Medically reviewed by Dr Sin Yong · Last reviewed · 3 min read
Published 13 October 2026 · Reviewed by Dr Sin Yong
Q-switched laser is a laser in which a shutter, the Q-switch, releases stored energy as a single pulse of about a billionth of a second, a nanosecond, commonly at 532 and 1064 nm. Q-switched lasers fragment pigment and tattoo ink so the body can clear them, but with more photothermal, heat-based contribution than a picosecond laser, whose pulses are roughly a thousand times shorter. It is the older generation; neither is a brand or a treatment plan.
Key facts
Pulse width
About one billionth of a second (nanosecond)
Mechanism
Fragments pigment with a mix of pressure and heat; the spread of heat is what inflames surrounding tissue
Wavelengths
532 nm for superficial pigment, 1064 nm for deeper pigment and darker skin
Still used for
Low-fluence 1064 nm toning across diffuse tone; nanosecond emissions sit alongside the picosecond mode on the DEKA TORO
Illustrative image, not a patient.
Where Q-switched lasers matter on this site
A Q-switched laser is defined by its nanosecond pulse, not its wavelength: Q-switched Nd:YAG at 1064 and 532 nm, Q-switched alexandrite at 755 nm and Q-switched ruby at 694 nm all exist, with melanin and tattoo ink as the chromophores. On this site the term appears wherever the older and newer pigment lasers are compared.
Q-switched is not obsolete and pico is not magic; the pulse I choose depends on the mark in front of me and the skin around it.— Dr Sin Yong
Laser toning: low-fluence 1064 nm passes for diffuse tone, the main job Q-switched lasers keep, with the site's caution on repetition.
T2 Frax Radiance: Dr Sin Yong's protocol on the DEKA TORO, which carries 532 and 1064 nm nanosecond emissions beside its 785 nm picosecond emission.
Tattoo removal: where nanosecond and picosecond pulses are chosen by ink colour and depth.
Pico laser: the newer class, with the Q-switched form as its reference point.
The pigmentation worse after laser post explains the heat-spread mechanism that makes nanosecond pulses riskier in darker skin.
Q-switched pulses in tattoo removal. In T2 Laser Tattoo Removal on the DEKA TORO, the TORO's Q-switched nanosecond pulses are used at 1064 nm for black and dark inks and at 532 nm for red, orange and purple, and its 785 nm picosecond pulse for green and blue. See T2 Laser Tattoo Removal.
Not to be confused with
Q-switched is a pulse mechanism, so it is confused with the wavelengths it is built in and the class that replaced it.
Picosecond laser. Pulses roughly a thousand times shorter, with more pressure effect and less heat spread. Not a brand; several platforms carry both pulse forms.
Nd:YAG laser. The crystal most Q-switched lasers are built on. A long-pulsed Nd:YAG is not Q-switched and does not fragment pigment.
Laser toning. A protocol, low-fluence 1064 nm, usually on a Q-switched or picosecond device. Toning is what is done, not what the machine is.
IPL. A broad-spectrum lamp with no Q-switch and no pigment-fragmenting pulse.
Carbon laser peel. A Q-switched 1064 nm pass over a carbon layer, marketed for pores and tone. The carbon laser peel post explains what it is and is not.
Neither Q-switched nor picosecond is a treatment plan; both are tools chosen per mark, per visit.
What decides whether a Q-switched laser matters for you
The older pulse form still has jobs, and the choice between it and picosecond is made on the mark, the skin and the history.
The mark. Discrete epidermal spots and dark tattoo ink respond to nanosecond pulses; stubborn, lighter or multicoloured ink and the pigment risk in darker skin push the choice toward picosecond.
Skin type. Heat spread from a nanosecond pulse is what inflames the surrounding skin, and in Fitzpatrick III to V skin that inflammation can leave post-inflammatory hyperpigmentation. Surveys of Q-switched 532 nm treatment of sun spots report this as the main complication.
Melasma. Managed with low-fluence passes and a stopping point, never with aggressive fragmentation; see pico laser for melasma.
Toning history. Many previous low-fluence passes raise the risk of mottled hypopigmentation, which changes what is added.
Platform. On the DEKA TORO both pulse forms are available, so the question is settings rather than which clinic to visit.
Dr Sin Yong treats the Q-switched emission as one setting among several, used where a nanosecond pulse is the right physics for the mark.
Where it fits
The difference between Q-switched and picosecond lasers is pulse width, and pulse width changes the mechanism: a pulse shorter than the time a pigment particle takes to pass heat to its surroundings shatters it by a pressure wave with little heat spreading outward, while a nanosecond pulse heats the particle and some of the skin around it. The comparison is set out on pico vs Q-switched laser. In Dr Sin Yong's practice the DEKA TORO used for T2 Frax Radiance carries 532 and 1064 nm nanosecond emissions alongside its 785 nm picosecond emission, so the choice is made per mark and per visit. Q-switched toning keeps a role in low-fluence 1064 nm work for diffuse tone, with a stopping point; the newer class is defined under picosecond laser and the main platform on pico laser.
Related on this site
How Q-switched nanosecond lasers compare with picosecond, multi-wavelength and non-laser methods is set out under tattoo removal in Singapore.
Which pulse and wavelength suit each ink colour is set out under colour tattoo removal.
For the crystal and its long-pulsed, Q-switched and picosecond forms, see Nd YAG laser.
Discrete sun spots are solar lentigines; see how they are diagnosed and treated.
Its shorter-pulse successor is the pico laser, whose pulses are about a thousand times shorter.
Its most familiar use is tattoo removal, defined in its own entry.
Frequently Asked Questions
Yes, in susceptible skin. A nanosecond pulse heats the pigment particle and some of the skin around it, and that inflammation can trigger post-inflammatory darkening, particularly in Fitzpatrick III to V skin and on sun-exposed marks. Multicentre surveys of Q-switched 532 nm treatment of solar lentigines list this as the main complication. Conservative settings, a test patch and strict photoprotection are how the risk is managed.
Yes, for selected inks and as one of two pulse forms on modern platforms. Dark black ink fragments well with nanosecond 1064 nm pulses; lighter and multicoloured inks, and darker skin where heat spread matters, are usually treated with picosecond pulses. On the DEKA TORO both are available, so the choice is made per tattoo and per visit rather than by machine.
It is a difference in delivery, not a verdict. Nanosecond pulses leave more heat in the skin, which matters for post-inflammatory hyperpigmentation in Fitzpatrick III to V skin, but fluence, spot size, wavelength and interval still decide the outcome on either pulse width.
In low-fluence 1064 nm toning for diffuse tone and brown marks after acne, yes, and not on an open-ended schedule. Discrete sun spots and freckles are usually treated with the picosecond emission instead.
References
Torbeck RL, Schilling L, Khorasani H, Dover JS, Arndt KA, Saedi N. Evolution of the picosecond laser: a review of literature. Dermatol Surg. 2019;45(2):183-194. doi:10.1097/DSS.0000000000001697. source
Postinflammatory Hyperpigmentation Associated with Treatment of Solar Lentigines Using a Q-Switched 532-nm Nd:YAG Laser: A Multicenter Survey. PubMed, 2016. pubmed.ncbi.nlm.nih.gov
Review of Laser Treatments for Post-Inflammatory Hyperpigmentation in Skin of Color. PubMed, 2023. pubmed.ncbi.nlm.nih.gov
Treatment of Solar Lentigines: A Systematic Review of Clinical Trials. Journal of Cosmetic Dermatology (PMC), 2025. pmc.ncbi.nlm.nih.gov
