Random Laser Research Articles

Towards a sensing model using a random laser combined with diffuse reflectance spectroscopy.

The previous research proves that the random laser emission reflects not only the scattering properties but also the absorption properties. The random laser is therefore considered a potential tool for optical properties sensing. Although the qualitative sensing using the random laser is extensively investigated, a quantitative measurement of optical properties is still rare. In this study, a generalized mathematical quantitative model using random laser combined with diffuse reflectance spectroscopy is proposed for optical sensing in turbid media. This model describes the gain effect of the active medium and the optical properties effect of the passive medium separately. Rhodamine 6G is used as the active medium. Intralipid and ink are employed to demonstrate the effect of the scattering and absorption, respectively. The peak wavelength shift of the random laser is proved to be an ideal sensing parameter for this sensing model. It is also revealed that the scaling parameters in the sensing model are interrelated and can be simplified to one. With this combined model, the direct sensing of optical properties in diverse turbid media is promising.

Controlling the spectral persistence of a random laser

Random lasers represent a relatively undemanding technology for generating laser radiation that displays unique characteristics of interest in sensing and imaging. Furthermore, they combine the classical laser’s nonlinear response with a naturally occurring multimode character and easy fabrication, explaining why they have been recently proposed as ideal elements for complex networks. The typical configuration of a random laser consists of a disordered distribution of scattering centers spatially mixed into the gain medium. When optically pumped, these devices exhibit spectral fluctuations from pulse to pulse or constant spectra, depending on the pumping conditions and sample properties. Here, we show clear experimental evidence of the transition from fluctuating (uncorrelated) to persistent random laser spectra, in devices in which the gain material is spatially separated from the scattering centers. We interpret these two regimes of operation in terms of the number of cavity round trips fitting in the pulse duration. Only if the cavity round-trip time is much smaller than the pulse duration are modes allowed to interact, compete for gain, and build a persisting spectrum. Surprisingly this persistence is achieved if the pumping pulse is long enough for radiation in the cavity to perform some 10 round trips. Coupled-mode theory simulations support the hypothesis. These results suggest an easy yet robust way to control mode stability in random lasers and open the pathway for miniaturized systems, as, for example, signal processing in complex random laser networks.

Replica symmetry breaking in 1D Rayleigh scattering system: theory and validations

Spin glass theory, as a paradigm for describing disordered magnetic systems, constitutes a prominent subject of study within statistical physics. Replica symmetry breaking (RSB), as one of the pivotal concepts for the understanding of spin glass theory, means that under identical conditions, disordered systems can yield distinct states with nontrivial correlations. Random fiber laser (RFL) based on Rayleigh scattering (RS) is a complex disordered system, owing to the disorder and stochasticity of RS. In this work, for the first time, a precise theoretical model is elaborated for studying the photonic phase transition via the platform of RS-based RFL, in which we clearly reveal that, apart from the pump power, the photon phase variation in RFL is also an analogy to the temperature term in spin-glass phase transition, leading to a novel insight into the intrinsic mechanisms of photonic phase transition. In addition, based on this model and real-time high-fidelity detection spectral evolution, we theoretically predict and experimentally observe the mode-asymmetric characteristics of photonic phase transition in RS-based RFL. This finding contributes to a deeper understanding of the photonic RSB regime and the dynamics of RS-based RFL.

Influence of un-pumped EYDF on statistical properties of random fiber lasers based on Rayleigh scattering

In this paper the influence of un-pumped Erbium-Ytterbium doped fibers (EYDF) on the statistical properties of random fiber lasers (RFLs) with linear cavity based on Rayleigh scattering is investigated. The experimental results show that the probability density function (PDF) of temporal characteristics of both lasers with and without un-pumped EYDF are asymmetrically distributed near threshold and Gaussian distributed far away over threshold. The width of the PDFs first increases and then decreases with pump power when the un-pumped EYDF is not inserted, while the width of the PDFs continuously increases with pump power when the un-pumped EYDF is inserted, which indicates that EYDF insertion makes the laser more stable at lower pump power and more unstable at higher pump power. The radiation with un-pumped EYDF is fully uncorrelated at high pump power. And the radiation without un-pumped EYDF is also fully uncorrelated at high pump power.

