Red Light Therapy Glossary: Spec Terms in Plain English
Published October 2026. Updated October 2026.
Quick answer
This glossary explains the words you meet on a light device spec sheet, in plain English and in the order a buyer needs them. The core idea: irradiance (mW/cm²) is power on a surface at a stated distance, and dose here means energy, J/cm² = mW/cm² x seconds / 1000. Every definition describes what a device emits or how it is built. None of it describes an outcome for you, and your device manual sets how you use the device.
How to use this glossary
Spec sheets mix three kinds of words. Some describe the light itself, such as wavelength and bandwidth. Some describe how much light lands on a surface, such as irradiance and dose. Some describe the hardware that makes the light, such as the LED chip, the driver and the heat sink. Marketing pages blur the three. This page keeps them apart.
Each term below is defined in plain English, with the family it belongs to. The terms from N to Z (for example nanometer, near infrared, pulsed light, radiometer, spectrum and wavelength) are explained in the sections below.
One rule applies to every entry. A definition tells you what a number means. It does not tell you whether a number is right for you. For that, follow the manual for your device, and ask a qualified professional about any medical question.
Quick reference: terms A to M
Use this table to find the right entry fast. The last column says which family the word belongs to.
| Term | Plain English meaning | Family |
|---|---|---|
| Absorption spectrum | A chart of how much light a material takes in at each wavelength | Light |
| Bandwidth | How wide a band of wavelengths one LED emits around its peak | Light |
| Beam angle | How widely the light from one LED spreads out, in degrees | Hardware |
| Binning | Sorting LED chips into groups by measured color and brightness | Hardware |
| Coherence | Whether light waves move in step, as in a laser, or not, as in an LED | Light |
| Collimated light | Light whose rays run nearly parallel instead of spreading | Light |
| COB LED | Chip on board: many tiny LED dies mounted directly on one base | Hardware |
| Color temperature | How warm or cool a white light looks, in kelvin | Light |
| Continuous wave | Light that stays on steadily instead of pulsing | Light |
| Dose | Energy per square centimeter, J/cm² | Amount |
| Duty cycle | The share of each pulse cycle that the light is on | Light |
| EMF | Electromagnetic field: the electric and magnetic fields around powered electronics | Hardware |
| Flicker | Rapid changes in brightness over time, measured in Hz | Light |
| Fluence | Energy delivered per unit area, the same idea as dose in J/cm² | Amount |
| Heat sink | A metal part that draws heat away from the LEDs | Hardware |
| Hot spot | A small area that is brighter than the area around it | Amount |
| Infrared | Light with wavelengths longer than visible red, which the eye cannot see | Light |
| Inverse square law | How light from a small source weakens as distance grows | Amount |
| Joule | The unit of energy: one watt for one second | Amount |
| LED chip | The tiny semiconductor that makes the light | Hardware |
| LED driver | The circuit that feeds the LEDs a controlled electric current | Hardware |
| Light meter | A handheld sensor that reads how much light reaches it | Amount |
| Lumen | A measure of total visible light output, weighted to the human eye | Amount |
| Lux | Lumens per square meter on a surface, weighted to the human eye | Amount |
| mW/cm² | Milliwatts per square centimeter: the unit of irradiance | Amount |
Family labels are our own grouping to help you navigate. They are not an industry standard.
The two numbers that matter most
If you only learn two entries, learn irradiance and dose. Irradiance is power per area, written mW/cm². It depends on distance, so a spec means little unless it names the distance. Dose is energy per area, written J/cm². It adds time to the picture. Our irradiance guide and our dose calculation guide go deeper, and the dose calculator does the arithmetic for you.
Here are real stated irradiance figures for two AWA panels, taken from our irradiance specs guide. Notice how every figure comes with a distance.
| Device | Distance | Stated irradiance (mW/cm²) |
|---|---|---|
| FX300 | 1 inch | 220 |
| FX300 | 6 inches | 83.5 |
| FX300 | 12 inches | 43.3 |
| FX500 | 2 inches | 220 |
| FX500 | 6 inches | 94 |
| FX500 | 12 inches | 73.8 |
| FX500 | 20 inches | 58.6 |
Figures as listed in the AWA irradiance specs guide. Irradiance describes what a panel emits at that distance. It is not a target.
Arithmetic example: FX500 at 6 inches, 94 mW/cm², for 5 minutes (300 seconds). 94 x 300 = 28,200 mJ/cm², and dividing by 1000 gives 28.2 J/cm². That is arithmetic, not a recommended session.
Terms about the light itself
Wavelength and bandwidth. Wavelength, in nanometers, is the color of the light. Many red light devices list a red band and a near infrared band, for example around 660 nm and 850 nm. Our wavelength guide explains the labels. Bandwidth says how wide a band an LED covers around its peak, so a listing of 660 nm usually means a peak with some spread on either side. Binning is how chip makers sort LEDs so the peaks sit close to the label.
