Laser hair removal: diode laser, alexandrite, Nd:YAG, IPL and LED compared
Diode laser, alexandrite laser, Nd:YAG, IPL or LED: which technology is right for permanent hair removal depends on skin type, hair colour and the demands placed on speed and comfort. This page explains how laser hair removal works physically, how the wavelengths 755, 808 and 1064 nm differ and which technical data really count in a device.
The answers are aimed at studios, practices and clinics facing a device decision and at anyone who wants to understand the technology. The examples used are the SIACSKIN devices: the DEWEON 4LD diode laser, the AlexDUAL UFO with alexandrite and Nd:YAG, the VCL DERMALIGHT LED system, the DERMAFORCE BBL PRO and the KYROMASTER cooling device.
How does laser hair removal work?
The melanin in the hair absorbs the laser light and converts it into heat, and this heat damages the hair-forming cells in the follicle. The principle is called selective photothermolysis: wavelength, pulse duration and energy are chosen so that the dark hair absorbs the energy and the surrounding skin receives as little of it as possible. The hair acts like a wick that conducts the heat into the deeper layers. Once the follicle is sufficiently damaged, it no longer produces coarse hair.
That is why contrast and cooling matter: the darker the hair relative to the skin, the easier the treatment. The DEWEON 4LD works with four wavelengths (755, 808, 940 and 1064 nm) and cools the skin surface through a sapphire.
Why does the laser only work on hairs in the growth phase?
Only in the growth phase, the anagen phase, is the hair firmly attached to its root and rich in melanin, and only then does it conduct the heat to the hair-forming cells. In the transition and resting phases the hair has already detached from the root, and the laser pulse has nothing to act on. Depending on the body area, only a proportion of hairs is actively growing at any time: on the legs and arms about one fifth, on the face considerably more.
That is why every course of laser hair removal needs several sessions, whichever device is used. The device does, however, decide how reliably each session reaches the hairs that are currently active. With the AlexDUAL UFO, the SIA AI uses cameras on the handpiece to set skin type, body area and energy automatically.
What is the difference between a diode laser, an alexandrite laser and an Nd:YAG laser?
The difference lies in the wavelength: the alexandrite laser works at 755 nm, the classic diode laser at 808 nm and the Nd:YAG laser at 1064 nm. The shorter the wavelength, the more strongly melanin absorbs the light. The 755 nm wavelength therefore also picks up finer hairs, but puts more strain on heavily pigmented skin. The 1064 nm wavelength penetrates deeper and spares the epidermis, but requires coarse, dark hair. The 808 nm wavelength lies in between and is considered an all-rounder.
SIACSKIN covers all three: the AlexDUAL UFO combines alexandrite (755 nm) and Nd:YAG (1064 nm) in one device, and the DEWEON 4LD is a diode laser with 755, 808, 940 and 1064 nm.
What does a diode laser with four wavelengths offer compared with a pure 808 nm laser?
A diode laser with several wavelengths reaches hairs at different depths and can be adapted to more skin types than a pure 808 nm device. The 755 nm wavelength is absorbed most strongly by melanin and targets finer, superficial hairs. The 808 nm wavelength is the proven middle ground. The 940 and 1064 nm wavelengths penetrate deeper and are absorbed less by the epidermis, which matters for darker skin types and deep-seated hairs.
The DEWEON 4LD combines exactly these four wavelengths. Its AI skin analyser selects wavelength and energy automatically, so that a studio can treat all skin types with a single device.
For which skin and hair is the 755 nm alexandrite laser suitable?
The alexandrite laser is suitable for fair skin types (Fitzpatrick I to IV) with dark blonde to dark hair, even if it is fine. At 755 nm, melanin absorption is very high, so it picks up hairs that contain too little pigment for longer wavelengths. This very strength becomes a disadvantage on dark skin, because the epidermis then absorbs more energy too. With very light, white, grey or red hair, the pigment is hardly sufficient even for the alexandrite laser.
For this reason, the AlexDUAL UFO combines the alexandrite laser with an Nd:YAG laser at 1064 nm for the dark skin types V to VI. The square spot ranges from 10 to 40 mm.
Why is the 1064 nm Nd:YAG laser suitable for dark skin?
Light at 1064 nm is absorbed by the melanin of the epidermis much more weakly than shorter wavelengths, yet still penetrates deep to the hair root. In dark skin there is a lot of melanin in the epidermis. An alexandrite laser would release too much energy there, and the risk of burns and pigmentation changes rises. The Nd:YAG laser avoids this problem, but needs coarse, dark hairs, because the hair too absorbs this wavelength more weakly.
The AlexDUAL UFO has the Nd:YAG laser on board for skin types V to VI and, alongside it, the alexandrite laser for fair skin. The DEWEON 4LD also offers 1064 nm as one of its four wavelengths.
What is the difference between laser and IPL for hair removal?
A laser emits light of a single wavelength, while IPL emits a broad spectrum that is narrowed down to the desired range by filters. Laser light is collimated and targets the melanin in the hair more precisely. IPL spreads the energy over many wavelengths, also heats the melanin and reduces hair growth over several sessions, but is more dependent on fair skin with dark hair.
For a studio focusing on hair removal, a laser such as the DEWEON 4LD is the logical choice. The DERMAFORCE BBL PRO is BroadBand Light, that is, advanced IPL, and not a laser: its strength is skin rejuvenation, and the filters for hair reduction are an addition for skin types I to IV.
