Single-Shot Intensity- and Phase-Sensitive Compressive Sensing-Based Coherent Modulation Ultrafast Imaging

Ultrafast imaging can capture the dynamic scenes with a nanosecond and even femtosecond temporal resolution. Complementarily, phase imaging can provide the morphology, refractive index, or thickness information that intensity imaging cannot represent. Therefore, it is important to realize the simultaneous ultrafast intensity and phase imaging for achieving as much information as possible in the detection of ultrafast dynamic scenes. Here, we report a single-shot intensity- and phase-sensitive compressive sensing-based coherent modulation ultrafast imaging technique, shortened as CS-CMUI, which integrates coherent modulation imaging, compressive imaging, and streak imaging. We theoretically demonstrate through numerical simulations that CS-CMUI can obtain both the intensity and phase information of the dynamic scenes with ultrahigh fidelity. Furthermore, we experimentally build a CS-CMUI system and successfully measure the intensity and phase evolution of a multimode $Q$-switched laser pulse and the dynamical behavior of laser ablation on an indium tin oxide thin film. It is anticipated that CS-CMUI enables a profound comprehension of ultrafast phenomena and promotes the advancement of various practical applications, which will have substantial impact on fundamental and applied sciences.

Figure 1

The data flowchart of CS-CMUI. (a) Data acquisition diagram of CS-CMUI. (b) Data flowchart of CS-CMUI image reconstruction.

Figure 2

The simulation of CS-CMUI. (a) Ground truths and reconstructed intensity images, which consist of four butterfly images parallel moving in the horizontal direction. (b) Ground truths and reconstructed phase images, which consist of four changing letters of $\mathsf{E}$, $\mathsf{C}$, $\mathsf{N}$, and $\mathsf{U}$. (c) Compressed snapshot collected through CS-CMUI’s forward transmission. (d) PSNR (orange line) and SSIM (green line) values calculated by the reconstructed intensity and phase images compared with ground truths.

Figure 3

Experimental setup and system characterization. (a) System configuration of CS-CMUI. (b) Calibration of static spatial resolution. The subimage at the bottom right corner is the enlarged area in the red box. (c) Intensity variations along the orange (vertical strips) and green (horizontal strips) dashed lines in (b). (d) Test of the capability for dynamic phase quantitative detection. (e) Average phase variation along the $x$ direction in (d).

Figure 4

Optical field measurement of a $Q$-switched nanosecond laser pulse by CS-CMUI. (a) Schematic diagram of the generation of a nanosecond laser pulse with $\mathsf{E}$-shaped modulation for measurement. (b),(c) Representative reconstructed intensity and phase images of the $\mathsf{E}$-shaped laser pulse. (d) Integrated intensity over time from (b) (green line), associated with the pulse intensity evolution of 1D measurements by streak camera (orange line) and its Gaussian fitting (magenta line). (e) Phase gradient over time at the orange and magenta crosshair positions in (c).

Figure 5

Real-time detection of an ITO film laser ablation by CS-CMUI. (a) Schematic diagram of ITO laser ablation. (b),(c) Spatiotemporal intensity and phase evolutions during ITO ablation process, the green dashed circles indicate the relative aperture size after ablation. (d) Relative transmittance $\mathrm{\Delta }T/T$ (green dotted line) calculated from the 2D intensity images in (b), associated with the corresponding result of 1D measurement by a streak camera (orange line).