Random Lasing Behavior Research Articles

Electrically pumped random laser device based on Pd/SiO2/ZnO nanorods MIS structure

Electrically pumped random lasing based on Pd/SiO2/ZnO nanorods (NRs) structures is demonstrated. Chemical bath deposition (CBD) technique was used to synthesize the ZnO NRs. Then, an insulating layer of SiO2 was deposited via radio frequency (RF) magnetron sputtering. After that, direct current (DC) magnetron sputtering was used to deposit palladium (Pd) metal contacts on the sample through a shadow mask. The electrical, morphological as well as optical characteristics of the ZnO NRs were analyzed. The device exhibits typical Schottky diode current–voltage (I-V) characteristics at a turn-on voltage of 6.18 V. The electroluminescence (EL) spectra shows good random lasing behavior with lasing peaks centered at approximately 380 nm and exhibited a threshold current of 37.5 mA. This report reveals Pd as a relatively cheaper material and low-cost CBD fabrication method is sufficient to fabricate electrically pumped random laser devices. Furthermore, this report also present a new way to interpret the mechanism of random lasing in the device.

Investigation of random laser effect in structural disordered aperiodic multilayer

The gap states of a random Fibonacci-on-average multilayer exhibit strong localization and high Q-factors, indicating potential suitability for random lasing applications. This study investigates the gain threshold behavior of random lasing within the visible spectrum. Using the scattering matrix method with complex refractive indices, our simulations examine the relationship between the gain threshold, structural disorder, and the number of layers. The results contribute to the understanding of random lasing behavior of this type of quasi-crystal.

Plasmonic random lasing and amplified spontaneous emission from donor–acceptor–donor dyes covered biocompatible silk fibroin film

Amplified spontaneous emission and random lasing behavior are demonstrated from our synthesized donor–acceptor–donor dye-covered biocompatible silk fibroin (DC-SF) film and the DC-SF film with embedded silver nanoprisms, respectively.

Random lasing of the active organic nanocrystals of SFX-2-7-DDPA solution

In this paper, we demonstrated organic nanocrystals micro-lasers devices with different thickness from 0.4mm to 0.7mm. The N2, N2, N7, N7-tetraphenylspiro [fluorene-9,9-xanthene]-2,7-diamine, 95% (SFX-2-7-DDPA) structure (organic nanocrystals in a solution)- highly scattering medium is manipulated to generate a multiple light scattering. The manufacture technique can be used to a variety of water soluble SFX-2-7-DDPA, designed to work in the gain ethanol solution with SFX-2-7-DDPA nanocrystals devices, has been investigated at different input powers. A Nd-YAG laser based experiment tool has been measured including a from amplified spontaneous emission to random lasing. The analysis of photon travel distance has been thought about showing the random lasing behavior with particular attention on lasing tunability by using devices of different sizes. Particulary,for first time, we have demonstrated dye-doped SFX-2-7-DDPA nanocrystals based organic random lasers.

Bi-chromaticity and tunability of random lasing in mesoporous silica SBA16 doped with rhodamine B

The random laser emission from ordered mesoporous silica SBA16 doped with rhodamine B (RB) organic dye was investigated. Powdered SBA16 with 16 nm average pore diameter have been synthesized and doped with five different concentrations of the organic dye. Typical incoherent feedback random laser behavior was observed. The bi-chromatic emission was characterized for the sample with the highest dye concentration. Tunable random laser emissions from 578 to 618 nm were obtained depending on the excitation laser spot diameter and the rhodamine-B load. The results indicate that mesoporous RB-doped SBA16 is a promising material for the development of solid-state random lasers.

Random laser behavior in Gold-doped Zinc Oxide nanorods structures

The random laser was investigated in gold-doped Zinc Oxide nanorods (Au-doped ZnO NRs) under a range of pumping power 0.25 - 4.66 mW. The Au-doped ZnO NRs prepared by chemical bath deposition (CBD) on the ZnO seed layer, were pre-coated on glass substrate using radio frequency magnetron sputtering (Rf-sputtering). The morphological of Au-doped ZnO NRs shows a hexagonal and strong vertically alignment against the substrate. The Energy dispersive spectroscopy (EDX) spectrum and elemental mapping results confirmed that Au atoms (at.%) are doped and spread over the ZnO NRs. More interestingly, the random laser of Au-doped ZnO shows a redshift of ~38 nm. This study showed the ability of using doping as a tuning parameter in the random laser, also provided an emphasis on Au-doped ZnO NRs as suitable options for controllable random laser devices.

