A light source with narrowband, sufficient brightness, and low spatial coherence is required for certain applications such as optical imaging and free‐space optical communication. In this study, our focus was to investigate a novel imaging laser source, specifically a low‐threshold random laser enhanced by TiN nanoparticles. The results demonstrate that the random laser spectrum exhibits an impressive bandwidth of 0.23 nm, accompanied by an incredibly low spatial coherence factor of merely 0.15. Due to the low spatial coherence of random laser, the speck contrast is less than 0.02 when the light passes through a scattering system. Notably, when compared to traditional lasers, the use of a random laser yields significantly superior imaging quality in both scatterless and complex scattering environments. This finding highlights the immense potential of the random laser as a narrowband and low spatial coherence laser source for robust speckle‐free imaging applications, particularly in environments with intricate scattering phenomena. Furthermore, this breakthrough can be extended to various other domains, including free‐space optical communication.

Speckle is a persistent disease that damages image quality and needs to be suppressed for optical imaging. One effective method is to use light sources with low spatial coherence. In this article, a low spatial coherence and high brightness random laser based on TiN/Graphene self-assembly structures is proposed. The physical mechanisms of TiN/Graphene self-assembly structures enhancing the radiation properties of random lasers are analyzed in detail. Additionally, the speckle noise is significantly suppressed by the random laser in chaotic fluid environments. The speckle constant is as low as 0.04, making it difficult to observe with the naked eye. Due to its low speckle noise, the image quality illuminated by the random laser is more than 3 times better than that illuminated by a conventional laser. Furthermore, the random laser's high brightness and narrow spectral peaks enable the visualization of finer structures compared to using a halogen lamp. This study paves a new way for random lasers to be used in a variety of applications in chaotic fluid environments, such as speckle-free imaging, bioimaging, projection display, and free-space optical communication.

Manipulation of the performance of the random lasers from dye-doped nematic liquid crystals with TiN nanoparticles in non-oriented cells is studied. The experimental results show that the introduction of TiN nanoparticles into dye-doped nematic liquid crystals significantly reduces the threshold of random lasing due to the localized surface plasmon resonance of TiN nanoparticles. The emission spectrum of random lasers can be controlled by the shape of the pump spot. The threshold of random lasers increases with the decrease of the length of pump stripe. In order to obtain the emission spectrum with fine discrete sharp peaks, the narrow pump stripe is more effective than the circular pump spot. When the pump area is more like a circle, the emission spectrum is more like an amplified spontaneous emission. The underlying mechanisms of these phenomena are discussed in detail. This study provides a promising platform for designing the high-quality and low-threshold random lasers which can be controlled by the shape of the pump spot.

In this Letter, we designed a random laser based on a nematic liquid crystal with titanium nitride nanoparticles, which has low spatial coherence, and its spatial coherence can be dynamically manipulated by the applied voltage. In a scattering environment, the speckle effect can be effectively suppressed using the random laser as the light source, and the speckle degree is controlled by the applied voltage. Moreover, with the decrease of the spatial coherence of the random laser, the imaging edges become blurred. We provided a quantitative way to optimize the image quality between uniformity and edge sharpness while improving the signal-to-noise ratio.

Random lasers hold significant promise in the field of information encryption due to their advantages of low spatial coherence and multi-degree-of-freedom control. We propose a dynamic coded encryption approach based on the tunable spatial coherence of random lasers. By varying the magnitude of the external voltage applied to the sample, the spatial coherence of the random laser can be reversibly changed. This phenomenon derives from the electric dipole moment effect in liquid crystals, where the application of voltage causes deflection of the liquid crystal molecules, leading to a change in the refractive index, and consequently affecting the spatial coherence of the random laser. Therefore, multiple visibility outputs, which are utilized for dynamic coded encryption, can be achieved through the double-slit interference method by applying different voltages to the sample array. Information encryption transmission is accomplished by interconverting the data into ASCII code according to different systems based on binary or quaternary digits. Moreover, pulse time series of random laser visibility can be realized by modulating the voltage in real time for individual samples, facilitating a compact encryption system. This work is expected to inspire the application of random lasers in secure data storage and information encryption.