A light-emitting diode, or LED, makes light from a semiconductor. Unlike a laser, its light is not coherent, and it spreads out rather than holding a tight beam.
For the first decades of photobiomodulation research, lasers were the standard tool, and some researchers insisted they were essential. In recent years LEDs and broad-band lamps have become common. Their advantages include no laser safety concerns, easy home use, covering a large area at once, wearable designs, and a much lower cost (Heiskanen & Hamblin, 2018).
The old belief that a laser’s coherence adds some extra benefit is no longer widely held, and reviewers now describe LEDs as just as efficient as lasers at producing photobiomodulation (de Freitas & Hamblin, 2016).
Why it matters
A panel, a wand, and a clinical laser can share a color and still deliver very different amounts of light. What a device actually delivers depends on its wavelength, power, beam area, and time, which together make up the light dose.
References
de Freitas, L. F., & Hamblin, M. R. (2016). Proposed mechanisms of photobiomodulation or low-level light therapy. IEEE Journal of Selected Topics in Quantum Electronics, 22(3), 348–364. https://doi.org/10.1109/JSTQE.2016.2561201
Heiskanen, V., & Hamblin, M. R. (2018). Photobiomodulation: Lasers vs. light emitting diodes? Photochemical & Photobiological Sciences, 17(8), 1003–1017. https://doi.org/10.1039/c8pp00176f