2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009;
Pittsburgh, Pennsylvania
Session A22: Focus Session: Spins in Group III-V and II-VI Semiconductors
8:00 AM–11:00 AM,
Monday, March 16, 2009
Room: 324
Sponsoring
Units:
GMAG DMP FIAP
Chair: Paul Crowell, University of Minnesota
Abstract ID: BAPS.2009.MAR.A22.1
Abstract: A22.00001 : Electrically Injected Spin Polarized Lasers*
8:00 AM–8:36 AM
Preview Abstract
Abstract
Author:
Pallab Bhattacharya
(Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109-2122, USA)
The ability to electrically modulate orthogonal polarization
states in
spin-polarized lasers opens up avenues for a wide range of
applications such
as photochemical spectroscopy, optical switches, and
communications with
enhanced security [1]. This has motivated us to investigate the
properties
of quantum well (QW) [2] and quantum dot (QD) [3] spin-polarized
vertical
cavity surface emitting lasers (spin-VCSELs). The laser
heterostructures are
grown by molecular beam epitaxy (MBE). The active region consists of
In0.2Ga0.8As/GaAs QWs [2] or InAs QDs [3]. VCSELs are fabricated
using
standard micro-fabrication techniques. The FM Schottky tunnel
contact is
realized with Fe or MnAs re-grown by MBE. The QW spin-VCSELs
exhibit a
maximum threshold current reduction of 11 {\%} and output degree
of circular
polarization of 23 {\%} at 50 K. The corresponding values
observed in QD
spin VCSELs at 200 K are 8 {\%} and 14 {\%}, respectively.
Inhibition of the
D'yakonov-Perel spin scattering process results in higher operating
temperatures for spin-lasers with QD active region. In addition,
we have
demonstrated electrical modulation of the output polarization
with a peak
modulation index of 0.6. The spin polarization of carriers in the
active
region of a spin laser gives rise to large gain anisotropy at
biases near
threshold. As a result, the output polarization can be much
larger than the
spin polarization of the injected carriers. This is contrary to
the linear
relation between carrier spin orientations in the active region
and the
polarization of photons emitted upon their radiative
recombination in spin
light emitting diodes. The exact magnitude of the output
polarization in
spin lasers and the parameters upon which it depends have been
analytically
determined and are in excellent agreement with those obtained from
measurements. These results will be described and discussed.
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References:
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[1] M. Holub et al., J. Phys. D. 40, R179 (2007).
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[2] M. Holub et al., Phys. Rev. Lett. 98, 146603 (2007).
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[3] D. Basu et al., Appl. Phys. Lett. 92, 091119 (2008).
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[4] M. I. D'yakonov et al., Sov. Phys Solid State. 13, 3023 (1971)
*Work supported by the Office of Naval Research.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2009.MAR.A22.1