SEMICONDUCTOR OPTICAL ELEMENT, FIBER TYPE OPTICAL AMPLIFIER AND OPTICAL TRANSMISSION DEVICE

摘要

PROBLEM TO BE SOLVED: To improve the stability of optical coupling and branching ratios even if optical waveguide of multimodes are used with respect to a transverse direction by providing at least part of the optical waveguide with a mode filter which allows the transmission of the basic mode light of the optical waveguide and prohibits the propagation of higher order mode light and making the width of the mode filter larger than the width of the optical waveguide. SOLUTION: At least part of the optical waveguide 1 of the semiconductor optical element having the optical waveguide 1 consisting of a semiconductor is provided with the mode filter 2. The width w of the optical waveguide 1 and the width w1 and length of the mode filter 2 are so determined that the intensity distribution of the light in the inlet of the mode filter 2 is nearly equaled to the light intensity distribution in the outlet of the mode filter 2 with respect to the basic mode light of the optical waveguide 1. In such a case, the width w1 of the mode filter 2 is set 1.5 to 4 times the width w of the optical waveguide 1. The width w1 of the mode filter 2 is set 1.5 to 10μm and the width w of the optical waveguide 1 is set at 1 to 10μm.