S Shaoxian Zhang

Optical shift register based on an optical flip-flop memory with a single active element

We present an optical shift register that consist out of two serially connected optical flip-flop memories driven by common clock pulses. Each optical flip-flop consists out of two ring lasers sharing a single active element, which makes the optical flip-flops easily cascade with each other. The two cascaded optical flip-flops are controlled by the clock pulses in such a way that the input data set the new state of the first optical flipflop, after the state of the first flip-flop has been transferred to the second optical flip-flop. The concept is demonstrated at an operation speed of 20 kHz, which is limited by the 10 m long laser cavities formed by the fiber pig-tailed components.

Hybrid Integrated, All-optical Flip-flop Memory Element for Optical Packet Networks

We describe a novel, fully-packaged, hybrid-integrated all-optical flip-flop memory element. Static state contrast ratios of 10dB and 13dB are demonstrated and the flip-flop can have its state changed dynamically every 32ns with the introduction of state-setting pulses (pulse widths ≪150ps).

Multistate optical memory based on serially interconnected lasers

A multistate optical memory based on serially interconnected lasers is presented. We show that only one of the lasers can lase at a time, thus, the state of the optical memory is determined by the wavelength of the dominant laser. The light from the dominant laser suppresses its neighboring lasers through gain saturation, but still receives amplification by the active element of the suppressed lasers, compensating for coupling losses. This light passes through each of the successive lasers, simultaneously suppressing and being amplified. By this mechanism, all other lasers are suppressed. A five-state optical memory based on this concept is experimentally demonstrated. The contrast ratio between different states is over 30 dB. Dynamic flip-flop operation based on two different all-optical switching methods is also demonstrated.

Eight state optical flip-flop based on coupled unidirectional ring lasers with optical feedback

An eight-state optical flip-flop based on coupled unidirectional ring lasers with optical feedback is demonstrated. The flip-flop exhibits low power operation since it contains only one gain medium. The contrast ratio is over 35 dB.

Mode-locked ring lasers and their application in an all-optical flip-flop memory

We demonstrate the generation of picosecond and sub-picosecond optical pulses source by using a semiconductor optical amplifier (SOA) placed in a ring cavity. Sub-picosecond optical pulses are generated by using an SOA and a linear polarizer placed in a passively mode-locked ring-laser configuration. Nonlinear polarization rotation in the SOA serves as the mode-locking mechanism. The ring cavity generates pulses with duration below 800 fs (FWHM) at a repetition rate of 14 MHz. We also demonstrate an all-optical flip-flop based on two coupled identical actively mode-locked lasers. Each ring-laser outputs optical pulses with duration of 3 ps (FWHM) at a repetition rate of 10 GHz. We demonstrate flip-flop operation and regular toggling between the states.

Analysis of filter-assisted 160 Gb/s wavelength converter using a single semiconductor optical amplifier

We present for the first time a systematic analysis of the Q-factor and eye opening for wavelength conversion based on a single semiconductor optical amplifier and a detuned filter at 160 Gb/s.