What is a laser?

laser skin treatment

What is a laser?

The word laser is an acronym that means “Light Amplification by Stimulated Emission of Radiation”. A laser is an optical system that contains a gain medium composed atoms or molecules. These atoms or molecules are then stimulated to produce photons, or light particles. The laser pumps out so many photons that they form a concentrated light beam.

For a laser to work, we need three things:

  1. A medium. The medium is made up of atoms or molecules. These atoms are then stimulated to produce photons. The medium can be a liquid, a gas or solid material. 
  2. Something to stimulate the photons. This can be either a flash lamp, an electrical discharge or another laser.
  3. A cavity, typically a highly reflective mirror and a partially reflective mirror.  The medium sits between the mirrors.  Stimulated photons oscillate (bounce back and forth) between the two mirrors.  The partially reflective mirror allows a portion of the light out of the cavity forming the laser beam.

The laser creates light through the process of stimulated emission of radiation. The electrons inside the lasing medium are usually in a resting state. By discharging energy into the lasing medium, the electrons in the lasing medium become excited and unstable. Electrons, once excited, always want to go back to a resting state. Oscillating photons passing by excited state atoms or molecules stimulate the excited state atoms or molecules to release the excess energy in the form of photons having the same wavelength and phase as the oscillating photons. This process results in stimulated emission which is when we stimulate an atom to get radiation out of them. 

What are the three properties of laser?

  1. The beam is collimated. This means that the beam has a low divergence rate, meaning the beam radius stays fairly constant as it travels.  It also means the beam is directional, travels in one direction.
  2. The beam is coherent. Coherent meaning the crest (peak) of each wave lines up with the crest of every other wave generated. This allows the beam to be focused to very small volumes creating a very bright source of energy.  Brightness is an important property of the PicoWay® Resolve laser device allowing laser induced optical breakdown, and the CO2RE® system allowing tissue ablation.
  3. The beam is monochromatic. This means that it is one color. 

What products in the Candela line are true lasers?

In the Candela portfolio, the following devices are lasers: The VBeam®GentleMax Pro®, and PicoWay® systems.

¹Lasers: Understanding the basics. Coherent Inc., accessed October 30, 2018.