Picosecond vs Q-Switched Laser: How to Choose
Both of these lasers break pigment up with light, and the comparison between them is not a comparison between an older and a newer machine. The difference is how the pulse delivers its energy: one delivers it in the shortest pulses in clinical use, the other in pulses that are short but longer than that. That changes how pigment particles break apart, how many sessions a target needs, and what the skin does afterwards. This site compares them fact by fact, gives both the same weight, and names the spots that should not be lasered at all.
Reviewed by Ke He, MD, Deputy Director & Head of Skin & Laser Aesthetics at Chongqing West District Hospital. Neither device is the default here, cleared spots can recur, and no outcome is guaranteed.
What is the target, and whose skin is it in?
The comparison between these two lasers is decided by two things, and neither of them is the name of the device. The first is what the target is: a defined particle such as tattoo ink or a single dark spot behaves differently from pigment that is spread across an area. The second is the skin the target sits in, because light is absorbed by pigment everywhere in the skin and not only in the lesion. If the target is ink, or a defined spot, or pigment sitting deeper than the surface, the shorter pulse is where the advantage lies, because it concentrates on the particle. If the target is scattered sun-related freckling across an area, both can reduce it, and the choice comes down to how many sessions and how much downtime are acceptable. If the skin tans readily, or the mark has not been identified, settings and assessment matter more than which of the two is used, and in some cases neither should be used at all.
What a picosecond pulse changes, and what a Q-switched pulse changes
Both devices clear pigment with light, and each is suited to a different kind of target or a different acceptable cost. The cards below describe what each does. They are not a ranking, and no card marks either device as the answer.
Picosecond pulses: mechanical breakup
The pulse is short enough that heat has no time to travel away from the target before the energy has been delivered. Pigment particles are therefore broken apart by a mechanical effect rather than warmed until they break down, and the skin around them is heated less. That is what suits a defined particle: a spot, a patch of ink, pigment sitting deeper than the surface.
Q-switched pulses: short, but longer
These are short pulses that break pigment up substantially through heating of the particle. The pulses are longer than picosecond pulses and far shorter than the millisecond pulses used for hair removal and vascular work, and they clear freckles, sun spots and a good deal of tattoo ink perfectly well. The technology is established and widely used, which is not the same as outdated.
Ink is where the difference shows most
Tattoo ink is packed pigment sitting at a defined depth, and it is the clearest example of a defined particle. The mechanical breakup of a very short pulse tends to clear some inks in fewer sessions than a longer pulse does, and it produces less heating of the surrounding skin. Some ink colours still respond poorly to either device, and those are discussed honestly rather than promised away.
Surface pigment: both work
Freckling and sun spots that sit in the upper layer respond to either device. The difference is in how many sessions are needed, how much downtime follows, and what the skin does afterwards. This is the area where the two overlap most, and where the choice is least about the device and most about the skin.
Darker skin changes the calculation
In skin that tans readily, more of the light is absorbed by the surrounding skin rather than by the target. That narrows the margin between a useful treatment and a pigmentary injury, and it applies to both devices. The shorter pulse reduces the heating of surrounding skin, which is relevant here, but it does not remove the risk, and settings chosen for the individual matter more than the device class.
Neither device stops pigment returning
Both remove pigment that is present. Neither changes why it was there, so sun-related pigment returns with further exposure and hormonal pigment returns most readily of all. Tattoo ink is the exception: ink that has been cleared does not come back, which is why ink is the clearest case for the shorter pulse.
What the days after a session look like
Both are outpatient treatments and neither is a no-downtime procedure. After either, the treated area is red and feels warm, and mild swelling is usual, particularly around the eyes. A Q-switched treatment of a discrete spot typically produces frosting: the spot turns white for a short period as the pigment is disrupted, which settles within hours or a day. A picosecond treatment of ink or dense pigment can produce pinpoint bleeding, where tiny points of blood appear on the surface, and with some settings a bruise-like change that takes a week or more to clear. Pigment commonly darkens before it flakes away over the following days, which patients often mistake for the treatment having failed. Cover make-up is usually possible after the first day, sun exposure must be avoided while the skin is healing and protection used afterwards, and the area should be kept clean and left alone rather than scrubbed. How long the visible reaction lasts depends on the target, the settings and the individual, and it is one of the practical differences between treating a single spot and treating an area.
How long the clearance holds, and what it depends on
The honest division is between ink and everything else. Tattoo ink that has been cleared does not return, because the particles have been broken down and removed rather than moved, and that is the one lasting result either device produces. Everything else recurs. Sun-related freckling and sun spots return with further exposure, because the skin continues to respond to ultraviolet in the way that produced them; the timescale depends on how much sun the skin receives and how readily this person pigments. Hormonal pigment such as melasma is the most likely of all to return, and is the pigment least suited to an aggressive approach. Age-related spots continue to appear as the skin ages, so a patient who clears a face of spots today will usually develop more over the following years. None of that makes the treatment pointless: a cleared area can be kept clearer with daily protection and occasional maintenance, and recurrence is a reason to plan rather than a reason to decline.
What can go wrong with either device
The risks are largely shared, because the mechanism is shared: light absorbed by pigment in skin that contains pigment everywhere. Both can leave the treated area darker than it was, and less often lighter, which is the most common unwanted outcome and is more likely in skin that tans readily or has recently been exposed to the sun. Both can blister, crust or burn if the settings do not match the skin, and both carry a small risk of scarring. Both can trigger a cold sore outbreak around the mouth in someone who carries the virus, and both can leave a treated spot temporarily darker before it fades. The picosecond device adds pinpoint bleeding and, with some settings, a bruise-like change. The Q-switched device added the risk of the white frosting reaction, which is expected rather than a complication. Eye protection is mandatory for both, because the light is bright enough to damage the eye. The variable that decides most of this is not which of the two is used; it is whether the assessment matched the settings to the skin and identified the lesion before treating it.
