So, what is light? Something so simple is actually very complex and mysterious. Light itself is made of incredibly small, tiny, mass-less particles called photons. Photons travel like waves, but interact with matter like particles, and actually carry energy, momentum, and information.
**Work in**
It is important to keep in mind that electromagnetic radiation like radio waves, visible light, xrays, cosmic rays etc. always has its source in electric charges (like electrons in wires) that are accelerating or oscillating or in changing or alternating currents (AC) circuits.
The animation shown here gives the electric field lines in the neighborhood of a pair of oscillating electrical charges (dipole radiation); and the spreading of the electric field lines is accompanied by magnetic field lines at right angles to them (not shown). This gives rise to electromagnetic waves that propagate away from oscillating charges like radio waves
It is important to keep in mind that electromagnetic radiation like radio waves, visible light, xrays, cosmic rays etc. always has its source in electric charges (like electrons in wires) that are accelerating or oscillating or in changing or alternating currents (AC) circuits.
The animation shown here gives the electric field lines in the neighborhood of a pair of oscillating electrical charges (dipole radiation); and the spreading of the electric field lines is accompanied by magnetic field lines at right angles to them (not shown). This gives rise to electromagnetic waves that propagate away from oscillating charges like radio waves
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Part 2: Light is a photon or particle
It turns out that our view of light as an electromagnetic wave is only half the story. Quantum mechanics shows us that light also has a particle-like nature called the photon. So laser or LED light can be thought of not only as a wave, but also like a continuous series of minute shots fired from a gun.
So, we have two very different ideas of how light works; as waves like electromagnetic waves, and as the motion of mass-less particles called photons. The pair of explanations is called the wave-particle duality, and it’s a recurring theme in quantum mechanics. The energy (E) of each photon is given by E=hv where h is plancks constant and v is the frequency. The higher the frequency the more energy a photon has. For example a blue photon has 3 eV (electron volts) of energy while a red photon has on 2 eV. And similarly a red photon will have more energy than a near infrared photon as it has a higher frequency or smaller wavelength.
**Work In** NOTE: According to quantum mechanical theory, light energy is composed of photons or discrete packets of electromagnetic energy. The energy of an individual photon depends only on the wavelength. Therefore, the energy of a "dose" of light depends only on the number of photons and on their wavelength or color (blue photons have more energy than green photons, that have more energy than red, that have more energy than NIR, etc).
So, we have two very different ideas of how light works; as waves like electromagnetic waves, and as the motion of mass-less particles called photons. The pair of explanations is called the wave-particle duality, and it’s a recurring theme in quantum mechanics. The energy (E) of each photon is given by E=hv where h is plancks constant and v is the frequency. The higher the frequency the more energy a photon has. For example a blue photon has 3 eV (electron volts) of energy while a red photon has on 2 eV. And similarly a red photon will have more energy than a near infrared photon as it has a higher frequency or smaller wavelength.
**Work In** NOTE: According to quantum mechanical theory, light energy is composed of photons or discrete packets of electromagnetic energy. The energy of an individual photon depends only on the wavelength. Therefore, the energy of a "dose" of light depends only on the number of photons and on their wavelength or color (blue photons have more energy than green photons, that have more energy than red, that have more energy than NIR, etc).
This is very important in understanding the mechanisms behind how red light therapy transfers energy to chromophores in the mitochondria to enhance ATP production!!
In the classical view, the energy of an electron orbiting an atomic nucleus is larger for orbits further from the nucleus of an atom. However, quantum mechanical effects force electrons to take on discrete positions in orbitals. Thus, electrons are found in specific energy levels of an atom, two of which are shown below:
An electron in an atom can absorb energy from light (photons) or heat (phonons) only if there is a transition between energy levels that match the energy carried by the photon or phonon. For light, this means that any given transition will only absorb one particular wavelength of light. Photons with the correct wavelength can cause an electron to jump from the lower to the higher energy level. The photon is consumed in this process.