Function optimization of diffusive nanotriangles in random lasers

The random laser has the potential to be replaced with the conventional cavity laser for abundant nanophotonics applications. For this purpose, it is essential to investigate the effect of using different materials as the diffusive medium in the random laser. We theoretically studied two groups of diffusive nanoparticles with some common materials used in the random lasers: metals (Au, Ag, Al) and dielectrics (TiO2, Si, GaAs). First, we compared the random lasing behavior with metal and dielectric triangle/sphere nanoparticles through the scattering cross section calculations. Then, the physical characteristics of triangle/sphere nanoparticles of both categories were investigated, resulting in the optimum scattering condition for the nanoparticles. Noteworthy, we have supposed that the triangle nanoparticles are made with colloidal lithography and randomly distributed in Rhodamine 6G as a gain medium for all simulations. We investigated that aluminum and titanium dioxide are good scatterers to interact with the gain medium over the photoluminescence emission spectrum. This study paves the way to design a more effective and applicable random laser for many potential applications.

Tunable random lasing in dye-doped mesoporous silica SBA-15

Mesoporous silica, known as SBA-15, possesses a hexagonal pore structure, with 8-nm-diameter pores and high surface area $(\ensuremath{\sim}700\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{2}/\mathrm{g})$. The mesoporosity of SBA-15 is excellent to be filled with luminescent chromophores aiming at optical and photonic applications. SBA-15 powder infiltrated with Rhodamine B (RB) was prepared with different RB loads. Using the second harmonic of a pulsed Nd:yttrium aluminum garnet (YAG) laser (8 ns, 10 Hz) as the excitation source, the light emission spectra of the samples were investigated. Typical incoherent feedback random laser behavior was observed. Tunable random laser emissions from 579 to 585 nm were obtained depending on the excitation laser spot diameter and the RB load. The results indicate that mesoporous SBA-15 infiltrated with RB is a promising material for the development of solid-state random lasers.

Centimeter-long III-Nitride nanowires and continuous-wave pumped lasing enabled by graphically epitaxial lift-off

It remains a big challenge to elongate one-dimensional (1D) semiconductor nanowires (NWs), which can be attractive platforms for miniaturizing and/or integrating macroscopic devices, into centimeter-scale length. Herein, we report the innovative preparation of single-crystalline III-nitride NWs, with unprecedented length above 2 cm and the aspect ratio above 6000, by graphically epitaxial lifting-off (GELO) the epitaxial films on sapphire. The proposed GELO technology involves isotropic dry etching and selectively electrochemical (EC) etching. Reaction kinetics study of the EC etching indicate that two-steps processes are included, which is, to our best knowledge, firstly revealed and experimentally confirmed. Centimeter-long freestanding NWs, with predesigned structure of homogeneous GaN, p-GaN/(InGaN/GaN) 6 quantum-wells/n-GaN (simply InGaN/GaN QWs) and AlGaN/AlN/GaN heterostructure, are successfully obtained and exhibit superior morphological uniformity and robust flexibility. Optical properties of the released InGaN/GaN QW-NWs were well optimized owing to the relieved intrinsic strain. Random lasing behavior was unexpectedly observed by continuous-wave excitation of the individual InGaN/GaN QW-NW, with a low threshold of 232 kW•cm -2 . This work represents a low-cost and economic approach to yield structure-engineerable super-long III-nitride NWs, which would promote the development and integration of optoelectronic nanodevices. • Centimeter-long III-nitride NWs with engineerable structure are prepared by the graphically epitaxial lift-off method. • Reaction kinetics study of EC etching indicate that two-steps processes are included, which is experimentally confirmed. • Continuous-wave pumped random lasing of the individual InGaN/GaN QW-NW was observed with a low threshold of 232 kW•cm -2 .

Dye-doped electrospun fibers for use as random laser generator: The influence of spot size and scatter concentration

The development of electrospun polymer fiber networks embedded with metal oxide nanoparticles in organic dye media favors the photons waveguiding and multiple scattering, providing the adequate environment for random laser action. The use of water-soluble polymer solution as support for electrospun matrix introduces relevant application in biomedical applications. Herein, it is explored the use of block copolymers (Eudragit L100) as support for electrospinning of polymer fiber doped with titanium dioxide (scatter centers) and rhodamine B (gain media). The resulting fiber net presented random laser behavior that depends on aggregation degree of gain media (rhodamine B) due to the combination of reabsorption/reemission processes with tunable response (emission peak position). These results open new possibilities for use of low-cost and water soluble electrospun-based random lasers based on organic dyes and random network of polymer matrix.

