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Dye-doped polymer laser in self-formed waveguide with highly efficient Fabry-Perot cavity

Dye-doped polymer laser in self-formed waveguide with highly efficient Fabry-Perot cavity. K. Yamashita , M. Ito, S. Sugimoto, T. Morishita, and K. Oe Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan. Outline. Background Motivation

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Dye-doped polymer laser in self-formed waveguide with highly efficient Fabry-Perot cavity

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  1. Dye-doped polymer laser in self-formed waveguide with highly efficient Fabry-Perot cavity K. Yamashita, M. Ito, S. Sugimoto, T. Morishita, and K. Oe Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan

  2. Outline • Background • Motivation • Laser device fabricated withSelf-Written Active Waveguide technique • Unique process of fabrication • Advantageous structure for integration • Lasing characteristics • Summary

  3. Background • Laser devices based on organic materials • Materials: p-conjugated polymer and low molecules, Polymer doped with dyes and RE complexes, etc • Cavity: FP, DFB, VCSEL, etc • Advantages: Various operation wavelength, Versatility of substrates, Simple process for fabrication • Future Applications: Short range communication, Biosensor, Gas sensor, Compact projection • Key issue for the practical application:Technologies of downsizing and integration with other optical components

  4. Motivation • Features required for the organic laser as integrated light source • In-line waveguide with isotropic channel structure • Ease in optical coupling with external waveguides • Resonant cavity with a high Q value • Simplicity in fabrication Our approach, • Self-written active (SWA) waveguide technique High-reflection mirrors

  5. Mechanism of SWA waveguide Photo-polymerized resin doped with active medium • Channel waveguide with active function • Essentially coupled with external waveguides Putting photopolymer resin doped with active medium between waveguides (or fibers). Introducing laser light for photo-polymerization. Self-focusing of the laser light due to increase in the refractive index. Formation of polymeric waveguide doped with active medium. Waveguide or fiber ~ mm Laser light irradiation SWA waveguide

  6. Organic compounds O O H2C CH2 O O O CH2 O OH CH2 O Exposure Emission Normalized intensity(a.u.) Absorbance 400 500 600 700 800 wavelength (nm) • Precursors for polymer matrix:Pentaerythritol triacrylate (PETA)and Benzyl acrylate (BA) • Photoinitiator: Irgacure 184 and 859 • PETA : BA = 9 : 1 (in volume) • Active medium: Styryl 11 • Concentration = 0.1 – 0.6 wt% PETA n = 1.483 BA n = 1.513 Styryl 11

  7. Fabrication of SWA waveguide 405-nm cw laser light Photopolymer+Styryl 11 Fiber <0.1 sec Silica microcapillary 0.3 sec Optical fiber (GI-type core,50 mm-f) 0.7 sec 700 mm 1.0 sec

  8. Property of optical amplification Pumping pulse Output pulse SWA waveguide Input pulse Dye concentration = 0.3 wt% Pumping density = 2.5 mJ/cm2 Output ASE ~12 dB / mm Input x 10 [Jpn. J. Appl. Phys. 48, 102406 (2009)]

  9. SWA waveguide with FP cavity DTF mirrors Laser light irradiation • Fabrication of SWA waveguide as passing through a pair of dielectric thin film (DTF) mirrors. • Transmission of the DTF mirror(Silica plate with SiO2/TiO2 multilayer) • Formation of SWA waveguide with a high-Q FP cavity. Exposure Emission SWA waveguide with FP cavity

  10. Lasing of SWA-FP device Without cavity Cavity length = 1.14 mm Dye concentration = 0.3 wt% With FP cavity Threshold for lasing

  11. Lasing threshold cf. R ~ 0.2(Al-coated mirrors cavity) With FP cavity [IEEE J. Lightwave Tech. 27, 4570 (2009)] High Q effect Dye concentration = 0.3 wt% R > 0.99(DTF mirrors cavity) Dye concentration = 0.6 wt% • Drastically decreased threshold by using DTF mirrors

  12. Optical end pump Cavity length = 1.24 mm Dye concentration = 0.1 wt% Pump wavelength = 610 nm End pump 140 nJ 395 nJ Side pump

  13. Behavior of lasing threshold Cavity length = 1.24 mm Dye concentration = 0.1 wt% End pump Cavity length = 1.01 mm Local minimum showing effective absorption Cavity length = 0.72 mm ~45 nJ Best result of this study: Lasing at ~45-nJ pumping(For waveguide-type organic laser with a diameter of ~60 mm and a length of ~0.7 mm)

  14. Summary • Laser device based on the organic materials fabricated with self-written active waveguide technique • Channel waveguide structure with cylindrical profile • Essential coupling with waveguide ports • Ease in fabrication of FP cavity • Verification for impact of high-Q cavity on FP lasing • Effective optical pump at end-pump configuration • Lasing by 45-nJ pumping • SWA waveguide technique has a promise as fabrication method of light sources for integration. Multicolor laser Single wavelength laser

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