| Optical integrator – photonic equivalent of electronic capacitor |
| Radan Slavík, Ph.D., DSc. |
| Year: 2008 |
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Optical circuits should enable data processing at speeds inaccessible
by the state-of-the-art electronics. This is particularly important in
applications like ultrafast computing, ultrahigh-capacity
telecommunications, and analysis of ultrafast signals. Optical circuit
can resemble its electronic counterpart – consisting of on many
basic devices like (optical) bobbins, capacitors, memories, etc.
Generally, the optical devices have to be based on different
principles due to several reasons – e.g., it is not possible to
simply ‘stop’ photons like electrons. For example, electronic
capacitor accumulates (‘stops‘) electrons coming at its input,
which mathematically represents a time integration of the signal at
its input.
In collaboration with colleagues from EMT-INRS, Université du Québec in Montréal and COPL, Université Laval in Québec, Canada, we fabricated samples of the first temporal optical integrator, which is in fact an equivalent of an electronics capacitor. The device is based on a special diffractive grating made directly into an optical fiber doped with erbium and ytterbium. Besides showing the basic functionality of the integrator we also demonstrated its suitability for construction of a simple all-optical circuit that is capable of analog solving of partial differential equations with constant coefficients – in electronics, identical functionality is provided by the capacitor. The principal difference is in the processing speed – all-optical circuits are considerably faster than its electronics counterpart. 
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