Unprecedented random lasing in 2D organolead halide single-crystalline perovskite microrods.

Three-dimensional organic-inorganic hybrid halide perovskites have been demonstrated as great materials for applications in optoelectronics and photonics. However, their inherent instabilities in the presence of moisture, light, and heat may hinder their commercialization. Alternatively, emerging two-dimensional (2D) organic-inorganic hybrid perovskites have recently attracted increasing attention owing to their great environmental stability and inherent natural quantum-well structure. In this work, we have synthesized a high-quality long-chain organic diammonium spacer assisted 2D hybrid perovskite FA-(N-MPDA)PbBr4 (FA = formamidinium and N-MPDA = N-methylpropane-1,3-diammonium) by the slow evaporation at constant temperature method. The millimeter-sized single-crystalline microrods demonstrate low threshold random lasing behavior at room temperature. The single-crystalline 2D hybrid perovskite random laser achieved a very narrow linewidth (∼0.1 nm) with a low threshold (∼0.5 μJ cm-2) and a high quality factor (∼5350). Furthermore, the 2D hybrid microrod laser shows stable lasing emission with no measurable degradation after at least 2 h under continuous illumination, which substantially proves the stability of 2D perovskites. Our results demonstrate the promise of 2D organic-inorganic microrod-shaped perovskites and provide an important step toward the realization of high-performance optoelectronic devices.

Theoretical investigations of power fluctuations statistics in Brillouin erbium-doped fiber lasers.

We present theoretical investigations including simulations and statistical analyses on the fluctuations of the temporal output power in a Brillouin erbium-doped fiber laser. The generation of even Stokes waves up to the 5th order is considered by solving coupled-mode equations including SBS and Kerr nonlinearities. It is demonstrated that by increasing the EDFA pump power and generating a few orders of Stokes waves in such a laser, there are strong power fluctuations and rogue events are expected. Transition from Gaussian-like to levy-like regime is described as the power is increased from threshold resulting in the initial Stokes wave generation to well beyond threshold generating 5 effective even Stokes waves. Accordingly, phase portraits confirm increasing fluctuations as a function of the power. It is also shown that at the SBS lasing threshold, the output signals have the maximum correlation over replicas in round trips, nevertheless by enhancing the power, the correlation diminishes, which results in a full symmetry breaking and the system radiates in a chaotic manner and exhibits random laser behavior.

Tunable random lasing behavior in plasmonic nanostructures

Random lasing is desired in plasmonics nanostructures through surface plasmon amplification. In this study, tunable random lasing behavior was observed in dye molecules attached with Au nanorods (NRs), Au nanoparticles (NPs) and Au@Ag nanorods (NRs) respectively. Our experimental investigations showed that all nanostructures i.e., Au@AgNRs, AuNRs & AuNPs have intensive tunable spectral effects. The random lasing has been observed at excitation wavelength 532 nm and varying pump powers. The best random lasing properties were noticed in Au@AgNRs structure, which exhibits broad absorption spectrum, sufficiently overlapping with that of dye Rhodamine B (RhB). Au@AgNRs significantly enhance the tunable spectral behavior through localized electromagnetic field and scattering. The random lasing in Au@AgNRs provides an efficient coherent feedback for random lasers.

Enhanced random lasing from distributed Bragg reflector assisted Au-ZnO nanowire Schottky diode

An electrically pumped ultraviolet random laser based on an Au-ZnO nanowire Schottky junction on top of a SiO2/SiNx distributed Bragg reflector (DBR) has been fabricated. Electrical characterization shows typical Schottky diode current-voltage characteristics. Evident random lasing behavior is observed from electroluminescence measurement at room temperature. In comparison with a reference device having similar nanowire morphology but no DBR, this laser demonstrates almost 1.8 times reduction in threshold current and 4 times enhancement in output power. The performance enhancement originates from the incorporation of the DBR structure, which provides high reflectivity in the designed wavelength range.

Coherent random lasing behavior in low-dimensional active weakly scattering random systems

We report theoretical studies of the coherent random lasing behavior in active weakly scattering random fiber lasers by using finite-difference time-domain (FDTD) method. We design and simulate a model of active weakly scattering random fiber lasers. Results show that the scattering mean free path reduces significantly with reducing the dimension of systems. For same situation, the scattering mean free path in our model is at least two orders of magnitude lower than that in high dimensional systems. We calculate the length of lasing oscillation cavity by using power Fourier transform, and we found Lc<<L (the sample size) in one-dimensional active weakly scattering random systems. We attribute this effect to the low dimension of our system. Strong evidence is presented that the well-defined pump threshold and the coherent feedback behavior is existent in one-dimensional active weakly scattering random systems. We show that there is a one-to-one correlation between laser mode and oscillation cavity. These results provide essential mechanism to realize one-dimensional active random laser, for example, active random fiber laser. We believe that our study provides an original way to access coherent random laser in weakly scattering random systems.

