The clinical approach
Why the green line does this job and the infrared one doesn't
Selective photothermolysis is the governing principle — pick a wavelength your target absorbs better than its neighbours, deliver it faster than the target sheds heat, and damage stays where you aimed it. Anderson and Parrish published that in Science in 1983 (PubMed 6836297), and every dosing chart since is a variation on it.
Apply it to chromophores. Our engineering archive is blunt on this point: 532nm is absorbed heavily by red and brown chromophores and barely at all by black, cyan and blue ones, while 1064nm is the reverse. Penetration follows wavelength too, so the infrared line reaches dermal targets that green light never gets near. Ephelides sit in the epidermis. That settles the argument — 532nm, generated by frequency-doubling through a KTP crystal, is the working wavelength here, and 1064nm is the wrong tool aimed at the wrong depth.
Nanoseconds, not milliseconds
Look at the pulse width row on any spec sheet before anything else. Our Q-switched platforms run 6–8ns. Squeeze a fixed pulse energy into a window that short and peak power climbs by orders of magnitude — our archive works the arithmetic through explicitly for a Q-switch that drops pulse duration from hundreds of microseconds into the nanosecond range. What lands on the melanosome isn't gentle warming. It's a photoacoustic shock that fragments the particle while surrounding keratinocytes barely register the event.
A millisecond device delivering the same energy heats the whole neighbourhood instead. That's why long-pulse and pulsed-light platforms produce a slower, softer fade on freckles, and why a nanosecond pulse produces the crisp immediate greying you can see through the operator's goggles.
The evidence base is unusually settled
Frequency-doubled 532nm systems have been compared head-to-head for ephelides in randomised split-face work. A 2022 Journal of Cosmetic Laser Therapy trial by Ma and colleagues found both picosecond 532nm and Q-switched 755nm alexandrite effective on freckles, with the alexandrite arm scoring higher on satisfaction (PubMed 35400288). Different platforms, same underlying physics. For a clinic weighing capital cost, the nanosecond 532nm route stays the cheapest way into this indication that still works properly.
Treatment protocol
Fluence is derived, not dialled
This trips up new operators constantly. The console gives you pulse energy in millijoules and a spot adjustor in millimetres. Energy density is energy divided by spot area, so halving the spot diameter roughly quadruples the fluence at the same energy setting. Our device manuals spell out that relationship, and they add a second one people forget: with wavelength and energy density held constant, a larger spot pushes energy deeper into tissue. On a QN-03 the spot adjustor steps 1, 1.5, 2, 2.5, 3, 3.5 and 4mm. On the QE-01 the arm delivers 1–7mm continuously. Same wavelength, very different granularity of control.
Start low. Our manuals are explicit that excessive energy is what produces the post-inflammatory pigmentation you were hired to avoid, and the right move when a spot doesn't respond is a small step up, not a jump. Repetition rate sits at 1–5Hz on one platform and 1–10Hz on the other, but for facial ephelides you're placing shots deliberately, so the rate matters far less than your hand.
Endpoint, crust, interval
The endpoint described in our archive is the pigment turning lighter — a subtle immediate greying with surrounding erythema, not bleeding, not blistering. Over the following days each treated spot forms a fine dark crust that lifts on its own. Tell patients plainly: don't pick it. Keep it clean, keep it moist, let it drop.
Most faces need only a short course, and because the target is epidermal you'll usually see meaningful clearance early rather than after a long grind. Space sessions several weeks apart. Then the part everyone skips: ephelides are UV-driven, so daily broad-spectrum sunscreen is doing half the work. Published trials in this indication pair laser treatment with sun protection for exactly that reason. Without it, new spots surface the following summer and your case photos age badly.
Screening and risk
Higher Fitzpatrick types compete for that 532nm energy in the epidermis, so drop fluence, test a patch, and lengthen intervals; our starting-parameter guidance moves that way as skin gets darker. Exclude active tan, photosensitising medication, and treatment-area herpes or malignancy — the contraindication lists in our manuals also flag severe diabetes, uncontrolled hypertension, cardiac disease and epilepsy. Anything atypical, asymmetric or changing goes to a dermatologist for biopsy before a single pulse is fired. And if a patient's marks turn out to be inflammatory rather than sun-driven, the plan belongs on our post-inflammatory hyperpigmentation page instead.
