Random lasers in dye-doped polymer-dispersed liquid crystals containing silver nanoparticles
Introduction
Random lasers have attracted considerable attention over the last decade due to their interesting physics and potential applications in photonics and bio-medicine [1], [2], [3], [4], [5]. Many of the passive or active disordered materials, such as ZnO powders [2], polymers [6], dye-doped liquid crystals (DDLCs) [7], [8], [9], [10], [11], [12], and dye-doped polymer-dispersed LCs (DDPDLCs) [13], [14], can be employed to generate random lasing. In recent years, metal nanostructures have been realized to significantly enhance the spontaneous emission rate of semiconductor quantum wells [15], rare-earth ions [16], and laser dyes [17] because of the interaction between emission centers and surface plasmons. Utilizing these advantages, some researchers reported random lasers mediated by metal nanoparticles with incoherent emissions [18], [19]. They observed narrowing of an emission spectrum and increasing in emission intensity, which are typical characteristics of incoherent random lasers. However, metal nanoparticles have received little attention as scatters in dye-doped liquid crystals or polymer-dispersed liquid crystals random laser. And scarcely have people conducted experiments on amplifying random media have been made by combining three kinds of materials (polymer-dispersed liquid crystals, metal nanoparticles and dye) which give rise to multiple scattering and optical gain. To address the above situation, we experimentally and theoretically discuss on random lasing with coherent feedback effect in dye-doped polymer-dispersed liquid crystals containing silver nanoparticles. In this paper, we have made an amplifying random medium containing Ag nanoparticles with a size ( in diameter) and nano-sized liquid crystal droplets and demonstrated that coherent random laser emissions around 625 nm can be attained in dye-doped polymer-dispersed liquid crystals with embedded nano-sized liquid crystal droplets and silver nanoparticles.
A single sharp emission peak, with full width at half maximum (FWHM) less than 0.2 nm, appears at a threshold pump energy, while further increase in the pump energy brings about multiple laser spikes. With the purpose of comparison, we have studied stimulated emission in a random laser based on dye-doped polymer-dispersed liquid crystal containing nano-sized liquid crystal droplets, similar to those of Ag nanoparticles-dispersed dye-doped polymer-dispersed liquid crystals containing nano-sized liquid crystal droplets, and found that the Ag nanoparticles-dispersed one has a lasing threshold lower than those of the nano-sized liquid crystal droplets-dispersed ones. We have clarified the importance of the presence of Ag nanoparticles for the observation of distinctive laser spikes from the contribution localized surface-plasmon resonance (LSPR) and multiple scattering of light. The comparison indicates that Ag nanoparticles are better scattering elements toward the design of random lasers with high intensity and low threshold, thereby expanding the study of random lasers.
Section snippets
Sample preparation and experimental setup
The dye-doped PDLC films were prepared by mixing a prepolymer and 0.1 ml ethanol solution () containing 10 times diluted silver nanoparticles (with a diameter 5 nm) and photo-polymerized by an Q-switched, and frequency doubled 532 nm Nd: YAG (yttrium aluminum garnet) pulsed laser operating at 532 nm. The prepolymer consists of 44.41 wt% of monomer, trimethylolpropane triacrylate, 7.64 wt% of cross-linking monomer, N-vinylpyrrollidone, 0.54 wt% of photo-initiator, rose bengal, 1.02 wt% of
Results and discussion
For scanning electron microscopy (SEM) measurement, one side ITO glass of the test samples was removed so that the random distribution of LC droplets and Ag nanoparticles can be gauged by scanning electron microscopy (SEM). Fig. 2 shows the SEM image of the dye-doped PDLC film containing nano-sized liquid crystals and Ag nanoparticles. Fig. 3 depicts the evolution of emission spectra from the dye-doped PDLC containing nano-sized liquid crystal droplets without Ag nanoparticles with various
Summary
In conclusion, we have demonstrated, for the first time, random laser action with coherent feedback in an optically pumped dye-doped polymer-dispersed liquid crystals containing nano-sized liquid crystal droplets and silver nanoparticles. The lasing action is attributed to the coherent feedback due to multiple scattering of nano-sized liquid crystal droplets and field enhancement around the Ag nanoparticles. We found that the pump threshold was lowered and the emission intensity was enhanced by
References (23)
- et al.
Nature
(1994) - et al.
Phys. Rev. Lett.
(1999) Nature
(2000)- et al.
Phys. Rev. Lett.
(2002) - et al.
Appl. Phys. Lett.
(2004) - et al.
Phys. Rev. B
(1999) - et al.
Phys. Rev. B
(2001) - et al.
Appl. Phys. Lett.
(2005) - et al.
Opt. Express
(2006) - et al.
Opt. Lett.
(2007)
Opt. Lett.
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Advances in multicomponent systems: Liquid crystal/nanoparticles/polymer
2023, Materials Today PhysicsA coherence random lasing for gain media based on lnP/ZnS quantum dots
2022, Optics CommunicationsCitation Excerpt :It is worth putting forward that random lasers used in this paper, i.e., the lnP/ZnS quantum dots scattering mechanism [4–6] is able to create strong localization regime from random lasing. Random lasers were operated in either the solid materials [7] or liquid materials, such as semiconductor power (ZnO) [8], nanoparticles [9–11], polymers [12] and liquid crystals and so on [13–15]. Nonetheless, a research into liquid crystal random lasing [16] with lnP/ZnS quantum dots has not yet been reported [17–20].
Random lasers tuning by combining a dye-doped liquid crystal and CdS nanoparticles
2017, OptikCitation Excerpt :In order to achieve high Q factors in random lasers, material textures induced light scattering is essential, as a significantly reduced surface absorption results in low scattering losses of the devices. To date, the nanoparticles have been widely studied in organic gain media and proven to be an efficient scatterers suitable for direct integration in LCs host matrices [10–15]. More recently extensive work has been carried out towards using nematic liquid crystals as scatters for random lasers.
Analysis of morphological behaviour and electro-optical properties of silica nanoparticles doped polymer dispersed liquid crystal composites
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Random lasing from PM597-DCM solutions containing Pt nanoparticles
2016, Optics CommunicationsCitation Excerpt :The first experimental evidences of this phenomenon date back to 1993–1994, while later outstanding research in this field was carried out by Lagendijk [10,11], Wiersma [3] and Cao [11]. Liquid laser dye with scatterers (Ag nanoparticles) and surrounding environment which is a complicated system have been discussed in [15–17]. However, little attention is paid to the random lasing from PM597-DCM solution with Pt NPs in devices, so it is worthwhile to conduct such an experimental study about that.