Random Laser System Research Articles

Reconfigurable logic gates driven by spatially designed excitation: Spectra manipulation the coupled random laser system

Reconfigurable logic gates driven by spatially designed excitation: Spectra manipulation the coupled random laser system

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.

Tunable random laser in capillary with Nile red solution and TiO2 nanoparticles

We report a tunable random laser in Nile red (NR) solution with TiO2 nanoparticles (NPs). The good lasing characteristics and low-level threshold at 71.8 μJ is achieved in our random laser system. We analyze the influence of TiO2 NPs number density to the random laser threshold and obtain the optimal number density of TiO2 NPs in NR/ethanol solution as 2.018 × 1013 cm−3 with lowest threshold. Furthermore, on account of the solvatochromism characteristic of NR, we use sulfuric acid to change the polarity of the sample and obtain the continuously tunable random laser spectra, ranging from 642.7 nm to 668.8 nm. This random laser system containing NR and TiO2 NPs has advantages of easy operation, simple structure, and large tuning range, which could open up an avenue to the generation and tuning of random laser, and meanwhile provide innovative ideas such as speckle-free laser source used in laser display technology or other fields.

Replica symmetry breaking in a colloidal plasmonic random laser with gold-coated triangular silver nanostructures.

Plasmonic random lasers have drawn significant attention recently due to their versatility, low threshold, and the possibility of achieving tunable and coherent/incoherent outputs. However, in this Letter, the phenomenon of replica symmetry breaking is reported in intensity fluctuations of a rarely used colloidal plasmonic random laser (RL) illumination. Triangular nanosilver scatter particles produced incoherent RL action when used in a dimethylformamide (DMF) environment in a Rhodamine-6G gain medium. The use of gold-coated triangular nanosilver as the scatterer in place of triangular nanosilver offered a dual contribution of scattering and lower photo-reabsorption, which caused a reduction in the lasing threshold energy of 39% compared to that obtained with the latter. Further, due to its long-term photostability and chemical properties, a phase transition from the photonic paramagnetic to the glassy phase is observed experimentally in the RL system used. Interestingly, the transition occurs at approximately the lasing threshold value, which is a consequence of stronger correlation of modal behaviors at high input pump energies.

1337 nm Emission of a Nd3+-Doped TZA Glass Random Laser

Random lasers have been studied using many materials, but only a couple have used glass matrices. Here, we present a study of zinc tellurite and aluminum oxide doped with different percentages of neodymium oxide (4 wt.%, 8 wt.%, and 16 wt.%) and demonstrate for the first time random laser action at 1337 nm. Laser emission was verified and the laser pulse’s rise time and input–output power slope were obtained. A cavity composed of the sample’s pump surface and an effective mirror formed by a second, parallel layer at the gain-loss boundary was probably the main lasing mechanism of this random laser system. The reason for the absence of emission at 1064 nm is thought to be a measured temperature rise in the samples’ active volume.

Random laser emission from dye-doped polymer films enhanced by SiC nanowires

As the third-generation semiconductor electronic material, silicon carbide (SiC) has good chemical stability and mechanical properties, leading to wide use in optoelectronic components, fiber sensing and detectors. However, there are few important reports on its application in the research of random laser. Hereby, we built a polymer random laser system with SiC nanowires as a scattering medium doped with dye by the spin coating method. The effect of different SiC concentrations on random laser properties and the enhancement mechanism are studied. The lasing intensity increases and threshold decrease in large concentration SiC nanowires at the same lasing system, and the minimum threshold is 20 μJ/pulse. By increasing the SiC concentration, the mean free path of photon scattering decreases, which promotes the photon gain effect and improves the laser performance. However, when the concentration of SiC nanowires is too large, the mean free path of photon scattering decreases further, and the self-absorption of fluorescence radiation emerges. Thus, fluorescence quenching is produced, leading to a negative effect on laser performance. Furthermore, the lasing wavelength can be adjusted by tuning the SiC nanowires concentrations, reaching 14 nm. The random laser enhanced by SiC nanowires is stable and pumped repeatable, which could pave the way to promote the application of SiC and achieve low-cost and high-performance random laser.

Spectrum-tailored random fiber laser towards ICF laser facility

Broadband low-coherence light is considered to be an effective way to suppress laser plasma instability. Recent studies have demonstrated the ability of low-coherence laser facilities to reduce back-scattering during beam–target coupling. However, to ensure simultaneous low coherence and high energy, complex spectral modulation methods and amplification routes have to be adopted. In this work, we propose the use of a random fiber laser (RFL) as the seed source. The spectral features of this RFL can be carefully tailored to provide a good match with the gain characteristics of the laser amplification medium, thus enabling efficient amplification while maintaining low coherence. First, a theoretical model is constructed to give a comprehensive description of the output characteristics of the spectrum-tailored RFL, after which the designed RFL is experimentally realized as a seed source. Through precise pulse shaping and efficient regenerative amplification, a shaped random laser pulse output of 28 mJ is obtained, which is the first random laser system with megawatt-class peak power that is able to achieve low coherence and efficient spectrum-conformal regenerative amplification.