Recommended equipment
Which freckle removal machine: QN-03 against QE-01
Both carry 1064nm and 532nm, both work in the nanosecond domain, and either will clear ephelides. The difference is the Q-switch itself. QN-03 uses a passive design with a single lamp driving two rods; single-pulse output at 532nm reaches 200mJ and rises with double and triple pulsing, pulse width runs 6–8ns at 1–5Hz, and there's no articulated arm to align or repair. QE-01 uses an electro-optic Q-switch on a seven-joint arm, holds pulse width at 6ns, reaches 400mJ at 532nm and 1–10Hz, and gives you a continuously adjustable 1–7mm spot.
Practical translation. Buy QN-03 if freckles and sun spots are the bulk of your pigment work and you want the lower running cost. Buy QE-01 if you also handle dermal lesions and tattoo ink, where fixed pulse width and finer spot control earn their keep — with an EO switch, changing energy changes peak power predictably instead of changing pulse count the way passive designs do.
Where pulsed light fits, and where it doesn't
A filtered pulsed-light console with a 530nm cut-off will lighten freckles, and if you already own a PE-01 or MF-05, use it — broad coverage per shot suits a scattered field of light spots across cheeks and nose. But those platforms deliver milliseconds, not nanoseconds. Expect a gentler fade over more sessions and less crisp clearance of individual dark spots, and expect less tolerance of recently tanned skin. Nanosecond precision is exactly what a dedicated Q-switched platform sells you.
What to verify at acceptance
Ask for the paperwork, not the brochure. Medical and cosmetic laser equipment in this class falls under IEC 60601-2-22 for basic safety and essential performance (IEC 60601-2-22:2019), while laser product classification is governed by IEC 60825-1, which covers 180nm to 1mm (IEC 60825-1:2014). If you're cross-shopping a pulsed-light console, its equivalent for non-laser optical sources is IEC 60601-2-57. On install day, test the key switch, the footswitch, the interlock shorting stub and the emergency stop before your first paying patient. Confirm goggles rated for both wavelengths are actually in the room. Check the water circuit too — these cavities need periodic purified-water exchange, and a flow fault is the most common reason a unit quietly refuses to fire. Talk to our team about configuration, operator training and spares before you commit.
Frequently asked questions
How many sessions does freckle removal usually take?
Fewer than patients expect, and fewer than most other pigment work. Ephelides are epidermal, so a correctly set 532nm nanosecond pulse reaches the target directly rather than fighting through dermis. A short course spaced several weeks apart is typical. Your operator sets the pace by how the skin actually responds — a packaged session count is a sales device, not a protocol.
Why not just use 1064nm for everything?
Because absorption doesn't work that way. The infrared line is poorly taken up by the brown, superficial pigment that makes a freckle, and it penetrates well past it. You'd end up raising energy to compensate, which is how you buy a thermal injury instead of a result. Keep 1064nm for dermal targets and dark ink. Use the green line where the pigment actually lives.
Will the freckles come back?
They can, and sun exposure is the reason. Ephelides are UV-driven pigment, so treatment clears what's there now while daily broad-spectrum sunscreen protects the result. Patients who commit to sun care generally hold their outcome for a long stretch. Those who don't often see new spots surface within a season or two — worth saying at consultation rather than at the follow-up.
Is a scab afterwards normal, or did something go wrong?
Normal. A fine dark crust over each treated spot means the pigment took the energy, and it should lift on its own over several days. Blistering, bleeding or widespread whitening is a different story; that points at fluence set too high for the spot size in use. Picking the crust is the single most common cause of a mark that outstays its welcome.
Can this be done on darker skin?
With care, and with lower settings. More epidermal melanin means more competing absorption at 532nm, so a trained operator drops fluence, treats a test patch first, and stretches the intervals between sessions. Judgement matters far more than throughput here. Anyone selling you an aggressive protocol for Fitzpatrick IV and above is selling you a hyperpigmentation problem.
References
- Anderson RR, Parrish JA. Selective photothermolysis: precise microsurgery by selective absorption of pulsed radiation. Science. 1983;220(4596):524-7.
- Ma SY, et al. Split-face comparison of the efficacy of picosecond 532 nm Nd:YAG laser and Q-switched 755 nm Alexandrite laser for treatment of freckles. J Cosmet Laser Ther. 2022.
- IEC 60825-1:2014 Safety of laser products - Part 1: Equipment classification and requirements
- IEC 60601-2-22:2019 Medical electrical equipment - Particular requirements for surgical, cosmetic, therapeutic and diagnostic laser equipment