Current Research Areas

Hybrid Si/III–V Integration

It is widely recognized that the most important and exciting work in optoelectronics today is to combine optical functions (lasing, modulation, amplification, and detection) with traditional Si electronics. We have proposed a novel scheme by means of which the modal gain inside the hybrid structure can be enhanced several times without loss of other advantages. We are presently working on the experimental demonstration of this scheme.

• Modal control in hybrid Si/III–V laser oscillator
• Hybrid Si/III–V modulator

Optical Phase-Lock Loops

Phase-Lock Loop systems are the main enablers of many key applications in the field of RF (radio-frequency) electronics, such as wireless communications, CDMA, FM demodulation and clock recovery, to name a few. In contrast, almost all of the information applications of lasers to date have been based on a manipulation of their amplitude (Differential Phase-Shift Keying is one exception). The Semiconductor Laser is the prime candidate to play the role of the Voltage Controlled Oscillator in the optical domain. This is due to its very large current-frequency sensitivity, its fast response (>30 GHz), its small volume, and its compatibility with electronic circuits.

The research in our group focuses on the use of semiconductor lasers as current controlled oscillators in optical phase-lock systems to enable a range of diverse applications. The optical phase and frequency of the laser output is controlled by purely electronic means using RF VCOs and phase shifters, thus eliminating the need for bulky optical phase and frequency modulators. Recent and ongoing experiments have focused on the phase-locking of arrays of semiconductor lasers for many diverse applications such as coherent power combination, "coherence cloning" - where the spectral properties of a high quality laser are cloned onto a number of inexpensive semiconductor lasers, optical phase controlled apertures, and the generation of electronically controlled ultra-wideband optical waveforms.

Slow Light in Coupled-Resonator Optical Waveguides (CROWs)

Slow light by reducing the group velocity in engineered structures can find applications like optical delay lines, optical buffers, interferometers, and nonlinear optics. In our group, we have proposed, analyzed, and experimentally demonstrated Coupled-Resonator Optical Waveguides (CROWs), in which light propagates by virtue of the coupling between adjacent resonators.

We are presently working on

· CROWs based on grating resonators on Si waveguides

· Bandpass filter design based on CROWs

· Active CROWs with gain