Exciton-Assisted UV Stimulated Emission with Incoherent Feedback in Polydisperse Crystalline ZnO Powder

A comparative analysis of the features of UV-stimulated emission (SE) of various disordered active materials based on ZnO crystallites for a random laser (RL) was carried out. The superlinear increase in the intensity of the UV photoluminescence (PL) band of polydisperse nano-micro-crystalline (PNMC) ZnO powder at a wavelength of λ = 387 nm and some narrowing of its halfwidth in the range of 20 ÷ 15 nm with increasing pump intensity indicates random lasing with incoherent feedback (FB). The properties of similar UV PL bands under the same conditions of a thin film containing hexagonal ZnO microdisks, as well as samples of monodisperse ZnO nanopowder with nanoparticle sizes of 100 nm, indicate stimulated radiation with coherent feedback. It is shown that, among the studied materials, PNMC ZnO powder with widely dispersed crystallites ranges in size from 50 nm to several microns, which in turn, consists of nanograins with dimensions of ~25 nm, is the most suitable for creating a random laser with incoherent feedback at room temperature. The dominant factor of UV SE in PNMC ZnO powder is radiation transitions under exciton–exciton scattering conditions. The possible mechanisms of this random emission with the continuous spectrum are discussed. The average optical gain coefficient αg at λ = 387 nm in this RL system is estimated as αg~150 cm−1.

Manoeuvring a natural scatterer system in random lasing action and a demonstration of speckle free imaging

This report dominantly focused on employment of natural micro-pillars, embedded on the surface of bambusa tulda leaves, as scattering centres for achieving a single mode random laser (RL) at ∼582 nm with a lower line width (∼1.8 nm) and lasing threshold (132 W/cm2) in Rhodamine-B dye gain medium. The stability in performances is checked over 2 months of duration and scattering activities of the natural micro-pillars are confirmed via numerical simulation using COMSOL and power Fourier transform (PFT) analyses. The demonstration of speckle-free imaging established the low coherence of the RL light. The plant-extricated, handy, low-cost, and simple RL system is proposed to be a new platform having diverse future photonic applications.

External feedback assisted reduction of the lasing threshold of a continuous wave random laser in a dye doped polymer film and demonstration of speckle free imaging

The applications of random laser (RL) are still restricted, due to its complexity, high lasing threshold, unstable nature, difficulty in tuning and modulating its light emission characteristics. However, here a low threshold, continuous wave (CW) RL system has been designed in a fluoresecent laser dye (namely DCM) -doped in a polymer film with ZnO micro-cabbages as scatterers. Interestingly, by putting the active medium inside an external feedback (ExFB) system, a narrowed and stable RL emission at ~598 nm is observed with the subsequent reduction of CW lasing threshold (CWITh) by ~2.4 times. The effective cavity length (Leff) has been varied by an ingenious approach to demonstrate the role of Leff over the RL emission characteristics and the experimental results are supported by a theoretical explanation. The statistical fluctuation in the position of generated modes over time and the role of pump volume amplification on the emission characteristics of the developed RL has been studied in detailed. Thus, it is found here that due to the presence of ExFB, reinjection of pump light into scattering-formed cavities has taken place which has led to the generation of stable RL modes with the reduction of CWITh. The temporal coherency of the ExFB based RL light is found to be ~3.2 times less than that of a conventional He–Ne laser light. As a result, we could demonstrate here speckle free imaging with much lowered value of speckle contrast (C) on two different model systems, such as commercially available carbon film-coated TEM grid and cell membrane of Allium cepa. It is expected that this report will open up new possibilities for the development of stable and tunable RLs with other laser dyes for various optoelectronic applications including in bio-imaging.

Random lasing based on plasmonic enhancement from dye-doped capillary tubes with Ag-TiO2 composite nanostructure

Plasmonics have allowed revolutionary progress in field of random lasers through improvement of the lasing property via surface plasmon resonance (SPR). However, localized surface plasmon resonance (LSPR) spectra of conventional metal nanostructures are too narrow to sufficiently cover both the absorption and emission spectra of dyes. Therefore, in this paper, we fabricate a typical Ag-TiO2 composite nanostructure by a solution-reduction method and dope it into a random-laser system with a dye solution. With the assistance of this new nanostructure with a broadened plasmon-resonance band, the random-lasing device shows a lower threshold, sharper peak, and higher intensity compared with devices with pure TiO2 nanoparticles (NPs) and mixtures of TiO2 and Ag NPs as scattering media. The results further stimulate consideration of the plasmon effects in random laser systems and help in the design of high-performance, cost-effective random laser devices.

