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Nanocomposites for Photonic and Electronic Applications || Nanocomposite-based random lasers
摘要： First demonstrated in 1960 [1], the laser, as we know today, essentially consists of a pump source, a gain medium, and a cavity composed by a set of mirrors. The role of the cavity is to provide optical feedback, besides determining the directionality and modes of the laser [2]. A few years after the laser invention, V. S. Letokhov proposed in 1967 that coherent oscillation could be generated without the need for the mirror cavity [3], and the optical feedback would be provided by a scattering medium. Several years later, two publications described experimental results of stimulated emission in powders employing rare-earth materials of micron size [4,5]. However, the real breakthrough in the so-called random laser (RL) emission came in 1994 [6], when Lawandy and coworkers employed a nanocomposite prepared from a colloidal suspension of organic dye and nanometer-size TiO2 to clearly demonstrate laser emission in a gain medium in the presence of scatters. In the same year, Sha and coworkers studied the temporal emission of a similar nanocomposite RL with picosecond resolution, thus corroborating the laser action [7].
关键词： optical feedback,photonic devices,random lasers,nanocomposites,plasmonics
更新于2025-09-23 15:21:01
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Influence of the Fifth-Order Nonlinearity of Gold Nanorods on the Performance of Random Lasers
摘要： We present the first experimental evidence for the influence of the fifth-order nonlinearity on the characteristics of Random Lasers with plasmonic nanoparticles as scatterers. The experiments were performed with gold nanorods suspended in an ethanolic solution of Rhodamine 6G, pumped by a picosecond laser. It is shown that by varying the nanorods aspect-ratio, it is possible to control the cooperative influence of both transverse and longitudinal localized surface plasmons on the fifth-order nonlinear light scattering, a phenomenon that allows to manage the optical feedback causing significant changes in the threshold intensity and emission power of Random Lasers.
关键词： fifth-order nonlinearity,gold nanorods,Random Lasers,optical feedback,plasmonic nanoparticles
更新于2025-09-23 15:19:57
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Structured Light from Lasers
摘要： Structured light is derived from the ability to tailor light, usually referring to the spatial control of its amplitude, phase, and polarization. Although a venerable topic that dates back to the very first laser designs, structuring light at the source has seen an explosion in activity over the past decade, fuelled by a modern toolkit that exploits the versatility of diffractive structures, liquid crystals, metasurfaces/metamaterials, and exotic laser geometries, as well as a myriad of applications that range from imaging, microscopy, and laser material processing to optical communication. Here, the recent progress in creating and controlling structured light is reviewed, with particular emphasis on structuring light at the source: structured light lasers. The various design approaches, including pump shaping, cavity geometries, and the use of custom intracavity optical elements, implemented in a variety of lasers from microchip solutions to high-power fibers are covered in a tutorial style. The history and latest developments in the field are reviewed, elucidating the various structured light patterns that have been created from lasers, including orbital angular momentum and vector states of light. Finally, the present challenges and limitations are highlighted, along with comments on likely future trends.
关键词： optical modes,random lasers,topological lasers,orbital angular momentum,vector beams,structured light
更新于2025-09-19 17:13:59
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One-dimensional, surface emitting, disordered Terahertz lasers
摘要： Quantum cascade lasers are, by far, the most compact, powerful, and spectrally pure sources of radiation at terahertz frequencies, and, as such, they are of crucial importance for applications in metrology, spectroscopy, imaging, and astronomy, among many others. However, for many of those applications, particularly imaging, tomography, and near-field microscopy, undesired artifacts, resulting from the use of a coherent radiation source, can be detrimental. Random lasers can offer a concrete technological solution to the above issue. They, indeed, maintain a high degree of temporal coherence, as traditional lasers, while only exhibiting low spatial coherence, which can allow for the prevention of coherent artifacts, such as speckles. In this study, we report on the development of one-dimensional THz-frequency random wire lasers, patterned on the top surface of a double-metal quantum cascade laser with fully randomly arranged apertures, not arising from the perturbation of a regular photonic structure. By performing finite element method simulations, we engineer photonic patterns supporting strongly localized random modes in the 3.05–3.5 THz range. Multimode laser emission over a tunable-by-design band of about 400 GHz and with ～2 mW of peak power has been achieved, associated with 10○ divergent optical beam patterns. The achieved performances were then compared with those of perturbed Fabry–Perot disordered lasers, showing continuous-wave operation in the 3.5–3.8 THz range with an order of magnitude larger average power output than their random counterpart, and an irregular far field emission profile.
