Carrier-induced reduction of the index of refraction of GaInP measured with distributed feedback lasers

We present new results on the effective refractive index of GaInP/AlGaInP distributed feedback (DFB) lasers with grating periods around 100 nm, operated at 77 K and at room temperature. Double heterostructure (DH) lasers as well as multiple quantum well lasers show DFB-laser emission at 300 K over a range of 15 nm. For the DH lasers a clear difference of absolute value and dispersion of the effective refractive index was observed between 77 and 300 K, which is explained by high carrier density effects. For a carrier density of N=2.5×1018 cm−3 the refractive index of GaInP decreases by 0.05, which is compared with an ab initio calculation.