What is LED hair removal and which hair is it intended for?
Instead of a single laser wavelength, LED hair removal works with a broader band of light and is intended for light, blonde and very fine hairs that a laser barely picks up. Such hairs contain little melanin, which is why diode and alexandrite lasers reach their limits with them.
The VCL DERMALIGHT from SIACSKIN is such an LED system and not a laser. It works in the spectrum of 750 to 890 nm with 1 to 50 J/cm² and a spot of 18 × 24 mm. It is designed for hair reduction on light, blonde and fine hairs and vellus hair. It is not intended for dark or thick hairs; there a laser such as the DEWEON 4LD is the right tool. White, grey and red hairs also barely respond to LED.
Which technology suits which skin type and hair colour?
As a rule of thumb: fair skin with dark hairs tolerates short wavelengths, dark skin needs long ones, and very light hairs need a system of their own. For skin types I to IV with dark blonde to dark hair, the 755 nm alexandrite laser is suitable, and for skin types V to VI the 1064 nm Nd:YAG laser. Both are in the AlexDUAL UFO. With its four wavelengths, the DEWEON 4LD diode laser covers all skin types for pigmented hairs.
The LED system VCL DERMALIGHT is intended for light, blonde and very fine hairs. White, grey and red hairs barely respond to light and laser; for these, electrolysis remains the option.
Is laser hair removal better than waxing or sugaring?
For anyone who wants to get rid of hair in the long term, yes: waxing and sugaring pull the hair out but leave the follicle intact, so it grows back after 3 to 6 weeks. The laser, by contrast, damages the hair-forming cells themselves. After a course of treatment, a marked, long-term reduction in hair remains, although individual hairs can grow back. In addition, waxing promotes ingrown hairs and requires the hairs to grow a few millimetres between appointments. With lasering, you simply keep shaving.
For studios expanding from waxing to laser, a device that covers as many clients as possible makes sense. With four wavelengths, the DEWEON 4LD diode laser is designed for all skin types.
The laser treats many hairs at once via their melanin, while electrolysis destroys each follicle individually with a fine probe and electric current. The laser is therefore many times faster and suitable for whole body areas, but requires pigmented hairs. Electrolysis works regardless of hair colour, so also with white, grey and red hairs. It is, however, slow, more uncomfortable and practical only for small areas such as the chin or upper lip.
In practice, the two methods complement each other. A laser such as the AlexDUAL UFO, which covers skin types I to VI with alexandrite and Nd:YAG, takes care of larger areas and pigmented hairs, while the needle deals with individual light residual hairs. SIACSKIN does not offer a device for electrolysis.
Which technical specifications really matter in a hair removal laser?
The key parameters are wavelength, power, spot size, pulse duration, repetition rate and cooling. The wavelength determines which skin and hair types you can treat. High power allows short pulses with enough energy, even with a large spot. A large spot delivers the light deeper into the tissue and shortens the treatment, and the repetition rate determines the working speed. A widely adjustable pulse duration adapts the energy to fine as well as thick hairs.
For comparison, the specifications of the DEWEON 4LD: four wavelengths, 4000 W at the handpiece, spots from 15 × 15 to 15 × 40 mm, pulses from 1 to 200 ms, up to 30 Hz and sapphire cooling down to minus 50 °C. The AlexDUAL UFO reaches 7500 W total power with spots from 10 to 40 mm.
What role does pulse duration play in laser hair removal?
The pulse duration decides whether the heat stays in the hair or dissipates into the skin, and must therefore suit the hair thickness and skin type. Fine hairs release heat quickly and need short pulses. Thick hairs store it for longer and tolerate longer pulses. With dark skin, the pulse is deliberately lengthened: the epidermis can then release the heat during the pulse, while the thicker hair retains it.
A device with a narrow pulse range is therefore always a compromise. The AlexDUAL UFO works with pulses of 0.3 to 100 ms, the DEWEON 4LD with 1 to 200 ms. This allows the pulses to be adapted to fine as well as to coarse hairs.
What is the difference between the in-motion and stamping techniques with a diode laser?
With the stamping technique, you place pulse after pulse next to each other, while with the in-motion technique the handpiece glides over the area several times with many weaker pulses per second. The stamp delivers the full energy to the hair in a single shot and is precise on small areas and individual coarse hairs. The in-motion technique builds up the heat gradually. Most people find that more comfortable, and large areas such as legs or back are treated more quickly. However, the area must be passed over evenly and often enough.
The technical prerequisite for the in-motion technique is a high repetition rate. The DEWEON 4LD works with up to 30 Hz and spots up to 15 × 40 mm, plus sapphire cooling down to minus 50 °C.
Why is skin cooling so important in laser hair removal?
Cooling protects the epidermis from the heat generated on the way to the hair and makes higher energies tolerable in the first place. Without it, the risk of redness, blisters and pigmentation changes rises, and the treatment becomes markedly more uncomfortable. Contact cooling sits in the handpiece and cools exactly where the pulse lands. Cold air cools without contact and over a large area, including before and after the pulse.
The DEWEON 4LD cools through a sapphire at temperatures down to minus 50 °C. The AlexDUAL UFO has a compressor and quadruple cooling system and needs no external cooling unit. As a supplement for sensitive areas there is the KYROMASTER: cold air down to minus 50 °C for pre-, parallel and post-treatment cooling, without consumables.
