Coherent Random Laser Research Articles

Stable random laser of perovskite quantum dots based on SiO2-QDs-SiO2 composite nanostructure

In recent years, metal halide perovskite has gradually become a hotspot in the field of optoelectronics. However, the inherent instability of CsPbX3 quantum dots (QDs) seriously affects the amplified spontaneous emission (ASE) or lasing performance. Herein, the highly stable CsPbBr3 random laser is realized in SiO2-QDs-SiO2 (SQS) composite nanostructure doped with Ag nanoislands. The strong scattering generated by SQS composite nanostructure and the localized surface plasmon resonance (LSPR) of metal silver nanoislands provide optical feedback for the formation of random laser. Then a coherent random laser with low threshold (∼2.2 mJ/cm2) is obtained. SiO2 microspheres anchor QDs to avoid photoinduced regeneration and fluorescence quenching caused by QDs clusters. The inner QDs of SQS are effectively protected from water erosion, thus resulting that the samples have higher water resistance. The luminescence intensity still maintains 70 % of the original intensity after 40 days with the addition of pure water. Our research provides an effective method for improving the water stability of perovskite QDs. The highly stable random laser based on perovskite quantum dot film has a wide application prospect in integrated optoelectronics, display imaging and sensing measurement.

Coherent random fiber laser emission from CdSe/ZnS quantum dots.

We experimentally demonstrate the coherent random laser emission by combining CdSe/ZnS colloidal quantum dots (CQDs) with hollow optical fiber. Through the localized surface plasmon resonance (LSPR) induced by Ag nanoparticles (NPs), well-distinguished discrete spikes are observed from the Ag modified hollow fiber loaded with CdSe/ZnS QDs solution. In addition, coherent random laser action with low threshold is also realized in the hollow optical fiber filled with high packing-density CdSe/ZnS QDs even if the Ag NPs is not introduced. The self-assembled clusters of CdSe/ZnS QDs serve as the optical gain media as well as the strong scattering centers. The angle measurement experiments show that the directional emission of random laser can be adjusted by using different pumping manners. This facile, inexpensive, low pump threshold random laser could be widely used in photonic devices and display imaging.&#xD.

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.

Time sequence variation of incoherent and coherent random laser based on positive replica of abalone shell

Besides the scattering structures, the energy transfer (ET) process in the gain medium plays a significant role in the competition between coherent (comprising strongly coherent components) and incoherent (consisting of weakly coherent or “hidden” coherent components) modes of random lasers. In this study, bichromatic emission random lasers were successfully created using polydimethylsiloxane (PDMS) replicas with grooved structures that imitate the inner surface of abalone shells as scattering substrates. The influence mechanism of the ET process from the monomer to dimer in the Rhodamine 640 dye on the competition of random laser modes was thoroughly investigated from both spectral and temporal dimensions. It was confirmed that the ET process can reduce the gain of monomers while amplifying the gain of dimers. By considering the dominant high-efficiency ET processes, an energy transfer factor associated with the pump energy density was determined. Notably, for the first time, it was validated that the statistical distribution characteristics of the time sequence variations in the coherent random laser generated by dimers closely resemble a normal distribution. This finding demonstrates the feasibility of producing high-quality random number sequences.

Random laser on the surface of polymer optical fibre- A comparison of the effect of dielectric and plasmonic nanostructures

Here we demonstrate the effect of dielectric and plasmonic nanoparticles on the random lasing behaviour of a polymer optical fibre coated with an organic dye, Rh-640- perchlorate. Coherent random lasing was observed both in the presence of ZnO nanorods and Au nanourchins upon transverse optical pumping using a Q-switched Nd: YAG laser. With the same particle density, a significant reduction in the lasing threshold was observed in the case of the plasmonic random laser. The polymer optical fibre was fabricated using a custom-made fibre drawing tower, and the random lasing media was coated on its surface by the dip-coating method. The present analysis demonstrates that the combined effect of scattering by the nanoparticles and the cylindrical fibre geometry is responsible for the low threshold coherent random laser.

