Ac254 050 a ml

A schematic diagram of the imaging system is shown in Fig. 1. A pulsed laser (532 nm, 2 ns, 50 kHz, SPOT-10-200-532, Elforlight, Daventry, United Kingdom) was used as the light source for both PA and fluorescence imaging. A DMD with 768 × 1080 pixels (DLP7000, Texas Instruments, Texas, USA) was used to project binary patterns onto the proximal end of a MMF via a tube lens (AC254-050-A-ML, Thorlabs, New Jersey, USA), a circular polariser (CP1L532, Thorlabs, New Jersey, USA) and an objective (20 $\times$ , 0.4 NA, RMS20X, Thorlabs, New Jersey, USA). Two types of MMFs including a STIN 105  $\mathrm{\mu }$ m, 0.22 NA) and a GRIN (100  $\mathrm{\mu }$ m, 0.29 NA) fibre with the same length of 20 cm were employed. A sub-region of the DMD covering 128 × 128 micromirrors was used for light modulation. Prior to image acquisition, a fibre characterisation step was performed by a fibre characterisation unit that comprised a CMOS camera (C11440-22CU01, Hamamatsu Photonics, Shizuoka, Japan) for capturing the output speckle patterns after magnification by an objective (20 $\times$ , 0.4 NA, RMS20X, Thorlabs, New Jersey, USA) and a tube lens (AC254-0100-A-ML, Thorlabs, New Jersey, USA). The focal plane of the camera was set to approximately  $100\mathrm{\mu }\mathrm{m}$ away from the distal end of the fibre.

The hardware setup consists of a time-resolved sensor, pulsed laser, illumination and collection optics, and a set of scanning mirrors to achieve a raster scan illumination pattern. The sensor is a PDM SPAD from Micro Photon Devices with a 100 × 100 μm sensor area, 27 ps timing jitter (measured with a 100 kHz laser at 675 nm), and 40.9 dark counts per second. Timing of photon arrivals is captured with a PicoHarp 300 Time-Correlated Single Photon Counting (TCSPC) module. The illumination source is a 450 nm or 670 nm picosecond laser (ALPHALAS PICOPOWER-LD-450-50, PICOPOWER-LD-670-50). The 450 nm and 670 nm versions have pulse widths of 90 ps and 50 ps and average power of 0.406 mW and 0.11 mW respectively at a 10 MHz pulse repetition rate. The collection optics are designed to extend the field of view of the SPAD across the area scanned by the illumination source and consist of a 75 mm objective lens (Thorlabs AC508-075-A-ML), a 30 mm relay lens (Thorlabs AC254-030-A-ML) and a microscope objective (Olympus UPLFLN 20× objective). The laser spot is minified using a 50 mm (Thorlabs AC254-050-A-ML) and 250 mm (Thorlabs AC254-250-A-ML) lens relay and scanned with mirrors driven by a two-axis galvanometer (Thorlabs GVS012).

The experimental setup for fiber characterization was illustrated in Fig. 1(c). The intensity of a light beam from a pulsed laser (532 nm, 2 ns, SPOT-10-200-532, Elforlight, Daventry, United Kingdom) was spatially modulated using a DMD (DLP7000, 768×1080 pixels, Texas Instruments, Texas, USA) with a set of binary patterns, and then projected onto the proximal end of a MMF (Ø200 µm, 0.22 NA, 1 m, M122L01, Thorlabs, New Jersey, USA) via a tube lens (AC254-050-A-ML, Thorlabs, New Jersey, USA) and an objective (20×, 0.4 NA, RMS20X, Thorlabs, New Jersey, USA). After magnification with an objective (20×, 0.4 NA, RMS20X, Thorlabs, New Jersey, USA) and a tube lens (AC254-0100-A-ML, Thorlabs, New Jersey, USA), the intensities of the output speckles at the other end were captured by a CMOS camera (C11440-22CU01, Hamamatsu Photonics, Shizuoka, Japan).