What Is Near-Infrared Light?
Near-infrared (NIR) light occupies the portion of the electromagnetic spectrum just beyond what the human eye can see, with wavelengths ranging from approximately 700nm to 1400nm. While you cannot see NIR light, you can sometimes feel it as gentle warmth. It is a form of non-ionizing radiation, meaning it does not carry enough energy to damage DNA or disrupt molecular bonds.
In the context of red light therapy and photobiomodulation, the near-infrared wavelengths of greatest therapeutic interest fall between 700nm and 1100nm. Within this range, specific wavelengths have been shown to penetrate deeper into the body than visible red light, reaching muscles, joints, bones, and even the brain.
How NIR Light Penetrates Tissue
The depth to which light penetrates biological tissue depends on its wavelength. Visible red light (630-700nm) is largely absorbed in the first few millimeters of skin, making it effective for superficial conditions like skin health and wound healing. Near-infrared light, however, passes through the skin and underlying tissues much more effectively.
At 810nm, one of the most studied NIR wavelengths, light can penetrate several centimeters into the body. At 850nm, another commonly used wavelength, penetration is similarly deep. This depth of penetration is what makes NIR essential for targeting deeper structures like muscles, tendons, and joints.
The Optical Window
Biological tissue has what researchers call an "optical window" — a range of wavelengths where absorption by water, hemoglobin, and melanin is minimized, allowing light to pass deeper. The primary optical window spans roughly 650nm to 950nm, with a secondary window extending to about 1100nm. Hale devices operate across this range (630nm to 1060nm) to maximize both surface and deep tissue treatment.
NIR vs. Visible Red Light
- Visible red (630-700nm) — Best for skin, superficial wounds, collagen production, and surface-level cellular stimulation
- Near-infrared (700-1100nm) — Best for deep tissue, muscle recovery, joint pain, neurological applications, and systemic effects
Most effective red light therapy devices combine both visible red and near-infrared wavelengths to deliver benefits across all tissue depths. This multi-wavelength approach is supported by research showing that different cellular targets respond optimally to different wavelengths.
Clinical Applications of NIR
Near-infrared light therapy has been extensively researched for a variety of applications. In sports medicine, NIR is used for muscle recovery and reducing delayed-onset muscle soreness (DOMS). In pain management, it has shown promise for conditions like arthritis, back pain, and neuropathy. Neuroscience researchers have explored transcranial NIR therapy for conditions including traumatic brain injury, depression, and cognitive decline.
The ability of NIR to reach deeper tissues also means it can influence systemic processes. Research has demonstrated effects on blood flow, inflammation markers, and immune cell activity that extend beyond the immediate treatment area.
NIR and Hale Devices
Hale RLPRO panels incorporate near-infrared wavelengths alongside visible red, delivering a comprehensive multi-wavelength output from 630nm through 1060nm. This ensures that treatments address both surface-level and deep-tissue targets in a single session, with clinically relevant irradiance across the full spectrum.
The inclusion of wavelengths beyond 1000nm further extends the therapeutic reach, accessing the secondary optical window where specific chromophores are activated that are not responsive to shorter wavelengths.