关键词： Anderson localization,Disordered photonic systems,Quantum cascade lasers,Random lasers,Terahertz frequencies
更新于2025-09-16 10:30:52
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[IEEE 2019 SBFoton International Optics and Photonics Conference (SBFoton IOPC) - Sao Paulo, Brazil (2019.10.7-2019.10.9)] 2019 SBFoton International Optics and Photonics Conference (SBFoton IOPC) - Production of a microfluidic random laser using ultrashort laser pulses
摘要： A random rhodamine laser system is produced on board of a femtosecond laser machined microfluidic system. When pumped by a nanosecond pulsed laser beam at 532 nm, laser emission at 610 nm is observed together with the linewidth narrowing typical of random lasers. The system can be easily integrated as an optofluidic component into microfluidic circuits for assessment of optical parameters on board of the lab-on-chip.
关键词： lab-on-chip,random lasers,microfluidics
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Plasmonic Random Laser with the Embedding of Silver Nanostructure Materials
摘要： In contrast to conventional lasers, random lasers (RLs), without cavity mirrors, were generated based on recurrent light scattering within nano-materials and possessed peculiar properties for practical applications. To date, researchers are not only interested in the novel nano-materials for the generation of RL but also curious in the manipulated property of RL through temperature and electric filed [1]. In addition, plasmonic random laser (PRL)[2] based on the localized surface plasmon resonance (LSPR) of metallic nanoparticles has attracted great interest. In this work, the dye-covered PVA (DC-PVA) film with the embedding of silver nano-particles (AgNPs) was produced to investigate the enhancement of emission spike intensity from PRL and the underlying mechanism by varying the size and shape of AgNPs. Here, the AgNPs were synthesized by a soft solution-phase approach inside the DI water [3]. Depending on the size and shape of AgNPs in colloidal solution, the absorbance spectrum in Fig. 1(a) reveals different peak absorption wavelength (λp) at 404 nm and 610 nm, respectively, and shows deep yellow and navy color (Fig. 1(a)). The PVA film with embedding of AgNPs (PVA/AgNPs) was produced by dropping the mixed solution, comprising PVA powder and AgNPs, onto a glass substrate. After drying, the laser dye (Pyrromethene 597, Exciton inc.) was coated on the top of PVA film (Inset of Fig. 1: the structure of sample). In this work, the coherent back scattering measurement (CBS) measurement [4] was performed to obtain the transport mean free path (lp) of pure DC-PVA film (green squares: Sample-I) and DC-PVA/AgNP film [red triangles: Sample-II (λp at 405 nm), blue circle: Sample-III (λp around 610 nm)]. The solid lines represent the theoretical fitting curves to obtain the lp of three samples around 10.3, 8.7 and 3.6 μm. The value of lp decreases obviously after AgNPs was embedding in the PVA film to illustrate the enhancement of light scattering. In order to generate RL, we excited all the produced samples by a frequency doubling Q-switched Nd:YAG laser with a central wavelength of 532 nm. The 10 Hz pump pulses were focused onto the sample with a long line stripe by a cylindrical lens with focal length f = 7cm. The side emission of the sample was collected by the fiber tip and measured by the spectrometer (resolution about 0.3 nm, Ocean Optics Inc.). Inset of Fig. 1(b) shows the emission spectra of DC-PVA film without (Sample-I, green solid curve) and with (Sample-II: red solid curve and Sample-III: blue solid curve) AgNPs. Even at relatively high pulse energy, the Sample-I (without AgNPs) only reveals broad spontaneous emission spectrum with the maximum intensity at λ = 578 nm. For the sample-II and sample-III (DC-PVA/AgNP film), the discrete emission spikes at around about λ=576 and 583 nm on the top of broad spontaneous emission can be revealed which is the characteristic of RL. In order to qualitatively distinguish the operation state of RL, the α-stable distribution [5] proposed by Uppu et al. was used to analysis the intensity fluctuation (red) of the sample by sampling 1000 spectrum slots. The intensity distribution (red histogram) can be theoretical fitting by the equation (blue solid curves in Figs. 1(c) and 1(d)) to obtain the α=1.99 and 1.58, respectively, which reveals the Gaussian and Levy distribution.
