What are the characteristics of a double hetero junction laser?

The characteristics of a double heterojunction laser are best represented by the choice that describes two junctions of different materials with a smaller band gap in the middle. This configuration is essential for the efficient operation of the laser.

In a double heterojunction laser, the structure typically consists of three layers: a band gap material with a higher band gap on the outside and a middle layer with a smaller band gap. This setup is crucial because the smaller band gap layer facilitates the confinement of charge carriers (electrons and holes) as well as the light generated within the laser. The higher band gap layers serve to restrict the movement of these carriers, ensuring they remain in the active layer where recombination can occur to produce laser light.

Furthermore, this design allows for increased efficiency and higher performance in laser emission, allowing for better control over the optical properties and the threshold current required for lasing. The choice accurately captures the essence of what makes the double heterojunction laser distinctive and effective compared to simpler junction configurations.