Magnetic field induced sum frequency mixing in sodium vapour

A study of magnetic field induced sum frequency mixing (SFM) in sodium vapour was carried out using continuous-wave lasers as the sources of the fundamental radiation. The three-wave mixing nonlinear optical process was resonantly enhanced by tuning the laser frequencies close to single and two-photon resonances in the sodium atoms. The coherent ultraviolet radiation at the sum frequency of the two input laser frequencies was emitted by the coherently driven 3S-4D electric-quadrupole, which was rotated by the transverse magnetic field to allow collinear generation of the sum frequency wave. Two single-frequency dye lasers were used to examine in detail the role of the intermediate 3P atomic states in the coherent two-photon absorption. Resonant single photon transitions were investigated for the first time in a nonlinear optical process in an atomic vapour. High resolution SFM line profiles were obtained which illustrated the complicating contributions of hole-burning, velocity selection, optical pumping, saturation and frequency dependent phase mismatching to the three-wave mixing effect. The use of additional single photon resonant enhancement and control over the refractive index of the sodium vapour showed that large effective nonlinear X(2) susceptibilities were possible in atomic vapours which could exceed those of nonlinear crystals. The variation of SFM power with atomic particle density due to bulk phase mismatching reflected the wavelength dependence of the sodium dispersion with the 3P intermediate state off-resonance. Phase shifts of the focused Gaussian laser beams led to an asymmetric behaviour of the phase matching with respect to the sign of the phase mismatch k. Saturation spectroscopy was utilised for the first time to examine the Zeeman spectra of the sodium 3S-3P D line resonances in a transverse magnetic field. A novel experimental method was used to restrict the detrimental effects of velocity changing collisions on the resolution of the nonlinear laser spectroscopic technique. The possibility of using optical pumping with a transversal, resonant light beam to induce the second-order nonlinearity necessary for second harmonic generation in sodium vapour was experimentally investigated

All-optical binary counter

We experimentally demonstrate an all-optical binary counter composed of four semiconductor optical amplifier based all-optical switching gates. The time-of-flight optical circuit operates with bit-differential delays between the exclusive-OR gate used for modulo-2 binary addition and the AND gate used for binary carry detection. A movie of the counter operating in real time is presented

Use of semiconductor optical amplifiers in signal processing applications

We describe a 42.6 Gbit/s all-optical pattern recognition system which uses semiconductor optical amplifiers (SOAs). A circuit with three SOA-based logic gates is used to identify the presence of specific port numbers in an optical packet header

42.6 Gbit/s fully integrated all-optical XOR gate

We demonstrate an SOA-based all-optical high-speed Mach-Zehnder interferometer exclusive- OR (XOR) gate fabricated in a silica III-V hybrid-integration technology platform.  The device includes integrated time delays for rapid differential operation as well as integrated phase shifters for fine tuning of power splitters and interferometer bias enabling highly optimized XOR gate operation.  XOR functionality is verified through inspection of the output pulse sequence and the carrier-suppressed output spectrum.  A 2.3 dB penalty for a 42.6 Gb/s RZ-OOK signal at a 10-9 bit error rate is observed

All-optical header processing in a 42.6Gb/s optoelectronic firewall

A novel architecture to enable future network security systems to provide effective protection in the context of continued traffic growth and the need to minimise energy consumption is proposed. It makes use of an all-optical pre-filtering stage operating at the line rate under software control to distribute incoming packets to specialised electronic processors. An experimental system that integrates software controls and electronic interfaces with an all-optical pattern recognition system has demonstrated the key functions required by the new architecture. As an example, the ability to sort packets arriving in a 42.6Gb/s data stream according to their service type was shown experimentally

42.6 Gbit/s fully integrated all-optical XOR gate

We demonstrate an SOA-based all-optical high-speed Mach-Zehnder interferometer exclusive- OR (XOR) gate fabricated in a silica III-V hybrid-integration technology platform.  The device includes integrated time delays for rapid differential operation as well as integrated phase shifters for fine tuning of power splitters and interferometer bias enabling highly optimized XOR gate operation.  XOR functionality is verified through inspection of the output pulse sequence and the carrier-suppressed output spectrum.  A 2.3 dB penalty for a 42.6 Gb/s RZ-OOK signal at a 10-9 bit error rate is observed

160-Gb/s all-optical packet switching over a 110-km field installed optical fiber link

Demonstration of all-optical packet switching at 160 Gb/s over a total of 110-km field installed optical fiber link is reported. The packet switch architecture is based solely on photonic circuits: an optical filter as label processor, an all-optical flip-flop as memory element and an ultrafast wavelength converter as router. Both flip-flop and wavelength converter uses semiconductor optical amplifiers which allows for photonic integration. The switch operates at low power levels and shows potential scalability. Error-free operation is shown without forward error correction technology.</p