Infrared and the absorption spectrum. Infrared is light longer than visible red. You cannot see it, and skin and eyes take it in as warmth, which is one reason eye protection matters. An absorption spectrum is a chart of how strongly a material takes in each wavelength. It is a physics tool, not a promise about any device.
Coherence, collimation and continuous wave. A laser is coherent and collimated, which means its waves move in step and its rays run parallel. An LED is neither. LEDs also differ from laser diodes under federal rules, as the FDA notes. Continuous wave light stays on. Pulsed light switches on and off, and duty cycle is the share of time it is on. Flicker is any fast change in brightness, whether or not it is by design.
Terms about amount and measurement
Joule, fluence and dose all point at energy. A joule is one watt for one second. Fluence and dose both mean joules per square centimeter in this context. Lumen and lux measure brightness as the human eye sees it, so they say almost nothing about red or near infrared output. A light meter that reads lux is not a substitute for a radiometer that reads mW/cm². The inverse square law says a small source weakens with the square of distance. A large panel does not follow it closely up close, which our irradiance by distance chart shows with real figures. A hot spot is a brighter patch, usually just under a cluster of LEDs.
Terms about the hardware
The LED chip is the semiconductor that emits the light. Many chips can share a base, and in a COB LED they are mounted together on one board. The LED driver keeps the current steady so brightness does not drift. The heat sink carries heat away so the chips stay within their working temperature. Beam angle is how widely one LED spreads its light. EMF is a term for the fields around any powered electronics. We explain what it measures, and we do not claim a number the product page does not list.
Chip count alone tells you little. As one example, the AWA LX500 face mask uses 306 LED chips across its modes, but that count is a hardware fact, not a measure of how much light reaches a surface. Read it next to the stated irradiance, not instead of it.
How to read a spec sheet in order
- Find the wavelengths and check what each band is labeled as.
- Find the irradiance in mW/cm² and note the distance it was measured at.
- Check whether the light is continuous or pulsed, and note any flicker information.
- Look at the hardware terms last: chip count, driver and heat sink explain the build, not the output.
- Run the arithmetic yourself with the dose formula, or use the session time table for example numbers.
- Follow the device manual for time and distance.
Common mistakes
- Taking chip count or total watts as a measure of how much light reaches you. Only irradiance at a stated distance does that.
- Reading lumens or lux as red light output. Those units follow the human eye and miss most of the red and near infrared band.
- Using a spec at a distance that was not stated. Every irradiance figure needs its distance.
- Calling every red LED "laser like". An LED is not coherent or collimated, and the two light sources are regulated differently.
- Using the dose formula as a target. The formula describes emitted energy. It does not tell you how long to run a session.
Before you use any light device: read the label, follow the device manual, and use eye protection as directed. Ask a doctor first if you have a medical condition, take medications, are pregnant, or have light sensitivity.
Related guides in this series
- What irradiance means on a spec sheet
- How the dose arithmetic works
- AWA FX300 and FX500 irradiance specs
- 660nm vs 850nm wavelength guide
- Wavelengths, sessions and devices explained
- Red light therapy buyers checklist for home use
Device pages
Read the full page and label for each device before you use it: AWA FX300 panel, AWA FX500 panel, AWA LX500 face mask. You can also browse the full AWA red light therapy collection.
Frequently asked questions
What is the difference between irradiance and dose?
Irradiance is power per area in mW/cm² at a stated distance. Dose here means energy per area in J/cm², which adds time: J/cm² = mW/cm² x seconds / 1000.
Are fluence and dose the same thing?
In this glossary, yes. Both mean energy per unit area, usually written as J/cm². Different fields prefer different words for the same idea.
Do lumens or lux tell me how strong a red light device is?
No. Lumens and lux are weighted to what the human eye sees, so they miss most red and all near infrared output. Irradiance in mW/cm² at a stated distance is the useful figure.
Is an LED the same as a laser?
No. A laser is coherent and collimated, while an LED is neither. The FDA also notes that LEDs are not subject to the federal laser product performance standard.
Does this glossary say what dose I should use?
No. It defines terms. Session time and distance for your device come from its manual and product page, and a qualified professional can answer medical questions.
Sources
- FDA: General Wellness policy for low risk devices. Guidance from the agency's device center (January 2026) on its compliance policy for general wellness products. It is a policy document, not a statement about any one device.
- FDA: Laser Products and Instruments. Describes laser hazard classes I to IV and states that LEDs differ from laser diodes and are not subject to the federal laser product performance standard.
- OSHA: Nonionizing Radiation overview. Describes nonionizing radiation as electromagnetic waves spanning ultraviolet, visible, infrared, microwave, radio frequency and extremely low frequency, and notes that infrared is absorbed as heat by skin and eyes.
Regulatory note: select devices carry FDA 510(k) clearance for specific, limited uses. Most light devices are sold as general wellness products. Read each product page and label.
How we create this guide
AWA sells red light therapy devices. We write these guides to explain how devices work and how to choose and use one. This is general information, not medical advice. Read each product page and label. See our editorial standards.