A complete quantum generalization of microwave mixer theory is constructed for nonlinear single-particle tunnel junctions. The result represents a unification of the concepts used to describe these "classical" resistive mixers with the language of photon detection. Tunneling devices are predicted to undergo a transition from energy detectors to photon counters when operated at frequencies where the photon energy becomes comparable to the voltage scale of the dc nonlinearity. The small-signal video current response is found to approach one electron for each photon absorbed at high frequencies. In a heterodyne receiver, sufficiently nonlinear tunnel junctions are predicted to be capable of achieving the fundamental quantum noise limit for sensitivity in the detection of electromagnetic radiation. The theory presented here thus provides a framework for systematically extending the techniques of quantum electronics to considerably lower frequencies than are currently being exploited. Recent measurements of heterodyne mixer performance using superconductive tunneling devices are already beginning to approach quantum limited results at microwave and millimeter wave frequencies. Eventual application of tunnel barriers as photon detectors in the submillimeter and infrared spectral regions also appears to be possible, and the fast response times of such devices could give them an advantage over photoconductors even at the higher frequencies. The development of suitable nonlinear tunnel junctions contains the potential to bridge the present gap in quantum detectors between the infrared photon devices and microwave masers.

Quantum limited detection in tunnel junction mixers

A whiskerless millimeter-wave mixer diode that yields performance comparable to that of the highest-quality whisker-contacted diodes is discussed. The diode uses an etched surface channel and planar air bridge to obtain greatly reduced parasitic capacitance. At 94 GHz, the room-temperature diode exhibited a conversion loss of 5.3 dB+or-0.5 dB and an equivalent input noise temperature of 518 K+or-50 K SSB (single sideband). >

RF performance of a novel planar millimeter-wave diode incorporating an etched surface channel

A novel GaAs monolithic integrated circuit mixer has been fabricated which is impedance matched to fundamental waveguide. It consists of a slot coupler, coplanar transmission line, surface-oriented Schottky-barrier diode, and RF bypass capacitor monolithically integrated on the GaAs surface. At 110 GHz, a monolithic mixer module mounted in the end of a waveguide horn has an uncooled double-sideband (DSB) mixer noise temperature of 339 K and conversion loss of 3.8 dB.

High-performance quasi-optical GaAs monolithic mixer at 110 GHz

Spectral analysis of high‐power pulsed D2O lasers has been accomplished using SAW dispersive delay lines. Both the contributions of longitudinal modes and the tuning of the stimulated Raman line at 385 μm have been observed.

Real‐time spectral analysis of far‐infrared laser pulses using an SAW dispersive delay line

A S A TRIBUTE to individuals who have contributed significantly, and over many years, to the terahertz community, and as a guide and inspiration for those who are just beginning their professional association with this field of study, these transactions have included, on a regular basis, a series of biographical interviews with technical researchers who have appreciably impacted the THz community in a positive manner. In order to go beyond a strict technical review and to take better advantage of the information and commentary only available through a direct discussion, these articles take on a less formal style than the research articles that can be found within the remaining pages of the transactions. The Editor-in-Chief has taken some leeway in this regard, for the benefit of communicating more fully the character, experiences, and historic circumstances that have shaped our community and set the directions for our collective research. As a further means of assuring that the true flavor and circumstances of the contributions are expressed in the text, all of the articles are compiled after a face-to-face interview. The final text is shared with, and often helped considerably, by comments from the subject of the article. This month we travel to Japan to speak with Dr. Hiromasa Ito,1 a longterm affiliate of the Research Institute of Electrical Communication (RIEC), Tohoku University, Sendai, and a former Team Leader in Terahertz Photonics at Japan's premier science research institution, RIKEN (Institute of Physical and Chemical Research). Professor Ito is a link in a long chain of noted THz advocates and researchers at Tohoku. This chain began with Jun-Ichi Nishizawa2 who according to Ito, “predicted the possibility of using the resonance of phonons and molecular vibrations to generate THz electromagnetic radiation”3 in 1963. Nishizawa came to RIEC in 1953, and established

http://ieeexplore.ieee.org/iel7/5503871/6759772/06759793.pdf

Terahertz Pioneers

Planar surface-oriented Pt/GaAs Schottky-barrier diodes have been fabricated and used to detect signals at submillimeter wavelengths. Video detection has been observed up to frequencies as high as 890 GHz. Harmonic mixing between the ninth harmonic of a 74.21-GHz signal and the second harmonic of 333.95-GHz radiation has also been obtained.

J.P. Donnelly

Papers

Submillimeter Heterodyne Detection with Planar GaAs Schottky-Barrier Diodes