Temporal wavelength multiplexing of a Quantum Cascade laser

A bi-directional and multi-wavelength Quantum Cascade (QC) laser based system is presented that is both time and wavelength multiplexed, that is, it can emit two widely different wavelengths, at two alternate time slots. The QC laser source emits at 10.8 mum wavelength for positive polarity current and 8.6 mum for negative polarity current. A diode based adder circuit was designed to drive the QC laser such that it added the two opposite polarity current pulses with a variable time delay. Versatile multi-wavelength and time multiplexed QC laser light signals with time delays of 0.5 s to 2.5 mus were obtained.