曲率調控羅丹明6G與氧化鋅奈米柱同調隨機雷射系統之閥值研究

Abstract

本論文使用水熱法成長氧化鋅奈米柱陣列，並整合羅丹明6G(Rhodamin 6G)增益介質，透過短脈衝雷射激發來產生隨機雷射(random laser)。藉由無序氧化鋅奈米柱陣列散射，R6G出射光子其輻射強度隨著外加脈衝雷射激發能量的改變，主要可分成三種不同光子輻射區間，分別為自發輻射(spontaneous emission)、放大自發輻射(amplified spontaneous emission, ASE)及具同調性(coherent)的隨機雷射輻射。此外，產生隨機雷射的臨界激發閥值，與氧化鋅奈米柱陣列的外在表徵有強關聯性。我們進一步地將氧化鋅奈米柱陣列生長在可撓曲之軟性基板; 藉由改變基板之彎曲曲率，有效地改變R6G出射光子與氧化鋅奈米柱陣列間的碰撞平均自由路徑(mean free path, MFP)，進而調控該隨機雷射系統的臨界激發閥值。我們相信該新穎閥值可調控式隨機雷射，在建築上或管線監控中，將有很大的產業利用性，也將近一步地擴充無序隨機散射雷射的相關應用。

We have demonstrated a random laser that can be brought above and below the threshold for different lasing emissions by simple changes in the curvature of flexible PI substrate underneath, and that creates a lasing emission with curvature-controllable optical spectra. In this study, the ZnO nanorods synthesized by the hydrothermal method was randomly distributed on the flexible PI substrate to serve as optical scattering centers, and the gain material of rhodamin 6G (R6G) was then spin-coated to cover the entire ZnO nanorods. Consequently, by bending different curvatures on the flexible PI substrate to select an appropriate mean-free-path (MFP) for the emitted photons interacting with the ZnO nanorods, the tunable random laser can be designed and shows different spectralbehaviors. This laser may find specific applications, for example a remote sensor to monitor the deformation of pipes within the buildings, and explore the functionality of disorder based photonic devices.