Semiconductor lasers are used for which applications?

• A. Heat treatment of materials
• B. Ranging, infrared illumination, intrusion alarms, fiber-optic communications, and optical scanning
• C. Medical imaging
• D. Water purification

Answer: (B)

Semiconductor lasers are compact, efficient light sources that can emit stable, often infrared, light and can be switched on and off or modulated at high speeds. Their small size and easy integration with electronics, plus the ability to couple their output into optical fibers or direct it over short distances, make them versatile for practical systems.

This combination explains why they’re used for ranging and LIDAR-style distance measurements, where precise, fast, coherent light helps determine how far away something is. They’re also ideal for infrared illumination in security and night-vision contexts, providing a reliable IR beam that isn’t visible to the naked eye. In intrusion-alarm setups, a detector watches for a beam interruption from a diode laser, which again plays to the strength of a compact, stable IR source. For fiber-optic communications, diode lasers are the workhorse light sources because they can deliver high data rates over long distances with high efficiency and easy modulation. And in optical scanning, the ability to rapidly and precisely direct a focused laser beam enables fast scanning in devices like barcode readers or laser scanners.

Heat treatment of materials or water purification isn’t typically powered by semiconductor lasers in the same way, because those applications usually require different laser types, wavelengths, or higher powers.