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

Stanford University PhD Dissertation Defense - Department of Electrical Engineering

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

 

Abstract:

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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.