Low-threshold Random Laser Research Articles

Coherent random laser in Enteromorpha prolifera

This study presents a novel approach in coherent dye random laser (RL) generation by utilizing the special properties of Enteromorpha prolifera (EP) within a micro-glass tube configuration. The methodological simplicity of injecting a mixed solution of dye and EP into the tube at room temperature achieves a novel way of realizing the RL system, characterized by tunable random lasing thresholds contingent upon the concentration of EP. This tunability stems from the synergistic interplay between photon enhancement and fluorescent dye absorption facilitated by the unique nanoporous structure of EP, culminating in the attainment of a low lasing threshold of 21.7 μJ/mm2 at an optimized EP concentration of 2 mg/mL. With an excess EP concentration, the nanoporous structure could absorb large amounts of dye, resulting in dye fluorescence reabsorption, and causing the threshold to increase. A power Fourier transition was performed to calculate the effective optical cavity of the RL system, depicting the process of the coherent RL generation. Furthermore, a comprehensive investigation into the emission stability of the RL system revealed remarkable consistency in emission intensity over a prolonged excitation duration of 20 min, underscoring the potential for integration with optoelectronic devices. The L-shape mask imaging of the RL provides high-quality images with low spatial coherence, paving a useful application for speckle-free imaging. These results offer an affordable approach to achieving high-quality and low-threshold RLs using novel biomaterials.

Robust speckle-free imaging using random lasers enhanced by TiN nanoparticles in complex scattering environments

Abstract 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.

Low-threshold random lasers based on the DCM-DEG gain system with graphene nanosheets.

In this article, low-threshold random lasers based on DCM-DEG (DD) gain system with graphene nanosheets are studied. The experiment results show that the threshold of random lasers reduces rapidly when an appropriate amount of graphene nanosheets is added in DD solution. Meanwhile, the quantity and quality of random lasing modes raise significantly. We discussed the potential reasons why the graphene nanosheets can strengthen the sample's random lasing. And, the influence of the graphene nanosheet concentration on the radiation characteristics of random lasers is further studied. When the concentration of graphene nanosheets is 0.088wt%, the lasing threshold of DD samples with graphene nanosheets (GDD) is only about 31.8% of the lasing threshold of DD samples, and the quality of random lasing modes is five times higher than that of the DD sample. To further reduce the lasing threshold, the gold (Au) nanoparticles are added in the mixed solution to form the GDD solution with Au nanoparticles (GGDD). The results show that the lasing threshold of the GGDD sample is about 7.73 µJ/pulse, which is 5.2% of the lasing threshold of the DD sample. This experiment provides a new method to study low-threshold and high-quality random lasers based on graphene.

Low-threshold random lasers enhanced by titanium nitride nanoparticles suspended randomly in gain solutions.

In this article, we report a low-threshold random laser enhanced by TiN nanoparticles (NPs) suspended randomly in gain solutions. Results show that the random laser with TiN NPs has a lower threshold than the random laser with TiO2 NPs and the underlying mechanisms are discussed in detail. The localized surface plasmon resonance of individual TiN NPs increases the pump efficiency and strengthens the fluorescence amplification efficiency of the DCM. The multiple scattering of integral TiN NPs extends the dwelling time of light in random systems, which provides more possibilities for the light amplification in the gain medium. Then, the random laser threshold as a function of the number density of TiN NPs is studied. Results show that the optimum number density of TiN NPs for the lowest-threshold random lasers is about 1.468 × 1012ml-1. When we substitute the ethanol solution with the nematic liquid crystal (NLC), the random laser threshold can be further decreased to 5.11 µJ/pulse, which is about 7.7 times lower than that of DCM dye solution with TiN NPs under the same conditions. These findings provide a cost-effective strategy for the realization of low-threshold random lasers with high-quality.

Pump-Controlled Plasmonic Random Lasers from Dye-Doped Nematic Liquid Crystals with TiN Nanoparticles in Non-Oriented Cells

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.

A fibre optic wedge type microcavity random laser

In this work, a fibre optic wedge type microcavity with arbitrarily distributed scattering centres is employed to construct a flexible, cost effective, and low threshold random laser. The wedge cavity is constructed within an optical fiber of 125 μm in diameter, using a conventional fibre drawing technique. The sharp edge corners of the triangularly shaped of the air holes are filled with a phenol-rhodamine 6 G mixture via a capillary effect to form the gaining medium. Randomly distributed air-bubbles are naturally formed in different sizes and shapes during the filling process of the phenol-rhodamine mixture, which serve as the scattering centres for obtaining the random lasing. By making a fine spatial tuning of the excitation beam spot towards the apex of the wedge, a single mode lasing is obtained at wavelength of 585 nm, with 1.4 nm of the FWHM.

