Kenneth J. Button

Ferrite Phase Shifters in Rectangular Wave Guide

The problem of the propagation of electromagnetic energy down an infinitely long rectangular wave guide partially filled by a ferrite slab is solved. The solution is expressed in the form of a transcendental equation involving the propagation constant. Calculations are carried out for a lossless ferrite, and the phase constant is evaluated as a function of the appropriate parameters, namely, the ferrite slab thickness, the lateral position of the slab in the guide, and the applied transverse static magnetic field intensity. The results are plotted in graphic form for values of the static magnetic field in the region of ferrite saturation both above and below ferromagnetic resonance. The electromagnetic field configurations within the wave guide are plotted in detail for values of the parameters of practical interest. Two versions of the nonreciprocal phase shifter are discussed. The first consists of a single slab placed asymmetrically in the wave guide, while the second consists of two symmetrically plac...

Submillimeter laser wavelength tables

Tables are presented that list submillimeter laser lines observed in the optical pumping of molecular gases with CO(2) laser radiation. The lines have been obtained from previous publications by various authors and are in the wavelength range from 34micron to 1.965 mm. One table lists, for each gas, the submillimeter wavelengths observed, the line of the CO(2) pump laser, references to the literature, and, where available, the polarization and power of the submillimeter laser and the power of the CO(2) pump laser. A second table lists all the observed laser wavelengths in numerical order together with the gas in which each line was observed. These tables should be useful to researchers working with submillimeter lasers.

Modulated submillimeter laser interferometer system for plasma density measurements

A high resolution submillimeter interferometer system for measurement of electron densities in the 10(14)-cm(-3) </= n(e) </= 2 x 10(15)-cm(-3) range has been developed for use in high density tokamaks. Phase modulation at ~1 MH(z) is accomplished by difference frequency mixing of two cavity tuned laser oscillators. The optically pumped CH(3)OH lasers, which operate on the 118.8-microtm line, feature a novel output coupling design that permits good mode quality and low beam divergence. The beat signals are detected using a newly developed Ge:Li photoconductor, and a direct measurement of the phase shift is obtained from the time lag between probe and reference signals. The sensitivity of the resulting phase measurement is independent of the instantaneous phase and unaffected by fluctuations in the amplitude or in the frequency of the modulation.

Oscillatory magneto-absorption in gallium antimonide JA-1149∗☆

Abstract High-resolution magneto-absorption measurements made at photon energies just above the intrinsic absorption edge in GaSb have revealed an oscillatory spectrum having a strong resemblance to the corresponding spectrum for direct transitions in germanium. Eight successive transmission minima were observed in magnetic fields up to 38.9 kG at both 1.5 and 4.2°K, using polarized incident radiation. The value of the energy gap found is g = 0.813±0.001 eV and is shown to be attributable to direct transitions of electrons between the valence and conduction bands. The electron effective mass, m∗ = (0.047 ± 0.003)m0, was determined by considering transitions from the heavy holes to the conduction band and employing the data of the E||B spectrum. The existence of fine structure, although not resolved, is indicated by the unsymmetrical character of some of the transmission minima. The first absorption line is believed to contain exciton absorption. The inability to resolve the fine structure and exciton absorption is attributed to line broadening and overlapping due chiefly to scattering by the high impurity density in the sample.

Millimeter Wave Dielectric Properties of Materials

Highly accurate continuous spectra of the absorption coefficient and refractive index of some potentially useful materials have been made over the 60-420 GHz range. Measurements have been made on some common ceramic, semiconductor, crystalline and glass materials. The absorption coefficient of low loss materials increases with frequency which implies that microwave data cannot be used for the design of millimeter wave dielectric waveguides, devices, windows and quasi-optical elements. The data in this paper show the millimeter wave frequency dependence of tan δ, the real and imaginary parts of the dielectric permittivity and the optical constants, namely, the refractive index and absorption coefficient. The measurements have been made in a plane-wave Michelson interferometer operating as a polarizing, dispersive Fourier transform spectrometer. The accuracy and reproducability of the refractive index is six significant figures.

Development of an efficient 9‐kW 496‐μm CH3F laser oscillator

A 496‐μm CH3F cavity laser characterized by an average power of 9 kW and predominant single longitudinal mode operation with a linewidth of 28 MHz has been constructed. The power conversion efficiency of the laser (CH3F power out/CO2 pump power in) is on the order of 1.5×10−3. The CH3F gas is pumped in a zig‐zag fashion by the CO2 laser radiation.

Millimeter and submillimeter wave measurements of complex optical and dielectric parameters of materials

These two promising millimeter wave materials were found to exhibit one order of magnitude higher absorption coefficient than the common low-loss ceramics such as alumina, fused silica and beryllia. A modular, polarizing, dispersive Fourier transform spectrometer capable of operating over the range 5 mm to 0.004 mm was used to provide a continuous spectrum of the refractive index and absorption coefficient to an accuracy of five decimal places and less than 1 percent, respectively.

High power optically pumped far infrared laser systems

Single mode, 60-80 ns pulse width, 50-70 kW peak power laser oscillators operating on the 384.6 μm line of D 2 O have been developed. The characteristic linewidths of these oscillators are less than 25 MHz full width at half maximum which favorably compares with the intrinsic width of 6-8 MHz associated with the pulse length of about 60 ns. A 12.7 mJ, 195 kW, 384.6μm D 2 O laser oscillator-amplifier combination has been constructed and tested. Although single longitudinal mode operation is attained from this oscillator-amplifier system, amplified spontaneous emission (superradiance) from the amplifier adds low power level wide-bandwidth background radiation. Studies of far infrared lasing action in CH 3 F and CH 3 I are also described.

Cyclotron resonance and impurity transitions in the valence band of tellurium

Abstract Cyclotron resonance transitions and transitions from acceptor levels to adjacent Landau levels were observed in p-type tellurium at wavelengths of 337 μ and 195 μ with the magnetic field perpendicular to the c-axis of the crystal. The temperature dependence of the spectra in the range of 5°K to 30°K and theoretical predictions of the line positions enabled us to identify each observed line unambiguously.

Efficient high‐power CH3F amplifier for a 496‐μm cavity laser

A CH3F amplifier has been constructed for use with a narrow‐linewidth pulsed 496‐μm CH3F cavity laser. The power conversion ratio of the amplifier, defined as the ratio of 496‐μm power emitted to CO2 power absorbed, had a maximum value of (4.7±2.5) ×10−3 at a CH3F gas pressure of 0.1 Torr. The highest average power, 6±1 kW, was produced by the oscillator‐amplifier laser system when the amplifier was run with a CH3F gas pressure of 0.9 Torr. At this pressure the power conversion ratio of the amplifier was (1.8±1.0) ×10−3. Analysis of the gain data yields values for the small‐signal gain and saturation intensity as a function of CH3F gas pressure.