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’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
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Y. Hayamizu unpublished
Motivation 2
－Photo excited electrons in
“optical Arm waveguide”
tunnel into Arm well ??
Y. Hayamizu
master’s thesis
Attempt the observation of wire
Trion absorption !!
Waveguide emission detection geometry with
“Stripe + Point” or “Point + Point” 2-laser excitation
Sample structure of single wire laser
Calculation results
Wire
hw = 1589.7 meV
(1st e/h
60.7
core Arm
hw = 1604.1 meV
(1st e/h
74.3
clad Arm
hw = 1609.1 meV
(1st e/h
74.3
Stem
hw = 1629.3 meV
(1st e/h
75.7
waveguide
hw = 1645.2 meV
(1st e/h
82.3
10.0 meV)
10.8 meV)
10.8 meV)
34.5 meV)
44.2 meV)
Ref. PL and PLE overview
－ Stem LH resonance : 1.646eV
－ Waveguide resonance : 1.660 eV
⊥ex
//ex
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Y. Hayamizu unpublished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.
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
1mW
2mW
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
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
core Arm
hw = 1604.1 meV
(1st e/h
74.3
clad Arm
hw = 1609.1 meV
(1st e/h
74.3
Stem
hw = 1629.3 meV
(1st e/h
75.7
waveguide
hw = 1645.2 meV
(1st e/h
82.3
10.0 meV)
10.8 meV)
10.8 meV)
34.5 meV)
44.2 meV)
－Target : observation of Trion absorption !!
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
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 !!
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) !?
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…
Conclusion
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 !!