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What Is The Meaning Of Laser In Physics

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How lasers work – a thorough explanation

laser, a device that stimulates atoms or molecules to emit light at particular wavelengths and amplifies that light, typically producing a very narrow beam of radiation. The emission generally covers an extremely limited range of visible, infrared, or ultraviolet wavelengths. Many different types of lasers have been developed, with highly varied characteristics. Laser is an acronym for light amplification by the stimulated emission of radiation.

What Is Laser Short Answer

The Short Answer: A laser produces a very narrow beam of light that is useful in many technologies and instruments. The letters in the word laser stand for Light Amplification by Stimulated Emission of Radiation. The letters in the word laser stand for Light Amplification by Stimulated Emission of Radiation.

Momentum Transfer And Radiation Pressure Atom

  • There are many variations of laser cooling, but they all use radiation pressure to remove energy from atomic gases .
  • In laser cooling , the frequency of light is tuned slightly below an electronic transition in the atom.
  • Thus if one applies light from two opposite directions, the atoms will always scatter more photons from the laser beam pointing opposite to their direction of motion .
  • Simple laser cooling setups can produce a cold sample of atomic gases at around 1mK starting from a room temperature gas.
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    Quantum Vs Classical Emission Processes

    The mechanism of producing radiation in a laser relies on stimulated emission, where energy is extracted from a transition in an atom or molecule. This is a quantum phenomenon that was predicted by Albert Einstein, who derived the relationship between the A coefficient describing spontaneous emission and the B coefficient which applies to absorption and stimulated emission. However, in the case of the free electron laser, atomic energy levels are not involved it appears that the operation of this rather exotic device can be explained without reference to quantum mechanics.

    How Does A Laser Work

    Measure the Wavelength of Laser Light. Diffraction Grating Stock Vector ...

    Light travels in waves, and the distance between the peaks of a wave is called the wavelength.

    Each color of light has a different wavelength. For example, blue light has a shorter wavelength than red light. Sunlightand the typical light from a lightbulbis made up of light with many different wavelengths. Our eyes see this mixture of wavelengths as white light.

    This animation shows a representation of the different wavelengths present in sunlight. When all of the different wavelengths come together, you get white light. Image credit: NASA

    A laser is different. Lasers do not occur in nature. However, we have figured ways to artificially create this special type of light. Lasers produce a narrow beam of light in which all of the light waves have very similar wavelengths. The lasers light waves travel together with their peaks all lined up, or in phase. This is why laser beams are very narrow, very bright, and can be focused into a very tiny spot.

    This animation is a representation of in phase laser light waves. Image credit: NASA

    Because laser light stays focused and does not spread out much , laser beams can travel very long distances. They can also concentrate a lot of energy on a very small area.

    This animation shows how a laser can focus all of its light into one small point. Credit: NASA

    NASA missions have used lasers to study the gases in Earths atmosphere. Lasers have also been used in instruments that map the surfaces of planets, moons, and asteroids.

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    What Is The Basic Working Principle Of A Laser

    • Electrons residing in a lower energy level possess a tendency to absorb light energy externally in the form of photons or phonons for reaching the higher energy level and energy in the absorbed photon or phonon is equal to the difference of energy between the two levels. In the case of light energy, this means that certain atoms can absorb only a specific wavelength of light for a transition.
    • After reaching the excited higher state, an electron cannot stay there forever. Electrons tend to decay to a lower energy level by losing energy. This transition of electrons generally occurs at different time intervals and emits energy in the form of photons. This entire process of electron transition without any external interference is termed spontaneous emission. In this, the emitted electron has a random direction and phase.
    • At times the electrons are subjected to external influence for transiting from a high-energy to a low-energy state. In this case, the photon emitted during the transition process matches the actual photons direction, phase angle, and wavelength. This process of photon emission is termed stimulated emission that is used in lasers to know more about this topic .

    How Does It Work

    A laser is an optical oscillator, which is made out of a solid, liquid or gas with mirrors at both ends. To make the laser work, the material is excited or “pumped,” with light or electricity. The pumping excites the electrons in the atoms, causing them to jump to higher orbits, creating a “population inversion.” A few of the electrons drop back to lower energy levels spontaneously, releasing a photon . The photons stimulate other excited electrons to emit more photons with the same energy and thus the same wavelength as the original. The light waves build in strength as they pass through the laser medium, and the mirrors at both ends keep reflecting the light back and forth creating a chain reaction and causing the laser to “lase.”

    In simple laser cavities, one mirror has a small transparent area that lets the laser beam out. In semiconductor lasers, both mirrors often transmit a beam, the second one being used for monitoring purposes.

    Laser Action

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    Working Of Liquid Laser

    The active medium in this laser type is organic dye and the solvent used for dissolving the dye is either water, alcohol, or ethylene glycol. The dye is pumped to the capillary tube from the storage tank. This dye leaves the tubes with a flash lamp. The output beam then passes through a Brewster window to the output coupler which is a 50% reflective mirror. The output wavelength can vary to a wide range and the maxim output possible is 618 nm.

