1. Single wire laser ’3-30-01.1 #5 C‘ Optical characterization
’05 10/25 For Akiyama Group members
Single wire laser　’ #5 C‘ Optical characterization
Toshiyuki Ihara
For a further investigation of single wire laser, I measured optical features such as PL, PLE and absorption/gain spectra by Haaki & Paoli method.
4 : Sample structure and experimental setup
5 : Perpendicular PL scan
6-7 : PLE by reflection geometry and waveguide emission
8-12 : Point excitation Hakki and Paoli ～ excitation energy and spot position dependence
13-16 : Stripe excitation lasing / gain spectra

2. Sample structure of single wire laser
Calculation results
Wire hw = meV
(1st e/h meV)
core Arm hw = meV
(1st e/h meV)
clad Arm hw = meV
Stem hw = meV
(1st e/h meV)
waveguide hw = meV
(1st e/h meV)

3. Reflection / perpendicular geometory for low power excitation (micro-PL / PLE)

4. Waveguide emission detection geometry for high power excitation (Lasing / Image)

5. Perpendicular PL scan from cap to substrate
－ Emission from the stem well is strongly polarized to [001] direction
⊥det
//det

6. PL and PLE by reflection geometry
－ Clear : Wireex./cont. & clad/coreArmHH & Waveguide (drift into Wire！)
－ Unclear : clad/coreArmLH & StemLH/HH (drift into Wire？)
⊥ex
//ex

7. PLE ～ Wire Waveguide emission probe
－ Clear peaks of wire Ground / excited / continuum state is observed.
－ Absorption intensity is not correct (due to the Fabry-Perot Fringe?).
⊥ex
//ex

8. Point excitation Haaki & Paoli
excitation energy Eex = 1.639eV (stem resonance)
－ At the excitation energy of 1.639eV (stem resonance), a clear absorption spectrum is obtained !!

9. Point excitation Hakki & Paoli ～ low energy excitation case
－ Scattered laser leads to excess carriers on whole region of the wire !!

10. Point excitation Hakki & Paoli ～ high energy excitation case
－ Waveguide absorption results in the formation of trion state on the whole wire region !!

11. Point excitation Hakki & Paoli ～ spot position dependence
－ Although the waveguide emission depends on the excitation spot position, the obtained absorption spectra by Hakki and Paoli method are almost same ! ※S/N ratio depends on the position largely !

12. Point excitation Hakki & Paoli ～ detection polarizer importance

13. Waveguide emission (& lasing) by Stripe excitation
spectrum
－L2 and L3 lasing are observed
Image
Select Arm
polarization
by polarizer
Image of
L2 and L3
lasing
Image of
L1,2 lasing

14. Carrier density dependence of gain spectra (Parm detection)
－Evolution from excitonic absorptions to L1 / L2 gain was observed !!

15. Carrier density dependence of gain spectra (Pstem detection)
－It is hard to observe the absorption feature of stem polarization on single wire laser.

16. Various L2 lasing energy (Excitation energy dependence)
－The energy of L2 lasing changes gradually with the excitation energy (carrier density ?) !!