PhD Defense: "Low Voltage Wide Bandwidth III-V Electro-optic Modulators"

Nak Ki Kim

September 8th (Thursday), 8:00am
ESB 2001

Wavelength division multiplexing (WDM) along with optical fiber revolutionized the capacity and speed of data communication system and as a result, fiber optic communication systems became essential in many data communication systems. In addition, the demands for the faster data communication system has been getting higher and higher as time goes. Therefore, constant efforts have been put on improving the performance of the essential components of the fiber optic communication systems including optical modulators; optical modulators are used for converting electrical signal to optical signal. For optical modulators, among others, there are two key factors that directly contributes to the system performance; one is the driving voltage and the other is bandwidth. Drive voltage is desired to be as low as possible since it reduces power consumption by eliminating modulator driver, and bandwidth is desired to be as wide as possible to achieve faster data transfer rate.
In this work, we demonstrated a substrate removed modulator having drive voltage under 3V while showing over 60GHz modulation is possible. This modulator also shows reduction in drive voltage under reverse bias. The drive voltage goes down to 1.3V under 18V reverse bias without hurting its bandwidth. In addition, a substrate removed modulator having drive voltage of 1.55V at no external bias is demonstrated. Then, the modulator designs are further modified for the comparability to conventional foundry processing; the devices are fabricated on substrate without substrate removal. The substrate-on devices exhibit lower bandwidth although their drive voltages stay the same as substrate removed devices. However, they still provide moderately wide bandwidth, and we demonstrated in this work that they can be modulated over 20GHz.

About Nak Ki Kim:

Nak Ki Kim received his B.S. degree in Electrical Engineering from the University of California, Santa Barbara in 2009, and his M.S. degree in Electrical and Computer Engineering from the University of California, Santa Barbara in 2012. His main research focus is on design and fabrication of III-V electro-optic modulators with low drive voltage and wide bandwidth. His research interests include electro-optic modulators, phtonic A/D, D/A converter, optical comm-link and photonic integrated circuits.

Hosted by: Professor Nadir Dagli