    Who Developed The Laser

    Important Definition of Laser – Laser – Physics 2

    This process is based on work by Albert Einstein in 1917 and many others. Physicists Charles H. Townes, Nicolay Basov, and Aleksandr Prokhorov received the 1964 Nobel Prize in Physics for their development of the earliest laser prototypes. Alfred Kastler received the 1966 Nobel Prize in Physics for his 1950 description of optical pumping. On May 16, 1960, Theodore Maiman demonstrated the first working laser.

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    Here’s How The Process Will Work Here:

  • First, an electric current is supplied to turn the flash lamp on and off, which excites the electrons of the ruby crystals.

  • These excited electrons of the high energy state return to the ground state, thereby emitting a photon of light by spontaneous emission.

  • These photons move in the medium, bouncing off the mirrors and exciting other electrons into the high energy states. This process emits more photons by stimulating emission.

  • Since now you have more number of excited electrons than the ground electrons, so it creates a population inversion.

  • The photons keep bouncing back and forth between the two mirrors of the medium, but one of the mirrors is a little less reflective and lets some photons through it.

  • What Makes Lasers So Useful

    Our fascination with light starts at an early age. Some of the first questions kids ask their parents are about light. What are rainbows? Why is the sky blue? What are shadows?

    So its no surprise that light has captivated philosophers and scientists for millennia. The first real progress in understanding light came in the Islamic Golden Age. In 1027 Muslim polymath Hasan Ibn al-Haytham, also known as Alhazen, wrote the Book of Optics. In it, he presented the latest knowledge about optics in seven volumes. Crucially though, he dispelled the popular idea that light came from our eyes like torches. Instead, al-Haytham proved that it is emitted and reflected from objects and travels in straight lines to our eyes.

    Little more was learned about light until Europes Scientific Revolution in the 16th century. From then to 1900, huge progress was made. For example, Isaac Newton showed that colour is a property of light and not the medium. Thomas Young revealed the wave nature of light. And James Clerk Maxwell went further, mathematically describing light as an electromagnetic wave. In fact, some believed we had not only mastered light, but learned everything there is to know about how the universe works. Scientist Lord Kelvin claimed: “There is nothing new to be discovered in physics now”.

    And then came relativity and quantum mechanics. Not only did these towering theories shape physics in the 20th century. They also revolutionised our understanding of light.

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    What Is The Meaning Of Laser In Physics

    Lasers Are an Amazing Application of Quantum Physics. Learn more about what lasers are and how they work.

    In simplest terms, a laser uses light to stimulate the electrons in a gain medium into an excited state . When the electrons collapse into the lower-energy unexcited state, they emit photons. These photons pass between two mirrors, so there are more and more photons exciting the gain medium, amplifying the intensity of the beam. A narrow hole in one of the mirrors allows a small amount of the light to escape .

    Video advice: Introduction to Lasers

    Watch this video to learn more about lasers, its characteristics and principles.

    Who Laid The Foundation Of Laser Physics

    How Laser Works Vector Diagram Photons Stock Vector 152709431 ...
    • In 1917, Sir Albert Einstein laid the foundation of a laser by re-deriving Max Plancks radiation law. Albert Einstein formalized probability coefficients on absorption, stimulated emission, and spontaneous emission of electromagnetic radiation.
    • In the year 1928, Rudolf W. Ladenburg set the existence of stimulated emission and Valentin A. Fabrikant made the first proposal for laser and stated the conditions needed for amplifying light with stimulated emission in 1939.
    • R. C. Retherford and Willis E. Lamb observed and demonstrated stimulated emission in hydrogen spectra in 1947.
    • In 1952, Alexander Prokhorov and Nikolay Basov described the theoretical principles behind the operation of a maser or microwave laser .
    • In 1960, Theodore Maiman built the first working ruby-pulse laser at the Hughes Research Laboratories.

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    Principles And Applications Of Laser

    Laser is the abbreviation of Light Amplification by the Stimulated Emission of Radiation. It is a device that creates a narrow and low-divergent beam of coherent light, while most other light sources emit incoherent light, which has a phase that varies randomly with time and position. Most lasers emit nearly monochromatic light with a narrow wavelength spectrum. Fig.1 is the spectrum of a helium neon laser, showing very high spectra purity.

    The released photon is like the stimulating photon with similar frequency, polarization, and direction of propagation. And theres a set phase relationship between light radiated from various atoms. The photons, consequently, are totally coherent. This is actually the critical property that enables optical amplification to occur.

    Laser is the abbreviation of Light Amplification by the Stimulated Emission of Radiation. It is a device that creates a narrow and low-divergent beam of coherent light, while most other light sources emit incoherent light, which has a phase that varies randomly with time and position. Most lasers emit nearly monochromatic light with a narrow wavelength spectrum. Fig. 1 is the spectrum of a helium neon laser, showing very high spectra purity.

