Several reports have been published on the quantitative analysis of kink formation mechanism in the output vs. current relation in stripe geometry injection lasers. The results, however, contradict with each other in basic points. In seeking for a better quantitative understanding of the transverse mode instabilities manifested by the kink formation, this paper examines basic aspects of the spatial hole-burning induced mode deformation, which is believed to cause the instabilities. Properties of the eigen functions and eigen values corresponding to the light propagation in a complex dielectric waveguide with a spatial gain and/or loss variation are examined, and an efficient approximation scheme is proposed for computing modal gain. This scheme is applied to a numerical model which approximates gain and refractive index profiles with spatially burned holes in a stripe geometry injection laser. It is found that the mode deformation induced by the hole-burning substantially affects the modal gain, and that the extent of the influence depends strongly on the refractive index contribution to the waveguiding.

The bandwidth of the single-mode fiber is derived for both the amplitude-modulation and the heterodyne-detection (AM) system and the intensity-modulation and the intensity-detection (IM) system, in case that the spectral width of the light source is much less than the modulation bandwidth. In the wavelength-division-multiplexing system, the bandwidth per carrier wave is given as a function of the wavelength, and also at the zero-dispersion wavelength. In case of IM system, the frequency dispersion of the fiber causes the harmonic distortion of the signal and reduces the bandwidth to about a third of that in case of AM system.

Two-dimensional diffracted fields from semiinfinite conducting plane with a circular cylinder of various types at its apex are studied for the purpose of suppressing the backward radiations from the reflector antennas. The basic policy for the suppression of the diffracted fields was already obtained by the authors. It concludes that the electrically and magnetically conducting cylinders are most effective in suppressing the diffraction for the E and H wave incidence, respectively. From the practical point of view, the main difficulty in this policy is how to realize the magnetically conducting cylinder which suppresses the H wave diffraction. In this paper, a corrugated cylinder is adopted for the purpose of the suppression of the H wave diffraction. The characteristics of this cylinder are analyzed by the mode-matching techniques and it is indicated that the corrugated cylinder fairly suppresses the diffracted fields, not only for the H wave but also for the E wave incidence, to almost the optimal level. Additionally, the wideband frequency characteristics are introduced. All these theoretical results are confirmed by the equivalent two-dimensional experiments. At the end of this paper, the applicability of the corrugated cylinder to the suppression of the three-dimensional diffracted fields is suggested experimentally.

This paper gives an experimental result on the measurement of the maximum coupling coefficient and the coupling length between the active waveguide and the passive output waveguide in GaAs/AlGaAs integrated twin-guide (ITG) injection lasers prepared by LPE. Very high coupling efficiency between the active and the passive waveguides was experimentally confirmed. The maximum coupling coefficient and the coupling length were measured to be about 90% and 250 µm, respectively. These values were in agreement with theory. At properly chosen parameters, the threshold current density on an ITG-type" laser was as low as 3 kA/cm² at room temperature.

Aliasing effect of a sampled signal can be reduced by estimating the signal from the samples and then updating the estimate by an iterative technique. This idea can be implemented easily by a multiplier and a feedback loop.