As a widely adopted tool across scientific, medical and industrial sectors, lasers are deployed worldwide for a variety of high-precision cutting and machining tasks. In surgical practice, lasers enable precise incisions for the resection of superficial polyps and small lesions. They can also be used alongside endoscopes for minimally invasive procedures, with the added benefit of rapid haemostasis. Beyond surgical cutting, lasers support both disease diagnosis and therapeutic intervention: they relieve pain, reduce inflammation, resolve oedema and facilitate tissue repair, and are now used in approximately 80% of clinical cases.

Wavelength stands as one of the core parameters governing laser therapeutic outcomes, directly determining where laser energy is absorbed within tissues and the depth of penetration. Generally speaking, longer wavelengths penetrate deeper into biological tissue. In high-power laser therapeutic devices, a selected wavelength can deliver both biostimulatory effects and thermal effects; thermal effects intensify as wavelength increases. Besides wavelength, laser energy density and irradiation duration are also critical factors influencing treatment efficacy.

Laser wavelength is measured in nanometres (nm). Visible light falls within the 400–700 nm range, with distinct colours corresponding to different wavelengths that are perceptible to the human eye: 400 nm corresponds to violet light, 450 nm to blue light, 532 nm to green light, and the 650–700 nm band to red light. Light with wavelengths beyond the visible spectrum is classified as infrared light, spanning from 700 nm to 1 mm.

Which laser wavelengths are commonly used in clinical therapy, and what are their respective functions?

Light at 450 nm and 532 nm activates light-gated calcium channels.

Compared with 660 nm and 810 nm, 450 nm and 532 nm more effectively stimulate osteoblast differentiation. Cells irradiated at 450 nm and 532 nm exhibit higher intracellular calcium concentrations. The photobiomodulation effects of 450 nm and 532 nm light upregulate osteogenic gene expression via the TRP/calcium signalling pathway.

Blue light exerts favourable effects on fibroblasts and can be applied for keloid and fibrosis management. Blue laser is primarily indicated for acne treatment and possesses antifungal properties.

Green light penetrates the skin less deeply than red light, reaching only the epidermis without stimulating nerve fibres. Moreover, green light promotes a higher rate of cell proliferation compared with red and infrared light.

650 nm accelerates superficial tissue repair.

When target areas are irradiated with 650 nm light, this wavelength is readily absorbed by cutaneous melanin, ensuring high radiant exposure to superficial layers. As this light suppresses bacterial proliferation while supporting cellular growth, laser therapy at this wavelength delivers notable benefits for wound healing and scar remodelling.

810 nm boosts ATP production.

The enzyme responsible for regulating the efficiency of cellular conversion of molecular oxygen into ATP shows peak absorption at 810 nm. Absorption of photons triggers conformational changes in this enzyme regardless of its baseline molecular state, accelerating the reaction and raising intracellular ATP levels.

915 nm enhances oxygen delivery.

A faster rate of oxygen release into the bloodstream supplies cells with more metabolic substrate to sustain endogenous repair mechanisms. Haemoglobin exhibits an absorption peak at 915 nm; upon absorbing radiation at this wavelength, greater oxygen availability is provided to cells.

980 nm improves blood circulation.

Water in animal blood transports oxygen to cells and removes metabolic waste, and strongly absorbs 980 nm light. Energy released from photon absorption is converted into heat, creating cellular-level thermal gradients that stimulate microcirculation and increase oxygen supply to tissues.

1064 nm penetrates deep tissues.

1064 nm laser light achieves superior deep-tissue penetration. Studies demonstrate that at 1064 nm, reduced melanin absorption and lower light scattering occur within biological tissue. This deep penetration enables activation of metabolic processes in deeper tissue layers. This wavelength is typically used as an auxiliary or third wavelength and is rarely employed as the sole therapeutic wavelength.

Lasers are widely utilised in orthopaedics, dermatology, neurology and other disciplines, with clinical indications including:

· Joint disorders: acute and chronic osteoarthritis, spondyloarthropathies

· Muscle injuries: muscle strains

· Skin wounds and abrasions

· Pain management: back pain, neck pain, shoulder pain

· Otitis media, sinusitis, stomatitis

· Periodontitis, gingivitis

· Intervertebral disc disorders

· Postoperative wounds and soft tissue rehabilitation

· Fracture healing