P-type isolation between qcl regions

A quantum cascade laser comprising one or more p-type electrical isolation regions and a plurality of electrically isolated laser sections extending along a waveguide axis of the laser, wherein:

• the quantum cascade laser comprises an active waveguide core sandwiched between upper and lower n-type cladding layers;
• the active core and the upper and lower n-type cladding layers extend through the electrically isolated laser sections of the quantum cascade laser;
• a portion of the upper n-type cladding layer comprises sufficient p-type dopant to define a p-type electrical isolation region that extends across at least a part of the thickness of the upper n-type cladding layer along a projection separating the electrically isolated laser sections of the quantum cascade laser;
• the p-type dopant defines a p-doping concentration that is higher than the n-doping concentration of the upper cladding layer;
• and
• the core layer comprises alternating semiconductor layers that are configured to amplify light emitted due to carrier transitions between energy states within the same energy band.