Search

Random lasers are generated by multiple light scattering in disordered optically gain medium, which are fundamentally different from conventional lasers. Control of emission properties, especially emission wavelength for random lasers is still challenging due to absence of optical cavity. Although plasmonic random lasers exhibit well‐controlled properties, most of studies on plasmonic random lasers to date are still focused on scattering amplification by disorder metal nanoparticles. Here, a tunable random laser based on emitters of Nile red/poly‐methyl methacrylate (PMMA) coupled to plasmonic resonant nanocavities of silver nanorod arrays is presented. The plasmonic random laser has very strong and narrow emission peaks and a very low lasing threshold of 22.8 µJ, resulting from plasmon resonance energy transfer (PRET), the enhanced absorption, scattering, and excitation rates of Nile red/PMMA due to strong localized electric fields in the nanocavities, and enhanced multiple light scattering from the disorder–order hybrid silver nanorod arrays. Furthermore, the lasing wavelength can be tuned in a wide range from 623 to 654 nm by different order harmonic modes of the plasmonic resonant nanocavities. This work not only provides a new strategy to design tunable random lasers, but also opens up their potential applications in medicine and sensing. [ABSTRACT FROM AUTHOR]

Electrically tunable random laser action has been demonstrated in a cavity-free structure. The scattering structure was shaped by the treatment of AC, and a polymer network structure is introduced to fix it. The fluorescence of the laser dye is scattered internally and selectively amplified at the band-edge of the photonic crystal, due to the concentrate of the photonic density of state. As the electric field increased, the deformation of the polymer network causes the cholesteric liquid crystal pitch to form a gradient distribution, resulting in the widening of the bandgap, and the random laser wavelength changes accordingly. This random laser with a broad tuning range (∼100 nm) opens new possibilities for the design of highly efficient incoherent light source in a large area with a thickness of micron level. [ABSTRACT FROM AUTHOR]

• A tunable narrow linewidth fiber ring laser based on parity-time (PT) symmetric double rings and variable optical attenuator (VOA) is demonstrated. • By tuning the VOA, the single-longitudinal-mode oscillation can be achieved when the PT symmetric is broken. • The tunable laser can be tuned from 1525 nm to 1563 nm, and the linewidth of the laser is at the sub-kHz level in the whole tuning process. A tunable narrow linewidth fiber ring laser based on parity-time (PT) symmetric double rings and variable optical attenuator (VOA) is demonstrated. The laser is composed of a fiber loop mirror (FLM), which creates two coupled rings: the reflective ring and the transmissive ring. The loss of the transmissive ring can be controlled by tuning the VOA, which balances with the gain of the reflective ring. When the PT symmetry is broken, a single-longitudinal-mode (SLM) laser is realized. The laser can be tuned by an optical tunable filter (OTF), and the tuning range is 38 nm, spanning from 1525 nm to 1563 nm. In the whole tuning process, the linewidth of the laser is at the sub-kHz level, and the optical signal to noise ratios (OSNR) is over 53 dB. The fluctuation of wavelength and power are less than 0.02 nm and 0.52 dB in an hour, respectively. [ABSTRACT FROM AUTHOR]

We have demonstrated a low threshold and tunable flexible random laser (RL) in dye-doped poly ethylene glycol diacrylate (PEG-DA) hydrogel, which was prepared by crosslinking polymerization using PEG-DA monomer and photoinitiator. The random lasering is attributed to the light scattering from the porous structure of hydrogels, and the wavelength of random lasing can be tuned by ~3.2 nm in the temperature range from 30 °C to 70 °C. Under the continuous increasing and decreasing temperature cycle, the random lasing tunable phenomenon can still be observed, which proves that this flexible material can be used as a new temperature sensor. In addition, we also explored the application of flexible laser in phototherapy. Considering the good elasticity and transparency of hydrogels, this thermo-responsive property will be of great significance to the biomedical applications of flexible material. • Lower threshold and cost than other lasers. • A good ability of temperature control emission wavelength. • Broad prospect of phototherapy based on flexible and biocompatible materials. [ABSTRACT FROM AUTHOR]