Tuning Multi-wavelength Lasing in Rhodamine 640/Methylene Blue/Ag NW Random Lasers

Tuning Multi-wavelength Lasing in Rhodamine 640/Methylene Blue/Ag NW Random Lasers

Generation of multiwavelength cylindrical vector beams from a random fiber laser assisted with nonlinear amplifying loop mirror

In past decades, vector mode random fiber laser (RFL) has attracted much exploration and rapid development. In this work, we proposed and demonstrated a novel multiwavelength RFL that produces cylindrical vector beams (CVBs). The gain profile is manipulated by a homemade Sagnac loop filter assisted with the nonlinear amplifying loop mirror (NALM) mechanism to improve multi-wavelength oscillation capability. The CVBs are generated with the help of long-period fiber grating and the wavelength switchablity CVBs random fiber laser is obtained. The wideband spectrum multiwavelength CVBs with the maximum channel number of seventeen are realized with NALM. This currently holds the record for the highest number of wavelength channels of vector mode random lasers which holds great promise for free-space optical communication. Coherent-tunable low-coherence high-order modes and cylindrical vector mode random lasers utilizing wavelength tailoring have been realized with high mode purity. The proposed CVBs with modeless behavior have potential applications prospects in optical signal multiplexing, space optical communication, and speckle-free laser active imaging.

Continuous-wave quasi-single-mode random lasing in CH3NH3PbBr3 perovskite films on patterned sapphire substrates.

We report intriguing continuous-wave quasi-single-mode random lasing in methylammonium lead bromide (CH3NH3PbBr3) perovskite films synthesized on a patterned sapphire substrate (PSS) under excitation of a 532-nm laser diode. The random laser emission evolves from a typical multi-mode to a quasi-single-mode with increasing pump fluences. The full width at half-maximum of the lasing peak is as narrow as 0.06 nm at ∼547.8 nm, corresponding to a high Q-factor of ∼9000. Such excellent random lasing performance is plausibly ascribed to the exciton resonance in optical absorption at 532 nm and the enhanced optical resonance due to the increased likelihood for randomly scattered light to re-enter the optical loops formed among the perovskite grains by multi-reflection at the perovskite/PSS interfaces. This work demonstrates the promise of single-mode perovskite random lasers by introducing the exciton resonance effect and ingeniously designed periodic nano/micro optical structure.

A brief report on nanophotonics and metamaterials landscape in India

AbstractHere, we describe a set of research results in the domain of Nanophotonics and Metamaterials that represent the broad N &M landscape in India. These results were presented in an online BRICS meeting, and were collated based on the criteria deemed appropriate for the said forum. Results presented at the meeting encompass various areas, including nano-optics, nano-opto-mechanics, integrated photonic devices, plasmonics, metal-enhanced fluorescence, bio relevant photonics and metamaterials. Research topics such as Anderson localization of light, exceptional points in non-Hermitian systems, manipulation of nanoscale mechanical motion, efficient mode coupling in integrated photonics etc are discussed. Furthermore, miniaturized SPR sensors, coupling between metal nanostructures and semiconductor quantum dots, biosensing applications, metamaterials and random lasing, and customizable optical functionalities for sensing, and energy conversion are also elaborated upon. In the end, a brief listing of more recent selected publications is presented. This review article highlights the diverse and promising avenues in nanophotonics and metamaterials research in India.

Two-photon pumped random lasing in MAPbBr3 with directional output for far-field applications

We investigate the random lasing properties of polycrystalline MAPbBr3 grown in a hollow fiber. Coupling of the random lasing on the inner wall of the hollow fiber into the annular cylinder and guided by the inner surface of hollow cavity enable directional output of the random lasing emission. The polycrystalline MAPbBr3 was grown by the capillary effect, when one end of the hollow fiber was dipped into the precursor solution. A two-photon pumping scheme was employed, where femtosecond pulses centered at about 800 nm was focused onto the MAPbBr3 polycrystals through the side wall of the hollow fiber. Random lasing was achieved due to the strong optical scattering by the interfaces within the polycrystals on the inner wall of the hollow fiber. The random lasing output was re-collimated into a roughly parallel beam with a circular transverse mode, which favors far-field applications of random lasers. Two-photon pumping enables larger penetration depth and larger excitation volume than single-photon pumping, so that strong lasing spot can also be observed in the center area of the output laser beam.

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.