In the classical view, the energy of an electron orbiting an atomic nucleus is larger for orbits further from the nucleus of an atom. However, quantum mechanical effects force electrons to take on discrete positions in orbitals. Thus, electrons are found in specific energy levels of an atom, two of which are shown below:
An electron in an atom can absorb energy from light (photons) or heat (phonons) only if there is a transition between energy levels that match the energy carried by the photon or phonon. For light, this means that any given transition will only absorb one particular wavelength of light. Photons with the correct wavelength can cause an electron to jump from the lower to the higher energy level. The photon is consumed in this process.
**Work In**
When we think of light we think of visible light (and colours) that we see, but this is only a tiny portion of the electromagnetic spectrum – between 400 to 700 nanometers. At the limits of these two points the frequencies change in intensity which our eyes cannot perceive. Visible light is simply the range of electromagnetic radiation which human eyes are sensitive to.
Light itself is made up of incredibly small (tiny) mass-less particles or ‘quanta’ called photons that travel as quantum WAVES but interact with matter like particles that carry energy, momentum (and information). As we'll see in this video, light, especially light from the Sun is the very cornerstone of life itself. But something so seemingly simple is one of the most diffilcult concepts in all of physics, needing a full treatment of general relativity and QED (quantum electrodynamics)
The quantum waves of light (in QED) contain ALL the weirdness of quantum mechanics AND relativity which LIFE utilizes (new science of quantum biology). Twin paradox, time dialation, length contraction, E=mc^2, Tunneling, bilocation, teleportation, superposition, entanglement, wave particle duality, quantum information, quantum computing and more.
But for simplicity and practicality we'll look at LIGHT IS mainly a carrier of ENERGY and INFORMATION (think radio waves which are bundles of lower frequency light). AND also as the basis of matter itself - particle pair production. Light seems to zip in and out of the vacuum of space contributing to the zero point energy that pervades the universe.
Two Quotes below sum it up nicely
When we think of light we think of visible light (and colours) that we see, but this is only a tiny portion of the electromagnetic spectrum – between 400 to 700 nanometers. At the limits of these two points the frequencies change in intensity which our eyes cannot perceive. Visible light is simply the range of electromagnetic radiation which human eyes are sensitive to.
Light itself is made up of incredibly small (tiny) mass-less particles or ‘quanta’ called photons that travel as quantum WAVES but interact with matter like particles that carry energy, momentum (and information). As we'll see in this video, light, especially light from the Sun is the very cornerstone of life itself. But something so seemingly simple is one of the most diffilcult concepts in all of physics, needing a full treatment of general relativity and QED (quantum electrodynamics)
The quantum waves of light (in QED) contain ALL the weirdness of quantum mechanics AND relativity which LIFE utilizes (new science of quantum biology). Twin paradox, time dialation, length contraction, E=mc^2, Tunneling, bilocation, teleportation, superposition, entanglement, wave particle duality, quantum information, quantum computing and more.
But for simplicity and practicality we'll look at LIGHT IS mainly a carrier of ENERGY and INFORMATION (think radio waves which are bundles of lower frequency light). AND also as the basis of matter itself - particle pair production. Light seems to zip in and out of the vacuum of space contributing to the zero point energy that pervades the universe.
Two Quotes below sum it up nicely
**Work In**
Light and LaserLight is part of the spectrum of electromagnetic radiation (ER), which ranges from radio waves to gamma rays. ER has a dual nature as both particles and waves. As a wave which is crystallized in Maxwell’s Equations, light has amplitude, which is the brightness of the light, wavelength, which determines the color of the light, and an angle at which it is vibrating, called polarization. The wavelength (λ) of light is defined as the length of a full oscillation of the wave, such as shown in Fig. 1a. In terms of the modern quantum theory, ER consists of particles called photons, which are packets (“quanta”) of energy which move at the speed of light. In this particle view of light, the brightness of the light is the number of photons, the color of the light which is the energy contained in each photon.
