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

Shinichi Koseki koseki at
Wed May 21 09:49:40 PDT 2008

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)


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.

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