P. E. Tannenwald

Resonant tunneling through quantum wells at frequencies up to 2.5 THz

Resonant tunneling through a single quantum well of GaAs has been observed. The current singularity and negative resistance region are dramatically improved over previous results, and detecting and mixing have been carried out at frequencies as high as 2.5 THz. Resonant tunneling features are visible in the conductance‐voltage curve at room temperature and become quite pronounced in the I‐V curves at low temperature. The high‐frequency results, measured with far IR lasers, prove that the charge transport is faster than about 10− 1 3 s. It may now be possible to construct practical nonlinear devices using quantum wells at millimeter and submillimeter wavelengths.

Quantum well oscillators

Oscillations have been observed for the first time from double barrier resonant tunneling structures. By eliminating impurities from the wells, we have been able to increase the tunneling current density by a factor of nearly 100. With the attendant increase in gain and improved impedance match to the resonant circuit, the devices oscillated readily in the negative resistance region. Oscillator output power of 5 μW and frequencies up to 18 GHz have been achieved with a dc to rf efficiency of 2.4% at temperatures as high as 200 K. It is shown that higher frequencies and higher powers can be expected.

Far‐ir heterodyne radiometric measurements with quasioptical Schottky diode mixers

We have made heterodyne radiometric measurements with GaAs Schottky diode mixers, mounted in a corner‐reflector configuration, over the spectral range 170 μm to 1 mm. At 400 μm, system noise temperatures of 9700 K DSB (NEP=1.4×10−19 W/Hz) and mixer noise temperatures of 5900 K have been achieved. This same quasioptical mixer has also been used to generate 10−7 W of tunable radiation suitable for spectroscopic applications.

Submillimeter detection and mixing using Schottky diodes

Schottky diodes have been used for the first time as harmonic mixers in the 0.1–1.0‐mm wavelength region. Beat notes between the 33rd harmonic of a 74‐GHz V‐band klystron and 118.8‐μ laser radiation are observed directly without the need of narrow‐band synchronous detection. The demonstrated performance of these room‐temperature diodes as wide‐band or heterodyne detectors of submillimeter radiation and their rugged construction make them superior to current point contact devices.

Measurement of Susceptibility Tensor in Ferrites

Experimental techniques for measuring the magnetic susceptibility tensor components in microwave cavities are described. General expressions for the perturbation of microwave cavities by the magnetic properties of ferrites are developed. Experimental results are given for Ferramic 1331 measured at 9165 Mcps. Since these results indicate that both the real and imaginary parts of the tensor components χ and κ are approximately equal to each other in the resonance region, only measurement of the diagonal components may suffice to specify the complete tensor. However, whenever the small differences between χ and κ are desired, measurement of the tensor susceptibility in a degenerate cavity will be necessary. An attempt has been made to compare the experimental results with the Bloch‐Bloembergen magnetic resonance theory as applied to circularly polarized excitation.

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

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.

cw generation of tunable narrow‐band far‐infrared radiation

Tunable narrow‐band cw generation of far‐infrared radiation has been achieved for the first time in the 70‐μm to 1‐mm wavelength region by noncollinear difference‐frequency mixing of two single‐mode CO2 lasers in GaAs at 80 K. Using a Schottky diode as a heterodyne harmonic mixer with a carcinotron local oscillator, the far‐infrared signal is shown to have a linewidth of less than 100 kHz and a fine tuning capability in excess of 50 MHz.

Printed Dipole-Schottky Diode Millimeter Wave Antenna Array

This paper introduces a proposed imaging system suitable for millimeter and submillimeter wavelengths, based on heterodyne mixing at the focal plane of an optical system. We have designed a prototype planar antenna array and quasi-optical system and present measurements at 9 GHz and at 140 GHz of beam patterns and sensitivity for a single two-element, full-wave, printed dipole array incorporating a GaAs beamlead diode. Scale model studies were carried out in the 8-10 GHz range, where the design was optimized. Subsequent measurements were made with a tunable carcinotron at 128-140 GHz on an appropriately scaled array.

Mode Pulling in a Stimulated Raman Oscillator

Stimulated Raman scattering has been observed in quartz at low temperatures in which the 467 cm−1 Stokes line is split into two or more sharp components. The quartz samples, which were in the form of resonant cavities, behaved as Raman oscillators pumped by a ruby laser. Measurement of the Fabry—Perot mode spacings of the oscillators showed that substantial mode pulling was occurring. This was interpreted according to mode‐pulling theory.

Mixing of 10-μm radiation in room-temperature Schottky diodes

Schottky diodes have been used as room-temperature mixers of CO2-laser radiation. When a microwave local oscillator signal was introduced directly into the diode, beat notes between lasers separated by up to 69 GHz were observed. At CO2 frequencies (30 THz) the photon energy exceeds the measured dc nonlinearities, and the device is expected to approach operation as a photon counter rather than a classical resistive mixer.