Light and LaserLight is part of the spectrum of electromagnetic radiation (ER), which ranges from radio waves to gamma rays. ER has a dual nature as both particles and waves. As a wave which is crystallized in Maxwell’s Equations, light has amplitude, which is the brightness of the light, wavelength, which determines the color of the light, and an angle at which it is vibrating, called polarization. The wavelength (λ) of light is defined as the length of a full oscillation of the wave, such as shown in Fig. 1a. In terms of the modern quantum theory, ER consists of particles called photons, which are packets (“quanta”) of energy which move at the speed of light. In this particle view of light, the brightness of the light is the number of photons, the color of the light which is the energy contained in each photon.
This property of light determines whether or not an atom or a molecule will absorb the photon there are energy values for the electron fields that constitute the atom or molecule. This is key, because if the frequency (or wavelength) doesn't "match" what is available in the molecule, then it will pass right through. As we'll see later in this chapter key molecules called Chromophores have energy levels or bands that are able to resonate or "catch" certain wavelengths or frequencies and transduce or convert that energy into usable work. THIS is why wavelength or frequency is so important! The right frequency is literally like an energetic vitamin the body can harness and use to create vibrancy and health. Frequencies "matters". Literally!
Now that we have defined what light is, next let's look at what light is most biologically active and beneficial. In this chapter we'll focus on the source light be it a laser or led (mainly led), and the key parameters we need for creating the best possible red light therapy device. In the next chapter we'll go into detail on the mechanisms involved in how the body USES this light to create healing and regeneration in the body!
Now that we have defined what light is, next let's look at what light is most biologically active and beneficial. In this chapter we'll focus on the source light be it a laser or led (mainly led), and the key parameters we need for creating the best possible red light therapy device. In the next chapter we'll go into detail on the mechanisms involved in how the body USES this light to create healing and regeneration in the body!
Part 1) Irradiation Parameters -
The irradiation parameters for a red light therapy panel, applicator or bed can be defined in multiple ways, but essentially there are four key components: the wavelength, irradiance, total power and pulsing frequency and duty cycle.
Let's first look at wavelength and irradiance which are the two most important aspects. It is helpful to start with the sun as it is very well known and experience.
In terms of wavelength, 99.9% of the sun’s output of energy occurs between 250 and 2500 nanometers which as we pointed out in the last chapter is roughly 5% ultraviolet, 43% visible and 52% Near infrared. Red light therapy devices are typically between 600-1000nm. As we'll see, this is perhaps the most biologically active range of frequencies of light the human body needs rivaled only by UVB frequencies for vitamin D and blue frequencies for circadian rhythms, energy, and mood (via serotonin activation amongst other things). Because this is only about 20% of natural sunlight which we all know can cause sunburns and problems with overuse (and because sunlight is not as specific), supplementing with red light therapy makes perfect sense. Especially sense most people spend way too much time indoors OR live in parts of the world that don't have as much sun.
The irradiation parameters for a red light therapy panel, applicator or bed can be defined in multiple ways, but essentially there are four key components: the wavelength, irradiance, total power and pulsing frequency and duty cycle.
Let's first look at wavelength and irradiance which are the two most important aspects. It is helpful to start with the sun as it is very well known and experience.
In terms of wavelength, 99.9% of the sun’s output of energy occurs between 250 and 2500 nanometers which as we pointed out in the last chapter is roughly 5% ultraviolet, 43% visible and 52% Near infrared. Red light therapy devices are typically between 600-1000nm. As we'll see, this is perhaps the most biologically active range of frequencies of light the human body needs rivaled only by UVB frequencies for vitamin D and blue frequencies for circadian rhythms, energy, and mood (via serotonin activation amongst other things). Because this is only about 20% of natural sunlight which we all know can cause sunburns and problems with overuse (and because sunlight is not as specific), supplementing with red light therapy makes perfect sense. Especially sense most people spend way too much time indoors OR live in parts of the world that don't have as much sun.
