Picosecond gain-switched polymer fiber random lasers

Random lasers are a type of lasers that lack typical resonator structures,offering benefits such as easy integration,low cost,and low spatial coherence.These features make them popular for speckle-free imaging and random number generation.However,due to their high threshold and phase instability,the production of picosecond random lasers has still been a challenge.In this work,we have developed three dyes incorporating polymer optical fibers doped with various scattering nanoparticles to produce short-pulsed random fiber lasers.Notably,stable picosecond random laser emission lasting600 ps is observed at a low pump energy of 50μJ,indicating the gain-switching mechanism.Population inversion and gain undergo an abrupt surge as the intensity of the continuously pumped light nears the threshold level.When the intensity of the continuously pumped light reaches a specific value,the number of inversion populations in the“scattering cavity”surpasses the threshold rapidly.Simulation results based on a model that considers power-dependent gain saturation confirmed the above phenomenon.This research helps expand the understanding of the dynamics behind random medium-stimulated emission in random lasers and opens up possibilities for mode locking in these systems.

Temperature Sensitivity of Polymer Fiber Microlasers

There are many kinds of materials or methods used to make optical microcavities,and they have many different geometric structures.And electrospinning technique has become a very convenient and easy one to prepare polymer fiber.Based on this situation,PM597-doped polymer solution was prepared into high-performance fibers with different diameters by electrospinning technology in our work.In order to better study the temperature sensing of polymer fiber whispering gallery mode,we have placed it on two different substrates with gold and aluminum.A 532 nm pulsed laser beam was used to excite a single fiber in the radial direction,then the whispering gallery mode(WGM)laser was observed and the distribution of WGM was determined by theoretical calculations.The threshold of samples on aluminum substrate is 0.4μJ.In addition,it is found that the samples on aluminum substrate performed better in temperature sensing,and the value is 0.13 nm/℃.As a result,WGM polymer fiber microcavities on aluminum substrate made by electrospinning technology have very broad development prospects in biosensing,optical pump lasers and other applications.

Coherent Random Lasing Realized in Polymer Vesicles

We have demonstrated the realization of a coherent vesicle random lasing(VRL)from the dye doped azobenzene polymer vesicles self-assembled in the tetrahydrofuran-water system,which contains a double-walled structure:a hydrophilic and hydrophobic part.The effect of the dye and azobenzene polymer concentration on the threshold of random laser has been researched.The threshold of random laser decreases with an increase in the concentration of the pyrromethene 597(PM597)laser and azobenzene polymer.Moreover,the scattering of small size group vesicles is attributed to providing a loop to boost the coherent random laser through the Fourier transform analysis.Due to the vesicles having the similar structure with the cell,the generation of coherent random lasers from vesicles expand random lasers to the biomedicine filed.