High-speed modulation and switching with gain in a GaAlAs traveling-wave optical amplifier

We demonstrate optical amplification of 10-ps-long pulses in a traveling-wave type GaAs double heterostructure laser diode. A continuous train of mode-locked pulses from a dye laser focused end on into the GaAs active region is amplified by a factor of 10 under injection by a synchronous train of current pulses and attenuated by a factor of 10 in the absence of current injection. This gives a switch/modulator with modulation depths of 100, overall gain, and measured switching speed of many GHz. A cw beam can be modulated at similar gains and speeds and since the device is capable of integration the performance of many optical functions without loss is possible.