Black Body Radiation Curve
Black-body radiation is the thermal electromagnetic radiation within, or surrounding, a body in thermodynamic equilibrium with its environment, emitted by a black body (an idealized opaque, non-reflective body). It has a specific, continuous spectrum of wavelengths, inversely related to intensity, that depend only on the body's temperature, which is assumed, for the sake of calculations and theory, to be uniform and constant.
Black-body radiation is the thermal electromagnetic radiation within, or surrounding, a body in thermodynamic equilibrium with its environment, emitted by a black body (an idealized opaque, non-reflective body). It has a specific, continuous spectrum of wavelengths, inversely related to intensity, that depend only on the body's temperature, which is assumed, for the sake of calculations and theory, to be uniform and constant.
We will explore wavelengths in much detail throughout the rest of the book, but it seems from much research that the key range is 600-1000nm mainly because (as we'll see) there are many absorption peaks for cytochrome C oxidase in this range AND this frequency range is the deepest penetrating of all therapeutic and safe frequencies. Studies have shown frequencies in this range can penetrate over 1cm UP TO 5cm or 2 inches with wavelengths in the 690-850nm range penetrating deepest! Also it is in this frequency range that successful clinical trials have been performed EXCLUDING 700-750nm which don't seem to have as much benefit.
Within 600-1000nm there are 3 therapeutic ranges that are found in most red light devices. The 600-680nm range is your red light that is visibly red in color. The 800-880 nm range is the near infrared that is not visible but like the red light, interacts directly with mitochondrial chromophores like Cytochrome C oxidase. Then there is 900-1000 utilize water as the chromophore and seem to also be absorbed in the cell membrane structures causing molecular vibrations the sufficient stimulate ion channels in a beneficial way. So these longer wavelengths have different, but complementary mechanisms of healing which we will explore in the next chapter in detail.
Within 600-1000nm there are 3 therapeutic ranges that are found in most red light devices. The 600-680nm range is your red light that is visibly red in color. The 800-880 nm range is the near infrared that is not visible but like the red light, interacts directly with mitochondrial chromophores like Cytochrome C oxidase. Then there is 900-1000 utilize water as the chromophore and seem to also be absorbed in the cell membrane structures causing molecular vibrations the sufficient stimulate ion channels in a beneficial way. So these longer wavelengths have different, but complementary mechanisms of healing which we will explore in the next chapter in detail.
Irradiance is perhaps the most important intensity or power parameter. Light irradiance is the power density of red light over a given area. It refers to the number of photons that are flowing through a certain area and are available for absorption into your cells. In simple terms, irradiance is the amount of light energy output from a source at the point when it connects with its target (your skin), rather than the energy level at its source. The unit of measure for light irradiance is power divided by area which is usually expressed in milliwatts per square centimeter (mW/cm²).
Irradiance, while one of the most important parameters is also the most misreported. To accurately measure irradiance you need a lab grade spectrometer with a cosine correction otherwise you take in light from all directions. Most companies post inflated numbers by using a cheap solarmeters which can give values that are 600% too high! More on this in chapter 8. For now just understand irradiance is the power per unit area or you could say the brightness of the panel or led bed per unit area. Typically increasing irradiance is just a matter of increasing the power and density of the led bulbs used. For a give panel or bed with a set number of bulbs, if you double the wattage of the led bulbs you'll roughly double the irradiance.
It does seem from research literature that if an irradiance UNDER 5 mW/cm^2 will be ineffective regardless how long a time is used. It also seems the idea range is between 10 and 50 mW/cm^2. For full body light beds, the strongest we have tested have been around 30mW/cm^2 using a lab grade spectrometer (again, companies reporting over 100 mW/cm^2 are typically using a solarmeter and reporting skewed or rather just bogus results.
