Description

The helium-neon (HeNe) laser is a type of gas laser that produces a coherent and monochromatic light beam in the visible and near-infrared regions of the electromagnetic spectrum. It operates by using a mixture of helium and neon gases, which are excited by an electrical discharge to emit light.

The HeNe laser is typically a gas tube with a length of several tens of centimeters, containing a mixture of helium and neon gas at low pressure. The tube has two mirrors at its ends, one of which is partially transparent to allow some of the laser light to escape.

When an electrical discharge is applied to the gas mixture, it excites the gas atoms to higher energy levels, causing them to emit photons of light. These photons then bounce back and forth between the mirrors, stimulating other excited atoms to emit more photons of the same wavelength and phase, creating a highly coherent and monochromatic beam of light.

The HeNe laser emits light in the red-orange region of the electromagnetic spectrum, typically at a wavelength of 632.8 nanometers. It has a relatively low power output, typically in the range of a few milliwatts to a few tens of milliwatts, but its high coherence and narrow linewidth make it useful in a wide range of applications, such as in holography, interferometry, and alignment of optical components.