In this study, we choose to use a compact device which combines a semiconductor ring laser with on-chip ﬁltered optical feedback to achieve wavelength tunability. The ﬁltered optical feedback is realized by employing two arrayed waveguide gratings to split/recombine light into diﬀerent wavelength channels. Semiconductor optical ampliﬁers are placed in the feedback loop in order to control the feedback of each wavelength channel independently.
Experimental observations show that the stability of the clockwise and counterclockwise propagation modes depends on the feedback strength. Experiments also show that for a speciﬁc range of the feedback strength, anti-phase oscillations in the intensity of the clockwise and counterclockwise propagating modes can be induced. These oscillations could not be seen in the same semiconductor ring laser without ﬁltered optical feedback. We investigate how the frequency and the amplitude of these oscillations change under the eﬀect of ﬁltered optical feedback. We also discuss how these anti-phase oscillations can be suppressed by properly choosing the feedback strength.