laser

Band (frequency band): A range of wavelengths within the electromagnetic spectrum

Chromophores: The parts of a molecule that give it color by absorbing certain wavelengths and reflecting others

Cluster probe: A light therapy applicator with multiple diodes that may consist of any combination of laser diodes, light-emitting diodes, or supraluminous diodes. Use of multiple diodes allows coverage of a larger treatment area, takes advantage of the properties of different types of diodes, and may reduce treatment time.

Coherent: Light in which all waves are in phase with each other

Diathermy: The application of shortwave or microwave electromagnetic energy to produce heat within tissues, particularly deep tissues

Directional (collimated): Light with parallel waves

Divergent: Light that spreads; the opposite of collimated.

Electromagnetic radiation: Radiation composed of electrical and magnetic fields that vary over time and are oriented perpendicular to each other. This type of radiation does not need a medium to propagate.

Energy: The total amount of electromagnetic energy delivered over the entire treatment time. Energy is usually measured in joules (J). Energy is equal to power multiplied by time.

Energy density (fluence): The total amount of electromagnetic energy delivered per unit area over the entire treatment time. Energy density is generally measured in joules per centimeter squared (J/cm2)

Frequency: The number of waves per unit time, generally measured in hertz (Hz), which indicates waves per second.

Hot laser: A laser that heats and destroys tissue directly in beam and is used for surgery; also called high-intensity laser.

Ionizing radiation: Electromagnetic radiation that can penetrate cells and displace electrons from atoms or molecules to create ions; includes x-rays and gamma rays. Ionizing radiation can damage the internal structures of living cells.

Laser: Acronym for light amplification by stimulated emission of radiation. Laser light has the unique properties of being monochromatic, coherent, and directional.

Laser diode: A light source that uses semiconductor diode technology and optics to produce laser light

Light-emitting diode (LED): A semiconductor diode light source that produces relatively low-power light in a range of frequencies; light may appear to be one color (e.g., red) but will always have a range of wavelengths and will not be coherent or directional.

Low-level laser therapy (LLLT): Application of laser light for therapeutic purposes. LLLT generally uses laser light diodes that have less than 500 mW power per diode

LLLT cluster probes: may contain a number of diodes with a total combined power greater than 500 mW; also known as cold laser, low-intensity, low-power, or soft laser

Monochromatic: Light of single frequency, wavelength, and color. Laser light is monochromatic. Other light sources produce light with a range of wavelengths

Power: Rate of energy production, generally measured in milliwatts (mW) for laser light

Power density (irradiance): The concentration of power per unit area, measured in watts per centimeter squared (W/cm2).

Stimulated emission: Occurs when a photon hits an atom that is already excited (i.e., electrons are at a higher energy level than usual). The atom being hit releases a new photon that is identical to the incoming photon—the same color, traveling in the same direction

Supraluminous diode (SLD): A light source that uses semiconductor diode technology to produce high-power light in a narrow frequency range.

Ultraviolet (UV) radiation: Electromagnetic radiation with wavelength from less than 290 to 400 nm, which lies between x-ray and visible light.

Wavelength: The length of a wave of light from peak to peak determines frequency and color. Longer wavelengths are associated with deeper penetration