All-Optical Differentiators |
Radan Slavík, Ph.D. |
Year: 2006 |
Optics-based signal processing systems and devices with operation
speeds inaccessible to electronics (hundreds GHz and more) are
required for a wide variety of applications, including ultrafast
computing, ultrahigh-bit-rate telecommunications, ultrafast pulse
shaping, and analysis of ultrashort optical pulses. In collaboration
with EMT-INRS, Université du Québec, Montréal, we realized one of the
basic signal processing devices – a universal all-optical temporal
differentiator. Our devices calculate the time derivative of an
envelope of an arbitrary optical field with temporal features as short
as a few hundreds of femtoseconds. This corresponds to a processing
speed of several terahertz, which is about three orders of magnitude
faster than with the current state-of-the-art electronics-based
systems and computers.
We demonstrated two devices [1-3], the first one based on an all-fiber implementation [1,2] and the second one based on bulk-optics components [3]. The first implementation is low-loss, low-cost, robust, and compatible with fiber optic technology; the other can be implemented using off-the-shelf components and thus is widely accessible for research laboratories. In the fiber implementation, a special in-fiber-made filter based on a long-period fiber grating (LPFG) was made and tested [1,2]. Further, we developed a tuning technique [4] to get the desired performance. In the bulk-optics-based implementation, the device consists of an imbalanced, symmetric Michelson interferometer. This technique is also straightforward to be extended for higher-order temporal derivatives – as a ‘proof of concept’ we have successfully demonstrated the second-order temporal differentiation [3]. Principle and experimental setup for the fiber-based differentiator characterization. |
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