Stabilized Narrow-Linewidth Brillouin Random Fiber Laser With a Double-Coupler Fiber Ring Resonator

A stabilized coherent narrow-linewidth Brillouin random fiber laser with low lasing noise is proposed and investigated experimentally, which employs stimulated Brillouin scattering and Rayleigh scattering in optical fibers to provide the gain and the random distributed feedback, respectively. The stabilized lasing output with suppressed noise is realized utilizing a simple structure of a double-coupler fiber ring resonator, which is composed of a section of single-mode fiber and two optical couplers with different coupling ratios. Compared with the existing free-running Brillouin random fiber lasers, much more stabilized laser output can be obtained as the double-coupler fiber ring resonator effectively acts as a narrow-bandwidth mode filter through the Vernier effect that constrains the dense random longitudinal modes competition within a small frequency range. In the experiment, a stable ultra-narrow linewidth of approximately 586.4 Hz is obtained from the laser output. Statistical analysis of mode hopping in the proposed laser indicates a great improvement in multi-mode resonances and frequency jitters with the imbedding of the ring resonator. In addition, measurement results of relative intensity noise and frequency noise of the proposed laser showcase a great suppression in mode-competition-induced lasing instability and a significant improvement in the noise level compared to the free-running Brillouin random fiber lasers. The proposed all-fiber-based stabilization technique makes a step forward for developing practically robust and reliable Brillouin random fiber lasers. Such a stabilized highly coherent narrow-linewidth laser source with low cost and low power consumption will find promising applications in high-resolution spectrometers, microwave photonics, and optical sensing.

Random laser action in the visible region by dye-based sliver nano-hexagonal colloid media

In our attempt to reduce the threshold for dye-based random lasers, a new kind of random lasing media is demonstrated based on silver nano-hexagonal as scattering centers. For this purpose, we use a chemical method to synthesize nano hexagonal silver scatterer points and dissolve them in polymer and Rhodamine B dye media in different concentrations and different sizes. Our results from these samples under different pumping power, confirm the strong dependence on the sizes and concentration on the transition from incoherent to the coherent random laser, which is starts from 0.061 MW cm−2 as threshold power. This threshold power and linewidths of emission peaks decrease by an increase in the size and concentrations of nano-hexagonal points to 0.04 MW cm−2 and 0.2 nm, respectively.

Mode locking of a coherent random fiber laser with selectable repetition rates.

Controlling emission of light in random structures/disordered systems, e.g., implementing mode-locked pulses in a laser system with a random structures/disordered systems, is a complex task. Usually, the generation of laser pulse by mode locking needs a stable fixed-length cavity that determines a specific repetition rate of the mode-locked pulses. Here, mode-locking laser pulses with selectable repetition rates are achieved in a typical one-dimensional disordered laser by passive mode locking. The laser includes disordered reflectors to provide multiple resonant modes associated with different cavity length. The regular pulses with adjustable repetition rates can be generated and selected by a nonlinear polarization rotator and a semiconductor saturable absorber mirror. The proposed work utilizing the advantages of multiple resonances in random lasers could pave a new way for regulating emission of light in the random structures/disordered system. And it displays an effective and realistic technical route to study ultrafast pulses generation and optical soliton dynamics in random structures/disordered systems.

Random laser in dye-doped electrospun nanofibers: Study of laser mode dynamics via temporal mapping of emission spectra using Pearson's correlation

The development of optically active flexible nanostructures has been pursued in the last years owing to their potential application in photonic devices. Herein, we report a random laser architecture based on a flexible Rhodamine B-doped PMMA nanofibers produced via electrospinning technique with 1% and 5% (w/w) of dye. The lower concentrated sample provided only incoherent emission due to the low absorption mean free path. The most concentrated one provided both coherent and incoherent random laser emission depending on the position of the sample the excitation took place. Pearson's correlation coefficient maps showed a clear correspondence with the already established mode locking transition in random laser. A temporal mapping of successive emission spectra was performed, which provided qualitative information about mode competition dynamic when applied to coherent emission spectra and a highly sensitive way of tracking line widening and red/blueshift in incoherent random laser emission spectra. The developed system can be further employed to design novel miniaturized chemical and temperature sensors.

