Question

The crucial component of a semiconductor laser that provides optical feedback and helps to build up the stimulated emission process is:

• A. Optical cavity
• B. Heat sink
• C. Doping gradient
• D. Quantum well

Hint:

No optical cavity, no laser! It reflects light back and forth to amplify it — that’s how lasers build up strong, coherent beams.

Answer 1

The Correct Option is A

A semiconductor laser (like a laser diode) produces coherent light via the process of stimulated emission. For this process to amplify light efficiently, a key component is required: the optical cavity.
What is an Optical Cavity?

• It consists of two parallel mirrors (or reflective surfaces) placed at the ends of the semiconductor gain medium.
• The cavity allows photons to reflect back and forth through the gain medium, stimulating more electron transitions and hence more emitted photons.
• This feedback mechanism builds up the intensity of light until laser threshold conditions are met.
• The cavity also selects specific resonant wavelengths, making the output monochromatic.

Why the Other Options Are Incorrect:

• (B) Heat sink: Used to manage heat in the device, but does not contribute to optical feedback or stimulated emission.
• (C) Doping gradient: Used to control carrier concentration or junction properties, not directly responsible for optical amplification.
• (D) Quantum well: Enhances carrier confinement and efficiency but is not the source of feedback in laser operation.

Thus, the essential element that provides optical feedback for lasing action is the optical cavity.