    Disadvantages Of Semiconductor Lasers

    • The divergence of the beam is more than 125 to 400 milliradians which is greater than other laser types.
    • The output beam has an unusual shape as the medium used is short and rectangular.
    • The working of this laser type is dependent on the temperature.

    Stay tuned to learn more about other concepts of Physics.

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    What Is The Physical Meaning Behind Negative Slope Of Laser Characteristics

    Sometimes I measure LIV curves of many semiconductor lasers with the same material and width and different cavity length.

    There should be positive slope and intercept of Threshold current vs inverse cavity length dataset, and also positive intercept of Inverse External Differential Quantum Efficiency vs cavity length dataset.

    Those qualities correspond to:

    • intercept of threshold current vs inverse cavity length = transparency threshold current
    • intercept of IEDQE vs cavith length = internal quantum efficiency
    • slope of IEDQE vs cavith length = internal loss

    Sometimes those values from my data are negative. Obviously it means that something went wrong. But what can be physical reasons behind that?

    Who Invented It

    How lasers work (in theory)

    In 1957, the laser was conceived by Gordon Gould, a graduate student in physics at Columbia University. When Gould filed for patents in 1959, he found that Columbia professor Charles Townes and Arthur Schawlow of Bell Labs had already filed for them. The year before, AT& T had, in fact, demonstrated a working laser at Bell Labs. In 1977, after years of litigation, a court awarded Gould rights to the first of three patents and later to all of them. He finally reaped millions in royalties.

    Developing the Laser

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    What Is A Laser

    The Short Answer:LASER

    The letters in the word laser stand for Light Amplification by Stimulated Emission of Radiation. A laser is an unusual light source. It is quite different from a light bulb or a flash light. Lasers produce a very narrow beam of light. This type of light is useful for lots of technologies and instrumentseven some that you might use at home!

    Advantages And Disadvntages Of Laser


    • Along with its huge ability to support information, it is employed for information transmission in the field of communication.
    • As laser radiation is free of electromagnetic interference, this technique is used in wireless communication systems via free space for both telephony and computer networking.
    • There is virtually little signal leakage in laser radiation.
    • Laser-based fiber optic wires are utilized in fiber optic networks because they are exceedingly light.
    • Because lasers are less dangerous than X-rays, they are extensively employed in the medical field for cancer diagnostics.


    • Lasers are costly, thus patients who require laser-based treatment choices will have to spend a lot of money.
    • Maintenance costs for lasers are significant, resulting in high costs for doctors and hospital administrators.
    • Based on laser equipment, lasers increase convolution and treatment time.

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    Laser Is An Acronym For Light Amplification By Stimulated Emission Of Radiation

    A laser is created when electrons in the atoms in optical materials like glass, crystal, or gas absorb the energy from an electrical current or a light. That extra energy excites the electrons enough to move from a lower-energy orbit to a higher-energy orbit around the atoms nucleus.

    A laser takes advantage of the quantum properties of atoms that absorb and radiate particles of light called photons. When electrons in atoms return to their normal orbitor ground stateeither spontaneously or when stimulated with a light or other energy source, even another laser in some cases, they emit more photons.

    Light moves in waves. Ordinary visible light, say from a household light bulb or a flashlight, comprises multiple wavelengths, or colors, and are incoherent, meaning the crests and troughs of the light waves are moving at different wavelengths and in different directions.

    In a laser beam, the light waves are coherent, meaning the beam of photons is moving in the same direction at the same wavelength. This is accomplished by sending the energized 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 color.

    Questions And Comments From Users

    Explain the working of Ruby Laser with the help of energy level diagram ...


    Laser physics seems to be a very big field.I want to pursue a Ph. D. in laser physics how can I identify a specific area for my research?

    Answer from the :

    That’s an important and difficult question.You may consider many aspects for such a decision:

    • Did you come across interesting papers, where you feel you would be motivated to intensively work on such things?
    • Have you already got some expertise which makes it easier to get a corresponding position?However, it can also be advantageous to move to other subject areas in order to broaden your experience.
    • Importantly, you need a position where there are good opportunities to work in a certain direction for example, colleagues from which you can learn a lot, required infrastructure, etc.You may first want to identify interesting institutes and ask people working there for suggestions concerning topics.That is usually more realistic than first deciding for a subject and then searching for a suitable position.
    • Also consider how you may profit later on from the gained experience.For example, would it be suitable as a start of an interesting career as a researcher, or sufficiently practical for later getting an industry job, or even for both directions?

    Here you can submit . As far as they get accepted by the author, they will appear above this paragraph together with the authors answer. The will decide on acceptance based on certain criteria. Essentially, the issue must be of sufficiently broad interest.

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