D - centers in intracenter Si:P lasers
ABSTRACT The terahertz Si:P laser is based on the 2p0→1s(T2) transition of neutral phosphorus donors D0 that are photoionized by radiation from a C O 2 laser. The manifestation of negatively charged D- donor centers has been studied. The population of D- centers as well as D0 donor states are calculated and the amplification provided by D0 centers is compared with the absorption by D- centers. The small signal gain and laser threshold have been measured for a set of Si:P lasers with different degrees of compensation (doping by neutron transmutation). It is shown that absorption by D- centers terminates the laser action in Si:P lasers with small compensation (K≪1%) for pump intensities less than 1 kW cm -2 . At higher excitation levels (≫10 kW cm -2) , or for larger compensation, absorption by D- centers becomes negligible.