The present invention provides a terahertz oscillator utilizing a GaN Gunn diode. A terahertz wave is generated in the active layer of the Gunn diode fabricated on GaN substrate. A GaN substrate is designed to act as a waveguide of the terahertz wave. Since the waveguide and the Gunn diodes are integrated, the terahertz wave generated in the active layer couples well with the waveguide made of the GaN substrates. The terahertz wave is emitted from the edge of the waveguide efficiently. To ensure high-reliability through reduction of radiation loss and mitigation of electromigration of anode metal, a GaN substrate with low dislocation density is used. The dislocation density of the GaN substrate is less than 1×10.sup.6 cm.sup.−2. Particularly, usage of a GaN substrate made by the ammonothermal method is preferred.

A device, comprising: an antenna array provided with a plurality of antennas each having a semiconductor layer having terahertz-wave gain; and a coupling line for mutual frequency-locking of at least two of the antennas at a frequency of the terahertz-wave, wherein the coupling line is connected to a shunt device, and the shunt device is connected in parallel to the semiconductor layer of each of the two antennas.

A device includes a first antenna arranged on a substrate, with the first antenna comprising a first semiconductor layer having terahertz-wave gain and a first conductor layer, a second antenna arranged on the substrate, with the second antenna comprising a second semiconductor layer having terahertz-wave gain and a second conductor layer, and a third conductor layer arranged on the substrate and electrically connecting the first antenna and the second antenna. A shunt device is arranged on the substrate and electrically connected to the third conductor layer. In planar view, the shunt device does not overlap with at least the first conductor layer.

The present invention provides a terahertz oscillator utilizing a GaN Gunn diode. A terahertz wave is generated in the active layer of the Gunn diode fabricated on GaN substrate. A GaN substrate is designed to act as a waveguide of the terahertz wave. Since the waveguide and the Gunn diodes are integrated, the terahertz wave generated in the active layer couples well with the waveguide made of the GaN substrates. The terahertz wave is emitted from the edge of the waveguide efficiently. To ensure high-reliability through reduction of radiation loss and mitigation of electromigration of anode metal, a GaN substrate with low dislocation density is used. The dislocation density of the GaN substrate is less than 1×10.sup.6 cm.sup.−2. Particularly, usage of a GaN substrate made by the ammonothermal method is preferred.

Systems and methods for forming a mm wave resonant filter include a lithographically fabricated high Q resonant structure. The resonant structure may include a plurality of cavities, each cavity having a characteristic frequency that defines its passband. A filter may include a plurality of resonant structures, and each resonant structure may include a plurality of cavities. These cavities and filters may be fabricated lithographically.

Systems and methods for forming a mm wave resonant filter include a lithographically fabricated high Q resonant structure. The resonant structure may include a plurality of cavities, each cavity having a characteristic frequency that defines its passband. A filter may include a plurality of resonant structures, and each resonant structure may include a plurality of cavities. These cavities and filters may be fabricated lithographically.

A device, comprising: an antenna array provided with a plurality of antennas each having a semiconductor layer having terahertz-wave gain; and a coupling line for mutual frequency-locking of at least two of the antennas at a frequency of the terahertz-wave, wherein the coupling line is connected to a shunt device, and the shunt device is connected in parallel to the semiconductor layer of each of the two antennas.

Systems and methods for forming a compact gas sensor include using a lithographically fabricated high Q resonator coupled to at least one of a Gunn diode and an IMPATT diode. The resonator may include a plurality of cavities filled with a sample gas. A detector coupled to the resonator may measure the amplitude of the emitted mm wave radiation.

An element which oscillates or detects terahertz waves includes a resonance unit including a differential negative resistance element, a first conductor, a second conductor, and a dielectric body, a bias circuit configured to supply a bias voltage to the differential negative resistance element, and a line configured to connect the resonance unit and the bias circuit to each other. The differential negative resistance element and the dielectric body are disposed between the first and second conductors. The line is a low impedance line in a frequency f.sub.LC of resonance caused by inductance of the line and capacitance of the resonance unit using an absolute value of a differential negative resistance of the differential negative resistance element as a reference.

Systems and methods for forming a compact gas sensor include using a lithographically fabricated high Q resonator coupled to at least one of a Gunn diode and an IMPATT diode. The resonator may include a plurality of cavities filled with a sample gas. A detector coupled to the resonator may measure the amplitude of the emitted mm wave radiation.