A phase measurable optical heterodyne interferometer which is capable for measuring both the modulus r12(0) and the phase ψ12(0)arg{r12(0)} of the spatial coherence function r12(0) without the need of the optically stringent requirement for the equality of the path-lengths in the two arms of the interferometer is established. An extended formulation for the intensity correlation function of optical fields is also presented in relation to the theory of the interferometer. The experimental verifications are presented and are compared with the results obtained from other interferometric systems.

Two types of Si pnp punch-through BARITT diodes are fabricated and the d.c. and small-signal characteristics are studied both experimentally and theoretically. The d.c. solution of carrier-density and electric field distributions was numerically obtained with temperature- and field-dependent drift velocity for two types of diodes; uniform and non-uniform doping profiles. The calculated voltage-current curves were in good agreement with the measured ones from 210 K to 373 K. This agreement implies that the injection mechanism is not thermionic emission but diffusion-limited. Small-signal impedance was derived as functions of injection conductivity and transit-time-dependent space-charge impedance; the injection conductivity was given by perturbation of the d.c. solution and compared with other published theories. The present theory is applicable to a BARITT diode with non-uniform doping. The theory also succeeded in explaining the effect of self-heating. Because of neglect of the velocity-modulation and a.c. diffusion components, the theory overestimates the magnitude of negative resistance when a diode has low doping density (1015/cm3) in the emitter junction. Some predictions were made on effects of temperature, a doping profile and a velocity-field curve on the negative resistance by using the derived formula. As an example, the negative resistance of a GaAs BARITT diode is also predicted.

A concept of metric is defined in the set of labelled graphs. The concept is based on the idea that the extent of the difference in two graphs may be measured by the non-orthogonality of tie-set (loop) vectors of one graph to the cut-set vectors of the other. The meanings involved in the concept are discussed on the topics concerning flow and tension networks. Applications to electrical networks include the theorem that, for a non-reciprocal n-port network N which is realized by using λN controlled-sources, an inequality 1/2 rank (YYT)D(gc, gv)λN holds where Y is the admittance matrix of N and D(gc, gv) is the distance between the corresponding current graph gc and voltage graph gv of N. An example for which the equalities hold in the above inequality is given.

An optical-transmission error-rate experiment is described in which a single-mode fibre up to 5.9 km long is used as a transmission medium. It is shown that impairments of the transmission was mainly determined by material dispersion and wave-guide-delay distorsion of the transmission medium.

High speed pulse modulation of the injection lasers at non-bias condition has been studied to reduce the pattern effect. Rate equations involving the effect of spontaneous emission enable us to analyze the pulse response of carriers and photons both starting from zero in the cavity. The increase of threshold current and the decrease of delay time are derived as a function of the width of driving pulse current at the non-bias condition. Theoretical results were in good agreement with the experiments. The effect of accumulation carriers in the active region is analyzed in details. It is pointed out that the effect of accumulation carriers in the active region limits the rate of pulse repetition when the pattern effect is required to be small. To overcome this effect a new method which utilizes the application of reverse pulse to a laser diode immediately after the emission of light pulse is proposed. This method has been proved experimentally to be effective. A series capacitance to a laser diode was used to produce reverse pulse, and in this way two pulses have been applied at the interval of 2 nsec. Further investigation on the pulse repetition rate together with the consideration of series resistance in the driving circuit has lead to the conclusion that a few Gbit/sec is possible with AlGaAs DH lasers at the non-bias condition. In these lasers, however, very thin active layers with low impurity concentration are required.

The waveguide bandpass filter with dielectric resonators is usually constructed with a cutoff waveguide including dielectric resonators inside and waveguides which are connected at both ends of the cutoff waveguide. The coupling coefficient between dielectric resonators was obtained by S.B. Cohn. The external Q of a dielectric resonator, however, was not reported in the past, which is necessary for the design of the filter. In this paper, the external Q is obtained by calculating the radiation power by using the displacement current inside the dielectric resonator. The theoretical values of the external Q are obtained corresponding to the distance between input waveguide and a resonator. The results were compared with the experimental results and they were in a good agreement. The external Q is also calculated by using the radiation power from a magnetic dipole source of a resonator. It takes more error than the method by using a displacement current.

By application of Zolotarev polynomial, a difference pattern of a monopulse array antenna and a sum (conventional) pattern of an array antenna with an even number of elements are synthesized. The resulting patterns are optimum in a Chebyshev sense for monopulse array antennas and for even element arrays with the element spacing less than a half wavelength, respectively. Design procedure for difference and sum patterns is shown by numerical calculations.