Semiconductor laser and polarization modulator for W-band signal generation

A photonic microwave harmonic up-conversion is experimentally demonstrated using the local oscillator (LO) to directly modulate the distributed feedback laser and externally modulate the polarization modulator simultaneously. By feeding the initial radio frequency signal generated by the LO into the system, the second and fourth harmonic photonic microwaves are eventually available through the separation of the polarization beam splitter. The steady second and fourth harmonic photonic microwaves have a linewidth of about 100 Hz and a discrepancy of up to 60 dB between the central peak and the noise floor. Undesired harmonics and sidebands in the 30 GHz, 60 GHz, and 80 GHz fourth harmonic photonic microwaves can be suppressed without the use of optical amplifiers, resulting in a clear display of both tones. The single-sideband (SSB) phase noise of this proposed system adds about 6 dB of SSB phase noise in each cumulative harmonic, which is close to the ideal state.