Measurements in the millimeter to micron range

Measurement techniques and measuring instruments in the millimeter and submillimeter wavelength range are described. Included are discussions of devices in dominant (TE
10
)-mode rectangular waveguide such as a bolometer which possesses an efficiency of 95 percent, a gas absorption wattmeter with an accuracy of 5 percent and a sensitivity of 10
^-6
watts, and isolators and variable attenuators. Components in circular TE
01
-mode waveguide are described, including a standing-wave indicator with a residual VSWR of 1.02 and an adjustable attenuator with 30 dB of attenuation and a VSWR of 1.08. Devices for use in free space include a pair of dielectric prisms for use as an adjustable directional coupler, a hybrid junction, and an adjustable attenuator. Attenuation is readily adjustable from zero to 30 dB with directivity in excess of 15 dB. Also described are dielectric slab filters and calorimetric power meters with accuracies of 0.5 percent in the power range 1-50 mW. Interferometers for use as wavemeters with accuracy as good as 0.04 percent and for use as cavities with Q as high as 10
⁶
are described. They can be used in the measurement of dielectric constant with accuracies of 2 percent. Measurements of the characteristics, attenuation, field distribution, and loss per iteration of beam waveguides and reflecting beam guides have been made which yield good confirmation of theoretical predictions. Measurements of focal length, aberrations, and other characteristics of gas lenses for use in free-space waveguides are described. Measurements are carried out using the lateral shear interferometer, and the Mach-Zehnder interferometer.