Molly Ayala
Lasers are devices that emit light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word laser is an acronym for light amplification by stimulated emission of radiation. While lasers emit light, laser light does not need to be visible. NIF beams, for example, start as invisible infrared light and can be converted into ultraviolet light. Lasers can be used to transmit electricity wirelessly, as seen in new research from South Korea, where scientists transmitted 400 milliwatts of electricity over 100 feet using an infrared laser. However, lasers cannot be used as electrical conductors because they do not carry an electric charge.
| Characteristics | Values |
|---|---|
| Definition | A device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation |
| Working | The photons strike the atoms, creating more and more photons bouncing back and forth between the mirrors within the rod. The number of photons become so great that they pass through one of the mirrors, which is partially reflective, and the laser beam emerges |
| Components | A basic laser consists of a rod made of ruby crystals with a mirror on each end, and a flash tube |
| Power Source | Electric light, emitted by flashtubes, is usually used as a pumping source. But sunlight can also be used |
| Uses | Optical communication, laser cutting, lithography, laser pointers, lidar, free-space optical communication, surgery in hospitals, bar code scanners, playing music, movies, and video games at home |
| Limitations | Lasers cannot be used as a conductor under any circumstances as it contains no charge carriers such as electrons to produce a current flow |
| Interesting Facts | Lasers can be used to transmit electricity wirelessly up to 100 feet |
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What You'll Learn
- Lasers are devices that emit coherent light through optical amplification
- The laser's coherence allows it to remain narrow over great distances
- Lasers can be electrically pumped or pumped by other energy sources
- Lasers can transmit electricity wirelessly over short distances
- Lasers cannot be used as electrical conductors
Lasers are devices that emit coherent light through optical amplification
The gain medium absorbs pump energy, which raises some electrons to a higher energy ("excited") state. Particles can interact with light by either absorbing or emitting photons. Emission can be spontaneous or stimulated. When the number of particles in an excited state exceeds the number of particles in a lower-energy state, population inversion is achieved, and the light is amplified. This system is called an optical amplifier. When an optical amplifier is placed inside a resonant optical cavity, it becomes a laser.
The lasing material can be a solid, liquid, gas, or semiconductor, and it can emit light in all directions. The pump source is typically electricity from a power supply, lamp, or flash tube. The excitation medium is used to excite the lasing material, causing it to emit light. The optical cavity contains mirrors at each end that reflect this light and cause it to bounce between the mirrors, amplifying the energy from the excitation medium in the form of light.
Lasers differ from other sources of light in that they emit coherent light, which means the beam of photons moves in the same direction at the same wavelength. Spatial coherence allows lasers to be focused on a tight spot, while temporal coherence allows them to emit light with a very narrow frequency spectrum. Lasers have a wide range of applications, from surgery in hospitals to barcode scanners and entertainment systems.
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The laser's coherence allows it to remain narrow over great distances
Lasers are distinguished from other light sources by their coherence. Spatial (or transverse) coherence allows a laser to be focused to a tiny spot, enabling uses such as optical communication, laser cutting, and lithography. It also allows a laser beam to stay narrow over great distances (collimation), which is used in laser pointers, lidar, and free-space optical communication.
The laser's light waves are "coherent," meaning the beam of photons moves in the same direction and at the same wavelength. This is achieved by sending energised electrons through an optical "gain medium" such as a solid material like glass, or a gas. The particular wavelength of light is determined by the amount of energy released when the excited electron drops to a lower orbit. The levels of energy introduced can be tailored to the material in the gain medium to produce the desired beam colour.
The coherence time is not the time duration of the signal; the coherence length differs from the coherence area. The larger the bandwidth – the range of frequencies a wave contains – the faster the wave decorrelates. Narrow-bandwidth lasers have long coherence lengths. For example, a stabilised and monomode helium-neon laser can easily produce light with coherence lengths of 300 metres.
The coherence length can be used to quantify the degree of temporal (not spatial) coherence as the propagation length (and thus propagation time) over which coherence degrades significantly. It is defined as the coherence time times the vacuum velocity of light. For example, if the coherence length of a laser is 1km, the phase relationship between two points along the laser beam, with a distance of 1km between them, is still significant, but already substantially degraded by phase fluctuations in the laser.
While FEL beams share the same optical traits as other lasers, such as coherent radiation, their operation is quite different. FELs use a relativistic electron beam as the lasing medium, unlike gas, liquid, or solid-state lasers, which rely on bound atomic or molecular states.
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Lasers can be electrically pumped or pumped by other energy sources
Lasers are devices that emit light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The first laser was built in 1960 by Theodore Maiman at Hughes Research Laboratories, based on theoretical work by Charles H. Townes and Arthur Leonard Schawlow.
