Photonic microwave down-conversion using period-one nonlinear dynamics of semiconductor lasers is proposed, which provides high conversion efficiency and requires no local oscillators. Experimental demonstration of microwaves at 33.7GHz down-converted to a frequency ranging from 10 to 14 GHz is presented.
When a semiconductor laser is subject to an incoming optical carrier, equivalently an external optical injection, it
can enter nonlinear period-one dynamics through Hopf bifurcation due to the radical modification in field-carrier
coupling of the injected laser which results from the dynamical competition between injection-imposed laser oscillation
and injection-shifted cavity resonance. Equally-separated spectral components appear, of which intensity
and frequency depend strongly on the injection level and frequency. This suggests that a dynamical amplitude
or frequency variation of the incoming optical signal, such as amplitude-shift keying (ASK) or frequency-shift
keying (FSK), respectively, would lead to corresponding dynamical variation in amplitude and frequency of each
spectral component. Therefore, by properly selecting the optical frequency of the output optical carrier and
by minimizing the residual ASK and FSK modulation, both ASK-to-FSK and FSK-to-ASK conversions can be
achieved, where bit-error ratio down to 10<sup>-12</sup> is achieved with a slight power penalty. Only a typical semiconductor
laser is necessary as the key conversion unit. In addition, frequency shifts of the optical carrier can also
be achieved, which allows a simultaneous frequency conversion of the optical carrier if required.