George J. Simonis

Optical generation, distribution, and control of microwaves using laser heterodyne

Demonstrated is the optical generation and transmission of a microwave signal by the mixing of two high-quality optical signals from diode-laser-pumped Nd:YAG ring lasers, resulting in a narrow microwave line width (less than 5 kHz line width at 3 dB and less than -115 dBc/Hz at 300 kHz from line center) and broad microwave tunability (DC to 52 GHz). A III-V semiconductor waveguide with a doping superlattice active region is used to optoelectronically provide 20 dB of amplitude control and up to 5 pi of phase shift. This approach can be straightforwardly implemented using integrated optics and fiberoptic links for control of phased-array antenna elements. >

An intercomparison of measurement techniques for the determination of the dielectric properties of solids at near millimetre wavelengths

The results of a measurement intercomparison aimed at assessing the systematic errors in near-millimetre-wavelength dielectric measurements on reasonably transparent solid specimens are presented and discussed. Various monochromatic, broad band, guided wave and free space measurement methods were intercompared in the frequency region from 30 to 900 GHz using round-robin measurements of the refractive index and absorption coefficient of seven specimens. Typically, systematic errors of up to 1% were found in the refractive index results, while very much larger systematic errors were found in the absorption results. >

Index to the literature dealing with the near-millimeter wave properties of materials

An index to the literature of the near-millimeter wave (94 to 1000 GHz) properties of solid and liquid materials has been prepared which lists materials in alphabetical order, citing parameters measured, the frequency coverage, and the corresponding publication reference. An accompanying discussion deals with parameters and materials properties and present limitations in this frequency range.

Characterization of near-millimeter wave materials by means of non-dispersive fourier transform spectroscopy

We have used non-dispersive Fourier-transformspectroscopic techniques to measure the complex indices of refraction of materials between frequencies of 120 and 550 GHz. Results are presented for crystal quartz, crosslinked polystyrene (Rexolite 1422), glass-loaded polytetrafluoroethylene (Duroid 5880) and a nickel ferrite (Trans-Tech 2-111). These results are compared with other data on these materials in this frequency range. The accuracy of these measurements yields a considerable improvement in the near-millimeter-wave characterization of several of these materials. For materials other than crystal quartz, our results are the first measurements of their properties over the entire frequency range studied.

Near millimeter wave characterization of dual mode materials

Materials known to have useful properties in the IR were examined in the millimeter wave region. Their complex indices of refraction have been determined in the 90-550-GHz range. The method of determination was nondispersive Fourier transform spectroscopy. The instrument employed was a polarizing interferometer.

Optical control of microwaves with III-V semiconductor optical waveguides

A high-quality microwave signal is generated by heterodyning two diode-laser-pumped Nd:YAG lasers. A III-V semiconductor optical waveguide containing a doping superlattice is used to manipulate the phase and amplitude of one of the laser outputs before they are mixed. This manipulation appears directly as a corresponding change in the phase and amplitude of the heterodyne microwave signal. Results are presented from near dc to 52 GHz. Phase changes as large as 8 pi, and amplitude changes as large as 42 dB have been induced by means of a 1.2-mm-long optical waveguide and less than 3 V of control voltage.

Index of refraction determination in the near-millimeter wavelength range using a mesh Fabry-Perot resonant cavity

A plane–parallel mesh Fabry-Perot resonant cavity has been used to determine the indices of refraction of a number of low-loss materials at 245.351 GHz using a C13H3F far-IR laser. The necessary apparatus is readily available in many far-IR laser laboratories and is readily extendable to other laser and millimeter-wave source frequencies. The values were compared to the measurements of other researchers at neighboring frequencies as available.

Optical Generation And Distribution Of Microwave Signals

We report the results of the optical generation of microwave signals superimposed as a modulation on an optical carrier by means of laser heterodyning. The modulated optical carrier can be easily distributed with fiber-optic cables. This approach offers microwave distribution advantages in size, weight, cost, and frequency diversity, which are desirable in improtant applications such as phased antenna control.

Near-millimeter wave polarizing duplexer/isolator

Polarizing beam splitters made of closely spaced parallel tungsten wires have been configured in such a way as to convert linearly polarized radiation from a source into circularly polarized radiation tunably over a broad frequency range. When combined with a third filter polarizer this combination provided 20 dB of isolation of the source from back reflections while having less than 0.5 dB of insertion losses at 245 GHz.

Tunable kilowatt (12)CH(3)F-laser emission from an unstable resonator.

Using a half-meter unstable resonator configuration, over 1 kW of 0.496-mm radiation has been observed from CO(2)-pumped (12)CH(3)F. At a pressure of 2 Torr, a Ramanlike emission, tunable over 400 MHz, was identified. The emission spectrum contained resonator longitudinal modes of linewidth less than 70 MHz and separated by 275 MHz. The full-angle beam divergence was 18 mrad.