Laser Physics and the Crystals Behind Some Medical Lasers

Lasers can sound mysterious, but the basic idea is surprisingly elegant: energy is used to excite a material, and that material helps produce a focused beam of light with specific properties.

Where crystals come in

Some lasers use a solid-state gain medium made from a crystal that has been doped with specific ions. A classic example is the ruby laser. Another is Nd:YAG, where neodymium ions are incorporated into a yttrium-aluminum-garnet crystal.

The material matters because it helps determine the wavelength of light the laser produces.

Why wavelength matters in medicine

Different wavelengths interact differently with chromophores such as melanin, hemoglobin, water, and tattoo pigment. That is why one laser is not interchangeable with another even when the machines look similar.

A few examples from aesthetic medicine

Long-pulse 1064 nm Nd:YAG is often used when deeper penetration or reduced melanin absorption is useful. Q-switched 1064 nm and 532 nm wavelengths can be used for selected pigment or tattoo indications. Other wavelengths are chosen when water or different chromophores are the intended target.

The device is only part of the equation

Wavelength does not determine safety by itself. Pulse duration, fluence, spot size, cooling, treatment technique, skin type, recent tanning, and the clinical target all matter.

That is what makes laser medicine interesting to me: the treatment is really applied physics, but the physics has to be matched to the patient.

— Nora Phillips, DNP, APRN Central Health | Wahiawa, Hawaiʻi

Sources

FDA — Medical Lasers https://www.fda.gov/radiation-emitting-products/surgical-and-therapeutic-products/medical-lasers