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Organic Nonlinear Optical Devices and Integrated Optics

Organic Nonlinear Optical Devices and Integrated Optics. Outline. Directional Coupler Nonlinear Fabry-Perot Interferometer Frequency Converter Optical Limiter Integrated Optics Conclusions. Signal Switching I: Directional Coupler. Directional Coupler.

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Organic Nonlinear Optical Devices and Integrated Optics

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  1. Organic Nonlinear Optical Devices and Integrated Optics

  2. Outline • Directional Coupler • Nonlinear Fabry-Perot Interferometer • Frequency Converter • Optical Limiter • Integrated Optics • Conclusions

  3. Signal Switching I:Directional Coupler

  4. Directional Coupler • Interaction length and refractive index difference of the cores control the splitting ratio

  5. Fluorine doped polyimide • Fluorine content controls the refractive index of polyimide • Core and cladding layer can be made from the same polymer---polyimide.

  6. Fabrication • To make multi-layer patterned structure, only need: spin coating, photolithography and RIE mask

  7. Nonlinear directional coupler • Refractive index changes with light intensity • Splitting ratio changes with light intensity

  8. Material requirement • Low switching power: High n2 ,(2) • Fast switching: Low response time • Low propagation loss: Low absorption • High optical damage threshold • High thermal stability

  9. A candidate: DPOP-PPV • A side chain substituted PPV • Loss = 0.4 dB/cm at 920 nm • n2 = 1.1e-14 cm2/W • Imax > 16 GW/cm2 • Tg = 163C

  10. Experimental Result Waveguide 2 • Length = 1/3 beat length (0.67 cm) • Switching at 5.5 GW/cm2 Waveguide 1

  11. Advantages and applications Advantages: • All optical switching • Bar state splitting: 90/10 • Cross state splitting: 33/67 • Polymer: Easy processing Applications: • Beam splitter, Wavelength Add-Drop Multiplexer, Cross/Bar Switch

  12. Signal Switching II:Fabry-Perot Interferometer

  13. Nonlinear Fabry-Perot Device • A wavelength selective device • Wavelength of the output signal depends on refractive index of the middle medium Signal In Signal Out Pump Mirrors: Reflectivity > 95% Nonlinear medium

  14. Operation • Nonlinear middle medium: poly-1,6-dicarbazoly 1-2,4-hexadyne (DCHC) • Signal range: 700 - 900 nm • Pump range: 637 - 645 nm • Pump light changes the index of the middle medium and changes the wavelength selection at the output.

  15. Experimental Results

  16. Performance • Pump: 2 GW/cm2 at 641 nm for 0.8 ps • Turn on time: 0.33 ps • Recovery time: 3 ps • Can switch at 333 GHz • All optical switching • Very simple structure, easy processing

  17. Frequency Conversion:Second Harmonic Generation Device A waveguide-type with periodic structure

  18. Waveguide-type periodic structure • Waveguide-type: compact, easy coupling to fibre/laser • Periodic alternations of nonlinearities in the waveguide: enable phase-matching for light at  and 2. • Conversion:

  19. Periodic structure Linear material Nonlinear material

  20. Organic crystal + Semiconductor • Nonlinear material: mNA (organic crystal grown on the grating) • Linear material: SiN (grating)

  21. 5 mm 50 nm 3 m Performance • mNA: d33 = 20 pm/V • Period = 7 m • Length = 5 mm • Wavelength = 1.06 m • Conversion efficiency = 0.16% /W/cm2 (2) = 2*d33

  22. An all-polymer one • Nonlinear polymer: diazo-dye-substituted • Linear polymer: UV curable epoxy resin

  23. Fabrication Serial grafting technique: Photolithography RIE

  24. 5 mm 2 um 6 m Experimental Results • The nonlinear polymer: d33 = 15 pm/V (after poled at 35 MV/m at 140C) • Loss = 1.2 dB/cm • Period = 32 m • Wavelength = 1550 nm • Conversion efficiency = 0.5%/W/cm2

  25. Signal Processing:Optical Limiter

  26. Operation of Optical Limiter • Low fluence: Linear transmittance • High fluence: Clamped output level

  27. Reverse saturable absorption • Low intensity: Molecule is in low absorption state. Linear transmittance • High intensity: Molecule is in photoinduced absorbing state. The material becomes highly absorptive. • Candidate material: • Metallo-Phthalocyanines • Fullerenes

  28. Metallo-Phthalocyanines • Very weak ground state absorption • Strong excited state absorption

  29. Experimental Results C60 in toluene AlClPc in methanol • Length = 1 cm • Wavelength = 532 nm • Pulse width = 8 ns InClPc in toluene

  30. Fullerenes (Bucky balls) • All-carbon cluster • Abundance of C=C gives plenty delocalizeable electrons • C60, C70, C 76, ...

