Photon-Spin Controlled Lasing Oscillation in Semiconductor Lasers
Hiroaki Ando, Tetsuomi Sogawa, and Hideki Gotoh
Physical Science Laboratory
@We have succeeded in manipulating the spin, or rotation, of electrons to
control the polarization state of the lasing output from a vertical cavity
surface emitting laser (VCSEL). It is known that there are special polarization
states of light, right-handed and left-handed circularly polarized light, in
addition to usual linear polarizations. We have shown experimentally that the
electron-spin alignment, created by optical pumping with circularly polarized
light, drastically changes the polarization state of the lasing output, causing
circular polarized lasing emission at room temperature[1].
In the experiment, a GaAs VCSEL is irradiated with either right-handed or
left-handed circularly polarized light, and lasing is achieved by optical
pumping. It was confirmed in the experiment that lasing of right-handed
circularly polarized light actually occurs when irradiating the laser with
right-handed circularly polarized light, and likewise for left-handed circularly
polarized light. This polarization property is explained by an optical process;
optical pumping by circularly polarized light creates a large number of
spin-aligned electrons, and these electrons, in turn, emit the same
circularly-polarized light. Thus the electron-spin alignment greatly affects the
polarization characteristics of the lasing output.
A new research area called "spin electronics" has recently opened up
placing particular attention on "electron rotation". The purpose of
spin electronics is to control electron-spin states with the goal of creating
novel optical functions. The present results are significant because they
demonstrate that two types of circularly polarized light can be produced at will
by manipulating electron spin. We expect that the new degree of freedom, that
is, electron spin-state, will offer new possibilities for optical information
processing and communication.
[1] H. Ando, T. Sogawa, and H. Gotoh, Appl. Phys. Lett. 73(1998) 566.
Fig. 1: GaAs
surface emitting laser
Fig. 2: Lasing
emission spectra