EE PhD Oral Examination - Bryan Ellis, Monday, March 7th, 2011; 4:15 p.m.

Bryan Ellis bryane at
Wed Mar 2 17:19:51 PST 2011

Stanford University PhD Dissertation Defense - Department of Electrical

Title: "Ultralow threshold electrically pumped photonic crystal lasers"

Speaker: Bryan Ellis

Advisor: Jelena Vuckovic

Date: Monday, March 7th, 2011

Time: 4:15pm (refreshments served at 4 pm)

Location: McCullough 115



Efficient, compact, and low power optical sources are currently being
investigated for many applications including optical interconnects and high
speed communications. Conventional lasers such as edge-emitting and vertical
cavity surface emitting lasers consume far too much power for many
applications, particularly for optical interconnects. This has motivated
research into new approaches based on nanophotonics. Photonic crystal (PC)
nanocavities are an ideal platform for low power laser sources because they
can strongly confine photons in small volumes enabling enhanced light-matter
interaction.  Optically pumped PC lasers can have threshold power
consumption of only a few nanowatts and modulation rates of 100GHz.  However
they are very challenging to pump electrically and thus remain impractical
for many applications.

In this talk, I will present our work developing practical, low-threshold
electrically pumped PC lasers. We have investigated the dynamic properties
of optically pumped quantum dot PC lasers. The factors limiting the
modulation rate of quantum dot PC lasers are examined, and we demonstrate
that large signal direct modulation rates of 30GHz are possible in these
structures. We have also developed a technique to electrically pump active
PC devices using a lateral p-i-n junction defined by ion implantation.
Electrically pumped lasing is observed in continuous wave mode at
temperatures up to 150K. The lasers have a threshold of 181nA at 50K and
287nA at 150K, the lowest threshold of any electrically pumped laser to
date. Finally, I will discuss future applications of electrically pumped PCs
including low-power optical modulators and electrically pumped nanobeam
lasers. The low power dissipation of electrically pumped PC lasers makes
them very promising as sources for many emerging applications.
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