Single wire laser ’ #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 ’05 11/16 For Akiyama Group members

① Motivation 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 Y. Hayamizu unpublished

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

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

Sample structure of single wire laser Wire h  meV (1st e/h meV) core Arm h  meV (1st e/h meV) clad Arm h  meV (1st e/h meV) Stemh  meV (1st e/h meV) waveguide h  meV (1st e/h meV) Calculation results

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

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 Y. Hayamizu unpublished 5K 2mW 1mW

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.)

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

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 0mW 1mW 2mW 2.5mW 3mW

③ Verification 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 ?? Wire h  meV (1st e/h meV) core Arm h  meV (1st e/h meV) clad Arm h  meV (1st e/h meV) Stemh  meV (1st e/h meV) waveguide h  meV (1st e/h meV) (Calculated energy level) － Target : observation of Trion absorption !!

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

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

Hakki & Paoli results with “Point + Point excitation” 2-laser － case 2 : Hakki & Paoli method Trion absorption appears even averaged spectra by Hakki & Paoli method. Electrons distribute whole region of the wire ( ～ 500  m) !? pumping 1 : 1.666eV (above waveguide absorption) Strong excitation 2 : eV (stem resn.)

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

① “Stripe + Point” 2-laser excitation measurement improves S/N ratio of Hakki and Paoli method with Stripe excitation !! ② Wire 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 !!Conclusion