以卤化铅钙钛矿为增益介质的低阈值表面等离子体激光器研制

Surface plasmon polariton can localize light into the deep subwavelength region, providing an approach to realize ultra-small lasers. Surface plasmon lasers with traditional semiconductor structure as the gain medium have been extensively studied, but they still face the challenges of overcoming the ohmic loss and reducing the threshold. Lead halide perovskite is a new emerging organic-inorganic semiconductor material in recent years, with the advantages of long carrier life time and diffusion length, high photoluminescence yield, and so on. Up to date, lead halide perovskites in the form of nanowires, nanoplatelets, etc., have already been applied into microscopic lasers as the gain medium. However, such lasers are restricted by the diffraction limit. We propose to realize a low threshold laser with light spot size at deep-subwavelength scale by utilizing both the merits of lead halide perovskite and surface plasmon polaritons. In detail, we will construct a hybrid surface plasmon waveguide cavity by loading a hexagonal lead halide perovskite nanoplatelet on top of a silver/silica complicated substrate. Under illumination of pump light, the hybrid surface plasmon waveguide cavity can produce lasing by breaking through the diffraction limit. The prominent carrier properties of lead halide perovskite help overcome the ohmic losses of surface plasmons, ensuring high enough gain for lasing. The natural formed crystalline structure of perovskite can bring forward strong feedback in the cavity, favoring the reduction of the threshold. The experimental and theoretical outcomes of this project would contribute to the realization of ultra-small low-threshold lasers.

表面等离子体激元可以将光局域在深亚波长区域，是实现超小型激光的一条主要途径。以传统半导体结构为增益介质的表面等离子体激光被广泛研究，但它们在克服损耗及降低阈值方面存在挑战。卤化铅钙钛矿是近年来新兴的一种有机-无机复合半导体材料，具有长载流子寿命和扩散长度、高荧光产率等优点，可用作激光增益介质。目前，以卤化铅钙钛矿为增益介质的激光主要采用纳米线、纳米片等方案，受衍射极限限制。我们提出结合卤化铅钙钛矿与表面等离子体技术二者的优势，实现一种光斑尺寸在深亚波长的低阈值激光器。具体地，将六边形卤化铅钙钛矿纳米片加载于银/二氧化硅复合基底上方，构成一种混合型表面等离子体波导腔，在泵浦光照射下产生突破衍射极限的光激射。卤化铅钙钛矿优越的载流子特性足以克服欧姆损耗，为激光的产生提供足够的增益；其自然长成的高品质晶体结构能提供有效的腔反馈，从而实现低阈值激射。为低阈值超小型激光器的研发提供实验及理论依据。

表面等离子体激元可以将光局域在深亚波长区域，是实现超小型激光的一条主要途径。以传统半导体结构为增益介质的表面等离子体激光被广泛研究，但它们在克服损耗及降低阈值方面存在挑战。卤化铅钙钛矿是近年来新兴的一种有机-无机复合半导体材料，具有长载流子寿命和扩散长度、高荧光产率等优点，可用作激光增益介质。目前，以卤化铅钙钛矿为增益介质的激光主要采用纳米线、纳米片等方案，受衍射极限限制。本项目首先研究了采用化学气相沉积法制备钙钛矿纳米片时制备条件对钙钛矿纳米片形貌的影响，并成功制备出原子级平滑的钙钛矿纳米片（平均粗糙度2nm左右）。基于此纳米片我们成功实现了世界上阈值最低（18.7 uJ/cm2，品质因子高达2600）钙钛矿纳米片激光。我们研究了采用PDMS，PDMS结合压力胶带以及热释放胶带等方法转移钙钛矿纳米片并比较转移效果，发现热释放胶带转移方法转移效率较高。我们详细研究的表面形貌，压力大小，加热时间，加热温度等条件对钙钛矿纳米片转移的影响，成功实现了钙钛矿纳米片的有效转移。我们研究了采用PMMA，油酸，DBP等材料作为保护层来保护钙钛矿免受破坏的效果，最后成功制备出一种DBP保护膜可以实现对钙钛矿纳米片的有效保护，经过保护的钙钛矿纳米片可以稳定的输出激光长达1小时以上。我们研究了制备银膜的方法，通过银膜生长速度的控制，我们可以制备出原子级平滑的银膜。在上述工作的基础上，我们成功实现了钙钛矿，二氧化硅以及银膜表面等离子体激光，钙钛矿，PMMA以及银膜表面等离子体激光，并实现了纳米激光阈值的进一步降低（<18.7 uJ/cm2）。本项目的成功开展为集成光子学领域提供了一种具有成本低，性能高的全新光源。此外本项目所开发出来的钙钛矿材料以及表面等离子体也可用于光电探测，太阳能电池等领域。