Study Of Organic Distributed Feedback Lasers

Since the first laser was invented in1960, laser’s technology has been developedgreatly. The laser satisfies various requirements of other industries and it plays animportant role in the information technology. Today, the applications of laser havepermeated our daily life. However the lasers we used are all founded on the inorganicmaterials which have stable property. Their basic theories and processing technologiesare very mature. But the metallic elements of inorganic materials are harmful toenvironment, and some of them are scarce resources. As a new area of research,organic light-emitting materials have developed rapidly recently. Just like inorganicmaterials, organic light-emitting materials blend in our life gradually.Organic semiconductor laser has been hotspot in the area of laser. In fact theresearch history of organic laser is almost as long as lasers. It experienced three stages:dye solution laser, dye doped solid laser and polymer laser. People have realized laseremission from organic semiconductor under optical pump. In term of application, thelaser under optical pump could not be commercialized. How to realize laser underelectrical pump is still a problem.Our research selects distributed feedback(DFB) structure as the resonator.Compared with other structures, DFB has been demonstrated that it could decreasethreshold of laser easier, and it has mode selective function. We fabricate gratings ofSU8on the glass substrates by dual beam interference. As a kind of negativephotoresist, SU8has table physical property, so it could be used in a long time. Wechoose2,5,2’,5’-tetrakis(2,2-diphenylvinyl)biphenyl (TDPVBi) as gain medium.TDPVBi is a kind of small molecular materials which has high luminous efficiencyand good quality of film. We evaporate the TDPVBi onto DFB structures and pump itwith pulse laser whose wavelength is355nm, andthen observe the spectra fromedge-emission. We fabricate gratings with different periodsand evaporate differentfilm thickness of TDPVBi onto the gratings. By optimizing the grating period andfilm thickness, we realize laser based on SU8gratings. It should be a kind of DFB laser based on special leaky mode which could also be called cutoff mode. This modehas advantage of low optical loss, and the DFB resonator plays the role of modeselection.Compared with etching gratings on Si substrates, our DFB laser could be simplyprocessed. And threshold of DFB laser still have possibility of decrease benefitingfrom the low optical loss in cutoff mode. This presents a new idea for realizingelectrically pump laser.