A STUDY OF INTERNAL ABSORPTION IN ZN(CD)SE/ZNMGSSE SEMICONDUCTOR-LASERS

Based on two different experiments and an optical field calculation, we show that the free-carrier absorption alpha(fc) in Zn(Cd)Se/ZnMgSSe semiconductor lasers is about 4 cm-1 and that it is smaller than that of GaAs/AlGaAs semiconductor lasers. We have measured the dependence of the L-I characteristics on the cavity length of double heterostructure (DH) lasers under photopumped operation and of single quantum well-separate confinement heterostructure (SQW-SCH) lasers under current-injected operation. For the DH laser, the total absorption coefficient alpha(i) and beta X J0 product (beta is a gain constant, and J0 is the nominal current density that makes the gain equal to zero) are estimated to be 4.2 cm-1 and 8.6 X 10 cm-1, respectively. For the SQW-SCH laser, alpha(i), beta, and J0 are estimated to be 21 cm-1, 4.23 X 10(-3) cm X mum/A, and 1.9 X 10(-3) A/(cm2 X mum), respectively. By calculating the optical fields of these lasers, we have estimated that the absorption in a GaAs substrate is 16.53 cm-1 in the SQW-SCH laser and that it is negligible in the DH laser. We have shown that the large loss in the SQW-SCH laser is caused by both alpha(fc) and the absorption in the substrate and that alpha(i) in the DH laser is caused only by free carrier absorption.