Chromaticity-tunable white random lasing based on a microfluidic channel.

The color and/or chromaticity controllability of random lasing is a key factor to promote practical applications of random lasers as high luminance sources for speckle-free imaging. Here, white coherent random lasing with tunable chromaticity is obtained by using broadband enhancement Au-Ag nanowires as scatterers and the resonance energy transfer process between different dyes in the capillary microfluidic channel. Red, green and blue random lasers are separately fabricated with low thresholds, benefiting from the plasmonic resonance of the nanogaps and/or nanotips with random distribution and sizes within Au-Ag nanowires and positive optical feedback provided by the capillary wall. A white random laser system is then designed through reorganizing the three random lasers. And, the chromaticity of the white random laser is flexibly tunable by adjusting pump power density. In addition, the white random laser has anisotropic spectra due to the coupling role between the lasers. This characteristic is then utilized to obtain different random lasing with different chromaticity over a broad visible range. The results may provide a basis for applying random laser in the field of high brightness illumination, biomedical imaging, and sensors.

Rare earth doped PDMS elastomeric random lasers

We report a very stable elastomeric random laser (SERL) system composed of two stable materials: inorganic Nd: YAB nanoparticles and polydimethylsiloxane (PDMS). Lasing at a wavelength of 1064.5 nm is observed when the samples are exposed to pulsed nanosecond excitation at 808 nm or 532 nm, with long term (days) operation without degradation. Contrary to other RLs based on polymers, this very stable RL is the first elastomeric system, hence tunable, which allows the systematic investigation of its dynamics over a long time, without the complication of gain reduction or deterioration of the polymer. The RL threshold is estimated to be around 1.0 mJ at 808 nm. The measured linewidth decreases from 3.2 nm to 0.5 nm. The spectral peak position as well as the intensity is conveniently tuned by stretching the elastomer polymer composite. As an application which requires long term operation, Levy-like statistics and replica symmetry breaking in this open cavity random laser were also demonstrated. These lasers have been used over several months without noticeable degradation.

Replica Symmetry Breaking in FRET‐Assisted Random Laser Based on Electrospun Polymer Fiber

AbstractSpin‐glass theory has been widely introduced to describe the statistical behaviors in complex physical systems. By analogy between disorder photonics and other complex systems, the glassy behavior, especially the replica symmetry breaking (RSB) phenomenon, has been observed in random lasers. However, previous studies only analyzed the statistical properties of the random laser systems with single gain material. Here, the first experimental evidence of the glassy behavior in a random laser with complex energy level structure is reported. This novel random laser is demonstrated based on the electrospun polymer fibers with the assistance of Förster resonance energy transfer (FRET). The electrospinning technology employed in the experiment herein promises high‐volume production of random laser devices with multiple energy levels, enabling the comprehensive investigation of lasing properties in multi‐energy level random laser system. Clear paramagnetic phase and spin‐glass phase are observed in the FRET‐assisted random laser under different pump energies. The RSB phase transition is verified to occur at the laser threshold, which is robust among the random lasers with different donor–acceptor ratio. The finding of RSB in FRET‐assisted random laser provides a new statistical analysis method toward the laser system with complex energy level, for example, quantum cascade laser.

Random lasing emission from WO3 particles dispersed in Rhodamine 6G solution

We experimentally investigate the random lasing emission from tungsten oxide (WO3) particles dispersed in Rhodamine 6G solution. Due to the growing interest in tungsten oxide materials and also their importance and applications in gas sensors, electrochromic and optochromic materials, photoelectrodes and other optoelectrical devices, we choose this material as the scattering elements in a random laser system. Up to our knowledge, the use of WO3 materials as the scattering elements in a random laser system has not yet been reported. WO3 particles provide optical feedback by multiple light scattering. Optical gain is provided by Rhodamine 6G solution through stimulated emission process. Our results show that by adding WO3 particles to Rhodamine 6G solution, single peak random lasing emission is achieved. Furthermore, we investigate the effects of changing the concentration of WO3 particles on the random lasing characteristics. Our results confirm that the increase of WO3 particles leads to the decrease of random lasing threshold, blue-shift of the emission peak, enhancement of the laser emission peak and decrease of its line-width. Due to electrochromic and gasochromic properties of WO3 nanostructures this work can open an avenue for design and fabrication of new tunable and controllable random lasers.

