Wavelength

Wavelength is a physical property of light expressed in nanometers (nm), which determines the color of visible light, the depth of its penetration into tissues, and its biological effect on mitochondria - in red light therapy, selecting the correct wavelength is just as important as the device’s power.

Wavelength (symbol λ) is the distance between two adjacent peaks of an electromagnetic wave. In the context of light, it determines which color we perceive and - which is crucial for photobiomodulation - how deeply the light penetrates biological tissue and which molecular targets in cells it activates. It is measured in nanometers (nm), where 1 nm = one billionth of a meter.

The human eye perceives light in the range of approximately 380 to 700 nm. Below this range lies ultraviolet radiation (UV), and above it infrared. For red light therapy and photobiomodulation, the relevant range is 600 to 1,000 nm - the so-called therapeutic optical window (therapeutic window), where light can penetrate tissue without thermal damage and biologically interact with Cytochrome C oxidase (CCO) in mitochondria.

Why wavelength matters

Not all light affects biological systems equally. Different molecules absorb different wavelengths - this selective absorption is the physical basis of photobiomodulation. Wavelength directly determines:

• Depth of tissue penetration - shorter wavelengths (630 to 670 nm) reach several millimeters into the skin, while longer wavelengths (810 to 850 nm) penetrate centimeters deep into muscles, joints, and organs
• Which chromophore absorbs the energy - CCO primarily absorbs wavelengths in the range of 600 to 900 nm; water strongly absorbs above 970 nm; hemoglobin and melanin absorb mainly below 600 nm
• Cellular biological response - depending on the absorbed wavelength, different biochemical cascades are triggered (production of ATP, release of nitric oxide, activation of ion channels)
• Therapeutic indication - skin applications require different wavelengths than deep tissues or neurological indications

This is why wavelength is not just a technical parameter on a product label - it is a decisive biological parameter that determines whether the therapy will be effective or not. [R]

Therapeutic optical window (600 to 1,000 nm)

Research has identified a range of wavelengths in which light has proven therapeutic potential when biologically dosed. This range is called the therapeutic optical window and includes wavelengths of 600 to 1,000 nm.

Within this range:

• Hemoglobin and melanin have low absorption - light penetrates tissue instead of being absorbed at the surface
• Cytochrome C oxidase (CCO) in mitochondria has absorption peaks - light is biologically active
• Water does not yet significantly absorb - it penetrates without a thermal effect
• Devices operate at low power without the risk of thermal tissue damage

Below 600 nm (green, blue, UV light), energy is lost in hemoglobin and melanin at the surface of the skin. Above 1,000 nm, energy is primarily absorbed by water - the biological mechanism shifts from photochemical to thermal, representing a different therapeutic principle than photobiomodulation.

Key wavelengths and their biological effects

630 nm - red, visible
Historically one of the first wavelengths documented in photobiomodulation. It penetrates to a depth of 2 to 3 mm - primarily into the superficial layer of the skin (epidermis and superficial dermis). It is used for wound healing, acne, superficial skin care, and antimicrobial applications. It has lower penetration than 660 nm, but a well-documented clinical foundation.

670 nm - red, visible
A wavelength intensively studied in connection with retinal health, mitochondrial recovery, and neuroprotection. The research group of Glen Jeffery from University College London has documented its ability to restore ATP production in aging mitochondria and reverse photoreceptor damage in the retina. It penetrates slightly deeper than 660 nm and shows strong activation of CCO. The 670 nm wavelength is also one of the most clinically important for the release of nitric oxide from blood reservoirs. [R]

760 nm -  The wavelength 760 nm is unique in that it targets cytochrome c oxidase - the fourth complex of the mitochondrial respiratory chain. This complex is responsible for energy production and deuterium-depleted water. Researcher Tina Karu identified action peaks at 620, 680, 760 and 820 nm, which correspond to absorption bands of the redox centers of cytochrome c oxidase.

810 nm - near infrared, invisible
Referred to as the neurological wavelength. It has exceptionally strong absorption by Cytochrome C oxidase and deep tissue penetration - reaching muscles, bones, joints, and even the brain in transcranial applications. Studies on TBI (traumatic brain injury) show that 810 nm was the most effective wavelength among those tested. It is used in protocols for cognitive function, neural tissue regeneration, and musculoskeletal conditions.

850 nm - near infrared, invisible
The wavelength with the greatest depth of penetration among those commonly used in photobiomodulation devices. It reaches 4 to 6 cm into tissues - deep muscles, joint capsules, and organs. It is the primary choice for musculoskeletal issues, back pain, joint conditions, and indications requiring penetration through thicker tissue layers. The 850 nm wavelength can penetrate virtually the entire human body, which is also reflected in observations of positive effects on vision from applications at the back of the head. Learn more about infrared light penetration.

