Markedly Improved Performance of Optically Pumped Organic Lasers with Two-Dimensional Distributed-Feedback Gratings
Markedly Improved Performance of Optically Pumped Organic Lasers with Two-Dimensional Distributed-Feedback Gratings
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DOI：
10.1021/acsphotonics.0c01728
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发表时间：
2021-03-11
期刊：
影响因子：
7
通讯作者：
Adachi, Chihaya
中科院分区：
文献类型：
--
作者：
Senevirathne, Chathuranganie A. M.;Sandanayaka, Atula S. D.;Adachi, Chihaya
连续波（CW）激光在有机激光染料中仍然难以实现，原因之一是强烈的光激发引起的热降解。激光阈值的降低抑制了热降解，因此有机激光染料可以产生持久的激光。在这里，我们表明，通过将有机激光染料 4,4-双[(N-咔唑)苯乙烯基]联苯（其激光发射和激发态三重态吸收之间的光谱重叠很小）与二维（2D）分布反馈（DFB）光栅相结合，可以降低激光阈值。我们使用二阶二维十字双晶格和方晶格 DFB 光栅，在两个正交方向提供光反馈，以及二阶和混合阶圆形 DFB 光栅，在径向提供光反馈。在这些光栅结构中，混合阶圆形DFB光栅结构由于具有良好的光反馈，在短脉冲光激发下具有接近0.015μJ cm(-2)的最低激光阈值。此外，当具有该光栅结构的激光器在1 s、重复频率0.01 Hz的长脉冲光激发下工作时，获得了10 W cm(-2)的低平均功率阈值(峰值功率阈值1 kW cm-2)。此外，使用混合阶圆形 DFB 光栅结构提高了 CW 光激发下的激光稳定性，因为光学谐振腔中激子寿命较短，抑制了化学分解。这些结果证明了选择光学谐振腔结构对于提高有机激光器性能的重要性。
Continuous-wave (CW) lasing is still difficult to realize in organic laser dyes, one reason being the thermal degradation caused by intense photoexcitation. A decrease in laser threshold suppresses the thermal degradation and, therefore, leads to long-lasting lasing from organic laser dyes. Here, we show that it is possible to decrease the laser thresholds by combining the organic laser dye 4,4-bis[(N-carbazole)styryl]biphenyl, which has a small spectral overlap between the laser emission and the excited-state triplet absorption, with two-dimensional (2D) distributed-feedback (DFB) gratings. We used second-order 2D cross double and square lattice DFB gratings, which offer light feedback in two orthogonal directions, and second-order and mixed-order circular DFB gratings, which offer light feedback in radial directions. Among these grating structures, the mixed-order circular DFB grating structure led to the lowest lasing threshold of similar to 0.015 mu J cm(-2) under short-pulse photoexcitation because of the excellent optical feedback. Moreover, a low average-power threshold of 10 W cm(-2) (a peak-power threshold of 1 kW cm-2) was obtained when laser devices with this grating structure were operated under 1 s of long-pulse photoexcitation with a repetition rate of 0.01 Hz. Additionally, using the mixed-order circular DFB grating structure improved the laser stability under CW photoexcitation since shorter exciton lifetimes in the optical resonator suppress the chemical decomposition. These results demonstrate the importance of choosing an optical resonator structure for improving organic laser performance.