Quantum cascade laser

A quantum cascade laser comprising:

• a laser structure having an output face for emitting laser light in a first direction;
• and
• a lens having an entrance surface and a convex surface, the entrance surface receiving the laser light from the output face, the convex surface emitting the laser light condensed by the lens,
• wherein
• the laser structure includes a semiconductor substrate and a mesa waveguide provided on a first region of a principal surface of the semiconductor substrate, the mesa waveguide extending in the first direction,
• the lens includes a semiconductor and is provided on a second region of the principal surface of the semiconductor substrate,
• the first region and the second region are arranged in the first direction,
• the laser structure includes a current blocking region embedding a side surface of the mesa waveguide,
• the current blocking region includes an undoped or semi-insulating semiconductor,
• the lens includes a semiconductor mesa extending in the first direction and a semiconductor embedding region embedding a side surface of the semiconductor mesa, and
• the semiconductor embedding region includes an undoped or semi-insulating semiconductor.