Vertical-cavity surface-emitting laser

A vertical-cavity surface-emitting laser (VCSEL), comprising a substrate, a first distributed Bragg reflector (DBR), an active layer, an oxide layer, and a second DBR;

• wherein the first DBR, the active layer, the oxide layer, and the second DBR are stacked sequentially in a direction away from the substrate and arranged on a front side of the substrate;
• the active layer comprises a first heterojunction layer, a quantum well layer, and a second heterojunction layer;
• and the first heterojunction layer, the quantum well layer, and the second heterojunction layer are stacked sequentially in the direction away from the substrate;
• and
• a material of each of the first heterojunction layer and the second heterojunction layer comprises aluminum gallium arsenide;
• and an aluminum composition in the first heterojunction layer is configured to increase in a first direction away from the quantum well layer, and an aluminum composition in the second heterojunction layer is configured to increase in a second direction away from the quantum well layer, wherein the first direction is a direction pointing from the quantum well layer to the first heterojunction layer, and the second direction is a direction pointing from the quantum well layer to the second heterojunction layer.