Single wire laserSingle wire laser 　’　’ 3-30-01.1 #5 3-30-01.1 #5 C‘C‘

excited by Two Ti:Sapphire lasersexcited 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

①①Motivation 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Y. Hayamizu unpublished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 2Motivation 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 Waveguide emission detection geometry with “Stripe + Point” or “Point + Point” 2-laser excitation“Stripe + Point” or “Point + Point” 2-laser excitation

Sample structure of Sample structure of single wire lasersingle wire laser

Wire h1589.7 meV

(1st e/h 60.7 10.0 meV)

core Arm h1604.1 meV

(1st e/h 74.3 10.8 meV)

clad Arm h1609.1 meV

(1st e/h 74.3 10.8 meV)

Stem h1629.3meV

(1st e/h 75.7 34.5 meV)

waveguide h1645.2 meV

(1st e/h 82.3 44.2 meV)

Calculation results

Ref. PL and PLE overviewRef. PL and PLE overview－ Stem LH resonance : 1.646eV

－ Waveguide resonance : 1.660 eV

⊥ex //ex

②②Problem of the Stripe excitation by Hakki and Paoli methodProblem 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Y. Hayamizu unpublished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 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 The result of “Stripe + Point” 2-laser excitation

2mW

1mW

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

0mW

1mW

1mW

2mW

2.5mW

3mW

③③Verification of trion formation of non-dope single wire laserVerification of trion formation of non-dope single wire laser ～ ～ Electrons tunnel from “optical Arm waveguide” region.Electrons tunnel from “optical Arm waveguide” region.

－ Photo excited Electrons in “optical Arm waveguide” tunnel into Arm well ??

Wire h1589.7 meV

(1st e/h 60.7 10.0 meV)

core Arm h1604.1 meV

(1st e/h 74.3 10.8 meV)

clad Arm h1609.1 meV

(1st e/h 74.3 10.8 meV)

Stem h1629.3meV

(1st e/h 75.7 34.5 meV)

waveguide h1645.2 meV

(1st e/h 82.3 44.2 meV)

(Calculated energy level)

－ Target : observation of Trion absorption !!

Idea : “Point + Point excitation” 2-laser excitationIdea : “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-laserPLE 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-laserHakki & 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 ( ～ 500m) !?

pumping 1 : 1.666eV (above waveguide absorption)

Strong excitation 2 : 1.646 eV (stem resn.)

④④The evolution of absorption spectra on The evolution of absorption spectra on electron-hole system / electron system electron-hole system / electron system

※ It is not clear whether carrier density is the same on the whole area of the wire…

Electron-hole system Electron 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 !!

ConclusionConclusion