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Where 532 nm comes from
The KTP laser does not have its own active medium. The beam starts as 1064 nm radiation, the same as in the Nd:YAG laser, and passes through a potassium titanyl phosphate crystal, KTP for short. In the crystal, frequency doubling takes place: two photons combine into one with twice the energy, and so with half the wavelength.
Hence the name of the device, which does not refer to the source of the light but to the crystal that converts it. And hence the fact that in our fleet of lasers, 532 nm is not a separate laser but a second output of the same system.
One beam, two outputs
1
The active medium emits 1064 nm. A long wavelength, weakly absorbed, reaching deep.
2
The KTP crystal doubles the frequency. At the output, 532 nm, green light, visible.
3
The person carrying out the treatment selects the output, matching it to the depth and type of the change.
This is the only wavelength in our fleet of lasers visible to the eye. The others lie in the infrared and are invisible, which is why they have an aiming beam; with 532 nm, the working beam itself can be seen.
Strong absorption and shallow action
The 532 nm range falls within the band where haemoglobin absorbs light most strongly, and it is also strongly absorbed by melanin. Both chromophores capture the energy almost immediately, so little of it remains for the deeper layers.
In practice, this means precision bought at the cost of reach. A vessel lying directly beneath the epidermis or a cluster of pigment in the epidermis will absorb the energy effectively, even at a low dose. A vessel located a few millimetres deeper will remain untouched, because the beam will not reach it.
That is why, for vessels on the face, 532 nm is often the first choice, while for vessels on the legs it is not an option. It is not about the power of the device but about how far the wavelength can reach before it gives up all its energy.
Pulse durations and the gap in the middle of the scale
As with 1064 nm, the effect depends not only on the wavelength but also on the pulse duration. At 532 nm we work at two extreme ends of the scale, while the middle remains unused, and that in itself is informative.
Pulse durations at 532 nm
1 ps
1 ns
1 µs
1 ms
1 s
A logarithmic scale: each section between markers is a thousandfold difference in time.
Picoseconds
Pigment broken down mechanically by a pressure wave. At 532 nm this applies to pigments that longer wavelengths do not see: red, orange and brown.
Nanoseconds
Q-switched mode. The energy shatters clusters of melanin in the epidermis, with minimal effect on the surrounding tissue.
Microseconds, unused range
At 1064 nm, this is the domain of the micropulse technique, meaning gradual heating of the dermis. At 532 nm it makes no sense: the wavelength is absorbed too superficially to heat the dermis, and it would instead heat the epidermis.
Milliseconds
Pulse duration matched to the size of the vessel. The energy heats the entire vessel wall until it closes. This is where classic closure of facial vessels takes place.
The ranges are given as a guide, to show the difference in orders of magnitude.
Three applications
Milliseconds
Facial vessels and redness
The energy heats the vessel wall until it closes. For small vessels on the nose, cheeks and chin, this range is often the first choice, because it reaches exactly where the lesion lies.
Nanoseconds
Superficial pigmentation
Clusters of melanin in the epidermis absorb the energy and are broken down. This range is effective for superficial lesions; pigment situated deeper requires a longer wavelength.
Picoseconds
Red and warm tattoo pigments
Red, orange and brown pigments absorb green light and let longer wavelengths pass through. Without this range they cannot be removed.
Red tattoo pigments deserve a separate mention, because this is a situation where 532 nm has no substitute. A pigment absorbs light of the colour complementary to its own: black absorbs everything, but red lets long wavelengths pass and absorbs green. Longer wavelengths simply do not see it.
The pair of 532 and 1064 nm
These two wavelengths come from a single system and are exactly opposite in every important respect. The comparison below explains why having access to both matters more than owning two separate devices.
532 nm
Green, visible
Absorbed very strongly, by haemoglobin and melanin.
Shallow reach, of the order of one millimetre.
A low energy dose is sufficient.
Superficial lesions: facial vessels, epidermal pigmentation, red pigments.
Lighter skin phototypes only. A tan rules out the treatment.
1064 nm
Near infrared, invisible
Absorbed weakly, by the same chromophores.
Deep reach, up to a few millimetres.
Requires a higher energy dose.
Deeper lesions: leg vessels, hair follicle, dermis.
All phototypes, including dark and tanned skin.
For lesions of varying depth in a single area, both wavelengths are sometimes used within one protocol. We describe the details of such combinations at combined therapies, and the full spectrum of pulse durations for the longer wavelength on the Nd:YAG laser page.
Phototypes and tanning
Here, 532 nm behaves the opposite way to the longer wavelength. Strong absorption by melanin means that epidermal pigment intercepts the energy before it reaches its target. With a lighter complexion this is not a problem, because there is little melanin. With a darker complexion, the risk of burns and post-inflammatory pigmentation increases.
