The Light Spectrum &
Therapeutic Applications
From visible blue, green, and yellow light to invisible near-infrared and deep infrared wavelengths -- understanding how each band interacts with biological tissue is the foundation of effective light therapy device design.
400-495 nm
495-570 nm
570-590 nm
620-700 nm
700-800 nm
800-1100 nm
1100-3000 nm
Blue Light
Blue light operates at the shortest visible wavelengths with relatively high photon energy. It penetrates only the superficial layers of skin (epidermis), making it ideal for surface-level biological targets such as bacteria and sebaceous glands.
Key Applications
- ✦ Acne treatment (kills P. acnes bacteria)
- ✦ Sebum regulation
- ✦ Circadian rhythm modulation
- ✦ Mood and cognitive support (photobiomodulation)
Green Light
Green light sits in the middle of the visible spectrum and is strongly absorbed by melanin and oxyhemoglobin. It penetrates into the upper dermis, making it particularly effective for targeting pigmentation irregularities, calming vascular activity, and supporting pain-signaling pathways in the skin.
Key Applications
- ✦ Hyperpigmentation and melasma reduction
- ✦ Migraine and pain signal modulation
- ✦ Skin tone balancing and brightening
- ✦ Calming redness and superficial vascular lesions
Yellow Light
Yellow light (also called amber light) sits between green and red in the visible spectrum. It penetrates slightly deeper than blue light and is particularly well-absorbed by hemoglobin and melanin, making it effective for vascular and pigmentation concerns.
Key Applications
- ✦ Redness and rosacea reduction
- ✦ Hyperpigmentation and sunspot treatment
- ✦ Skin tone evening and brightening
- ✦ Superficial vascular lesions
Red Light
Red light is the cornerstone of photobiomodulation therapy. At 630-660 nm, it is strongly absorbed by cytochrome c oxidase (CCO) in mitochondria, stimulating ATP production and cellular energy metabolism in the dermis and superficial connective tissue.
Key Applications
- ✦ Skin rejuvenation and anti-aging
- ✦ Collagen and elastin stimulation
- ✦ Wound healing acceleration
- ✦ Hair follicle stimulation
Far Red Light
Far red light occupies the transition zone between visible red and near-infrared. It is barely visible to the human eye and penetrates significantly deeper than red light. At 730-780 nm, it continues to activate mitochondrial photoreceptors while reaching subcutaneous tissue.
Key Applications
- ✦ Deep skin rejuvenation
- ✦ Subcutaneous fat metabolism support
- ✦ Enhanced combination therapy with red light
- ✦ Cellular regeneration in deeper tissue
Near-Infrared (NIR)
Near-infrared is invisible to the naked eye and is the primary wavelength range for deep photobiomodulation. At 810-850 nm and 940-980 nm, NIR penetrates through skin, fat, and muscle to reach joints, nerves, and bone tissue, activating mitochondria throughout the treatment area.
Key Applications
- ✦ Muscle recovery and sports performance
- ✦ Joint pain and arthritis relief
- ✦ Nerve regeneration support
- ✦ Neurological and brain health research
Deep Infrared (FIR)
Far/deep infrared (FIR) wavelengths are primarily absorbed by water molecules in tissue, generating gentle thermal energy. Unlike photobiomodulation, FIR therapy works through a thermal mechanism -- raising tissue temperature to promote circulation, detoxification, and metabolic activity.
Key Applications
- ✦ Sauna and full-body thermal therapy
- ✦ Chronic pain and inflammation management
- ✦ Improved blood circulation
- ✦ Detoxification and metabolic support
Side-by-Side Comparison
A quick reference for understanding how each wavelength range differs in mechanism, depth, and clinical application.
| Light Type | Wavelength | Visible | Mechanism | Depth | Primary Use |
|---|---|---|---|---|---|
| Blue | 400-495 nm | Yes | Photochemical (bacteria, porphyrins) | ~0.5-1 mm | Acne, surface sterilization |
| Green | 495-570 nm | Yes | Chromophore absorption (melanin, oxyhemoglobin) | ~1-2 mm | Pigmentation, pain modulation, tone |
| Yellow | 570-590 nm | Yes | Chromophore absorption (melanin, Hb) | ~1-2 mm | Pigmentation, redness, vascular |
| Red | 620-700 nm | Yes | Mitochondrial (CCO activation, ATP) | ~2-5 mm | Collagen, wound healing, hair |
| Far Red | 700-800 nm | Barely | Mitochondrial + deeper cell signaling | ~5-10 mm | Deep skin, fat, regeneration |
| Near-IR | 800-1100 nm | No | Deep photobiomodulation (CCO, mitochondria) | ~20-40 mm | Muscle, joint, nerve, pain relief |
| Deep IR | 1100-3000 nm | No | Thermal (water molecule absorption) | Surface-moderate | Sauna, circulation, detox |
Blue Light
400-495 nmGreen Light
495-570 nmYellow Light
570-590 nmRed Light
620-700 nmFar Red Light
700-800 nmNear-Infrared
800-1100 nmDeep Infrared
1100-3000 nmHow These Wavelengths Work Together
The most effective light therapy devices combine multiple wavelengths to address different tissue depths and biological targets simultaneously.
Red + Near-Infrared
The most widely used combination in photobiomodulation. Red light (660 nm) targets surface collagen and skin cells while NIR (850 nm) penetrates to muscles and joints. Together they provide a dual-layer treatment addressing both cosmetic and functional outcomes.
Blue + Red
The standard combination for acne treatment devices. Blue light eliminates surface bacteria while red light reduces inflammation and accelerates healing in the dermis. This dual approach addresses both the cause and the aftermath of breakouts.
Blue + Green + Red
A powerful three-wavelength combination for comprehensive facial treatment. Blue light clears surface bacteria, green light targets pigmentation and calms vascular activity, and red light stimulates collagen and promotes tissue repair. Together they address acne, uneven tone, and aging in a single session.
Multi-Wavelength Devices
Advanced therapy devices integrate 4-6 wavelengths -- including green -- to simultaneously target bacteria, calm pigmentation, stimulate collagen, promote deep tissue healing, and improve circulation all in a single treatment session.
Sequential Protocols
Some clinical protocols apply wavelengths in sequence -- using blue light first for sterilization, green for pigment and calming, followed by red and NIR for healing. Programmable devices allow operators to customize treatment sequences.
Depth-Layered Targeting
By combining wavelengths from visible to NIR, a single device can address all tissue layers -- from the epidermis to deep muscle -- enabling comprehensive treatment for complex conditions like chronic pain or post-surgical recovery.
Tissue Penetration Depth
Longer wavelengths penetrate deeper into tissue. This fundamental principle determines which conditions each light type can effectively treat.
415-470 nm
520-540 nm
570-590 nm
630-660 nm
730-780 nm
810-850 nm
1500+ nm
* Penetration depths are approximate and vary based on tissue type, water content, melanin concentration, and device irradiance.
Ready to Build Your Light Therapy Device?
MedLight's engineering team can help you select the right wavelength combinations for your target application, from facial masks to full-body panels and wearable recovery devices.