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Submillimeter magneto-spectroscopic measurements of the shallow donor impurity in InAs epi-layer crystals have been made at low temperatures. Several excited state transitions have been observed for the first time, together with various transitions from the ground state.

The results are presented of the detailed studies on the exciton absorption spectra in ultrapure Ge in the spectrum regions 0.67-1.1 and 1.7-3.7 meV with a backward-wave tube radiation. It is shown that the measured spectrum corresponds to the exciton's transitions from the ground to excited states. As a result of temperature measurements at 1.6-4.2 K the phase transition of excitons into the condensed state has been observed without the formation of excitonic molecules.

Surface and volume magnetostatic mode resonances of an axially magnetized YIG rod is used for the diffraction and intensity modulation of 1,15? He-Ne laser beam. YIG crystal is excited with a dielectric microwave resonator at S band. Amplitude modulation of the microwave source produces intensity modulation on the diffracted laser beam. Critical Bragg angles are not needed and the first order diffracted beams are found symmetric about the zero order.

The transversely excited 337 μm-HCN-laser with an output power near 1 kW is described. Relevant data on the construction, laser-gases and performance are presented.

Absorption and photoconductivity of 337-mu m radiation in Sb-doped Ge with excess donor concentrations ranging from 1.2 x 10/sup 16/ to 3.6 x 10/sup 17/ cm/sup -3/ have been investigated at liquid-He temperatures. The result suggests the existence of a "delocalized" excited state between the conduction band and the donor ground state which arises from the overlapping of donor wave functions.

A perturbation technique is employed for dielectric waveguides with a small dielectric difference between the guide and its surrounding medium, resulting in an analytically simple, selfconsistent, theory for surface modes. The field equations are shown to manifest bounded waveguide simplicity. In partitular the transverse electric and magnetic fields are related by a constant and possess the orthogonality of a metal waveguide. Furthermore, an analytic expression is presented for the eigenvalues. Although the analysis is based on small dielectric differences, it is shown to be adequate when the inside dielectric is as large as twice the outside. The results of the perturbation analysis are applied to the excitation of a semi-infinite dielectric rod excited by a uniform field.

A simple measurement technique has been developed for determining the amplitude and relative phase of individual modes propagating in overmoded waveguide. This development was performed a s a portion o f the program on in-guide multimode power measurements.* The mode-measurement technique represents a significant step toward bridging the gap between total in-guide measured power and spectrum signature prediction. Also o f importance i s the use of the technique t o measure mode conversion when standard waveguide components are excited at frequencies outside of their design band.

In the usual technique for the display of ferroelectric hysteresis loops, the specimen is excited from a sinusoidal a.c. voltage source, signals proportional to D and E are derived and these are respectively applied to the vertical and horizontal deflection plates of a cathode ray oscilloscope. Ordinarily, the frequency of excitation is 60 c.p.s., the choice being purely one of convenience. Actually, it would be preferable to obtain a plot of the quasi-static loop except where one is specifically interested in frequency dependent hysteresis effects. Quasi-static loops can be obtained by a point by point ballistic method, but this is a tedious procedure and there is always the uncertainty in distinguishing between the effects of the polarization current and the conduction current.