An optical flip-flop circuit with a single semiconductor optical amplifier (SOA) using two orthogonal polarization states is proposed. The optical set / reset input and output signals are at a single wavelength. The flip-flop circuit consists of an SOA, a polarization combiner, a polarization splitter, two directional couplers, and two phase shifters. No continuous light source is required to operate the circuit. In this paper, we theoretically analyze the operation performance. Polarization dependence in SOA is considered in the analysis at a single wavelength operation, and numerically simulated results are presented. We confirm that the flip-flop circuit with a feedback-loop length of 15~mm can be operated at switching time of around 3~ns by 1~ns set / reset pulses. The flip-flop performance is discussed from viewpoints of transient overshoot and contrast at the steady on-off states.

A novel broad-band ring-slot array antenna for simultaneous use of orthogonal polarizations is presented in this paper. In this antenna, the broad-band performance is obtained by integrating a 22 ring-slot array antenna and a broad-band π/2 hybrid circuit. The simultaneous use of the right-hand circular polarization (RHCP) and the left-hand circular polarization (LHCP) is achieved using orthogonal feed circuits on three layers. The both-sided MIC technology is effectively employed in forming this type of slot array antenna. Experimental results show that the proposed antenna has good circular polarization characteristics for both the LHCP and the RHCP. The measured impedance-bandwidth of return loss better than -10 dB are about 47% both for the LHCP and the RHCP. The 3 dB axial ratio bandwidths are 25% (RHCP) and 29% (LHCP). The isolation between the two input ports is better than -35 dB at center frequency of 7.5 GHz.