  We propose and demonstrate a technique to control the balance between the two
amplitudes of a dual-wavelength laser based on a phase-controlled optical
feedback. The feedback cavity length is adjusted to achieve a relative phase
shift between the desired emission wavelengths, introducing a boost in gain for
one wavelength while the other wavelength experiences additional losses. Tuning
the optical feedback phase proves to be an effective way to control the gain
and losses, and, thus, to select one or balance the amplitude of the two
emission wavelengths. This concept can be easily adapted to any platform,
wavelength range and wavelength separations providing that a sufficient carrier
coupling and gain can be obtained for each mode. To demonstrate the feasibility
and to evaluate the performance of this approach, we have implemented two
dual-wavelength lasers with different spectral separations together with
individual optical feedback loops onto a InP generic foundry platform emitting
around 1550 nm. An electro-optical-phase-modulator is used to tune the feedback
phase. With this single control parameter, we successfully achieved extinction
ratios of up to 38.6 dB for a 10 nm wavelength separation and up to 49 dB for a
1 nm wavelength separation.
