Research On The Tunable Distributed Feedback Dye Laser

Unlike traditional solid-state dye laser, Distributed Feedback (DFB) dye laser hasno mirrors which are used to supply resonant feedback. In DFB laser, the feedback isdistributed in the medium. So DFB laser have many advantages, such as little capacity,easy to integrate, tunable output and narrow linewidth output. So DFB dye laser has avariety of important applications in many areas, such as optical information technology,optical device and medical science.For the research on gain DFB laser, in former experiments, researchers pay moreattention to obtaining wider tunable output. They have no interest in discover whether itis liquid crystal which makes contribution to tunable output.In this paper, the authorproposed a contrast test which contains two laser medium, dye doped liquid crystal anddye doped ethyl alcohol. This research method has not been sported all over the world.In the experiments, a second-harmonic light of a Q-switched Nd:YAG laser wasused to coherent pump these two kinds of samples, the linewidth of laser is less than0.2nm. When the applied voltages changed, the tunable ASE is obtained in dye dopedliquid crystal experiment. The tuning ranges are9nm. In contrast, there is no tunablelaser in dye doped ethyl alcohol experiment. So the results showed that liquid crystal isthe key to obtain tunable laser.For the research on refractive index DFB laser, in the former experiments, thewidest tuning range is about10nm. This is because there is no theoretical mode indesign DFB laser, so the best parameters of grove structure can not be determined. Inthis paper, the author proposed the method of designing refractive index DFB laser. Thismethod can not be found home and aboard.In the theoretical calculation, through changing different duty cycle, period, depthand inclination, the relationship between these parameters and output laser was obtained.Then the grove structure was determined: depth is1μm, the period length is3μm, thelengths of convex and concave are both1.5μm. Meanwhile, in the simulation study, theauthor simulated different electric fields and introduced the gain curve, and thenobtained tunable output wavelength and narrow linewidth laser. At last, the authorcalculated the group velocity of the forbidden band edge, and then derived the gain oflaser at the band edge.