PhD Oral Examination - Shinichi Koseki (Friday, May 23, 2008, 1:30pm)

Department of Electrical Engineering
University Oral Examination

Monolithic Waveguide Coupled GaAs Microdisk Microcavity
Containing In0.3Ga0.7As Quantum Dots

Shinichi Koseki
Department of Electrical Engineering
Advisor: Professor Yoshihisa Yamamoto

Friday, May 23, 2008, 1:30 pm, CIS-X Auditorium
(Refreshment to be served at 1:15 pm)

Abstract:

After the intensive development of dielectric microcavities
containing semiconductor quantum dots (QDs), a variety of
cavity quantum electrodynamics (CQED) effects have been
demonstrated such as Purcell effect, Rabi splitting, or
single photon emission in the strong-coupling regime.
To enable more complicated functionality, the main interest
of such devices is now shifting to construct a microphotonics
circuit that consists of arrays of cavities and waveguide
structures for interconnection. Entanglement distribution
based quantum repeater protocol for long-distance quantum
communication is proposed based on such a system. Among the
microcavity structures, microdisk microcavity that supports
whispering gallery mode (WGM) has high quality (Q) factor
and small mode volume. For the entanglement distribution,
cavities with high quality factor, small mode volume (V),
large Purcell factor (Fp), as well as with the overcoupling
to the waveguide, are required.

In this talk, I will present our experimental effort to
fabricate and characterize our monolithic waveguide coupled
GaAs microdisk microcavity structure, where light is coupled
by the grating coupler. In the first part, I will introduce
our device design and process flow. In the second part, I
will present the results of the microphotoluminescence
spectroscopy of isolated microdisks, where we observed strong
coupling of CQED by the temperature tuning of the cavity.
In the third part, I will present the results of the optical
spectroscopy of waveguide coupled microdisks. Out-coupling
from the disk to the waveguide is evidenced by extracting
the cavity mode photon from the output port. In-coupling
into the disk from the waveguide is evidenced by the
transmission measurement between input and output ports,
where we observed 35% dip in the transmission spectra.
This system should play an important role in realizing
the entanglement distribution, and photonic quantum
information processor.