The quickest information-processing circuits in the future will be photonic, rather than electronic. Researchers are now figuring out ways of building the components for such circuits. For example, a group at the Institut National de la Recherche Scientifique-Énergie, Matériaux et Télécommunications (INRS-EMT; Varennes, Quebec, Canada) has created an ultrafast photonic intensity integrator, an analog temporal device that integrates optical intensity signals, and which would be used in incoherent (intensity-based) optical-signal processing. The device has a full-width half-maximum impulse response of about 12 ps.
In operation, an almost-rectangular incoherent spectrum with a width of about 4.35 THz is first generated from a semiconductor optical amplifier; the spectrum is then temporally modulated by an input intensity signal (for example, two 33 ps pulses separated by 104 ps) via a Mach-Zehnder electro-optic modulator. The signal is then sent through a section of single-mode optical fiber that induces a wavelength-dependent time delay. When examined over a short-enough time interval (about 200 ps or less for the double pulse), the fiber’s temporal output appears as the integral of the device’s input. A fast photodiode (with a 3 dB bandwidth of 18 GHz) is used to measure the integrated optical signal. Contact Yongwoo Park at park@emt.inrs.ca.