| Summary: | 碩士 === 國立臺北科技大學 === 光電工程系研究所 === 101 === In comparing with traditional laser, random lasers produced by dye doped liquid can be a mirrorless lasing. To investigate the influence of the alignment of scattering material on random laser behavior, dye doped liquid crystals are injected into three different kinds of glass cells, including the rubbing polyimide on two and one plate and without any rubbing on each plate to produce the ordering, disordering and completely disordering alignment of liquid crystal. Comparing with emission spectrum linewidth of three types of cell, the disordering alignment dye-doped liquid crystal (DOA-DDLC) shows the narrowest linewidth and the completely disordering alignment dye-doped liquid crystal (CDOA-DDLC) reveals the broadened linewdith. For the ordering alignment dye doped LC (OA-DDLC), the multiple emission peaks measured from optical spectrum will shift obviously as we horizontally rotate the LC cell. Besides, the output intensity of lasing beam depends on the angle of the pump polarization relative to the director of LC molecular for the OA-DDLC. Maximum output intensity is obtained as input polarization perpendicular to the director of LC and minimum output intensity is obtained as input polarization parallel to the director of LC. For the CDOA-DDLC cell, the value of output intensity does not change apparently as we rotate the input polarization. Besides, the output beams from OA-DDLCs are linear polarized lights whose electric field is parallel to the director of NLC, but the output beam for the CDOA-DDLC is unpolarized light. For the DOA-DDLC, the output beam is near polarized light as pump beam is incident on the un-rubbing polyimide plate. While the pump beam is incident on the rubbing polyimide plate, the polarization of output beam is different at different location due to alignment of assembled LCs.
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