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Single wire laser 　’ 3-30-01.1 #5 C‘ excited by Two Ti:Sapphire lasers

’05 11/16 For Akiyama Group members. Single wire laser 　’ 3-30-01.1 #5 C‘ excited by Two Ti:Sapphire lasers. Toshiyuki Ihara. ① : Motivation / experimental setup / Sample structure / PL and PLE overview

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Single wire laser 　’ 3-30-01.1 #5 C‘ excited by Two Ti:Sapphire lasers

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  1. ’05 11/16 For Akiyama Group members Single wire laser　’3-30-01.1 #5 C‘excited by Two Ti:Sapphire lasers Toshiyuki Ihara ① : Motivation / experimental setup / Sample structure / PL and PLE overview ② : “Stripe + Point” 2-laser excitation experiment (improvement of Hakki & Paoli S/N ratio) ③ : “Point + Point” 2-laser excitation experiment (observation of wire Trion absorption) ④ : The evolution of absorption spectra on electron-hole system / electron system

  2. ①Motivation 1 Low e-h density region with stripe excitation by Hakki & Paoli method is not clear. Attempt an improvement of Hakki & Paoli S/N ratio !! Y. Hayamizu unpublished

  3. Motivation 2 －Photo excited electrons in “optical Arm waveguide” tunnel into Arm well ?? Attempt the observation of wire Trion absorption !! Y. Hayamizu master’s thesis

  4. Waveguide emission detection geometry with “Stripe + Point” or “Point + Point” 2-laser excitation

  5. Sample structure of single wire laser Calculation results Wire hw = 1589.7 meV (1st e/h 60.7 10.0 meV) core Arm hw = 1604.1 meV (1st e/h 74.3 10.8 meV) clad Arm hw = 1609.1 meV (1st e/h 74.3 10.8 meV) Stem hw = 1629.3 meV (1st e/h 75.7 34.5 meV) waveguide hw = 1645.2 meV (1st e/h 82.3 44.2 meV)

  6. Ref. PL and PLE overview － Stem LH resonance : 1.646eV － Waveguide resonance : 1.660 eV ⊥ex //ex

  7. ②Problem of the Stripe excitation by Hakki and Paoli method Low e-h density region with stripe excitation by Hakki & Paoli method is not clear. 5K (Eex : 1.646eV stem resn.) 2mW 1mW Y. Hayamizu unpublished ※Point excitation results in a broad emission spectrum that is desirable for a light source.

  8. Idea : “Stripe + Point” 2-laser excitation －Point excitation : broader emission light source. －Stripe excitation : make carrier in the whole region of wire. ※the laser photon energy are almost the same for both excitation (～1.646eV : stem resn.)

  9. The result of “Stripe + Point” 2-laser excitation 1mW 2mW

  10. The result of “Stripe + Point” 2-laser excitation ～ Electron-hole density dependence of Absorption －Almost same result as the pump probe absorption measurement by Y. Takahashi 1mW 0mW 1mW 2mW 2.5mW 3mW

  11. ③Verification of trion formation of non-dope single wire laser～ Electrons tunnel from “optical Arm waveguide” region. －Photo excited Electrons in “optical Arm waveguide” tunnel into Arm well ?? (Calculated energy level) Wire hw = 1589.7 meV (1st e/h 60.7 10.0 meV) core Arm hw = 1604.1 meV (1st e/h 74.3 10.8 meV) clad Arm hw = 1609.1 meV (1st e/h 74.3 10.8 meV) Stem hw = 1629.3 meV (1st e/h 75.7 34.5 meV) waveguide hw = 1645.2 meV (1st e/h 82.3 44.2 meV) －Target : observation of Trion absorption !!

  12. Idea : “Point + Point excitation” 2-laser excitation －I tried two methods to obtain absorption spectra ( PLE / Hakki and Paoli ) PLE Local information Hakki and Paoli Averaged information

  13. PLE spectra of “Point + Point excitation” 2-laser －case 1 : PLE measurement pumping l1 : 1.666eV (above waveguide absorption) PLE excitation l2-l3 : 1.58 – 1.593V (wire PLE) Clear Trion absorption was observed by PLE !!

  14. Hakki & Paoli results with “Point + Point excitation” 2-laser －case 2 : Hakki & Paoli method pumping l1 : 1.666eV (above waveguide absorption) Strong excitation l2 : 1.646 eV (stem resn.) Trion absorption appears even averaged spectra by Hakki & Paoli method. Electrons distribute whole region of the wire (～500mm) !?

  15. ④The evolution of absorption spectra on electron-hole system / electron system Electron-hole system Electron system 0mW 1mW 2mW 2.5mW 3mW ※ It is not clear whether carrier density is the same on the whole area of the wire…

  16. Conclusion ①　“Stripe + Point” 2-laser excitation measurement improves S/N ratio of Hakki and Paoli method with Stripe excitation !! ②Wire Trion absorption was observed by probe laser when the “optical Arm waveguide” was excited by pump laser. These results provide prospects of the future study on doped 1D system, such as the evolution of continuum state with increasing electron density, and the gain mechanism of doped quantum wire laser !!

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