Chinese Optics Letters, Volume. 23, Issue 6, 061404(2025)
Dynamic coherence control of random lasers and its effect on speckle and edge sharpness of images
Fig. 1. Schematic diagram of the experimental setup. HWP, half-wave plate; POL, polarizer; NBS, neutral beam splitter; CL, cylindrical lens; DC, DC voltage source; L, convex lens; F, filter; FS, fiber spectrometer; DS, double slit plate; S, scatterer; M, mirror; AF, 1951 US Air Force resolution test chart; Ob, 20× microscope objective.
Fig. 2. Radiation characteristics of the electrical controllable random laser. (a) The emission spectrum of the random laser as a function of the pump energy. Inset: the random laser spectrum is captured at the pump energy of 4.35 µJ/pulse. (b) The peak intensity of the corresponding emission spectrum as a function of the pump energy. (c) The emission spectrum of the random laser as a function of the number density of the TiN nanoparticles. Inset: the peak intensity of the corresponding emission spectrum as a function of the number density of the TiN nanoparticles. (d) The emission spectrum of the random laser as a function of the applied voltage when the pump energy is 18.5 µJ/pulse. (e) The peak intensity of the emission spectrum as a function of the voltage. (f) Transmission spectrum intensities of the nematic liquid crystal at different voltages.
Fig. 3. Spatial coherence. (a) Spatial coherence of the Nd:YAG laser. (b)–(d) Spatial coherence of the random laser at different voltages when the pump energy is 18.4 µJ/pulse: (b) 0, (c) 4.5, and (d) 11 V. Top, the interference fringes. Down, the intensity distributions of interference fringes along the white dotted lines. (e) The variation curve of the random laser spatial coherence as a function of the applied voltage.
Fig. 4. Speckle. (a) Speckle pattern for the Nd:YAG laser. (b)–(d) Speckle patterns for the random laser at different voltages: (b) 0, (c) 4.5, and (d) 11 V. Top, speckle images captured by a CCD camera. Down, intensity distributions along the white dotted lines. The pump energy is 18.2 µJ/pulse. (e) The speckle contrast as a function of the applied voltage.
Fig. 5. (a) Image illuminated by the Nd:YAG laser. Inset: enlarged images. (b)–(d) Images illuminated by the random laser with different voltages from left to right are 0, 4.5, and 11 V. (e)–(h) The intensity obtained from the image along the white dashed line. (i)–(l) The intensity obtained from the inset image along the dashed line. Inset: enlarged images showing the details of the speckle in the same area. (m)–(p) The intensity obtained from the inset image along the dashed line. Inset: enlarged images showing the image edge in the same area.
Fig. 6. Values of the signal-to-noise ratio (SNR), speckle contrast (SC), and edge sharpness (ES) of the image as a function of the voltage.
Get Citation
Copy Citation Text
Zhihao Li, Jianghao Li, Yanyan Huo, Yangjian Cai, Yuan Wan, "Dynamic coherence control of random lasers and its effect on speckle and edge sharpness of images," Chin. Opt. Lett. 23, 061404 (2025)
Category: Lasers, Optical Amplifiers, and Laser Optics
Received: Oct. 22, 2024
Accepted: Dec. 31, 2024
Published Online: May. 19, 2025
The Author Email: Yangjian Cai (yangjian_cai@163.com), Yuan Wan (wanyuansdnu@163.com)