Multi-Wavelength Coherent Random Laser In Bio-Microfibers And Imaging

Biological materials with the special features such as biological affinity,oxygen permeability and hydrophilicity,have attracted more and more attention in recent years.Some optical devices based on bio-materials have been made by some talent researches.Bio-fibers composed by nature silk are interesting research materials among them.In this thesis,we studied the electrospinning bio-fibers made of silk protein,aiming to find out their advantages in random lasers as the gain medium and the diffusion modes of the light in this structure.Tunable random lasers were obtained by changing the pumping position,the performance of the random lasers and its applications in imaging of the coherent muti-wavelength random lasers were investigated.The research contents and results are given below:The electrospinning bio-fibers mixed with laser dye-Rh6 G was fabricated.After mixed with Rh6 G,the bombyx mori silk was reconstructed by electrospinning technology.Moreover,the morphology features of the electrospinning bio-fibers were observed by optical microscope and SEM.We got an approximate refractive index of the silk protein sample because it is not elementary substance.The properties of the random lasers of the bio-fibers were studied.The coherent muti-wavelength random lasers at the visible wavelengths were detected by pumping laser at 532 nm.The lasing spectra of the bio-fibers were collected for different time intervals,it is found the stability of random lasers is good since it has a feasible fluctuation.The life of the bio-fiber random lasers is about 300 s,and it has a very low threshold at about 2.86 ?J.The emissioin spectra were collected at different polarization angles,which indicate the polarization degree of them is 0.41.Further more,the transmission mode of the pumping light and random laser were studied,the pumping light with a localization state propagates in the electrospinning silk protein,while the mode is diffusive when the random laser propagates through the bio-fibers.The applications in multi-wavelength random lasers and imaging were studied in this thesis.The wavelength of the random laser in the electrospinning of silk protein can be tuned by changing the pumping position for the electrospinning of silk protein because of the complex electrospinning structure.The tunable wavelength is in the range from 555 nm to 590 nm.Additionally,we studied the thresholds of random lasers at different wavelength and all of them were very low.When the random lasers were used as illumination source of speckle-free imaging and non-invasive imaging,there was no interferometric fringe due to the very low spatial coherence of random laser.C(Speckle contrast)was introduced to analysis the ability of speckle-free imaging.The multi-wavelength random lasers have a very low number of C at 0.02.As a result,information of object from speckle imaging was achieved.