| 摘要 |
PURPOSE:To improve wavelength characteristics of oscillation and oscillation efficiency, by constituting a lambda/4-shift DFB laser structure wherein a large- reflection region composed of corrugation having a large coupling coefficient is arranged so as to connect with a light waveguide on one end surface side. CONSTITUTION:The period of corrugation in a large-reflection region 9 is equal to the period in a main oscillation region 10, but the depth is very deep, which is selected as 800Angstrom in the large-reflection region, for example, in the case where the depth in the main oscillation region 10 is 200Angstrom . In this example, the coupling coefficients in the main oscillator region and in the high-reflection region are 30cm<-1> and 200cm<-1>, respectively. When the length of the main oscillation region L is made as 300Angstrom , and that of the large-reflection region l is made as 100Angstrom , the light output efficiency is 0.15mV/mA in the case of a conventional structure where not provided with the high reflection region, but the data of 0.3mW/mA is obtained by this example. A figure shows that a lambda/4-shift is symmetrically formed on the both sides with respect to a center point A in the main oscillation region 10. But any problem does not occur even if the high-reflection region 9 extends to the left side and the shallow corrugation region on the right side of the point A is made narrow. |
