Zhai Tianrui

Microscopic Investigation into the Optically Pumped Polymer Lasers Based on Distributed Feedback

Polymeric semiconductors spin-coated onto the photoresist grating form discontinuously distributed flocci, which do not fill grating grooves with nanoscale widths. Thus, the polymer layer neither forms a continuous gain channel nor creates a waveguide that enhances the distributed feedback (DFB) mechanism provided by the grating structures. This is verified by the microscopic and spectroscopic investigations on the topographic surface of the polymer-covered grating as it is etched layer by layer using oxygen plasma. This gives more insights into the mechanisms involved in optically pumped polymer lasers and provides new guidance for constructing DFB lasers.

Band Compression of Plasmonic Filters

We demonstrate theoretically and experimentally the difference between the band compression mechanisms of plasmonic gratings and plasmonic heterogratings. The plasmonic grating can pick out a fixed polarization bandwidth with changing the incidence angle, while the plasmonic heterograting composed of two different nanogratings can pick out a tunable bandwidth with changing the incidence angle and the period ratio of two gratings. The range of the plasmonic resonances of the heterograting is about 30% wider than that of a conventional grating. Thus, the plasmonic heterograting can work efficiently in a wider wavelength range. Moreover, high polarization extinction ratio is achieved in these plasmonic devices. This gives more insights into the mechanisms in plasmonic filters and is helpful to promote the actual applications.

Doping Defects in Two-Dimensional Holographic Photonic Crystals Using a Continuous-Wave Visible Laser

It is demonstrated that defects of any shape or size can be doped in holographic photonic crystals using a cw visible laser and spherical/cylindrical lens. Defects with different sizes at any depth in the material can be obtained by controlling the position of the focal point of the lens and exposure value. We facilitate the implementation of sub-wavelength arbitrary point or line defects in large-size 2D holographic photonic crystals.

Wavelength Variation of a Random Laser with Concentration of a Gain Material

The wavelength variation of a laser-dye-type random laser is observed experimentally. It is found that the emitting wavelength of a random laser changes with the change of concentration of the gain material. Also, the actual radiation wavelength is influenced by the pumping rate of the source, the cavity competition and the concentration of scatterers.