Study of tunable random lasing in blue phase liquid crystals

Disordered platelet texture enables random lasing in liquid crystal blue phases, whose switchability and tunability of laser characteristics are reported in this letter. The lasing action can be switched between coherent type and incoherent type by the thermal hysteresis effect. The randomness of lasing wavelengths can be determined by the platelet size, which can be set by controlling the cooling rate. After the blue phase scattering system is polymer-stabilized, coherent random lasing may occur in both the blue phase with an extended temperature interval and the isotropic liquid state; also, the selected modes are constant from one pulse to another. Additionally, when the laser dye is sensitive to temperature, the excitation threshold and the emission spectrum may be altered by thermal control.

關鍵字

random lasing ； liquid crystal ； blue phase

並列摘要

本篇論文研究雷射染料摻雜藍相液晶之散亂晶體排列引致的隨機雷射現象，及其切換與調控性質。利用藍相液晶的熱遲滯效應，我們能夠將此元件輸出之隨機雷射切換在同調型和非同調型之間。另外，輸出波長之隨機程度亦可利用降溫速率控制藍相液晶的晶體大小達成調控。利用聚合物穩固效果，可以固定隨機雷射輸出之多波長，並且將雷射輸出之溫度範圍大幅擴展到較寬之藍相溫度區間及均勻相區間。最後，利用雷射染料放射頻譜隨溫度變化之特性，製作出可溫控輪出閾值及波長之隨機雷射元件。

並列關鍵字

隨機雷射；液晶；藍相

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