A higher power density/irradiance output also makes for more efficient therapy. Greater therapeutic benefits are achieved in less time because the light you are absorbing is more intense.
Comparing this to the sun for reference, a typical sunny day in Florida around noon you'd receive an irradiance of about 100 mW/cm^2. But, of this, only about 15-20 mW/cm^2 (at best) will be in the therapeutic red and near infrared range. And it will be much less focused and much more diffuse.
Intensity Example
At the surface of the earth the sunlight brings roughly I = 1000 Watts/m^2. That is pretty amazing: Over the entire surface of the earth facing the sun, it is pumping in 1000 joules per square meter every second!! The sun is 93 million miles away emitting power in all directions and we lie on a sphere of radius 93 million miles and still 1000 W/m^2 is our share. You can imagine the enormous output of energy from the sun.
It does seem from research literature that if an irradiance UNDER 5 mW/cm^2 will be ineffective regardless how long a time is used. It also seems the idea range is between 10 and 50 mW/cm^2. For full body light beds, the strongest we have tested have been around 30mW/cm^2 using a lab grade spectrometer (again, companies reporting over 100 mW/cm^2 are typically using a solarmeter and reporting skewed or rather just bogus results.
A higher power density/irradiance output also makes for more efficient therapy. Greater therapeutic benefits are achieved in less time because the light you are absorbing is more intense.
Comparing this to the sun for reference, a typical sunny day in Florida around noon you'd receive an irradiance of about 100 mW/cm^2. But, of this, only about 15-20 mW/cm^2 (at best) will be in the therapeutic red and near infrared range. And it will be much less focused and much more diffuse.
Intensity Example
At the surface of the earth the sunlight brings roughly I = 1000 Watts/m^2. That is pretty amazing: Over the entire surface of the earth facing the sun, it is pumping in 1000 joules per square meter every second!! The sun is 93 million miles away emitting power in all directions and we lie on a sphere of radius 93 million miles and still 1000 W/m^2 is our share. You can imagine the enormous output of energy from the sun.
Radiance vs Irradiance vs Insolation
Next there is irradiance...
We receive solar energy at an intensity of 1 kilowatt per square meter (1o0 mW/cm^2 at sea level for many hours of the day, but the effective red and near infrared
The amount of sunlight we receive, and at which wavelengths is called Earth’s insolation curve. “Insolation” – see the word Sol? – is the amount of energy received in sunlight. It is the AREA under the curve that represents the amount of energy at those wavelengths.
The earth receives more energy from the Sun in just one hour than the world's population uses in a whole year.
Energy received at sea level is about 1kW/m2 at noon near the equator = 100 mW/cm^2
For Red Light Therapy we are interested in Red and IR-A
Solar Irradiance at sea level 100 mW/cm^2
IR-A 20mW/cm^2
What is the difference between radiance and insolation? To a lay persn, they are probably the same thing. To a scientist, there is a distinct difference. Radiation is usually short for electromagnetic radiation and radiance is an instantaneous measurement at a distinct point in time. Solar radiation "emits" from the sun equally in all directions at frequencies that are visible and non-visable. On the other hand "insolation" is the amount of radiation "received" on a given surface (usually a square meter) on a plane perpendicular to the sun in a given amount of time (usually a day). The name comes from a combination of the words "incident solar radiation".
Like solar panels, we want to make sure our red light panel or bed is perpendicular to the surface to avoid scattering. HERE we can see one the clear benefits of whole body beds over even full body panels you can stand in front of. The amount of photons is not only considerably greater, but the angles will be a lot better as well to avoid reflection.
Next there is irradiance...
We receive solar energy at an intensity of 1 kilowatt per square meter (1o0 mW/cm^2 at sea level for many hours of the day, but the effective red and near infrared
The amount of sunlight we receive, and at which wavelengths is called Earth’s insolation curve. “Insolation” – see the word Sol? – is the amount of energy received in sunlight. It is the AREA under the curve that represents the amount of energy at those wavelengths.
