Measured τ_meas curves during the PCD decay. (a) The high quality n-type slab featuring negligible injection level dependence (ILD) shows a similarly increasing τ_eff(t) regardless of laser wavelength and power. In the case of stronger ILD (b and c) longer wavelength and elevated laser power makes possible to determine the lifetime closer to the saturation value of τ_b. (Low power: 3 × 10¹⁸ cm⁻² s⁻¹ used in WT-1200I, High power: 2 × 10¹⁹ cm⁻² s⁻¹ is used in WT-1200. IL).