Ultrafast Optoelectronics Laboratory Research

Department of Electrical Engineering
University of Maryland at College Park

Professor Lee's research interest has been in the area of femtosecond lasers and ultrafast optoelectronics. Most of the research will be conducted at the Ultrafast Optoelectronics Laboratory and the newly established Laboratory for Atomic, Molecular and Optical Science and Engineering (LAMOS).

One great advance in science and technology that we have witnessed in the past two decades has been the merging of optics and electronics. One of the most astonishing developments has been the rapid advance in ultrafast optics. As the capacity of information increases, the ability to handle information has to increase as well, creating a demand for high speed technology. The objective of Professor Lee's research is to use femtosecond optics to generate, control, manipulate, and characterize high speed/high frequency electronics singals, devices, circuits and systems. The physical mechanisms through which these tasks can be performed are:(1)ultrafast photoconductivity in semiconductors, (2)ultrafast photoresistivity in high-temperature superconductors(HTS) and (3) electro-optics effect in semiconductors and dielectrics. The first two effects allow conversion of ultrafast optical signals into electrical signals; and third, optical probing of materials.

Using photoconductors and short optical pulses, Dr. Lee's group has demonstrated an on-wafer optoelectronic characterization of millimeter-wave circuits (MMICs), with 150 GHz bandwidth in the time-domain, by inventing a near "real-time" (with data acquisition in micro-seconds) technique with optical-microwave phase-locking. The time resolution surpasses that of the best Tektronix sampling scope (18 ps), and is only limited by the laser pulse duration. With femtosecond laser pulses we can push the bandwidth to terahertz. His group has also demonstrated a new way to generate ultrawide-band millimeter (mm) waves by feeding a laser generated delta-function electrical input to a broadband MMIC amplifier, and optical control of true-time-delay (TTD) phase shifter, which are important for wireless communications using mm waves and terahertz radiations. To construct a broad-band mm-wave phased array system, one can activate each element with the fan-out of a high-power fs optical pulse. Using these techniques, spread-spectrum communications, jam-resistance tranceiver and TTD beam-sterring have been demonstrated.

In all these applications, optical drivers (lasers) always set the technology path. To reduce the size and cost of lasers a research effort has been concentrated in developing compact, ultrafast laser sources which include semiconductor MQW lasers and diode pumped solid-state lasers. To have a complete research capability in ultrafast optoelectronics and electronics, a new research effort in making high speed MSM photodetector has been added.

Dr.Lee's research has been funded by NSF, ARL, NSA, ONR and industrial laboratories.

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