Fabrication of the glass microlens arrays and the collimating property on nanolaser

The influence of the glass microlens array on the collection efficiency and beam collimating with the ZnO/GaN nanoheterojunction nanolaser is investigated. Ultraviolet random lasing behavior from the ZnO/GaN nanoheterojunction array has been demonstrated with both optical and electrical pumping. The refractive microlens arrays are designed and fabricated on the glass slide using the microfabrication procedures and integrated on the nanolaser. We show that, for the nanolaser with divergent output beams, the introduction of glass microlens arrays reduces the beam divergence and increases transmission. The detected optical power is enhanced by more than 1.8 times for the nanolaser integrated with glass microlens arrays. The drastic increase in the optical collection efficiency is resulted from the laser beam collimating.

Random lasing with spatially nonuniform gain

Spatial and spectral properties of random lasing with spatially nonuniform gain were investigated in two-dimensional (2D) disordered medium. The pumping light was described by an individual electric field and coupled into the rate equations by using the polarization equation. The spatially nonuniform gain comes from the multiple scattering of this pumping light. Numerical simulation of the random system with uniform and nonuniform gain were performed both in weak and strong scattering regime. In weak scattering sample, all the lasing modes correspond to those of the passive system whether the nonuniform gain is considered. However, in strong scattering regime, new lasing modes appear with nonuniform gain as the localization area changes. Our results show that it is more accurate to describe the random lasing behavior with introducing the nonuniform gain origins from the multiple light scattering.

An Sb-doped p-type ZnO nanowire based random laser diode

An electrically pumped Sb-doped ZnO nanowire/Ga-doped ZnO p–n homojunction random laser is demonstrated. Catalyst-free Sb-doped ZnO nanowires were grown on a Ga-doped ZnO thin film on a Si substrate by chemical vapor deposition. The morphology of the as-grown titled nanowires was observed by scanning electron microscopy. X-ray photoelectron spectroscopy results indicated the incorporation of Sb dopants. Shallow acceptor states of Sb-doped nanowires were confirmed by photoluminescence measurements. Current–voltage measurements of ZnO nanowire structures assembled from p- and n-type materials showed a typical p–n diode characteristic with a threshold voltage of about 7.5 V. Very good photoresponse was observed in the UV region operated at 0 V and different reverse biases. Random lasing behavior with a low-threshold current of around 10 mA was demonstrated at room temperature. The output power was 170 nW at 30 mA.

The glassy random laser: replica symmetry breaking in the intensity fluctuations of emission spectra.

The behavior of a newly introduced overlap parameter, measuring the correlation between intensity fluctuations of waves in random media, is analyzed in different physical regimes, with varying amount of disorder and non-linearity. This order parameter allows to identify the laser transition in random media and describes its possible glassy nature in terms of emission spectra data, the only data so far accessible in random laser measurements. The theoretical analysis is performed in terms of the complex spherical spin-glass model, a statistical mechanical model describing the onset and the behavior of random lasers in open cavities. Replica Symmetry Breaking theory allows to discern different kinds of randomness in the high pumping regime, including the most complex and intriguing glassy randomness. The outcome of the theoretical study is, eventually, compared to recent intensity fluctuation overlap measurements demonstrating the validity of the theory and providing a straightforward interpretation of qualitatively different spectral behaviors in different random lasers.

Optically pumped lasing and electroluminescence in ZnO/GaN nano-heterojunction array devices

The preparation of a highly ordered ZnO/GaN nano-heterojunction array is introduced. Combining the merits of nanolaser and plasmonic Fabry–Perot nanolaser, we designed and fabricated an ultraviolet nanolaser with Ag-dielectric hybrid film-coated n-ZnO nanowires (NWs) array on p-GaN substrate. Ultraviolet random lasing behavior from the ZnO/GaN nano-heterojunction array has been demonstrated with both optical and electrical pumping, where the surface plasmon enhancement effect in the lasing process is discussed. The numerical simulation results show the surface plasmon at the Ag/SiO2/ZnO interface may be excited and strongly compress the wave-guided modes, which were found to optimize the lasing spectrum and increase the light intensity compared to the bare NWs array. With the electric pumping of the device, the electroluminescence parameters are characterized and the underlying mechanism is also discussed.