Apparatus for millimeter-wave signal generation

A millimeter-wave electrical signal generator, comprising:

• (a) a semiconductor ring laser formed on a substrate and having a ring cavity and passive mode-locking means for generating a train of mode-locked lasing pulses;
• (b) a waveguide photodetector formed on the substrate proximate to the semiconductor laser;
• and
• (c) an active optical waveguide with gain formed on the substrate and optically coupling the train of mode-locked lasing pulses from the semiconductor ring laser into the waveguide photodetector to an electrical signal at a millimeter-wave frequency from the train of mode-locked lasing pulses, the active optical waveguide being tapered with a width that increases with distance away from the semiconductor ring laser.

A method of generating an electrical signal at a frequency .gtoreq.10 GHz, comprising steps for:

• (a) generating in a ring cavity on a substrate a continuous train of mode-locked lasing pulses at the frequency of the electrical signal;
• (b) amplifying the lasing pulses;
• and
• (c) detecting with a high-speed photodetector on the substrate the continuous train of mode-locked lasing pulses after amplification thereof for generating the electrical signal.

A method of generating an electrical signal at a frequency .gtoreq.10 GHz, comprising steps for:

• (a) generating in a ring cavity on a substrate a continuous train of mode-locked lasing pulses at the frequency of the electrical signal;
• (b) detecting with a high-speed photodetector on the substrate the continuous train of mode-locked lasing pulses and generating the electrical signal therefrom;
• and
• (c) stabilizing the frequency of the electrical signal by feeding back a portion of the electrical signal to a saturable absorber in the ring cavity.

Apparatus for generating an electrical signal at a frequency .gtoreq.10 GHz, comprising:

• (a) a semiconductor ring laser formed on a substrate for generating a continuous train of mode-locked lasing pulses at the frequency of the electrical signal, the semiconductor ring laser further comprising:
• (i) a plurality of semiconductor layers formed on the substrate, including a pair of cladding layers sandwiched about an active layer, one of the cladding layers being n-type doped and the other cladding layer being p-type doped to form a semiconductor junction about the active layer;
• (ii) a ring cavity formed in the plurality of semiconductor layers, and including a saturable absorber portion and a gain portion and at least one reflection output coupler comprising a pair of oppositely oriented 45-degree reflecting mirrors for coupling the lasing pulses out of the ring cavity in each of a clockwise ring direction and a counterclockwise ring direction;
• and
• (iii) electrodes for electrically activating the gain and saturable absorber portions to generate the train of mode-locked lasing pulses;
• and
• (b) photodetector means located on the substrate proximate to the semiconductor ring laser for detecting the train of lasing pulses and generating the electrical signal therefrom.