The earth receives more energy from the Sun in just one hour than the world's population uses in a whole year.
Energy received at sea level is about 1kW/m2 at noon near the equator = 100 mW/cm^2
For Red Light Therapy we are interested in Red and IR-A
Solar Irradiance at sea level 100 mW/cm^2
IR-A 20mW/cm^2
What is the difference between radiance and insolation? To a lay persn, they are probably the same thing. To a scientist, there is a distinct difference. Radiation is usually short for electromagnetic radiation and radiance is an instantaneous measurement at a distinct point in time. Solar radiation "emits" from the sun equally in all directions at frequencies that are visible and non-visable. On the other hand "insolation" is the amount of radiation "received" on a given surface (usually a square meter) on a plane perpendicular to the sun in a given amount of time (usually a day). The name comes from a combination of the words "incident solar radiation".
Like solar panels, we want to make sure our red light panel or bed is perpendicular to the surface to avoid scattering. HERE we can see one the clear benefits of whole body beds over even full body panels you can stand in front of. The amount of photons is not only considerably greater, but the angles will be a lot better as well to avoid reflection.
What is a Watt?
A Watt is a unit of power named after James Watt, a Scottish inventor. It describes the energy (Joules) delivered per second. In other words, Watts describe the speed at which energy is transferred.
Power and Energy can have many forms, such as electricity, heat, chemical energy, mechanical energy, and radiant (light) power. Accordingly, Watts can be used universally to describe all of these different types of power. So the context is always important when talking about Watts, which we will see soon.
Four Types of Watts:
Believe it or not, there are 4 types of Watts commonly discussed in Red Light Therapy (maybe more)!
1) Rated Watts: The maximum electrical power rating for all of the LEDs.
2) Consumed or Actual Watts: The electrical power that is actually consumed by the device.
The consumed watts are the amount of electricity consumed by the LED device. It does not tell us a lot about the intensity yet. That is because LEDs aren’t perfectly efficient (usually only 15% to 30% conversion from electricity to light), as well some electrical power is spent in the drivers and fans.
3) Optical, Emitted, “Light”, or Radiant Watts: The total amount of radiant (optical) power emitted by the device. Where we may say Optical or Light as a general term even though the power can also be invisible Near-Infrared. Now it is getting interesting! More important than Rated or Consumed Watts, we need to know how many Watts of optical power is actually emitted from the device. To do this properly, usually companies need to send their panels to a 3rd party lab. Where they measure the panel inside an integrating sphere to measure the Total Watts output.
Pulsed Beam vs Continuous Wave (CW)
Most red light beds and panels have a constant or continuous light source but there is good research showing that pulsed the LED or laser light has added benefit as long as the pulsing frequency is under 100 Hz (according the Michael Hamblin). Two well tested pulsing rates are 10 hz and 50hz and showing added benefits in research compared to continuous wave only. Duty cycle is simply the percentage of time the light is on versus off, which is usually 50:50 or 50% duty cycle. This DOES however decrease the optical power by 1/2 in this case (reported as average power), but the benefits seem to outweigh the cost. Michael Hamblin suggested in an interview the 10Hz was likely effective because of brain entrainment effects as one of several proposed reasons for its effectiveness. Another is the idea of giving the body a small rest in between each burst of light, etc. We'll talk more on the benefits of using a pulsed beam throughout the book!
Most red light beds and panels have a constant or continuous light source but there is good research showing that pulsed the LED or laser light has added benefit as long as the pulsing frequency is under 100 Hz (according the Michael Hamblin). Two well tested pulsing rates are 10 hz and 50hz and showing added benefits in research compared to continuous wave only. Duty cycle is simply the percentage of time the light is on versus off, which is usually 50:50 or 50% duty cycle. This DOES however decrease the optical power by 1/2 in this case (reported as average power), but the benefits seem to outweigh the cost. Michael Hamblin suggested in an interview the 10Hz was likely effective because of brain entrainment effects as one of several proposed reasons for its effectiveness. Another is the idea of giving the body a small rest in between each burst of light, etc. We'll talk more on the benefits of using a pulsed beam throughout the book!
