Single wire laser 33001'1

1
Single wire laser 3-30-01.1 5 COptical
characterization
05 10/25 For Akiyama Group members

• 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 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)
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 ?) !!