The advantage of a DH laser is that the region where free electrons and holes exist simultaneously—the active region—is confined to the thin middle layer. This means that many more of the electron-hole pairs can contribute to amplification—not so many are left out in the poorly amplifying periphery. In addition, light is reflected within the heterojunction; hence, the light is confined to the region where the amplification takes place.
The advantage of a DH laser is that the region where free electrons and holes exist simultaneously—the active region—is confined to the thin middle layer This means that many more of the electron-hole pairs can contribute to amplification—not so many are left out in the poorly amplifying periphery In addition light is reflected within the heterojunction; hence the light is confined to the region where the amplification takes place