Whether the change can be undone
Laser treatment of pigment is not reversible in the way a filler can be dissolved. It is also not permanent in the way an operation is, with the one exception of cleared ink. Most of what either device does drifts back over months if nothing maintains it, and a patient who dislikes the result usually has the option of waiting rather than correcting. The exceptions are the ones that matter. Pigment that has been lightened can darken again, and in skin that responds badly, a treatment that did not suit the skin can leave a lasting change in colour that is harder to correct than the mark it was meant to remove. That is the main reason a test area is sometimes treated before the rest, and the main reason settings are chosen conservatively. Once pigment has changed in the wrong direction, further laser treatment during the reactive period tends to make it worse, and the management is protection, time and topical care.
What drives the total, and what does not
No figure on this site would be a quotation for your skin, so none is given. What drives the total is worth understanding before a plan is priced. Device time and handpieces: a picosecond laser is a costlier device to acquire and maintain, and some wavelengths need a separate handpiece, which is reflected in session pricing. Number of sessions: ink and stubborn pigment take a course, and the number is decided as treatment proceeds rather than fixed at the first appointment. Number and size of lesions: a single spot and a face of scattered freckling are different propositions, and a tattoo is priced by its area rather than by its complexity alone. Consumables: cooling, eye protection, dressings, and topical anaesthetic where it is used. Who operates the device: the assessment, the settings and the decision to stop are the parts that carry clinical risk. What follows: review appointments, aftercare, and the cost of treating a pigmentary change belong in an honest total. A total quoted before anyone has looked at the skin is a number rather than a plan.
Picosecond and Q-switched lasers, side by side
The dimensions below are the ones that differ in practice. Each row is a pair of facts, not a score: the two columns carry equal weight, nothing is highlighted, and neither device is marked as the answer. Individual response varies, and the target and the skin decide.
The comparison, in eight parts
Each guide takes one part of the decision between a picosecond and a Q-switched laser — what pulse length changes, how ink and surface pigment respond, frosting and pinpoint bleeding, pigment change in darker skin, recurrence, and the spots that should not be lasered at all. Read the two or three that match your question.
Picosecond Or Q-Switched: Choosing A Pigment Laser
Both devices clear pigment with light. The choice follows from the target and from the skin it sits in, not from which machine is newer.
Read the guide →What Pulse Length Changes In Practice
Why a shorter pulse changes how pigment breaks up, and what that means in practice for how many sessions a target needs and how the skin heals.
Read the guide →Tattoo Ink And Which Laser Clears It
Colour, depth and layering decide how ink responds, why some inks need a different approach, and why clearance takes a course rather than a session.
Read the guide →Freckles And Sun Spots: One Session Or Many
How discrete surface pigment responds to each device, why the number of sessions diverges, and what decides whether a spot clears in one pass.
Read the guide →Frosting And Pinpoint Bleeding After A Pigment Laser
What frosting and pinpoint bleeding are, which device produces which, and what is normal while the skin settles rather than a sign of damage.
Read the guide →Darker Skin And Pigment Laser Risk
Why pigment change is a greater risk in darker skin, how settings and test spots reduce it, and the cases where treatment should be declined.
Read the guide →The target and the skin decide, not the device
An assessment establishes what the mark is, how deep it sits, and how your skin type responds to injury. We will say plainly which pulse — if either — matches it, and what we would advise if the answer is that a lesion should be examined rather than treated.
Frequently asked questions
Is a picosecond laser better than a Q-switched laser?
It is different rather than better, and the difference lies in how the pulse delivers its energy. A very short pulse breaks pigment apart mechanically with less heating of the surrounding skin, which matters most for defined targets such as tattoo ink and for skin that pigments easily. A Q-switched pulse clears freckles, sun spots and a good deal of ink perfectly well, and it is a widely used and established device.
Will one session clear my tattoo or my dark spot?
Usually not. Tattoo ink takes a course of sessions, and the number depends on the colours, the depth and how the ink was placed. A single freckle or sun spot may clear in one or two sessions, while scattered pigment across a face takes more. A clinic that promises one session for either has not examined the target.
Why does the treated spot look darker before it fades?
Pigment that has been broken up often darkens on the surface before it flakes away over the following days, and frosting on a Q-switched treatment is the same process seen differently. It is expected rather than a sign that the treatment failed, and it is judged once the area has settled rather than on the day.
Is this safe on darker skin?
It can be, and it carries more risk. In skin that tans readily, more of the light is absorbed by the surrounding skin, which narrows the margin between a useful treatment and a pigmentary injury. The shorter pulse reduces heating of the surrounding skin, but it does not remove the risk, and settings chosen for the individual are what matter most. In some cases the honest answer is to decline treatment.
Can a mole be treated with a pigment laser?
Not before it has been examined. A lesion that is new, changing in size, shape or colour, bleeding, itching or failing to heal is a diagnostic question first, and treating it delays the answer and can obscure what a clinician would have seen. No laser diagnoses anything, and a clinic that treats a changing mole as a cosmetic problem has skipped the step that mattered most.
Who reviews the medical content on this site?
Every guide is medically reviewed by Ke He, MD, Deputy Director of the Plastic Surgery & Aesthetics Medical Center and head of skin and laser aesthetics at Chongqing West District Hospital. The review date appears on each article, and the site's own limits are set out in the health disclaimer.
Part of Lasers and Energy Devices — 22 sites on this topic