In optics

Optics

Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...

, wall-plug efficiency or radiant efficiency is the energy conversion efficiency

Energy conversion efficiency

Energy conversion efficiency is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The useful output may be electric power, mechanical work, or heat.-Overview:...

 with which the system converts electrical power into optical power

Power (physics)

In physics, power is the rate at which energy is transferred, used, or transformed. For example, the rate at which a light bulb transforms electrical energy into heat and light is measured in watts—the more wattage, the more power, or equivalently the more electrical energy is used per unit...

. It is defined as the ratio of the radiant flux

Radiant flux

In radiometry, radiant flux or radiant power is the measure of the total power of electromagnetic radiation...

 (i.e., the total optical output power) to the input electrical power.

In laser

Laser

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...

 systems, this efficiency includes losses in the power supply and also the power required for a cooling system, not just the laser itself.

See also

• Luminous efficiency
• Luminous coefficient
• Luminous efficacy
  Luminous efficacy
  Luminous efficacy is a measure of how well a light source produces visible light. It is the ratio of luminous flux to power. Depending on context, the power can be either the radiant flux of the source's output, or it can be the total electric power consumed by the source.Which sense of the term is...
  
   - Efficacy, weighted by the eye's response to light
• Coefficient of utilization
  Coefficient of utilization
  A coefficient of utilization is a measure of the efficiency of a luminaire in transferring luminous energy to the working plane in a particular area. The CU is the ratio of luminous flux from a luminaire incident upon a work plane to that emitted by the lamps within the luminaire...