Apparatus and method for optical heterodyne conversion

A radiation source comprising:

• a first source of optical radiation for providing optical radiation of a first frequency;
• a second source of optical radiation for providing optical radiation of a second frequency;
• a photomixer comprising:
• a substrate;
• a first layer of at least one III-V compound formed on the substrate for receiving said optical radiation of a first frequency and said optical radiation of a second frequency, the bottom of the first layer facing the substrate and the first layer including molecules of the at least one compound bonded to form a uniform crystal lattice and additional atoms of a column V element in addition to those required to form the uniform crystal lattice, the additional atoms being disposed within the uniform crystal lattice to form defects in the uniform crystal lattice;
• and
• a second electrically conductive layer formed on the first layer comprising a region of electrically conductive interdigitated electrodes with openings in the conductive layer between the interdigitated electrodes which expose said first layer, whereby an electrical signal of a third frequency is coupled from the first layer to the electrically conductive layer as the first layer receives the radiation of the first and second frequencies, the third frequency being the difference between the first and second frequencies of the optical radiation;
• and
• an antenna coupled to the conductive layer to radiate said electrical signal of the third frequency away from the photomixer.

A photomixer comprising:

• a substrate;
• a low-temperature-grown epitaxial first layer of at least one III-V compound, the bottom of the first layer facing the substrate and the first layer including molecules of the at least one compound bonded to form a uniform crystal lattice and additional atoms of a column V element in addition to those required to form the uniform crystal lattice, the additional atoms being disposed within the uniform crystal lattice to form defects in the uniform crystal lattice;
• and
• a second electrically conductive layer formed over the first layer comprising a region of electrically conductive interdigitated electrodes with openings formed in the conductive layer between the electrodes to expose the first layer, whereby an electrical signal of a third frequency is coupled from the first layer to the electrically conductive layer as the first layer receives the optical radiation of a first and second frequency, the third frequency being the difference between the first and second frequencies of the optical radiation.

A radiation source comprising:

• a first source of optical radiation for providing optical radiation of a first frequency;
• a second source of optical radiation for providing optical radiation of a second frequency;
• a photomixer comprising:
• a substrate;
• a low-temperature-grown epitaxial first layer of at least one III-V compound formed on the substrate, the bottom of the first layer facing the substrate and the first layer including molecules of the at least one compound bonded to form a uniform crystal lattice and additional atoms of a column V element in addition to those required to form the uniform crystal lattice, the additional atoms being disposed within the uniform crystal lattice to form defects in the uniform crystal lattice;
• a second electrically conductive layer formed over the first layer comprising a region of electrically conductive interdigitated electrodes with openings formed in the conductive layer between the electrodes to expose the first layer, whereby an electrical signal of a third frequency is coupled from the first layer to the electrically conductive layer as the first layer receives the optical radiation of a first and second frequency, the third frequency being the difference between the first and second frequencies of the optical radiation;
• and
• an antenna coupled to the conductive layer to radiate a signal of the third frequency away from the photomixer.

A sweep oscillator comprising:

• a first tunable source of optical radiation for providing optical radiation of a first frequency;
• a second tunable source of optical radiation for providing optical radiation of a second frequency;
• a photomixer comprising:
• a substrate;
• a first layer of at least one III-V compound formed on the substrate for receiving said optical radiation of a first frequency and said optical radiation of a second frequency, the bottom of the first layer facing the substrate and the first layer including molecules of the at least one compound bonded to form a uniform crystal lattice and additional atoms of a column V element in addition to those required to form the uniform crystal lattice, the additional atoms being disposed within the uniform crystal lattice to form defects in the uniform crystal lattice;
• and
• a second electrically conductive layer formed on the first layer comprising a region of electrically conductive interdigitated electrodes with openings in the conductive layer between the interdigitated electrodes which expose said first layer, whereby an electrical signal of a third frequency is coupled from the first layer to the electrically conductive layer as the first layer receives the radiation of the first and second frequencies, the third frequency being the difference between the first and second frequencies of the optical radiation, and being sweepable over a range of frequencies as at least one of the first and second tunable sources of optical radiation is tuned;
• and
• a planar antenna coupled to the conductive layer to radiate said electrical signal of the third frequency away from the photomixer.