Demonstration of a Magnetically Controllable Fabry--Perot Laser and an Unidirectional Ring Laser Utilizing a Nonreciprocal Semiconductor Optical Amplifier

We report on the photon density redistribution in nonreciprocal semiconductor optical amplifiers. The photon density redistribution is useful for clearly separating input and output signals in photonic integrated circuits to ensure robust operation. An Fe--InGaAlAs/InP nonreciprocal semiconductor optical amplifier showed an emitted intensity difference of 1.9 dB upon magnetization reversal. By utilizing the photon density redistribution, we fabricated a unidirectional semiconductor ring laser integrated with a nonreciprocal semiconductor optical amplifier for magnetically reconfigurable all-optical signal processing. The fabricated device exhibited intensity modulation by reversing the direction of the magnetic field, and the extinction ratio was 2.8 dB.