Plasmonics has brought revolutionary advances to laser science by enabling deeply subwavelength nanolasers through surface plasmon amplification. However, the impact of plasmonics on other promising laser systems has so far remained elusive. Here, we present a class of random lasers enabled by three-dimensional plasmonic nanorod metamaterials. While dense metallic nanostructures are usually detrimental to laser performance due to absorption losses, here the lasing threshold keeps decreasing as the volume fraction of metal is increased up to ∼0.07. This is ∼460 times higher than the optimal volume fraction reported thus far. The laser supports spatially confined lasing modes and allows for efficient modulation of spectral profiles by simply tuning the polarization of the pump light. Full-field speckle-free imaging at micron-scales has been achieved by using plasmonic random lasers as the illumination sources. Our findings show that plasmonic metamaterials hold potential to enable intriguing coherent optical sources.

We report on plasmon-enhanced random lasing in bio-compatible light emitting Hydroxypropyl Cellulose (HPC) nanofiber networks doped with gold nanoparticles. HPC nanofibers with a diameter of 260 ± 30 nm were synthesized by a one step, cost-effective and facile electrospinning technique from a solution-containing Rhodamine 6G and Au nanoparticles. Nanoparticles of controlled diameters from 10 nm to 80 nm were dispersed inside the nanofibers and optically characterized using photoluminescence, dark-field spectroscopy, and coherent backscattering measurements. Plasmon-enhanced random lasing was demonstrated with a lower threshold than that in dye-doped identical HPC networks without Au nanoparticles. These findings provide an effective approach for plasmon-enhanced random lasers based on a bio-compatible host matrix that is particularly attractive for biophotonic applications such as fluorescence sensing, optical tagging, and detection.

We demonstrate a VECSEL (vertical external cavity surface emitting laser) based degenerate source with an adjustable degree of spatial coherence that is electrically pumped, mechanically compact and supports continuous-wave emission. The laser operation can be switched between a large number of mutually incoherent spatial modes and few-mode operation at little power loss. This technology allows multimodality imaging, where low spatial coherence illumination is used for traditional high-speed video-microscopy and high spatial coherence illumination is used to extract dynamic information of flow processes. The initial demonstration is performed on imaging embryo heart function in Xenopus, which is an important animal model for human heart disease.Traditional single-mode lasers are characterized by their brightness, efficiency, and output directionality. These properties have enabled tremendous advances in imaging and sensing. However, to date, lasers have not been widely used as illumination sources for full-field imaging and display applications. This limitation exists because the high spatial coherence of existing lasers results in coherent artifacts such as speckle. In order to avoid coherent artifacts, sources with low spatial coherence typically are used. Unfortunately, traditional low spatial coherence sources such as incandescent lamps and light emitting diodes (LEDs) are not sufficiently bright for certain high-speed imaging or wide-area projection applications. One approach to overcoming the brightness limitations of traditional low spatial coherence sources is to use bright single-mode lasers in conjunction with various extracavity compounding methods to synthesize low spatial coherence light [1]. Although conceptually straightforward, these methods have not reached large deployment in imaging, sensing, and display. Moreover, several of these methods require multiple sequential image acquisitions or integration over a longer exposure time, thereby limiting their use in high-speed imaging. A new and promising approach for laser-based illumination focuses on intracavity design as opposed to extracavity compounding. Specifically, this designdriven approach develops laser cavities with large numbers of mutually-incoherent lasing modes (≈ 10 3 ). Consequently, the emission out of the cavity has low spatial coherence and thus mitigates or eliminates speckle artifacts. To this end, different types of laser have been developed for speckle-free imaging including dye-based random lasers [2], chaotic microcavity semiconductor lasers [3], broad-area vertical cavity surface emitting lasers (VC-SEL) [4][5][6], VCSEL arrays [7], and pulsed, solid-state degenerate (self-imaging cavity) lasers [8].In this paper we report our development of a degenerate laser with spatial coherence switching capability that is designed around a semiconductor gain element. This laser overcomes barriers presented by previous low spatial coherence lasers and demonstrates the unique potential of spatial coherence tuning for multimodal biomedi...

This Letter presents a polarimetric study of the emission of random lasers from organic dyes. Coherent lasing modes from samples with ethanol solvent showed a high degree of polarization and did not influence each other in polarization. The proper choice of a laser dye with asymmetric absorption momenta, a highly viscous solvent, and a linear pump polarization can cause the random lasing emission to be completely linearly polarized for all wavelengths within the amplification range.

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