Multiphoton upconversion lasing in scattering gain media has attracted considerable attention in recent years. LAPONITE® is a scattering medium consisting of 2-D nano-discs that can be dispersed as a transparent solution in aqueous media and forms a gel at high concentration. In this paper, we demonstrate two-photon pumped upconversion regular lasing along forward and backward directions as well as random lasing along all other directions. The gain medium was a mixture of PRL-L5 dye solution in DMF with a water solution of LAPONITE® in which LAPONITE® nano-discs of 25–30 nm diameter may form large-size particles of several hundred nanometers due to electrostatic binding between the dye molecules and the LAPONITE® nano-discs, and therefore can produce more efficient scattering feedback for random lasing generation. Using 795 nm and 100 fs laser pulses as two-photon pump sources, we observed random lasing at around 500 nm, characterized by both spectral and temporal narrowing in all directions apart from the traditional (colinear forward/backward) lasing directions. The peak spectral intensity of random lasing is ∼3.4 times higher than the normal fluorescence emission, but 10⁵–10⁶ times lower than the traditional forward lasing. This study shows the feasibility of generating both traditional forward/backward and random lasing in a moderately scattering gain medium for applications in diverse fields such as remote sensing, optical communications, and upconversion imaging.

中文翻译：

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双光子在以 LAPONITE® 为散射中心的二唑染料纳米复合溶液中向前、向后和随机泵浦


近年来，散射增益介质中的多光子上转换激光引起了相当大的关注。LAPONITE® 是一种由 2-D 纳米圆盘组成的散射介质，可以作为透明溶液分散在水性介质中，并在高浓度下形成凝胶。在本文中，我们演示了沿向前和向后方向的双光子泵浦上转换规则激光以及沿所有其他方向的随机激光。增益介质是 DMF 中的 PRL-L5 染料溶液与 LAPONITE® 水溶液的混合物，其中直径为 25-30 nm 的 LAPONITE® 纳米圆盘由于染料分子与 LAPONITE® 纳米圆盘之间的静电结合而可能形成数百纳米的大尺寸颗粒，因此可以产生更有效的散射反馈用于随机激光的产生。使用 795 nm 和 100 fs 激光脉冲作为双光子泵浦源，我们在 500 nm 左右观察到随机激光，其特征是除了传统的（共线正/后）激光方向外，所有方向的光谱和时间都变窄。随机激光的峰值光谱强度比正常荧光发射高 ∼3.4 倍，但比传统前向激光低 10 5-10 ⁶ 倍。这项研究表明了在中等散射增益介质中产生传统前向/后向和随机激光的可行性，可用于遥感、光通信和上变频成像等不同领域的应用。