The quality factor, also known as the Q factor, is a dimensionless parameter that describes how underdamped an oscillator or resonator is, and characterizes a resonator's bandwidth relative to its center frequency. A higher Q indicates a lower rate of energy loss relative to the stored energy, meaning the system is more selective in its frequency response and has a narrower bandwidth.
A laser medium is the material used in a laser that amplifies light by stimulated emission, determining the laser's wavelength and efficiency. It can be a solid, liquid, gas, or semiconductor, and its properties are crucial for the laser's application in various fields such as medicine, communications, and manufacturing.