| 摘要 |
PROBLEM TO BE SOLVED: To widen an optical semiconductor device in a wavelength range where a TE mode gain and a TM mode gain are balanced with each other by a method, wherein quantum wells laminated on an active region are made to have different band gaps with respect to each other. SOLUTION: An active layer 3 is divided in two, a tensile strain region 23 and a non-strain region 24. The tensile strain region 23 is constituted in such a manner that a well 11 is grown on an optical guide layer 22, then a barrier layer 14 is formed thereon, and wells 12 and 13 are successively laminated thereon. The wells 11, 12, and 13 are changed in width (90 Å, 110 Å, and 130 Å), whereby the wells 11, 12, and 13 are changed in quantum levels so as to possess different band gaps equivalent to inter-quantum level transition energies, and emission light rays are changed in wavelength. Therefore, the gain wavelength bands by the wells 11, 12, and 13 overlap favorably and continuously with each other, so that a gain (mainly, TM-mode gain) which is of considerable size, sufficiently high and substantially uniform over a wide band can be realized. |