Comparison of laser power of a pulsed laser with a continuous wave laser beam. The average power of both are the same so that the peak power of the pulsed laser is far higher.
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Part 2) How the light is administered - "the dose" - operator controlled
The second part to red light therapy application is the dose. Just like with supplements and pharmaceuticals, it is not just the vitamin or medicine given, but how many pills, how often and how to take them. This is referred to as dosimetry and we'll revisit this in more detail in chapter 9, but it is worth mentioning here briefly to emphasize that in order to create healing from red light therapy, the length of time of a session and how often to do the session is important. Also choosing the intensity and pulsing or no pulsing is important.
While the wavelength, irradiance and total optical power are "baked in" to the device itself, how long and how often and at what intensity to use depends on the user. Because energy is simply power multiplied by time (power/watts x time/seconds = energy/joules), the dosage itself is usually measured in either total energy or fluence (energy density). Total energy pairs up with total optical power and fluence pairs up with irradiance such that EACH is simply the power or power density multiplied by the treatment time. So it is more simple than it sounds.
The downside to these energy parameters is they do not distinguish between a high power and low time and a low power and high time. For example, an ineffective 1 mW/cm^2 device applied for 100 minutes = 6000 seconds would give a fluence or energy density of 6 Joules per square centimeter (6 J/cm^2). But you could use a 10 mW/cm^2 device for only ten minutes and get the same 6 J/cm^s. Still, fluence and total energy are important in reporting dosage, just make sure the device used is at least 5-10 mW/cm^2 irradiance, preferably AT LEAST 10 mW/cm^2. Cheap devices on ebay, amazon and alibaba many times have very weak irradiances that will not be effective with any treatment time! Usually most quality red light therapy devices can be used as little as 2-3 times a week for 10-20 minutes with good result!
The second part to red light therapy application is the dose. Just like with supplements and pharmaceuticals, it is not just the vitamin or medicine given, but how many pills, how often and how to take them. This is referred to as dosimetry and we'll revisit this in more detail in chapter 9, but it is worth mentioning here briefly to emphasize that in order to create healing from red light therapy, the length of time of a session and how often to do the session is important. Also choosing the intensity and pulsing or no pulsing is important.
While the wavelength, irradiance and total optical power are "baked in" to the device itself, how long and how often and at what intensity to use depends on the user. Because energy is simply power multiplied by time (power/watts x time/seconds = energy/joules), the dosage itself is usually measured in either total energy or fluence (energy density). Total energy pairs up with total optical power and fluence pairs up with irradiance such that EACH is simply the power or power density multiplied by the treatment time. So it is more simple than it sounds.
The downside to these energy parameters is they do not distinguish between a high power and low time and a low power and high time. For example, an ineffective 1 mW/cm^2 device applied for 100 minutes = 6000 seconds would give a fluence or energy density of 6 Joules per square centimeter (6 J/cm^2). But you could use a 10 mW/cm^2 device for only ten minutes and get the same 6 J/cm^s. Still, fluence and total energy are important in reporting dosage, just make sure the device used is at least 5-10 mW/cm^2 irradiance, preferably AT LEAST 10 mW/cm^2. Cheap devices on ebay, amazon and alibaba many times have very weak irradiances that will not be effective with any treatment time! Usually most quality red light therapy devices can be used as little as 2-3 times a week for 10-20 minutes with good result!
Ok, now that light gets into the tissue how does it convert the energy of the photon E=hv into the energy molecules of life, ATP, NADPH, Glucose, Glycogen, etc.
Molecular Antenna are the Energy Gaps E=hv
Molecular Antenna are the Energy Gaps E=hv
A photon is a photon whether it pops out of a laser or a led