Fig. 3: Spatial and temporal performances of the FLASH focusing technique.

a Schematic of the production of focal spots over a large 3D space. A photomultiplier tube (PMT) is used for recording ultrafast modulation of the focal spot. b Measured full-width at half-maximum (FWHM) of foci for different x positions on a plane of z = 1.5 mm. b1-b2, Measured intensity profiles of foci at x = 0 and 2.5 mm. Scale bar: 1 μm. c Measured FWHM of foci for different z planes at x = 0 mm. c1-c2, Measured intensity profiles of foci at z = 1 and 5 mm. Scale bar: 1 μm. d Schematic of periodic on/off focusing modulation. The line beam is scanned across the DMD, where ‘Focusing’ pattern and ‘Random’ pattern are alternatively encoded into each single column. e Optical signals acquired with the PD shown in (a) during a single line-scan of the line beam. ‘Active’ time and ‘Inactive’ time indicate the time for serial wavefront modulation using 340 columns and the time for the update of the DMD frame, respectively. The velocity signal from the scanner board is plotted for reference in black line. f Close-up of the signals in the dotted orange box shown in (e) with the sinusoidal curve fitting in dotted black line.