Tandem pumping architecture enabled high power random fiber laser with near-diffraction-limited beam quality

In this contribution, we present the tandem pumping avenue leveraged performance scaling of random fiber laser to record 3 kW level with inherent temporal stability and near-diffraction-limited beam quality. The high power system employs a four-stage master oscillator power amplifier chain. The master oscillator is a half-opened cavity structured random distributed feedback fiber laser centered at 1080 nm and pumped by incoherent amplified spontaneous emission source. Narrowband random laser seed is selected by employing a spectral filtering module with a maximum output power of 1.08 W, full width at half maximum linewidth of 0.47 nm and spectral optical-signal-to-noise ratio of about 42 dB. As to the main amplification stage, for given 104 W pre-amplified random laser seed and 3.61 kW pump laser, an ultimate output power of 3.03 kW can be obtained, corresponding to an optical-to-optical conversion efficiency of 81.05%. Nearly single-transverse-mode amplified random laser can be achieved even at full power level for inherent high thermal modal instability threshold enabled by tandem pumping and inducing bending loss for high-order transverse-mode. Further performance scaling of this high power random laser system, such as power boosting, operation wavelength tuning and linewidth alteration, is the next goal.

Wrinkled 2D Materials: A Versatile Platform for Low-Threshold Stretchable Random Lasers.

A stretchable, flexible, and bendable random laser system capable of lasing in a wide range of spectrum will have many potential applications in next- generation technologies, such as visible-spectrum communication, superbright solid-state lighting, biomedical studies, fluorescence, etc. However, producing an appropriate cavity for such a wide spectral range remains a challenge owing to the rigidity of the resonator for the generation of coherent loops. 2D materials with wrinkled structures exhibit superior advantages of high stretchability and a suitable matrix for photon trapping in between the hill and valley geometries compared to their flat counterparts. Here, the intriguing functionalities of wrinkled reduced graphene oxide, single-layer graphene, and few-layer hexagonal boron nitride, respectively, are utilized to design highly stretchable and wearable random laser devices with ultralow threshold. Using methyl-ammonium lead bromide perovskite nanocrystals (PNC) to illustrate the working principle, the lasing threshold is found to be ≈10 µJ cm-2 , about two times less than the lowest value ever reported. In addition to PNC, it is demonstrated that the output lasing wavelength can be tuned using different active materials such as semiconductor quantum dots. Thus, this study is very useful for the future development of high-performance wearable optoelectronic devices.

Observation of Lévy distribution and replica symmetry breaking in random lasers from a single set of measurements.

Random lasers have been recently exploited as a photonic platform for studies of complex systems. This cross-disciplinary approach opened up new important avenues for the understanding of random-laser behavior, including Lévy-type distributions of strong intensity fluctuations and phase transitions to a photonic spin-glass phase. In this work, we employ the Nd:YBO random laser system to unveil, from a single set of measurements, the physical origin of the complex correspondence between the Lévy fluctuation regime and the replica-symmetry-breaking transition to the spin-glass phase. A novel unexpected finding is also reported: the trend to suppress the spin-glass behavior for high excitation pulse energies. The present description from first principles of this correspondence unfolds new possibilities to characterize other random lasers, such as random fiber lasers, nanolasers and small lasers, which include plasmonic-based, photonic-crystal and bio-derived nanodevices. The statistical nature of the emission provided by random lasers can also impact on their prominent use as sources for speckle-free laser imaging, which nowadays represents one of the most promising applications of random lasers, with expected progress even in cancer research.

Controlling directionality and the statistical regime of the random laser emission

Unlike a conventional optical cavity laser, a random laser system is generally characterized by a nondirectional output emission. In this work we report an experimental and theoretical study on the angular properties of the random laser emission and its dependence on the diffusive properties of the sample and the spatial gain profile, showing the possibility of controlling it by the total amount of available energy. We show that the directional characteristics are associated with the statistical regime of fluctuations in the emission spectrum and, in particular, with a L\'evy statistical regime. A model based on a phase-insensitive feedback mechanism has been used in order to explain the experimental data and two different L\'evy subregimes have been identified.

Gold nanoparticle-based plasmonic random fiber laser

We have reported the realization of a plasmonic random fiber laser based on the localized surface plasmonic resonance of gold nanoparticles (NPs) in the liquid core optical fiber. The liquid core material contains a dispersive solution of gold NPs and laser dye pyrromethene 597 in toluene. It was experimentally proved that the fluorescence quenching of the dye is restrained in the optical fiber, which is considered one of the main sources of loss in the traditional laser system. Meanwhile, the random lasing can be more easily obtained in the random laser system with more overlap between the plasmonic resonance of the gold NPs and the photoluminescence spectrum of the dye molecules.