ABSTRACT
We have investigated the formation of in-bandgap delocalized modes due to random lattice disorder as determined from the longitudinal mode spacing in a distributed Bragg laser. We were able to measure the penetration depth, and from transfer matrix simulations, determine how the localization length is altered for disordered lattices. Transfer matrix simulations and studies of the ensemble average were able to connect the gap delocalized modes to localized modes outside of the gap as expected from consideration of Anderson localization, as well as identify the controlling parameters.
Subject(s)
Artifacts , Lasers , Models, Theoretical , Refractometry/instrumentation , Computer Simulation , Computer-Aided Design , Equipment Design , Equipment Failure Analysis , Light , Photons , Reproducibility of Results , Scattering, Radiation , Sensitivity and SpecificityABSTRACT
We have assembled and studied melt-processed all-polymer lasers comprising distributed Bragg reflectors that were fabricated in large sheets using a co-extrusion process and define the cavities for dye-doped compression-molded polymer gain core sheets. Distributed Bragg reflector (DBR) resonators consisting of 128 alternating poly(styrene) (PS) and poly(methyl methacrylate) (PMMA) layers were produced by multilayer co-extrusion. Gain media were fabricated by compression-molding thermoplastic host poly notmers doped with organic laser dyes. Both processing methods can be used in high-throughput roll-to-roll manufacturing. Optically pumped DBR lasers assembled from these components display single and multimode lasing in the reflection band of the resonators, with a slope efficiency of nearly 19% and lasing thresholds as low as 90microJ/cm(2). The lasing wavelength can be controlled via the layer thickness of the DBR resonator films, and variation of the laser dye. Studies of threshold and efficiency are in agreement with models for end-pumped lasers.
Subject(s)
Lasers , Optics and Photonics , Polymers/chemistry , Refractometry/instrumentation , Coloring Agents/chemistry , Equipment Design , Light , Materials Testing , Polymethyl Methacrylate/chemistry , Polystyrenes/chemistry , Refractometry/methods , Surface Properties , TransducersABSTRACT
Intense filaments of third harmonic generation have been observed in a variety of liquids when pumped by 1300 nm wavelength femtosecond light. The onset of third harmonic generation coincides with the threshold for self-focusing as deduced from n(2) measurements performed on the liquids using the z-scan technique. We have found self-phase modulation above the threshold leading to continuum generation at about 3 times threshold. In the third-harmonic regime, the third harmonic output power is independent of the input power. Our observations are consistent with those for similar processes in gases as described by a phase-locking model. The measured conversion efficiency was approximately 10(6).