Plasmonic enhanced low-threshold random lasing from dye-doped nematic liquid crystals with TiN nanoparticles in capillary tubes

We report a plasmonic enhanced low-threshold random lasing from dye-doped nematic liquid crystals with titanium nitride (TiN) nanoparticles (NPDDNLC) in capillary tubes. The NPDDNLC sample yields a coherent random laser with about 0.3 nm in the full width at half maximum (FWHM). We find the laser threshold is decreased by introducing the TiN NPs into the dye-doped nematic liquid crystal sample. The laser threshold decreases with increasing the number density of TiN nanoparticles from 5.613 × 1010/ml to 5.314 × 1011/ml. We suggest that the low-threshold random laser is caused by the cooperative effect of the recurrent multiple scattering and field enhancement in the vicinity of TiN nanoparticles. The localized electric field near the TiN nanoparticles enhances the energy absorption of the dye and strengthens the fluorescence amplification. Moreover, we provide a new parameter (the relative efficiency of the stimulated radiation photons) to quantify the quality of the random laser, and we give expressions for the wavelength, mode, and whole emission spectrum. Finally, we find the emission spectrum depends strongly on the emission angle and we discuss the reasons. These findings provide a simple and efficient way for the realization of low-threshold random lasers with low cost.

Mapping the energy density of shaped waves in scattering media onto a complete set of diffusion modes.

We study the energy density of shaped waves inside a quasi-1D disordered waveguide. We find that the spatial energy density of optimally shaped waves, when expanded in the complete set of eigenfunctions of the diffusion equation, is well described by considering only a few of the lowest eigenfunctions. Taking into account only the fundamental eigenfunction, the total internal energy inside the sample is underestimated by only 2%. The spatial distribution of the shaped energy density is very similar to the fundamental eigenfunction, up to a cosine distance of about 0.01. We obtain the energy density of transmission eigenchannels inside the sample by numerical simulation of the scattering matrix. Computing the transmission-averaged energy density over all transmission channels yields the ensemble averaged energy density of shaped waves. From the averaged energy density, we reconstruct its spatial distribution using the eigenfunctions of the diffusion equation. The results of our study have exciting applications in controlled biomedical imaging, efficient light harvesting in solar cells, enhanced energy conversion in solid-state lighting, and low threshold random lasers.

基于TiO2纳米粒子薄膜的低阈值随机激光器的动力学研究

基于TiO₂纳米粒子薄膜的低阈值随机激光器的动力学研究

Laser Emission in PMMA Nano-Composite Films

In this article, low-threshold random laser with one mirror and feedback is investigated in PMMA film containing Rhodamine 590 and TiO2 nano-particles. Incoherent and coherent laser emission is observed. Optics microscopy and Scanning Probe Microscopy are used to investigate the film structure and the principle of incoherent and coherent laser is analyzed.

One-Dimensional Random Lasing in a Single Organic Nanofiber

One-dimensional light amplification in individual p-sexiphenyl nanofibers is investigated. The influence of fiber morphology on light propagation properties is studied via optical and atomic force microscopy. Isolated nanofibers are shown to yield low-threshold random laser emission in the deep blue. Model calculations of coherent light propagation in one-dimensional random media qualitatively reproduce the experimental results. Implications for photonic nanosensors are briefly discussed.

Low-Threshold Random Laser with One Mirror and Feedbacks inPMMA Nano-Composite Films

A low-threshold random laser with one mirror and feedback isinvestigated in the PMMA film containing rhodamine 590 and TiO2nano-particles. Incoherent and coherent laser emission is observed.Effect of particle concentration on light emission is explored, and theoptimum particle concentration is obtained. Optical microscopy andscanning probe microscopy are used to investigate the film structure,and the principle of incoherent and coherent laser is analysed.

Localized surface plasmon singularities in amplifying media

The localized surface plasmon resonance of nanostructures is shown to exhibit a singularity when the surrounding medium exhibits amplification with a critical value of gain. This singularity can lead to large enhancements even when the gain is saturated. This composite medium should exhibit strong scattering within the plasmon band leading to low threshold random laser action and light localization effects. This effect could also greatly increase surface enhanced Raman scattering signals for rapid single, molecule detection, identification and sequencing.