Kenichi KASAHARA Takahiro NUMAI Hideo KOSAKA Ichiro OGURA Kaori KURIHARA Mitsunori SUGIMOTO
The VSTEP concept and its practical application in the form of an LED-type pnpn-VSTEP demonstrating low power consumption through electro-photonic operational modes are both shown. Further, with focus primarily on the new laser-mode VSTEP with high-intensity light output and narrow optical beam divergence, the design features such as threshold gain and optical absorptivity, device fabrication, and characteristics are explained. The possibility of ultimate performance based mainly on electrical to optical power conversion efficiency, important from the application viewpoint of optical interconnection, are also discussed. Also, as two examples of functional optical interconnection achieved by VSTEP, serial-to-parallel data conversion and optical self-routing switches are shown. Finally, future opto-electronic technologies to be developed for two-dimensionally integrable surface-type optical semiconductor devices, including the VSTEP, are discussed.
Noriyuki TANIDA Takashi YOKOMORI
This paper concerns a subclass of regular languages, called strictly regular languages, and studies the problem of identifying the class of strictly regular languages in the limit from positive data. We show that the class of strictly regular languages (SRLs) is polynomial time identifiable in the limit from positive data. That is, there is an algorithm that, for any strictly regular language L, identifies a finite automaton accepting L, called a strictly deterministic finite automaton (SDFA) in the limit from positive data, satisfying the property that the time for updating a conjecture is bounded by O(mN2), where m is the cardinality of the alphabet for L and N is the sum of lengths of all positive data provided. This is in contrast with the fact that the class of regular languages is not identifiable in the limit from positive data.
Akira ITOH Toshio HOSONO Yuuiti HIRAO
We studied transient fields on a perfectly conducting sphere excited by a half sine pulse wave and examined the Poynting vectors, the energy densities and the energy velocities of the creeping waves. We used FILT (Fast Inversion of Laplace Transform) method for transient analysis. We compared the amplitudes of the creeping wave with that of steady state high frequency approximation obtained by the Watson transformation. The main results are: (1) We confirmed in the transient response that the pulse propagates clockwise and counterclockwise along the geodesic circumference. (2) In the transient electromagnetic field observed in the E-plane we can recognize creeping waves clearly. (3) The existence of creeping waves is not clear in the H-plane. (4) The pulse wave propagation on the sphere is seen more clearly from the Poynting vectors and the energy densities than the field components. (5) The energy velocity of the wave front is equal to the light velocity as should be. The energy velocity of the wave body becomes smaller with the passage of time. (6) The amplitude of the creeping wave for a beat pulse and the amplitude obtained by the Watson transform for mono spectrum agree in the order of relative error below 25%.