ultrafast laser writing with elliptical polarization
a, b The birefringence image of data voxels from the top and bottom layer. 4 bits per voxel were realized by 2 retardance and 8 azimuth levels. c, d Polar diagram of the measured retardance and azimuth of all voxels in (a) and (b). Writing conditions: 1 MHz repetition rate, 300 fs pulse duration, 45 mm/s translating speed, 215 nJ pulse energy, 20 pulse number, 0.3 NA lens