Origin of light scattering in dye doped polymeric waveguides and the dependence of excitation geometry on coherent random lasing

We present an experimental investigation on the origin of coherent random laser (RL) emission from 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminos-tyryl)-4H-pyran (DCM) doped polyvinyl alcohol (PVA) thin film (DCM-PVA) planar waveguide using various characterization techniques. Absorption and fluorescence spectra of the DCM-PVA thin film confirm the presence of aggregates at dye concentrations greater than 0.08 wt. %. Time correlated single photon counting measurements were perfomed to confirm the presence of dye aggregates in PVA matrix. x-ray diffraction studies reveal the semi-crystalline nature of the DCM-PVA thin film. The optical gain coefficient was determined by the variable stripe length method under 532 nm pulsed laser excitation and was found to be 2.1 cm−1 using the one-dimensional amplifier model for the 0.08 wt. % thin film. The RL emission of the planar waveguide depends on the geometry of the excitation spot. The emission spectrum consists of randomly positioned narrow spectral lines under stripe excitation geometry whereas, a smooth spectrum lacking the narrow peaks is observed under circular spot excitation, both above the lasing thresholds. The origin of weak scattering in DCM-PVA waveguide is attributed to the formation of dye aggregates and inhomogeneities created by the semi-crystalline nature of the film. The RL threshold decreases with an increase of the stripe length due to weak waveguiding in the planar film under stripe excitation. The high optical gain and low lasing thresholds attainable in DCM-PVA waveguides make them a promising candidate for the fabrication of polymer waveguide based photonic devices.

Multi-wavelength coherent random laser in bio-microfibers.

In this paper, pure silk protein was extracted from Bombyx mori silks and fabricated into a new kind of disordered bio-microfiber structure using electrospinning technology. Coherent random lasing emission with low threshold was achieved in the silk fibroin fibers. The random lasing emission wavelength can be tuned in the range of 33 nm by controlling the pump location with different scattering strengths. Therefore, the bio-microfiber random lasers can be a wide spectral light source when the system is doped with a gain or energy transfer medium with a large fluorescence emission band. Application of the random lasers of the bio-microfibers as a low-coherence light source in speckle-free imaging had also been studied.

Coherent Random Lasing in Colloidal Quantum Dot-Doped Polymer-Dispersed Liquid Crystal with Low Threshold and High Stability.

High-concentration (2-10 wt %) ZnCdSeS/ZnS alloyed quantum dot-doped polymer-dispersed liquid crystals (QD-PDLCs) were prepared via ultraviolet (UV) curing. The QD-PDLC morphology and resonance characteristics of a coherent random laser were investigated. The doping concentration of the liquid crystal and quantum dots was varied to investigate its effect on the lasing threshold, line width, and stability with respect to the density and grain size of the liquid crystal droplets inside the PDLC structure. Furthermore, the QD-PDLC laser performance was influenced by the pump position and area because of spatial localization of the random resonators. Moreover, the QD-PDLC showed good long-term stability; after 15 days of laser excitation (3 h/day), the laser output was maintained at 92% of the original emission intensity. The random laser threshold was as low as 50 μJ/cm2 with the optimized preparation process, which suggested strong potential for applications in polymer random fiber lasers, sensors, and displays.

Coherent Random Lasing Realized in Polymer Vesicles

We have demonstrated the realization of a coherent vesicle random lasing (VRL) from the dye doped azobenzene polymer vesicles self-assembled in the tetrahydrofuran-water system, which contains a double-walled structure: a hydrophilic and hydrophobic part. The effect of the dye and azobenzene polymer concentration on the threshold of random laser has been researched. The threshold of random laser decreases with an increase in the concentration of the pyrromethene 597 (PM597) laser and azobenzene polymer. Moreover, the scattering of small size group vesicles is attributed to providing a loop to boost the coherent random laser through the Fourier transform analysis. Due to the vesicles having the similar structure with the cell, the generation of coherent random lasers from vesicles expand random lasers to the biomedicine filed.

Near-field scattering enhancement of perylene based aggregates for random lasing

Strong near-field scattering enhancement (NFSE) of polyhedral oligomeric silsesquioxanes (POSS) nanoparticles (NPs) aggregates is found through physical simulation. An aggregation of N,N’-di-[3-(isobutyl polyhedral oligomeric silsesquioxanes) propyl] perylene diimide (DPP) which possesses POSS as scatteres experimentally performs strong NFSE, which confirms the physical simulation results. Moreover, coherent random laser is triggered from the DPP aggregates in carbon disulfide. It is the NFSE of POSS NPs connected to both ends of DPP through covalent bonds and the NFSE of their aggregation thanks to DPP’s aggregation that is responsible for the coherent random laser. So, this work develops a method to improve weak scattering of system through construction of molecules, and opens a road to a variety of novel interdisciplinary investigations, involving molecular designing for disordered photonics.