  31. Experimental Results • Solvent used plays an important role

  32. Linear + Nonlinear:Integrated Optics

  33. Advantages of polymer • Low loss: 0.1 dB/cm at 1550 nm • Controllable nonlinearities by doping/poling • Low cost: only need spin-coating, photolithography and RIE • Mechanical properties: rugged, flexible • Precise control of refractive index: conveniently done by doping • Convenient thickness control: spin-coating

  34. Example 1: All polymer waveguide and MZ • All polymer 3-D structures • Achieve multi-level interconnections

  35. Material • UV15LV: low loss polymer as waveguide • Polyurethane with tricyano chromophores: Active polymer with electro-optic coefficient = r33= 12 pm/V • Waveguide loss = 0.5 dB/cm

  36. Phase modulator • Upper level: EO modulator • Lower level: waveguide

  37. Example 2: Optical Transceiver

  38. Characteristics • Integrate polymer waveguide into semiconductor system • Use polymer for waveguide and splitter • Easy fabrication of polymer Y-branch structure

  39. Example 3: Laser array and beam combiner Laser array Polymer beam combiner

  40. Material Polymer waveguide The polymers are spin-coated on the laser-array-existing semiconductor substrate

  41. Features and applications • Loss < 1 dB/cm • Good polymer adhesion to the substrate • Applications: • Wavelength multiplexer/demultiplexer • MW-O-CDMA transmitter

  42. Conclusions Polymers are good for: • waveguide structure: low loss • EO or nonlinear operation: high and controllable nonlinearities • Multi-level structure (3D): result of easy processing Hybrid semiconductor/polymer structures or all polymer structures give rise to ample opportunities

  43. Reference 1 • Polymer Directional Coupler • J. Kobayashi et al., “Directional Couplers Using Fluorinated Polyimide Waveguides,” Journal of Lightwave Technology, Vol.16, No. 4, pp. 610-613, 1998. • T. Gabler et al., “Application of the polyconjugated main chain polymer DPOP-PPV for ultrafast all-optical switching in a nonlinear directional coupler,” Journal of Chemical Physics, Vol. 245, pp. 507-516, 1999. • Polymer Fabry-Perot Device • M. Bakarezos et al., “Ultrafast nonlinear refraction in an integrated Fabry-Perot etalon containing polydiacetylene,” Proc. CLEO ‘99, CWF12, pp. 258, 1999.

  44. Reference 2 • Polymer waveguide second harmonic generation devices • T. Suhara et al., “Optical Second-Harmonic Generation by Quasi-Phase Matching in Channel Waveguide Structure Using Organic Molecular Crystal,” IEEE Photonic Technology Letters, Vol. 5, No. 8, pp. 934-936, 1993. • Y. Shuto et al., “Quasi-Phase Matched Second-Harmonic Generation in Diazo-Dye-Substitued Polymer Channel Waveguides,” IEEE Journal of Quantum Electronics, Vol. 33, No. 3 pp. 349-357, 1997. • Optical limiter • Y. Sun et al., “Organic and inorganic optical limiting materials. From fullerenes to nanoparticles,” International Reviews in Physical Chemistry, Vol. 18, No. 1, pp. 43-90, 1999. • Integrated Optics • S. M. Garner et al., “Three-Dimensional Integrated Optics Using Polymers,” IEEE Journal of Quantum Electronics, Vol. 35, No. 8 pp. 1146-1155, 1999. • N. Bouadma et al., “Monolithic Integration of a Laser Diode with a Polymer-Based Waveguide for Photonic Integrated Circuits,” 1994. • T. Ido et al., “A simple low-cost polymer PLC platform for hybrid integrated transceiver modules,” 2000

  45. Appendix A

  46. Semiconductor NLDC • Based on MQW SC laser • Operate at the transparency point

  47. Properties • Good nonlinearity • Fast response • Lower switching power • Complicated structure (e.g. MQW) • Need current injection (120 mA) • Loss = 25 dB/cm at 879 nm

  48. Other SC structures [Villenevue, 1992] • no current injection is required • still need MQW • splitting ratio and switching power are comparable to the nonlinear polymer ones. • Semiconductor Directional coupler • S. G. Lee et al., “Subpicosecond switching in a current injected GaAs/AlGaAs multiple-quantum-well nonlinear directional coupler,” Applied Physics Letters,Vol. 64, pp. 454-456, 1994. • A. Villeneuve et al., “Ultrafast all-optical switching in semiconductor nonlinear directional couplers at half the band gap,” Applied Physics Letters, Vol. 61, pp. 147-149, 1992.

  49. Appendix B

  50. Carrier generation through nonlinear optical process • Direct bandgap material: • 2PA • intensity dependent: effective for ultrashort pulse (ps to sub-ps) • Indirect bandgap material: • linear indirect absorption • fluence dependent: good for ps to 100s ns

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