What is a He-Ne laser?

He-Ne Laser

The Helium-Neon (He-Ne) laser is a type of gas laser that emits a continuous wave of light in the visible red spectrum, typically at a wavelength of 632.8 nm. It was one of the first gas lasers to be invented and has since become a staple in various scientific, educational, and industrial applications due to its reliability, coherence, and stable output.

Operation Principle

The He-Ne laser operates based on the principle of optical amplification through the stimulated emission of radiation. The laser construction consists of a glass tube filled with a mixture of helium and neon gases at low pressure. Electricity is introduced into the system via electrodes to excite the helium atoms. These excited helium atoms then collide with neon atoms, transferring energy and causing them to become excited. When these excited neon atoms return to their ground state, they emit photons. The glass tube also has mirrors at both ends that reflect the photons back and forth, causing more excited neon atoms to emit photons in a process known as stimulated emission. This amplification results in the production of a coherent, monochromatic beam of light that exits one of the mirrors, which is partially reflective.

Applications

• Laboratory Research: Used in spectroscopy, interferometry, holography, and as a standard for calibrating other optical instruments.
• Commercial Use: Barcode scanners, leveling, and alignment tools.
• Educational Purposes: Demonstrations in physics regarding the properties of light and laser operation.
• Medical Field: Dermatological treatments and biomedical research.

Advantages and Limitations

The He-Ne laser is known for its excellent beam quality with low divergence and a long operational life. It provides a good coherence length and stability which makes it suitable for precision measurements. However, its output power is generally low, often less than 10 mW, which limits its use in applications requiring high power. It also tends to be more expensive and bulkier in comparison to solid-state lasers, like diode lasers.

In conclusion, the He-Ne laser continues to be an important tool in various fields due to its stable and high-quality laser beam. Despite the emergence of newer laser technologies, the characteristics of the He-Ne laser ensure its relevance in both educational and precision measurement contexts.