Published 13 October 2026 · Reviewed by Dr Sin Yong
Alexandrite laser is a laser built on a chromium-doped chrysoberyl crystal, emitting at 755 nm, a wavelength strongly absorbed by melanin, the pigment in hair and in sun-induced spots. That absorption is the alexandrite laser's power and its caution: it suits lighter skin types and discrete benign spots, while deeper skin tones are often matched to 1064 nm Nd:YAG instead. It exists in long-pulsed and picosecond forms, and melasma is not treated with it.
Key facts
Wavelength
755 nm, strongly absorbed by melanin
Long-pulsed
Dark terminal hair; discrete benign spots such as freckles and lentigines
Picosecond
Pigment fragmentation by a pressure effect, with a fractional lens array for texture
Caution
Chosen by skin phototype; deeper tones are often matched to 1064 nm instead, and melasma is not treated with it
Where the alexandrite laser matters on this site
At 755 nm the alexandrite wavelength sits where melanin absorbs strongly and haemoglobin still absorbs usefully, with less depth than 1064 nm. That makes it precise for hair and discrete spots on lighter skin and demanding on darker skin, and the site places it accordingly.
Seven-five-five is a precise wavelength, and precision cuts both ways; I decide after I have examined the skin, never from the brochure.— Dr Sin Yong
Alexandrite laser: the treatment page, setting out when 755 nm fits and when 1064 nm is the better match.
R2 Glow: long-pulsed 755 nm paired with 1064 nm, aimed at the UV-driven inflammation behind pigment and redness rather than at the pigment itself.
Laser hair removal: where 755 nm is the usual choice for dark hair on lighter skin types.
Pico laser for freckles: the picosecond form of the wavelength, used for discrete benign spots.
The pairing logic is the point: on this site 755 nm is rarely used alone on Singapore skin, and never for melasma.
Not to be confused with
Alexandrite names a crystal and a wavelength. The lookalikes are other wavelengths and other pulse forms sold under similar promises.
Nd:YAG 1064 nm. Deeper, less absorbed by epidermal melanin, the usual match for Fitzpatrick IV to V. The two are partners, not rivals.
Diode 808 to 810 nm. A hair-removal laser between the two in wavelength, often sold as "SHR". It is not an alexandrite.
PicoSure. A brand of picosecond alexandrite at 755 nm. Same wavelength, ultrashort pulse, different job: pigment fragmentation rather than heating. The PicoSure vs other pico lasers post explains the difference.
IPL. A lamp emitting a band that includes 755 nm among many others; it does not have the selectivity of a single wavelength.
Ruby 694 nm. An older, even more melanin-selective wavelength, largely replaced because of its pigment risk in darker skin.
"755" on a price list tells you the wavelength; it does not tell you whether the pulse is long or picosecond, and that decides what it treats.
What decides whether an alexandrite laser matters for you
The decision is made after the skin is examined, not before, because the same absorption that makes 755 nm effective makes it risky in the wrong skin.
Skin type. Lighter types tolerate 755 nm well; in Fitzpatrick IV and above, epidermal melanin competes for the energy and 1064 nm is usually chosen. The Fitzpatrick grade is assessed in person.
Target. Dark terminal hair and discrete freckles or lentigines are the classic targets; diffuse pigment and melasma are not.
Pulse form. Long-pulsed for hair and inflammation; picosecond for pigment fragmentation. Ask which form is being proposed.
Recent sun. A tan raises the pigment risk sharply with any melanin-absorbed wavelength, so treatment is timed around it.
Melasma. Not treated with 755 nm on this site; the melasma page begins with sun protection and medical treatment.
When in doubt in Singapore skin, Dr Sin Yong reaches for the longer wavelength and pairs 755 nm only where the assessment supports it.
Where it fits
On this site the alexandrite wavelength is chosen after the skin is examined, not before. The long-pulsed alexandrite laser page sets out when 755 nm fits and when 1064 nm does not: on lighter skin types it is usually the better match for laser hair removal and for discrete freckles and sun spots. In long-pulsed, non-ablative form it is also one half of Dr Sin Yong's R2 Glow protocol, paired with 1064 nm Nd:YAG and directed at the UV-driven inflammation that keeps producing pigment rather than at the pigment itself. Melasma is not treated with it; the site's approach to melasma starts with sun protection and medical treatment.
Frequently Asked Questions
Neither is better in the abstract; skin type decides. 755 nm is absorbed more strongly by melanin, so it is effective on dark hair in lighter skin but competes with epidermal melanin in darker skin. 1064 nm is absorbed less by the epidermis and penetrates deeper, which is why it is usually matched to Fitzpatrick IV and V. Dr Sin Yong assesses the skin and the hair before choosing, and some platforms blend the two.
Because melasma is driven by inflammation and heat, and 755 nm is strongly absorbed by melanin, so an aggressive pass can darken the patch or convert it into a mixed pigment problem. On this site melasma is managed, not removed: sun protection and medical treatment come first, and any laser used is low-fluence and staged. R2 Glow uses long-pulsed 755 nm at gentle settings for inflammation, not to strip pigment.
It depends on the phototype. 755 nm is strongly absorbed by melanin, so in deeper Fitzpatrick types more energy is taken up by the epidermis; those patients are often matched to 1064 nm Nd:YAG instead. The laser is chosen after the skin is examined.
Long-pulsed, for dark terminal hair and discrete benign spots such as freckles and lentigines, and within R2 Glow for the inflammation behind pigment. In picosecond form it is used for pigment fragmentation and, with a fractional lens, for texture.
References
Chan JC, Shek SY, Kono T, Yeung CK, Chan HH. A retrospective analysis on the management of pigmented lesions using a picosecond 755-nm alexandrite laser in Asians. Lasers Surg Med. 2016;48(1):23-29. doi:10.1002/lsm.22443. source
Tanghetti EA. The histology of skin treated with a picosecond alexandrite laser and a fractional lens array. Lasers Surg Med. 2016;48(7):646-652. doi:10.1002/lsm.22540. source
The effects of long-pulsed alexandrite laser therapy on facial redness and skin microbiota compositions in rosacea: A prospective, multicentre, single-arm clinical trial. Photodermatology, Photoimmunology & Photomedicine (PubMed), 2023. pubmed.ncbi.nlm.nih.gov
Hair Removal With Blended 755/1064 nm Laser Energy. Lasers in Surgery and Medicine (PubMed), 2021. pubmed.ncbi.nlm.nih.gov
A randomized split-face comparative study of long-pulsed alexandrite plus low-fluence Nd:YAG laser versus pulsed-dye laser in the treatment of rosacea. Lasers in Surgery and Medicine (PubMed), 2022. pubmed.ncbi.nlm.nih.gov
