Research On Femtosecond Laser Fabrication And Optical Characteristic Of Perovskite Microcavity

As a carrier of information,photons have many advantages,such as extremely fast speed and huge capacity.However,due to the diffraction limit of light,the miniaturization and integration of photonic devices are faced with dual pressures on mechanism and technology.As a typical representative of micro-optical devices,optical microcavities can greatly enhance the interaction between light and material by confining light in a small volume.Optical microcavities have broad application prospects,not only in the field of optical communications,but also in full-color displays,sensing,optical encryption and other frontier fields.The researches on the microcavity are still at the experimental stage up to now.First of all,there are many problems that limit its development greatly,such as large optical loss,high pump threshold and so on.Therefore,finding a new gain medium with high gain and low loss to replace traditional semiconductors is a key solution to carry out.Secondly,in order to realize the integrated development of photonic devices,it is urgent to find a method of preparing microcavities with high precision,high repeatability,large area production,and high stability.Finally,in-depth study of the regulation and mechanism of microcavity on light is an indispensable step for photonic devices’development.It is expected to provide theoretical support for the development of information processing about integrated photonic devices.As a new type of semiconductor material,perovskite not only has excellent photoelectric properties but also is a gain medium with very promising future.At present,most of the perovskite microcavities are prepared by solution self-assembly,which is easily affected by the external environment and lacks repeatability and controllability.Femtosecond laser technology is an important preparation method for micro-optical devices which has the characteristics of simple operation,one-time molding,low damage and non-contact processing.For this reason,we use FAPb I₃ perovskite material as the gain medium,and femtosecond laser direct writing technology as the preparation method to build the microcavity.Starting from the preparation of perovskite materials and the design of the microcavity,the coupling process and optical effects of perovskite microcavities with different structures have been systematically studied.Finally,a low threshold,high quality factor perovskite micro-laser emission and ultra-high optical enhancement effect are realized,which provides theoretical guidance and experimental verification for the further development of perovskite microcavities.Firstly,the FAPb I₃ perovskite material prepared by the dual-source co-evaporation method is used as the gain medium for microcavity.The perovskite films prepared by the this method have many advantages,such as high coverage,high repeatability,low surface roughness,high uniformity and crystallinity.Secondly,we used femtosecond laser direct writing technology to prepare the FAPb I₃ perovskite microcavity.By adjusting the processing parameters and path of femtosecond laser,perovskite microcavities are processed different shapes and sizes.Such as disc-shaped microcavity,polygonal microcavity,and serrated grating structure microcavity.The method of preparing perovskite microcavities has low damage,high precision and high repeatability.At last,by building a micro-area photoluminescence system,the influence of FAPb I₃ microcavity on the optical characteristics were studied,such as the thickness and size in microdisk,the number of polygon sides and size in polygonal microcavities,the depth and period in grating.This research has realized the control of optical characteristics such as the mode number,mode spacing,laser threshold,quality factor in perovskite micro-laser and photoluminescence intensity in perovskite microstructures.It is found that the performance of WGM microcavity laser（i.e.,laser threshold,mode spacing and mode number）is highly dependent on the microdisks’diameter,and the thickness of the microdisk has no significant effect on it.The thicknesses FAPb I₃ perovskite films will cause a slight shift in the laser emission spectrum and affect the quality of the film（that is,carrier lifetime）.As the number of polygonal sides increases,the laser threshold and full width at half maxima of laser mode are decrease.Perovskite grating has obvious multifold emission enhancement effect.As the depth of the grating increases,the PL intensity first increases and then decreases and as the period increases,the PL intensity decreases.