High power quantum cascade lasers

High power quantum cascade lasers emitting at /spl lambda//spl sim/8 /spl mu/m are reported that make optimum use of the cascading scheme, in which electrons sequentially traversing N/sub p/ (typically N/sub p//spl sim/30) stacked active regions emit N/sub p/ laser photons. A near optimum performance was achieved by optimizing the design of the active regions and injectors. Additionally, the waveguide cladding layers were made from InP, the lower cladding being formed by the InP substrate, the upper cladding by InP grown by molecular beam epitaxy (MBE) using solid source phosphorous. This helps to improve in particular the high temperature performance of the lasers. The active region is of the so-called "three well vertical transition" design and consists of three InGaAs quantum wells closely coupled by thin AlInAs barriers.