Why Mitochondriak® devices combine multiple wavelengths

Different wavelengths reach different depths and activate different biological mechanisms. Combining red spectrum (630 to 670 nm) and NIR spectrum (810 to 850 nm) in a single device is therefore not a marketing trick - it is a logical consequence of physiology:

• Red component (630 to 760 nm) treats the skin, stimulates collagen, heals superficial tissues, and activates CCO in surface cells
• NIR component (810 to 850 nm) penetrates deeper, reaching muscles, joints, organs, and nervous tissue
• Both components act synergistically - one therapy covers both superficial and deep tissues in a single step

Research has confirmed that a multi-wavelength approach (combination of 590, 660, and 850 nm) is more effective for many indications than monotherapy with a single wavelength. [R]

Related terms

• nm (nanometer) - a unit of wavelength measurement; 1 nm = 10⁻⁹ meter; typical ranges: visible light 380 to 700 nm, NIR 700 to 1,000 nm
• Therapeutic optical window - the range of 600 to 1,000 nm where light penetrates tissue without damage and biologically interacts with CCO
• Cytochrome C oxidase (CCO) - an enzyme in mitochondria that absorbs photons of red and NIR light; the primary chromophore in photobiomodulation
• Chromophore - a molecule that absorbs specific wavelengths of light; in PBM mainly CCO, hemoglobin, water, and melanin
• Depth of penetration - the distance light travels into tissue; depends on wavelength, tissue type, and source intensity
• NIR - near infrared light (800 to 1,000 nm); invisible but biologically active and capable of deeper penetration than red light
• Photobiomodulation - therapy using precisely defined wavelengths of red and NIR light to stimulate mitochondria
• ATP - cellular energy; its production increases after absorption of photons of appropriate wavelengths by Cytochrome C oxidase
• Pulsing - the method of light delivery; optimal pulsing depends on wavelength and target tissue depth
• Action spectrum - a graphical representation of cellular biological response depending on wavelength; for CCO it has absorption peaks at 630 nm, 670 nm, 760 nm, 810 nm, and 850 nm
• Irradiance (W/m²) - the intensity of light power incident on a surface; together with wavelength and exposure time determines the biological dose
• Fluence (J/cm²) - the total energy dose per area; calculated as the product of irradiance and exposure time

Frequently asked questions about wavelengths

What is the wavelength of light and how is it measured?

Wavelength is the distance between two adjacent peaks of an electromagnetic wave. For visible light and infrared radiation, it is measured in nanometers (nm). Shorter wavelength = higher frequency = higher photon energy. Visible light ranges from 380 to 700 nm (violet, blue, green, yellow, orange, red). Above 800 nm lies infrared radiation - invisible to the human eye but biologically active.

Why do red light therapy devices list multiple wavelengths?

Because different wavelengths have different penetration depths and activate different biological mechanisms. The red spectrum (630 to 760 nm) affects surface tissues and skin; the NIR spectrum (810 to 850 nm) penetrates deeper into muscles, joints, and organs. Combining both in a single device allows full-body coverage in one therapy - both superficial and deep tissues simultaneously.

What is the difference between 810 nm and 850 nm?

Both are NIR wavelengths with biologically active effects on CCO. 810 nm has stronger absorption by CCO and is more suitable for neurological applications (transcranial photobiomodulation). 850 nm has slightly greater penetration depth and is preferred for deep musculoskeletal indications (joints, muscles, organs). Both wavelengths are included in Mitochondriak® devices and complement each other.

Why is light outside the 600 to 1,000 nm range not suitable for photobiomodulation?

Below 600 nm (blue and green light), energy is primarily absorbed by hemoglobin and melanin in the skin - light is lost at the surface and does not reach mitochondria in deeper tissues. Additionally, blue light in the evening suppresses melatonin and disrupts the circadian rhythm. Above 1,000 nm, absorption by water dominates - the biological mechanism shifts from photochemical to thermal, representing a different therapeutic modality.

Which wavelength is most effective for joint pain?

For deep joint issues (knee, shoulder, spine), the primary choice is 850 nm for maximum penetration depth. For treating superficial inflammatory conditions around joints (tendons, ligaments, synovial membrane), a combination of 670 nm + 850 nm is suitable. In scientifically tested protocols for knee osteoarthritis, wavelengths from 630 to 904 nm were used in various combinations - all showed statistically significant pain reduction in meta-analyses.

Do wavelengths outside standard values (for example 640 nm or 800 nm) also work?

Yes. The biological response of CCO is not discrete - it follows a continuous absorption curve with peaks at certain values. Wavelengths close to absorption peaks (for example 640 nm instead of 670 nm, or 800 nm instead of 850 nm) still have a measurable biological effect, only with slightly lower efficiency. More important than exact matching to a specific number is the presence of light within the correct spectral range (red 620 to 800 nm, NIR 800 to 1,000 nm).

Summary

Wavelength is a key parameter of photobiomodulation, expressed in nanometers (nm), which determines the depth of light penetration into tissues and the biological response of mitochondria. The therapeutic optical window (600 to 1,000 nm) includes the red spectrum (630 to 760 nm) suitable for superficial tissues and skin, and the NIR spectrum (810 to 850 nm) with deeper penetration into muscles, joints, and organs. Mitochondriak® devices combine both spectral groups simultaneously - for comprehensive full-body coverage in a single therapy.

Scientific studies and sources

• Review of light parameters and PBM efficacy - comparison of wavelengths, penetration depth, and biological response of CCO. PMC. 2021. PMC8355782
• Baskerville R et al. Effect of PBM on hereditary mitochondrial diseases - CCO absorption peaks at 670, 740, and 850 nm. J Lasers Med Sci. 2023. PMC10658120
• Photobiomodulation using LED for treatment of retinal diseases - 670 nm and 810 nm increase ATP production in retinal mitochondria. PMC. 2025. PMC10813238
• Immunomodulatory effects of PBM - wavelengths 600 to 1,000 nm and their mechanism via CCO. PMC. 2025. PMC11991943