Microcavity Complex Lasers: from Order to Disorder

AbstractMicrostructures, characterized by gain, nonlinearity, internal scattering, and boundary effects, offer an exceptional platform for exploring complex optical phenomena such as random lasing, chaos, and multidimensional speckles. Specifically, complex lasers generated within microcavities and optical fibers, where strong light confinement and scattering play diverse roles, have become a significant branch of laser research. Recently, the rapid advancement of materials, micro‐nano technologies, and artificial intelligence has introduced new opportunities and challenges for the generation, control, and application of complex lasers. This review systematically examines various types of microcavity complex lasers from the perspective of microcavity structures with different degrees of disorder. It primarily focuses on the historical development, characteristics, regulation, and applications of disordered microcavity lasers and concludes with a discussion on the future trends in the development of microcavity complex lasers.

Random lasing using laser generated and modified silver nanoparticles

The authors report incoherent random laser action in systems where the optical feedback is provided by multiple scattering generated by different classes of silver nanoparticles in the colloidal state, having plasmon resonances at different frequencies. They found improved performance of triangular silver nanoplates as compared to nanospheres, with a threshold as low as 1 mJ/cm2 and a 5 times lower optimal silver concentration, due to plasmonic enhancement effects and tuning of the plasmon resonance. The nanoparticles were also tested for stability against illumination by the pump laser, as the onset of pulsed laser melting is comparable to random laser threshold in terms of pump fluence, severely limiting the range of operation of nanoparticles with main plasmon resonance close to the pump wavelength. The optimal approach to choose plasmonic nanoparticles for random lasing must, therefore, take the stability aspect into serious consideration as well as the plasmonic enhancement of random lasing.

Principle and design of vanadium-doped fiber laser under simulation

Due to the low efficiency of traditional communications and many problems, the development of optical fiber communications is currently necessary. Among them, fiber laser is the core of fiber communication, and the higher the output band of a fiber laser, the more information it carries, and the information that can be transmitted increases accordingly. Therefore, the primary goal is to develop a fiber laser with high-band output. At present, research on high-band output fiber lasers is being carried out at home and abroad. Domestic research focuses on the selection of fiber media; foreign research focuses on random fiber lasers. This article adopts the domestic research route, based on the premise that vanadium ions can emit laser wavelengths that include the L+ band when performing energy level transitions. At the same time, vanadium-doped gallium lanthanum sulfide glass has good functions of absorbing pump light and emitting lasing light. Therefore, this article mainly discusses the design of vanadium-doped fiber lasers using vanadium-doped gallium sulfide as the gain medium under simulation conditions to achieve high-band output of fiber lasers.

Demonstration of standing cavity Brillouin random fiber lasers using double fiber Bragg grating arrays

Bidirectional feedback by fiber Bragg grating arrays (FBGAs) reduced the loss of the cavity and increased stimulated Brillouin scattering (SBS) gain by bi-directional Stokes wave through FBGA associated Rayleigh feedback of the pump wave. As a result, the Q value of the Brillouin random fiber laser (BRFL) increased significantly, which leads to narrow linewidth. This is different from the ring configuration with unidirectional SBS gain versus dual SBS gain of the same fiber length. Highly efficient use of the SBS gain fiber for coherent SBS amplification suppressed thermal noise associated Stokes wave. Such an efficient SBS laser is realized by a standing cavity BRFL based on double FBGAs. Multiple scattering of light traveling in strong scattering FBGAs enables light localization and the generation of high-Q reflection peaks. Coherent SBS amplification with high Q help to reduce laser relative intensity noise (RIN) and laser linewidth. Experimental results demonstrate that the BRFL supports localized modes by increasing the scattering strength of the FBGA random feedback, resulting in long lifetime and single-frequency emission with 20 dB noise floor reduction. The BRFL with a 1 km Brillouin gain fiber exhibits lower RIN and narrower linewidth than that with a 10 km Brillouin gain fiber due to the stronger gain competition of more modes in the longer cavity length. The optimized standing caivty BRFL with 1 km gain fiber leads to 3.5 kHz linewidth versus 40 kHz from the pump laser. These findings provide experimental evidence that double FBGAs offer a unique setting to control mode dynamics, realizing low-noise single-frequency lasing.

