Quantum cascade laser element and quantum cascade laser device

A quantum-cascade laser element comprising:

• a semiconductor substrate;
• a semiconductor mesa formed on the semiconductor substrate to include an active layer having a quantum-cascade structure and to extend along a light waveguide direction;
• an embedding layer formed to interpose the semiconductor mesa along a width direction of the semiconductor substrate;
• a cladding layer formed over the semiconductor mesa and over the embedding layer;
• and
• a metal layer formed on the cladding layer,
• wherein a pair of groove portions extending along the light waveguide direction are formed in a surface of the cladding layer on a side opposite to the semiconductor substrate,
• the pair of groove portions are disposed in two outer regions respectively when the cladding layer is equally divided into four regions in the width direction of the semiconductor substrate,
• the metal layer enters the pair of groove portions,
• the pair of groove portions reach the embedding layer, and
• bottom portions of the pair of groove portions are positioned within the embedding layer.