1. Work performed
In 2017-2019, I carried out research on polymer fibre random lasers: (1) Developing a comprehensive nonlinear model to analyse random lasing emission mechanism; (2) Using dip coating technique, I fabricated POF. I prepared a dye-coated POF and studied the RL properties emitted by the POF at different receiving positions, coating thicknesses, and lengths based on the pump light radiation mode effect; (3) Proposing a new organic/inorganic hybrid laser dye to enhance lasing lifetime. In addition, I report the experimental evidence of the glassy behavior in a random laser with more complex energy level structure; (4) Demonstrating the new mechanism of “band gap + scattering” to control random lasing in the cholesteric liquid crystal (CLC). Dye-doped polymer-stabilized cholesteric liquid crystals (PSCLCs) with negative dielectric anisotropy were fabricated, and mirrorless lasing with an electrically tunable wavelength was successfully achieved.
2. Main results achieved so far
(1) To simplify the fabrication procedures and decrease the cost of polarizers, the ultraviolet (UV) inscribed 45°-TFBG has been fabricated as a polarizer in a standard commercial SMF that possesses significant advantages, e.g. low-cost, effective and all fiber system, over traditional polarizers. In principle, the TE light through such grating shows large transmission loss whereas the TM-light loss remains small due to Brewster’s Law. Therefore, the 45°-TFBGs have been applied in optical communications and fiber laser systems as a broadband polarizer. The result was published at Optics Express.
(2) Our work mainly focuses on the influence of the pump radiation mode on the characteristics of the RL emitted from the axial and radial directions in the gain POFs with different coating thicknesses under the 532-ns laser-end pump. The mixed solution was applied to the bare POF surface instead of the end face by dip-coating. There is a whispering gallery modes laser has been found in our experiment. Meanwhile, the dye-doped POF system pump exhibits good photo stability and self-healing properties. The results were published at Physica Scripta and Journal of Physics D: Applied Physics.
(3) The POSS groups suppress the photo-bleaching effect to improve the luminous stability in the organic/inorganic hybrid laser system. And the phase transition between a continuous wave paramagnetic regime (below threshold) and spin-glass regime (above threshold) representing RSB phenomenon has been observed. The results have been published in Annalen der Physik (Inside Cover) and Nanophotonics.
(4) Based on the “band gap and scattering” mechanism, the random lasing wavelength can be tuned at 80 nm in the CLC. Meanwhile, the broad tuning range (∼110 nm) of PSCLC lasers, coupled with their stable emission performance, continuous tunability, and easy fabrication, has been obtained in the PSCLC. The results have been published at Phtonics Resarch.
3. Overview of the results and their exploitation and dissemination
Through two years research, I have controlled the random lasing emission in the liquid crystal and extended the random lasers in the polymer optical systems. In addition, the statistical dynamics of random lasers has been researched. Supported by the Marie Curie research fellowship I have published 12 high-impact papers including Nanophotonics, Photonics Research, Optics Express, ACS Sensors, Annalen der Physik.
