...
More complex lasers have four or more mirrors to form the cavity. Other optical devices, such as spinning mirrors, modulators, filters, and absorbers, may be placed within the optical resonator to produce a variety of effects on the laser output, such as altering the wavelength of operation or the production of pulses of laser light. [1]
4. Summary
During this assignment we found out about laser construction and that by using parallel mirrors we can make a more powerful amplification so that when the light is passing through the gain medium it gets amplified. Then it bounces off the first mirror (on the right side) and then passes to the other mirror and gets amplified. It repeats this process and jumps backwards and forwards so as it passes through the gain medium it becomes more powerful. One of the mirrors is partially reflective because light needs to shine out of the laser so if the mirror is fully reflective light will be trapped inside the cavity permanently. So with a partially reflective mirror on every cycle light loses a little of its energy and that makes laser beam output to have a limited power.
...