The Study Of Scale Effect And Resonant Model Based On Organic Fluorescent Microcrystals With Waveguide

Both the generation and transmission of laser are two significant aspects for optical communication.Attributed to the intense luminescence,tailor-made structure,multifunctional propagation,fluorescent materials in micro-or nano-scale have been widely applied in the field of integrated optical communication.Particularly,the organic crystals show great potentiality in building the optical components like resonance lasers,optical switches,and waveguide sensors,which have raised a huge amount of interests.With the modularization and integration of optical devices,the original materials of organic crystals need to be miniaturized as well.However,the influences caused by the size decreasing are still unknown.The improvements or modifications of the traditional theories are urgent to be studied.On the one hand,the decrease of sectional size would severely limit the volume of transverse electromagnetic mode,which would also make the optical loss coefficient to be unsteady before the size close to the minimum for waveguiding.The optical loss coefficient is the main parameter in the waveguide evaluation among the large-scale materials.But it may not be competent to that in micro-or nano-materials due to the scale effect.Herein,the first part of this project focused on the case study with the microfibers fabricated by coumarin derivative.By determining the optical loss coefficients of the microfibers with different sectional sizes,we found that the values of coefficients increased from 0.417 to 1.299 dBμm-1 with the size decreasing.The simulation based on the Finite-difference time-domain showed a similar trend of negative correlation,indicating the scale effect in waveguiding micromaterials.It is worth to note that the fitting of optical loss coefficient and sectional size demonstrated an exponential function,and the change rate approaches zero when the size is large enough.Although the optical loss coefficient is reasonable to represent the waveguide ability in large-scale materials,when evaluating that in micro-or nano-materials,the scale effect should not be neglected.On the other hand,current researches of resonance micro-laser rely on the theorical model of resonance cavity which is so ideal that the irregular side morphologies of crystal often be neglected.As is all known,microcrystals have several crystallographic planes and most of them are difficult to be smoothed by mechanical grinding.The existing models of resonance cavity exclude the nonstandard microcrystals from building micro-lasers.Herein,the second part of our research focused on the hexagonal microdisks fabricated by benzothiazole derivative,whose 153 ° protruding morphology crystal side was characterized by electron microscopies.The fluorescence spectra of hexagonal microdisks show the resonant peaks with intervals of 8.1 nm.Based on the optical path(21.87μm)calculated by interval difference,we deduced that the protruding side structure make the resonance light jolt up and down to form the cycle and emit the laser.When excited by pulse laser with high energy level,both the fluorescence emission and the resonance emission could be observed on the spectra Comparing with the fluorescence,the intensity of resonance was 231%but meanwhile its full width at half maximum was only 2.7%,indicating that the microdisk could emit the gained laser.As a result,we designed a modified model of hexagonal whispering-gallery-mode as the microdisk with protruding side,which provides the theorical support to the resonance micro-lasers built by irregular organic microcrystals.