关键词： random lasers,light scattering,localized surface plasmon resonance,plasmonic random laser,silver nano-particles
更新于2025-09-12 10:27:22
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Multiple Scattering from Electrospun Nanofibers with Embedded Silver Nanoparticles of Tunable Shape for Random Lasers and White-Light-Emitting Diodes
摘要： Random lasers (RLs) are convenient, tunable, and widely applicable. However, the influence of fluorescence lifetime on the scattering and nanofiber distribution of nanofibers with various shapes of silver nanoparticles (Ag NPs) embedded within is unclear. We prepared polyvinyl alcohol (PVA) nanofibers with Ag NPs through electrospinning (ES) and pyrromethene 597 dye doping. We determined the influences of the particles on scattering enhancement and localized surface plasmon resonance (LSPR) in RLs. The distinct scattering rates and LSPR can be used to control optical properties for sensing devices and other applications. Compared with traditional films, the threshold of the nanofibers with Ag NPs is 35% lower. In addition to improved matching between the LSPR and emission spectra, enhanced coupling of the electric field with nonradiative energy amplifies the radiative emission. Furthermore, the luminescence lifetime shortened by increasing the scattering rate. An excessive scattering rate may accelerate radiative recombination and convert some recombination into nonradiative recombination to produce a more sensitive device. Finally, we applied the prepared nanofibers to a backlight display and fabricated a white-light-emitting diode (LED) with a distinct thickness of nanofibers. The fabricated device is suitable for application in other LEDs and RL devices.
关键词： light scattering,silver nanoparticles,plasmonic,electrospun fibers,random lasers
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Random Laser Action from Electrospun Polymeric Nanofibers Doped Either with Organic Dye or Semiconductor Nanoprisms
摘要： The search for light sources with targeted characteristics motivates the work of a large part of the photonics community. One topical subject in this area is the study of Random Lasers (RLs), which use as feedback mechanism the light scattering in a random medium instead of a Fabry-Perot cavity. A large variety of RLs and a diversity of applications have already been demonstrated. Of interest in many applications are RLs based on flexible hosts, which act not only as mechanical support, but also as scattering agent. Such host can be obtained, for example, by electrospinning fibers made by environment-friendly materials. In this work, we report on a technique to produce a system composed by electrospun acetate ester of cellulose nanofibers (AEC-NFs) containing poly(ethylene oxide) – PEO (10% or 20% wt. - known to improve the mechanical properties of AEC-NFs), which presence originates a double-peaked diameter distribution centred around 120 nm and 600 nm. RL experiments were made with either Rhodamine 6G (Rh6G, 2 mM) or 40% wt. ZnO nanoprisms (NPs), that act as gain media. By varying the PEO amount in the AEC-NFs we investigate how the structures with smaller diameters act as scatterers for obtaining RL emission. Raman spectroscopy was performed in order to assure that PEO has been incorporated to the AEC-NFs in the desired amount.
关键词： poly(ethylene oxide),Rhodamine 6G,Random Lasers,ZnO nanoprisms,electrospun nanofibers
更新于2025-09-11 14:15:04