Studies For The Distributed Feedback Dye Laser Based On Holographic Polymer Dispersed Liquid Crystals

The holographic polymer dispersed liquid crystal grating consists of distinct polymer-rich and liquid crystal-rich lamellae that give rise to a periodic refractive index profile。Holographic polymer dispersed liquid crystal (HPDLC) grating have obtained widespread attention since they were first reported by R. L. Sutherland et al. in1993. Through holography, HPDLC gratings are formed by exposuring the mixture of photosensitive monomers and liquid crystals in the hologram forms from the interference of two laser beams. Because of the diffraction efficiency of optical and dielectric anisotropy of liquid crystal, holographic polymer dispersed liquid crystal grating has a distinct advantage that they can be easily tuned electrically or thermally. So holographic polymer dispersed liquid crystal grating can be widely applied in fields such as filter, reflected holographic display, optical sensor system, zoom lens, optical data storage, photon crystal, and optical computer.The distributed feedback dye laser based on holographic polymer dispersed liquid crystal grating is a new laser that integrate the technology of holographic polymer dispersed liquid crystal grating and the distributed feedback dye laser.Because of the distinct advantage of the low threshold, narrow linewidth and the wavelength can easily tuned electrically or thermally, the distributed feedback dye laser based on holographic polymer dispersed liquid crystal grating have attracted more and more attention for a wide range of potential application from fiber-optic communication to the tunable laser.But, the distributed feedback dye laser based on holographic polymer dispersed liquid crystal grating also has many disadvantages, such as high threshold, broad linewidth and low output energy, which restrict its applications. In order to resolve the problems above, this paper has done the following research:Fistly, the energy level structure and the spectral characteristics of the laser dye is studied. And the working mechanism of the distributed feedback dye laser based on holographic polymer dispersed liquid crystal grating is also studied. And the distributed feedback dye laser based on holographic polymer dispersed liquid crystal grating is successfully prepared.Then, we adjust the temperature of the temple and measured the lasing spectra from the DCM-doped holographic polymer dispersed liquid crystal grating with the grating period of610nm。There is an obvious12.6nm-blueshift from625.8nm to613.2nm for the lasing wavelength with the temperature increased from20℃to140℃。For the distributed feedback dye laser based on holographic polymer dispersed liquid crystal grating, there are two factors mainly influence the properties of the laser. One is the dye and the concentration of dye, the other is the appearance of the grating. So this paper studys the influence of the concentration of dye, the size of the grating, the prepared temperature to improve the properties of the laser. Then, the linewidth is reduced to0.2nm, and the threshold is also reduced to1/21. The onversion efficiency is increased to1.2%,6times as before.In addition, a two-dimensional (2D) electrically-tunable diffraction grating is prepared through single-step exposure experimental setup. Then, a2D diffraction model of phase only grating is constructed and the diffraction equations are obtained based on three hypotheses. At last, the morphologies and electro-optical performance of the2D grating formed by single-step exposure are discussed combined with our theoretical results. All results gotten from2D diffraction model have a good agreement with the experimental data. And we prepares a kind of two-dimensional photonic crystal laser based on holographic polymer dispersed liquid crystals with a threshold energy of about22.7P J, and the full width at half maximum (FWHM) is only0.4nm, which is evidently lower than previously reported.