Light emission from a ridge waveguide1.3 &mgr;mInGaAsP/InP semiconductor laser pumped both electrically and optically was analyzed by polarization- and time-resolved measurements. The electric and the optical excitation was realized with a dc-bias current and with 150 ps pulses from aQ-switched Nd-YAG laser at1.064 &mgr;mwavelength, respectively. The pump light was introduced into the InGaAsP/InP laser through a window opened in the substrate gold contact. The steady-stateP–Icharacteristics of the semiconductor laser exhibited a transition from TM- to TE-polarized light emission if the injection current surpasses a certain value that depends on the heatsink temperature. Depending on the dc-bias current and the optical pulse power, a variety of different emission characteristics of the semiconductor laser were observed: pure TE or TM pulsations, in combination with a background cw emission in some cases; simultaneous emission of TE and TM pulses and switching between TM and TE emission states with switching times as short as 30 ps. ©1997 American Institute of Physics.