Research Interests
Time Stretch Analog-to Digital Converter (TSADC)
With increasing bandwidth demands from internet backbones, optical links with 100 Gb/s and higher data rates per wavelength channel are being targeted. To meet these demands, spectrally efficient modulation formats are being developed. The receivers in such links will require very high speed and resolution analog-to-digital converters (ADCs), which are currently beyond the capability of present day electronics. High-bandwidth digitizers are also needed for defense applications such as radars, and in detection of ultrafast electromagnetic pulses. In science, such digitizers are central tools in particle accelerators or X-ray free electron laser systems as well as in time-resolved fluorescence microscopy. The goal of this research is to use photonics to extend the capabilities of electronics to meet these demands. This is achieved by photonic time-stretch technology, which uses photonics to slow down electrical signals in time. Hence, an electronic digitizer that would have been too slow to capture the original electrical signal can now capture the stretched and slowed down signal.
Time-stretched Enhanced Recording (TiSER) Oscilloscope
The Time-Stretch Enhanced Recording (TiSER) oscilloscope, which is the single channel version of TS-ADC, uses photonic time stretch pre-processing to perform Real-time Burst Sampling (RBS) of ultra-wideband signals. It can serve as a diagnostic and development tool for such high data rate communication systems. In particular, its ability to capture bursts of samples spanning several symbols in real-time provides detailed information about the channel impairments and its pattern dependence, and aid development of equalization algorithms and hardware. This sampling mode enables capture of fast non-repetitive dynamics and rare events that deviate from the average behavior of the signal. These deviations can not be captured with equivalent-time oscilloscopes because they lack real-time capability, or with real-time digitizers because of insufficient bandwidth.
Nonlinear Distortions Compensation in Ultra-high Speed Optical Communication Links
Nonlinear distortions in high speed optical communication is becoming problematic as higher optical power and high optical bandwidth is required for long haul transmissions. Reversing and/or compensating the nonlinear distortions significantly improve the performance of next generation (>100G) of optical links.
Serial Time Encoded Amplified Microscopy (STEAM)
STEAM is a new type of imaging modality for continuous real-time observation of fast dynamical phenomena such as shockwaves, chemical dynamics in living cells, neural activity, laser surgery, and microfluidics. STEAM maps the spatial information (image) of an object into a serial time-domain data stream and simultaneously amplifies the image in the optical domain. It captures the entire image with a single-pixel photodetector, not by a CCD or CMOS camera. With the optical image amplificaiton, STEAM overcomes the fundamental trade-off between sensitivity and frame rate - a predicament that affects virtually all optical imaging systems.
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