Understanding Continuous Wave Lasers vs Super Pulsed Lasers
On this webpage, I will walk you through sections that build upon one another to teach these concepts. Once understood, you will be able to make an informed choice on your next laser purchase. We'll start out with a waveform that all of us have seen...The ElectroCardioGram.
The ECG Waveform
Most are familiar with this waveform and understand what it means. It's a graphical representation of a healthy heartbeat. Each peak is the strongest part of the hearts contraction. The horizontal axis is time and in this image 6 heartbeats are represented. The distance between the peak pulses would be considered the wavelength even though we're not talking about a sine wave.
Section 1
Understanding Continuous Wave Lasers
The vast majority of therapeutic lasers on the market are called continuous wave (CW) lasers. Although they have the word "continuous" in the name, they are actually pulsed on and off. To be technically accurate, the term "continuous-wave-pulsed lasers" is better, but the industry refers to them as simply "continuous wave". We will refer to these more common lasers as CW lasers.
Looking at the waveform, you will see that the laser is cycled on and off, on and off, etc. The EKG signal has about 1 second between pulses, whereas many laser systems pulse the laser on and off 10,000 to 20,000 times per second. You cannot see this pulsating effect with your eyes, but it's happening within the circuitry that controls the laser.
Here we are only showing 8 of these pulses, with the zoom slider at 100. Take the slider from 100 to 1 and you will see that the pulses are so numerous, they cannot be visualized.
Take the zoom level back to 100 so you can see the individual pulses. The important thing to notice here is that the pulses are on just as long as they are off. This is called a 50% duty cycle. Most doctors never change this value even though it can be changed on most laser devices.
Move the second slider called, "Duty Cycle" and notice how the on/off time changes. A duty cycle of 50% means the laser is on exactly as long as it is off. A 10% duty cycle means it is on only 10% of the time, followed by off 90% of the time.
The third slider called "Pulse Power" determines the peak power of an individual pulse. For many lasers this is limited to 15 or 20 watts. This is only for an individual laser. The entire machine might have a much higher average energy than this.
Section 2
Understanding CW vs SP Waveforms
In this section you will learn what the pulses of a super pulsed laser look like. We'll start with the slider at "10" to, again show, the continuous waveform we just discussed. Now slide the slider handle to the right and notice how the pulses become taller and more narrow.
At any setting on the slider the total amount of power from each pulse remains the same, yet the pulse power has increased and the duty cycle has decreased. This cannot be done with most laser systems. They are limited to a max pulse power and cannot do what we are showing here. Only super pulsed lasers can create these types of pulses.
To get more depth you have to raise the pulse power, but this adds more heat with every watt you go up, unless you turn the pulses on and off at a faster rate so that the heat cannot build up.
Narrowing the pulses so instead of being on for 50% of the time, they are instead on maybe 1% of the time or 0.1%, 0.01% or 0.001% of the time?
Now slowly move the slider to the right and notice that as you decrease the on time from 50% down to 1%, the pulse power can go up considerably. What you're doing is taking the energy that would have gone into contributing to heat and shifting that energy into a higher pulse power.
This is a well thought out solution that deals with the biggest problem with the laser's on the market today.
Section 3
Understanding Pulse Power and Average Power
There are two power levels that need to be understood when it comes to laser therapy. Pulse Power and Average Power.
To the right, I am showing 12 different pulse powers, yet each pulse has the same average power. In fact, the 7 pulses to the far right are so tall that they go off the graphics canvas that I am using to plot these pulses. To see them, drag the slider to the left to zoom out and see the tallest pulse on the far right. Notice how you cannot even see the pulse on the left even more. A multiplication factor of 2048 times the pulse power.
This graph is to compare different types of pulses. You would never deliver pulses like this to someone however, so this graph is different then the graphs we've discussed so far.
Looking at the first pulse on the left, it has a certain height and width. The pulse next to it has double the height and half the width. Each consecutive pulse is double the height and half the width of the prior pulse. They all have the same energy however. If the first pulse actually represented 10 watts, then the last pulse would be 20,480 watts, but the energy in each pulse would be identical.
The point is, why not have your laser design incorporate much higher pulse powers, yet keep the average powers to reasonable levels. It's like having your cake and eating it to. You can have both depth and low average energy.
Heat is the enemy of laser therapy. When treatment is too hot, or when you have to be really careful not to stay in one spot too long because of heat build up, laser therapy could get too uncomfortable or even burn the skin. Super pulse technology allows the designer of the laser to get really high pulse powers to penetrate deeper into tissues, yet still have safe average powers. It's a win/win.
Section 4 - Laser Parameters
In this section, we have a representation of a laser head shooting out photons of light represented by white dots penetrating through the skin, muscle and bone. Experiment with the controls and notice what the particles do. Do they penetrate deeply or stay at the surface? Do they spread out or are they concentrated? Is there scattering more or less at certain wavelengths? We’ll go over each laser parameter and then have a general discussion about them based on what we’re trying to achieve clinically.
Average Power
The major factor in heat accumulation, but also determines how much you get done.
Lens Aperture
The focus of the laser beam. Either more wide (diffuse) or narrow (concentrated).
Pulse Power
This is the primary driver of depth of penetration into tissues. Most lasers have 15 to 20 watts worth of penetrating pulse power, but the Lumix Q can go up to 132,000 watts of pulse power.
Lens Distance
The distance from the lens of the laser to the skin.
Wavelength
This is the 'color' of the light when talking about violet to red colors, but wavelength applies to the entire spectrum of energy from radio waves, microwaves, infrared, red-->violet, ultraviolet, x-rays and gamma rays. Certain wavelengths penetrate better than other wavelengths.