Lasers differ from other sources of light in that they emit light that is coherent, meaning the beam of photons moves in the same direction at the same wavelength. This is achieved by sending energised electrons through an optical "gain medium" such as a solid material like glass, or a gas. The particular wavelength of light is determined by the amount of energy released when the excited electron drops to a lower orbit. The levels of energy introduced can be tailored to the material in the gain medium to produce the desired beam colour.
The gain medium absorbs pump energy, which raises some electrons into higher energy ("excited") quantum states. Particles can interact with light by either absorbing or emitting photons. Emission can be spontaneous or stimulated. In the latter case, the photon is emitted in the same direction as the light that is passing by. When the number of particles in one excited state exceeds the number of particles in some lower-energy state, population inversion is achieved. In this state, the rate of stimulated emission is larger than the rate of absorption of light in the medium, and therefore the light is amplified. A system with this property is called an optical amplifier.
Laser pumping refers to introducing energy into a laser system to produce a population inversion, where there are more atoms or molecules in an excited state than in the ground state. This increases the probability of stimulated emission of light and enables lasing to occur. Depending on the laser type, pumping can be achieved through various methods, including optical pumping, electrical pumping, and chemical pumping. The pump energy is usually provided in the form of light or electric current, but more exotic sources have been used, such as chemical or nuclear reactions.
For example, in the helium-neon laser, electrons from the discharge collide with the helium atoms, exciting them. The excited helium atoms then collide with neon atoms, transferring energy. This allows an inverse population of neon atoms to build up. Electric current is typically used to pump laser diodes and semiconductor crystal lasers (for example, germanium). Electron beams pump free-electron lasers and some excimer lasers.
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Lasers can transmit electricity wirelessly over short distances
Lasers are devices that emit coherent light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. While lasers cannot be used as electrical conductors, they can be used to transmit electricity wirelessly over short distances. This is achieved through a method called distributed laser charging, which allows for safe, high-power illumination with minimal light loss.
The process involves exciting the electrons in the atoms of optical materials like glass, crystal, or gas, causing them to move to a higher-energy orbit around the atom's nucleus. These excited electrons then release photons of light as they drop back down in energy. These photons are bounced off mirrors back at the optical atoms, creating more and more photons until a powerful laser beam is produced.
The laser beam can transmit a charge between the laser transmitter and a receiver when they are in a line of sight. This forms a laser cavity in the air between them, enabling light-based power transmission. However, if an obstacle blocks the line of sight, the system automatically switches to a power-safe mode to prevent damage to any objects or people that may be in the way.
Laser power transmission (LPT) technology has gained attention due to its potential to improve energy transmission efficiency, reduce energy loss, and minimize environmental pollution. LPT can be used to wirelessly power mobile devices, robots, and aerospace vehicles, enhancing their reliability and lifespan. Additionally, using LPT to replace power cords in certain environments could eliminate the risk of electrical fires and interference caused by wired connections.
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Lasers cannot be used as electrical conductors
Lasers are devices that emit light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". Lasers emit light that is coherent, meaning the beam of photons moves in the same direction at the same wavelength. This is achieved by sending energised electrons through an optical "gain medium" such as a solid material like glass or a gas.
Despite being based on electromagnetic radiation, lasers cannot be used as electrical conductors because they carry no electric charge. Electrical conduction is the net motion of electric charge, and it cannot take place without the motion of matter on some scale. While a laser beam can carry electric and magnetic fields, along with energy and momentum, it does not possess the necessary charge carriers, such as electrons, to produce a current flow.
However, there are certain cases where a laser can indirectly enable electrical conduction. For instance, if a laser beam of sufficient power density passes through a gas, it can ionise the gas molecules, creating a source of charged particles that can serve as charge carriers. This effect has been utilised in experiments, such as firing a laser into a charged storm cloud to initiate a lightning strike back down the light beam.
Additionally, in the presence of certain substances, such as powder suspended in the air, a laser can vaporise and ionise the substance, producing ions and electrons capable of conducting an electric current. While theoretically possible, creating an extraordinarily strong laser capable of directly ionising a transparent substance like air is considered impractical due to the extremely high intensity required.
In summary, while lasers themselves cannot act as electrical conductors due to the absence of charge carriers, they can play a role in facilitating electrical conduction by ionising specific materials or gases under certain conditions.
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Frequently asked questions
Yes, lasers can transmit electricity wirelessly across short distances. This is known as distributed laser charging.
No, a laser beam by itself cannot conduct electricity as it contains no charge carriers. However, if a laser beam of sufficient power density is transmitted through a gas, a small amount of ionization of the gas molecules will occur, which can then serve as charge carriers.
Distributed laser charging is a method of transmitting electrical power wirelessly using lasers. It provides safe high-power illumination with less light loss.
Distributed laser charging works by forming a laser cavity in the air between the transmitter and receiver, allowing the system to deliver light-based power. This only works if the transmitter and receiver are in line-of-sight with each other.
Yes, lasers can be powered by other energy sources such as sunlight, although this is less common.