A tan rules out the treatment
A fresh tan means an excess of melanin in the epidermis, exactly the chromophore that competes with the target for energy. At this wavelength, this is not a caution but a contraindication: the treatment is postponed until the tan fades. For darker phototypes, we use the 1064 nm range.
Contraindications
Pigmented and vascular lesions with an atypical appearance first require a dermatological assessment. We support this assessment with digital dermoscopy, but this aids the decision, it does not provide a diagnosis; in case of doubt, we refer to cooperating dermatologists before the treatment, not after it.
Where we describe the individual treatments
This page describes the technology: the wavelength, how it is generated, the pulse duration and the resulting limits. Qualification and the course of a specific treatment can be found on the treatment pages.
Closing thread veins and reducing redness
Treatment page: four methods, matched to vessel depth, the course of the treatment and aftercare.
Device page: the 532 and 1064 nm ranges for vascular lesions.
Condition page: symptoms, causes and when a medical assessment is needed.
Removal of tattoos and permanent make-up
Pigment colours, number of sessions and the realistic course of removal.
Types of pigmentation and the choice of method, including the limits of the approach with melasma.
Picosecond channels and the photoacoustic mechanism of breaking down pigment.
The source wavelength for 532 nm, across the whole spectrum of pulse durations.
Editorial responsibility
Responsible for the content
NL Clinic, Katowice
How the content is created
Last updated
14 August 2026
Factual basis: the phenomenon of frequency doubling in a KTP crystal, the light absorption profile of haemoglobin and melanin, the principle of selective photothermolysis and the dependence of the effect on the thermal relaxation time of the target. Information on the range of pulse durations available comes from the clinic. We do not give the trade names of devices and manufacturers, because regulations restrict the advertising of medical devices directed at the public; we give technical parameters. This material is informational in nature and does not replace a consultation or qualification.
The questions we are asked most often
How does a KTP laser differ from Nd:YAG?
Nothing, as far as the light source is concerned, because it is the same laser. The 1064 nm beam passes through a KTP crystal, which halves its wavelength, to 532 nm. The difference lies in what this shorter wavelength does in the skin: it is absorbed much more strongly, so it acts superficially and precisely, where the longer wavelength reaches deeper.
Why specifically 532 nm for vessels?
Because in this range haemoglobin absorbs light most strongly. The energy reaches the vessel effectively and at a low dose, and because it does not penetrate deeply, it does not affect structures beneath it. For small facial vessels lying directly under the epidermis, this is the decisive advantage.
Can this laser close vessels on the legs?
No. Vessels on the legs lie deeper, and 532 nm releases its energy in the first millimetre of skin, so it simply will not reach them. For deeper lesions we use the 1064 nm range, and the treatment is then carried out by a doctor.
Why does a tan rule out the treatment?
Because a tan means an excess of melanin in the epidermis, and melanin absorbs this wavelength strongly. The pigment intercepts the energy before it reaches its target, which risks burns and post-inflammatory pigmentation. At this wavelength this is a contraindication, not a caution; the treatment is postponed.
I have a darker complexion, can I have this treatment?
With darker phototypes the risk is high for the same reason as with a tan: there is more melanin in the epidermis, and it competes with the target for energy. In such situations we use the 1064 nm range, which melanin absorbs weakly. The choice is determined by qualification, not preference.
Why does a red tattoo need green light?
Because a pigment absorbs light of the colour complementary to its own. Black ink absorbs practically the whole spectrum, so it responds to many wavelengths. Red transmits long wavelengths and absorbs green, so longer ranges do not see it. Without 532 nm, red, orange and brown pigments remain untouched.
Can you see this laser's beam?
Yes, and it is the only such case in our range of equipment. The 532 nm range lies within visible light and has a green colour. The other lasers work in infrared, so their beam is invisible, which is why they have an additional aiming beam. Protective eyewear is required regardless of whether the beam is visible.
Why do you not use this wavelength for collagen treatments?
Because stimulating the dermis requires delivering heat to its depth, and 532 nm releases its energy in the epidermis and just beneath it. It would therefore heat the surface without reaching the target. For this task we use the 1064 nm wavelength in the microimpulse technique, described on the Nd:YAG laser page.
How many sessions are needed?
It depends on the treatment. A single vessel sometimes disappears after one session, diffuse erythema requires a series, and tattoo pigments need several to a dozen or so sessions, depending on the colour and depth. We set the plan at the consultation, after assessing the lesion, not over the phone.
Sources
Anderson RR, Parrish JA. Selective photothermolysis: precise microsurgery by selective absorption of pulsed radiation. Science, 1983;220(4596):524 to 527. The principle of matching pulse duration to the target's thermal relaxation time.
A Comparative Study of Intense Pulsed Light with Two Different Filters in Meibomian Gland Dysfunction. A description of the light absorption profile of haemoglobin, with the highest coefficient in the range from 400 to 600 nm, in which 532 nm lies.
The content is for information. It does not replace a consultation, an examination or an individual assessment.