Novel ultra-short light pulse emitters utilizing multiple wide quantum wells

We report a novel ultra-short light pulse emitters utilizing transient charge carrier behaviour in a multiple wide-quantum-well (WQW) heterostructure. The optical waveguide is implemented as a tandem-cavity laser diode with electro absorber section in the middle, surrounded by two end-firing gain sections. The ultrashort pulse production is achieved by employing the gain region with three wide GaAsP tensile strained quantum wells separated by GaInP barriers in an unintentionally doped active region of the p-i-n laser diode structure. At large negative absorber bias, lasing emission spiking starts with an unusually long delay of 7 mu s. By applying the current pulses of duration smaller than 7 mu s it is possible to quench entirely the lasing emission. With selection of the parameters of the electrical pump pulse and the absorber voltage it is possible to obtain ultra-short light pulse regime. This optical pulse appears at the end of the electrical pump pulse, as a single optical pulse on top of wide pedestal, due to amplified spontaneous emission. The duration of the pulse is 1.2 ps and pulse energy is 80 pJ. We attribute this behaviour to quantum confined Stark effect. Removal of the external bias field, enabling stronger overlap of carriers yields a sudden increase in the radiative recombination rate and optical gain enabling SR emission. We provide a detailed report on the pulse width and optical spectral behaviour as well as on possible non-classical correlation in the emitted light state seen from comparison to CW lasing regime.