Study On Liquid Crystal Laser Based On SU8 Grating

The dye-doped cholesteric liquid crystal laser is used as a micro-lens-free laser system,the laser dye is used as the gain medium,and the cholesteric liquid crystal spiral structure is used as the resonator cavity to provide feedback amplification.It has the advantages of small size,low cost,low threshold and high sensitivity.Due to the unique optical properties of liquid crystal,it can be controlled by the external environment to achieve wavelength tuning of radiation laser,which makes its application in integrated optics,optical sensing,photochemistry and other fields more broad.In this paper,a cholesteric liquid crystal laser based on SU-8 grating structure,a finger texture cholesteric liquid crystal laser and a finger texture cholesteric liquid crystal laser based on SU-8 grating structure are designed and fabricated.The laser radiation characteristics of the cell are studied from both theoretical and experimental results,carried out a thorough analysis.The high resolution grating structure with precise size was formed on the treated ITO substrate by using the optical mask method,and the SU-8 grating liquid crystal laser with a thickness of 15 ?m was prepared by using the photoresist layer as the supporting material.The grating structure and cell texture were characterized.The laser radiation characteristics of the cell side and front at room temperature and isotropic temperature were studied.The results show that the multiple scattering between liquid crystal molecules and Bragg reflection in SU-8 grating are feedback amplified by introducing SU-8 grating into liquid crystal devices,and the two mechanisms are complementary.At room temperature,both the front and side of the cell achieve random laser output,and at isotropic temperature,the side of the cell still has laser output.A finger-textured cholesteric liquid crystal cell was designed and fabricated.The fingerprint texture of cholesteric liquid crystal was realized in the cell by the coupling effect of electric field and substrate surface orientation.The variation of the texture state with voltage was characterized by polarizing microscope and grating diffraction effect experiment.The side laser radiation spectrum of the cell was measured and analyzed.The results show that the wavelength of the radiation laser shifts red first and then blue with the increase of voltage.According to the plane waveguide principle and the Bragg reflection mechanism,the laser radiation mechanism is analyzed in depth.The fingerprint texture of cholesteric liquid crystal was constructed in SU-8grating to study the side radiation laser performance of the device.Continuously applied 10 V alternating voltage,the cell side achieves random laser radiation in the range of 575-595 nm.And SU-8 grating has volume anchoring effect on fingerprint texture.After the electric field is removed,fingerprint texture can still be observed in the cell at a short time.