Laser pointers use a laser diode, which is a semiconductor device that emits coherent light when electrically driven.

What is a Laser Diode?

A laser diode is a type of semiconductor device similar to a light-emitting diode (LED), but it is designed to produce coherent, narrow-band light through stimulated emission rather than just spontaneous emission . Electrically, it functions as a PIN diode, with an intrinsic (undoped) region sandwiched between p-type and n-type semiconductor layers . When a forward voltage is applied, electrons and holes recombine in the intrinsic region, generating photons that are amplified to form a laser beam .

Characteristics in Laser Pointers

• Wavelength: Laser diodes in pointers typically emit visible light, commonly red (~635–650 nm), green (~520–532 nm), or blue (~445–450 nm), depending on the semiconductor material used .
• Power: They are low-power devices, usually in the 1–5 mW range, sufficient to produce a visible spot without being hazardous under normal use .
• Structure: Modern laser diodes often use a double-heterostructure with quantum wells in the active region to improve efficiency and reduce threshold current .

Materials Used

• Red laser diodes: Typically made from gallium arsenide (GaAs) or gallium arsenide phosphide (GaAsP) .
• Green and blue laser diodes: Often use gallium nitride (GaN) or related compounds .

Summary

In essence, a laser pointer contains a compact laser diode that converts electrical energy into a narrow, coherent beam of visible light. Its semiconductor design, material choice, and low-power operation make it ideal for handheld, battery-powered devices used for pointing, presentations, or educational purposes .