Narrow Linewidth Dye Laser Technology Research Based On Micro-periodic Structure

Distributed feedback (DFB) dye laser, which is a new kind of dye laser using adistributed feedback structure as periodic refractive index distribution while also as thelaser gain medium and resonator. This kind of laser has much advantage such ascompact structure, tuning method simple, tuning mode diverse, narrow pulse output andso on. In this paper, the author simulated the output characteristics of the distributedfeedback structure, basing on the mechanism of the distributed feedback structure，andusing finite difference time domain (FDTD) method. The author also fabricated thedye-doped distributed feedback structure actually.In this paper, the author discussed the mechanism of distributed feedback structureby solving the coupled-wave equations, and then obtain the laser threshold as well asoscillation frequency of the distributed feedback structure. In order to simulate theoutput characteristics of distributed feedback structure, the author brought inone-dimensional to three-dimensional finite-difference time-domain theoretical modeland considered PML boundary conditions at the same time. The author selectedappropriate software OptiFDTD to set up distributed feedback structure, and simulatedthe output characteristics of the distributed feedback structure.In the numerical simulation part of this paper, the author simulated the laser outputwith narrow linewidth and tunable characteristics in the case of short-period simulation,and gave the relationship between output laser wavelength and the effective refractiveindex of the media changes. Also took the situation where the medium does not containLC component into account. After the expansion of the modulation period, the authorsimulated the characteristics of the output laser under long-period situation. Thesimulation results showed that in long-period modulation, the output laser still meetnarrow linewidth and tunable characteristics, but the tuning range was limited. At last,the author considered the situation where the period structure had mutation inside,changing the boundary conditions and depth of periodic structure, and proved that thesesmall changes had an influence on the output characteristics of the microstructure.In the experimental part of this paper, the author prepared dye-doped holographic polymer-dispersed liquid crystals (HPDLC) with distributed feedback structure, andselect dye DCM and dye PM567incorporated into PDDA and DPHPA mixed in equalproportions as HPDLC monomer prepolymer matrix, stirred for12hours to get thedye-doped substrate. After getting the micro-period distributed feedback structure set upby dye-polymer and liquid crystal HPDLC, the period of microstructures were as longas10μm. The prepared microstructure was observed and made a scaling, and itsfluorescence spectrum, absorption spectrum and ASE spectrum were measured, whichmade advantage as broad fluorescence spectrum and strong absorption to the pumpinglight.