A Self-Consistent Quantum Field Theory for Random Lasing

The spatial formation of coherent random laser modes in strongly scattering disordered random media is a central feature in the understanding of the physics of random lasers. We derive a quantum field theoretical method for random lasing in disordered samples of complex amplifying Mie resonators which is able to provide self-consistently and free of any fit parameter the full set of transport characteristics at and above the laser phase transition. The coherence length and the correlation volume respectively is derived as an experimentally measurable scale of the phase transition at the laser threshold. We find that the process of stimulated emission in extended disordered arrangements of active Mie resonators is ultimately connected to time-reversal symmetric multiple scattering in the sense of photonic transport while the diffusion coefficient is finite. A power law is found for the random laser mode diameters in stationary state with increasing pump intensity.

The transition from incoherent to coherent random laser in defect waveguide based on organic/inorganic hybrid laser dye

Abstract This paper systematically demonstrated a variety of experimental phenomena of random lasers (RLs) of N,N′-di-(3-(isobutyl polyhedral oligomeric silsesquioxanes)propyl) perylene diimide (DPP) organic/inorganic hybrid laser dye, which is composed of perylene diimide (PDI) as gain media and polyhedral oligomeric silsesquioxanes (POSS) as scattering media at a mole ratio of 1:2. In this work, we observe the transition from incoherent RL in the DPP-doped solutions and polymer membrane systems using dip-coating method to coherent RL in the polymer membrane system with defect waveguide using semi-polymerization (SP) coating method. Meanwhile, we found that the hybrid dye-DPP has a long lasing lifetime compared with the traditional laser dyes, which indicates that the POSS group can suppress the photo-bleaching effect to extend the working life of laser dyes.

Experimental and Theoretical Investigation of the Polymer Optical Fiber Random Laser with Resonant Feedback

Abstract1D random fiber laser is a novel fiber‐based laser, which exhibits many unique optical properties and shows great promise for various applications including speckle‐free imaging. A multimode and coherent polymer optical fiber random laser (POFRL) is successfully fabricated by doping TiO2 nanoparticles and Rh640 perchlorate dyes in the core of a polymer optical fiber (POF). The waveguide effect provided by the POF greatly increases the multiscattering events for light propagation and results in laser cavity with much shorter length than the scattering mean free path. As an illustration of potential applications, a clear speckle‐free imaging is demonstrated using the POFRL as the illumination source. Furthermore, a four‐level Monte Carlo method‐based numerical model is proposed to describe the lasing dynamics in POFRL. The model supports the experimental work in the research field of POFRL.

Solid-state green-light-emitting upconversion coherent random laser in macroporous LiNbO3:Er

A solid-state green-light-emitting upconversion coherent random laser was realized by pumping macroporous erbium-doped lithium niobate with a 980 nm laser. The lasing threshold was determined to be about 40 kW/cm2. Above the threshold, the emission intensity increased sharply with the increasing pump intensity. Moreover, a narrow multi-peaks structure was observed in the green-light-emission band, and the positions of lasing lines were various at different angles. The results were the direct evidences of coherent random lasing emission from macroporous erbium-doped lithium niobate. These phenomena were attributed to the coexistence of upconversion emission and a multiple scattering feedback mechanism.

Ultra-photo-stable coherent random laser based on liquid waveguide gain channels doped with boehmite nanosheets

Construction of ultra-photo-stable coherent random laser based on liquid waveguide gain channels doped with boehmite nanosheets has been demonstrated. An Al plate uniformly coated with boehmite nanosheets was prepared by an alkali-treatment method and used as a scattering surface for the coherent random laser. Microcavity may be formed between these boehmite nanosheets owing to the strong optical feedback induced by the multiple light scattering. Many sharp peaks are observed in the emission spectra, and their laser thresholds are different, which confirms the feedback mechanism is coherent. The linewidth of the main peak at 571.74 nm is 0.28 nm, and the threshold of the main peak is about 4.96 mJ/cm2. Due to the fluidity of liquid waveguide gain medium, the photostability of this coherent random laser is better than the conventional solid state dye random lasers. The emission direction is well constrained by the waveguide effect within a certain angular range (±30°). This kind of coherent random laser can be applied in optical fluid lasers and photonic devices.

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.