Introduction to Lasers - Basics for workers

What is a Laser?

Laser is an acronym which stands for light amplification by stimulated emission of radiation (Donnelly et al., 2025). In a laser, an energy source stimulates the molecules in a gas or solid to emit light particles known as photons (ARPANSA). The photons bounce back and forth between two mirrors until a small, concentrated beam of light exits the laser (ARPANSA). Lasers are usually monochromatic meaning they are only one wavelength- which we see as one colour (Donnelly et al., 2025). Unlike most light sources, laser radiation travels far distances spreading out very little (Donnelly et al., 2025). Lasers are also coherent, meaning the light waves travel in step with one another rather than out of phase as they do in ordinary light sources. Because electromagnetic radiation emitted from a laser is small and concentrated, it can carry incredible amounts of power (ARPANSA). Whilst this can be useful in many settings including medical, dental, hair removal and construction, it can be dangerous without proper safety measures (ARPANSA). The eyes and skin are the organs most at risk from lasers (ARPANSA).

Common Terms Laser Operators Should be Familiar With

Irradiance: This is the power output of a beam divided by the area of the beam (Barat 2022). In other words, irradiance can describe the intensity of the laser beam.

Continuous wave (CW): This is a laser operating with an uninterrupted output for a period of 0.25 seconds or longer.

Pulsed beam: This is a laser that delivers its energy in pulses that are less than 0.25 seconds. Pulsed beam laser may operate as a single pulse or in a series of pulses of different durations.

Diffuse reflection: This is where a beam bounces off a surface that is not smooth and then disperses it into a series of directions, reducing its intensity. Although this can be beneficial for reducing the hazard potential of most lasers, diffuse reflections can remain dangerous for high powered lasers including class 4 lasers. This means standing anywhere near a class 4 laser has the potential to introduce exposure to diffuse reflections and cause harm. 

Specular reflection: This is where a beam bounces off a smoother surface allowing the beam to maintain its coherence, divergence and intensity (Barat 2022).

Controlled area: Controlled area is an area in which the activities of persons are controlled and supervised for the purpose of protection from laser exposure.

AS/NZS IEC 60825.14:2022: A laser safety standard produced by Standards Australia (2022) designed to help laser users and organisations understand laser safety management including identifying hazards in addition to assessing and managing risk.

Optical density: Describes how much light is inhibited from passing through a material such as the lenses in laser safety glasses (Standards Australia, 2022). A high optical density means less light will pass through a material. Optical density is commonly expressed as OD and works in a logarithmic scale. 

Maximum Permissible Exposure: The level of radiation to which people may be exposed under normal circumstances without suffering adverse effects. In other words, the highest level of laser radiation which the eye or skin can be exposed to without causing harm.

References

 ARPANSA. "Advice for providers: Lasers, IPL devices and LED phototherapy for cosmetic treatments and beauty therapy." 2026, from https://www.arpansa.gov.au/understanding-radiation/sources-radiation/more-radiation-sources/lasers-and-intense-pulsed-light-1.

ARPANSA. "Laser Hazards and Safety ". Retrieved 05/09/2026, from https://www.arpansa.gov.au/understanding-radiation/radiation-sources/more-radiation-sources/lasers.

ARPANSA. "Lasers." Retrieved 22/08/2026, from https://www.arpansa.gov.au/understanding-radiation/what-is-radiation/non-ionising-radiation/laser.

Barat, K. (2022). Laser safety : practical knowledge and solutions. Bristol [England] (Temple Circus, Temple Way, Bristol BS1 6HG, UK), IOP Publishing.

Donnelly, J., et al. (2025). Exploring light : investigations for optics education. Bellingham, Washington (1000 20th St. Bellingham WA 98225-6705 USA), SPIE.

Standards Australia (2022). Safety of laser products, Part 14: A user’s guide, Standards Australia.