A solar-pumped laser, is a 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...

 that shares the same optical

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...

 properties as conventional lasers such as emitting a beam

Beam

Beam may refer to:*Beam , a construction element*Beam , the most extreme width of a nautical vessel, or a point alongside the ship at the mid-point of its length*A narrow, propagating stream of particles or energy:...

 consisting of coherent

Coherence (physics)

In physics, coherence is a property of waves that enables stationary interference. More generally, coherence describes all properties of the correlation between physical quantities of a wave....

 electromagnetic

Electromagnetic radiation

Electromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...

 radiation

Radiation

In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...

 which can reach high 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...

, but which uses solar radiation for pumping

Laser pumping

Laser pumping is the act of energy transfer from an external source into the gain medium of a laser. The energy is absorbed in the medium, producing excited states in its atoms. When the number of particles in one excited state exceeds the number of particles in the ground state or a less-excited...

 the lasing medium

Active laser medium

The active laser medium is the source of optical gain within a laser. The gain results from the stimulated emission of electronic or molecular transitions to a lower energy state from a higher energy state...

. This type of laser is unique from other types in that it does not require any artificial energy source.

Lasing Media

The two most studied lasing media for solar-pumped lasers have been Iodine

Iodine

Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....

, with a laser wavelength of 1.31 micrometers, and NdCrYAG, which lases at 1.06 micrometers wavelength. Solar-pumped semiconductor lasers

Laser diode

The laser diode is a laser where the active medium is a semiconductor similar to that found in a light-emitting diode. The most common type of laser diode is formed from a p-n junction and powered by injected electric current...

 have also been proposed by Landis and others.

Applications

Solar pumped lasers are not used commercially because the low cost of electricity in most locations means that other more efficient types of lasers that run on electrical power can be more economically used. Solar pumped lasers might become useful in off-grid locations.

Hydrogen Production

A leader in this field is Shigeaki Uchida and his team in Japan (Tokyo/Osaka). Their design uses fresnel lens

Fresnel lens

A Fresnel lens is a type of lens originally developed by French physicist Augustin-Jean Fresnel for lighthouses.The design allows the construction of lenses of large aperture and short focal length without the mass and volume of material that would be required by a lens of conventional design...

es and a solar-pumped NdCrYAG laser to drive a magnesium-based cycle, which produces hydrogen gas as its product.

Potential Spacecraft Applications

Since there is no "grid power" in space, most spacecraft today use solar power sources, mostly photovoltaic solar cells. Powering lasers requires high levels of power, so the inefficiency of PV solar cells (usually less than 27% efficiency) motivates interest in solar pumping of lasers.
Other potential benefits of solar pumped lasers might be reduced weight and reduced number of components affording higher reliability (reduced number of failure modes) versus an electrically pumped laser powered from PV cells.

Space Propulsion

There have been proposals to use solar-pumped lasers for spacecraft beam-powered propulsion

Beam-powered propulsion

Beam-powered propulsion is a class of aircraft or spacecraft propulsion mechanisms that use energy beamed to the spacecraft from a remote power plant to provide energy...

.

Solar power satellite

There have been proposals to use solar pumped lasers for Space-based Solar Power.

Military applications

There have been proposals to use solar pumped lasers in space for ballistic missile defense.

Current research

The largest solar pumped laser is currently being operated by a research faciliy in Uzbekistan.
It is a 1 MW solar input power NdYAG type laser, operating at 3,000 Degrees C. It is cooled by distilled water.