Plasmonic triple compound cavity random lasing: fabrication and characterization

Plasmonic triple compound cavity random lasing: fabrication and characterization

Observation of the photonic Hall effect and photonic magnetoresistance in random lasers

Modulation of scattering in random lasers (RLs) by magnetic fields has attracted much attention due to its rich physical insights. We fabricate magnetic gain polymer optical fiber to generate RLs. From macroscopic experimental phenomena, with the increase of the magnetic field strength, the magnetic transverse photocurrent exists in disordered multiple scattering of RLs and the emission intensity of RLs decreases, which is the experimental observation of photonic Hall effect (PHE) and photonic magnetoresistance (PMR) in RLs. At the microscopic level, based on the field dependence theory of magnetic disorder in scattered nanoparticles and the replica symmetry breaking theory, the magnetic-induced transverse diffusion of photons reduces the scattering disorder, and then decreases the intensity fluctuation disorder of RLs. Our work establishes a connection between the above two effects and RLs, visualizes the influence of magnetic field on RL scattering at the microscopic level, which is crucial for the design of RLs.

Boundary Feedback Fiber Random Microcavity Laser Based on Disordered Cladding Structures

The cavity form of complex microcavity lasers predominantly relies on disordered structures, whether found in nature or artificially prepared. These structures, characterized by disorder, facilitate random lasing through the feedback effect of the cavity boundary and the internal scattering medium via various mechanisms. In this paper, we report on a random fiber laser employing a disordered scattering cladding medium affixed to the inner cladding of a hollow-core fiber. The internal flowing liquid gain establishes a stable liquid-core waveguide environment, enabling long-term directional coupling output for random laser emission. Through theoretical analysis and experimental validation, we demonstrate that controlling the disorder at the cavity boundary allows liquid-core fiber random microcavities to exhibit random lasing output with different mechanisms. This provides a broad platform for in-depth research into the generation and control of complex microcavity lasers, as well as the detection of scattered matter within micro- and nanostructures.

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.

Crystallization-driven tuneable lasing of perylene doped into the nematic liquid crystal

Versatile devices with tunable capabilities for controlling lasing wavelength and intensity are in high demand. Liquid crystals (LCs) exhibit immense potential for such applications, offering fine-tuning possibilities through external factors. On the other hand, laser technology is currently a research hotspot in optoelectronics, and also in practical applications. The recent market introduction of laser television marks a significant stride toward making such advanced technology accessible in every household. In synergy with laser pumping, the LCs unquestionably can be rediscovered. This study presents a comprehensive investigation into the crystallization phenomenon within a host-guest device, compact in size, free from moving parts, and integrating the liquid crystalline (LC) matrix doped with 3,4,9,10-tetra-(3-alcoxy-carbonyl)-perylene (THCP) dye. The focus lies in examining the influence of varying dye concentrations on multicolor fluorescence, lasing behavior, and device morphology. The systematic analysis of Random Lasing (RL) energy thresholds and the impact of DC voltage on light intensity modulation is demonstrated. Morphological changes were monitored in real-time using optical microscopy techniques, including crossed polarizer, and fluorescence imaging under 450 nm excitation. Utilizing advanced Transmission Electron Microscopy (TEM) techniques, we explore exceptional insights into our set of devices, providing novel information about the THCP crystallization process for the first time in the literature. To gain a comprehensive understanding of the crystal forming and molecular geometry we examined additionally the THCP dye, using X-ray diffraction and Raman spectroscopy. Furthermore, we showcase that varying the pumping energy enables multicolor tuning in the fabricated systems, presenting an attractive feature in the context of laser display technologies.

Observation and all-optical manipulation of replica symmetry breaking dynamics in a multi-Stokes-involved Brillouin random fiber laser photonic system

In this paper, we propose and demonstrate an all-optical control of RSB transition in a multi-wavelength Brillouin random fiber laser (MWBRFL). Multi-order Stokes light components can be subsequently generated by increasing the power of the Erbium-doped fiber amplifier (EDFA) inside the MWBRFL, providing additional disorder as well as multiple Stokes-involved interplay. It essentially allows diversified laser mode landscapes with adjustable average mode lifetime and random mode density of the 1st order Stokes, which benefits the switching between replica symmetry breaking (RSB) and replica symmetry (RS) states in an optically controlled manner. Results show that the average mode lifetime of the 1st order Stokes component gradually decreases from 250.0 ms to 1.2 ms as high orders from the 2nd to the 5th of Stokes components are activated. Meanwhile, the order parameter q of the 1st order Stokes random lasing emission presents distinct statistical distributions within the selective sub-window under various EDFA optical powers. Consequently, all-optical dynamical control of the 1st Stokes random laser mode landscapes with adjustable average mode lifetime turns out to be attainable, facilitating the RSB transition under an appropriate observation time window. These findings open a new avenue for exploring the underlying physical mechanisms behind the occurrence of the RSB phenomenon in photonic complex systems.