What is Laser: Definition and 1000 Discussions

A laser is a device that emits 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 H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow.
A laser differs from other sources of light in that it emits light which is coherent. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over great distances (collimation), enabling applications such as laser pointers and lidar. Lasers can also have high temporal coherence, which allows them to emit light with a very narrow spectrum. Alternatively, temporal coherence can be used to produce ultrashort pulses of light with a broad spectrum but durations as short as a femtosecond.
Lasers are used in optical disc drives, laser printers, barcode scanners, DNA sequencing instruments, fiber-optic, semiconducting chip manufacturing (photolithography), and free-space optical communication, laser surgery and skin treatments, cutting and welding materials, military and law enforcement devices for marking targets and measuring range and speed, and in laser lighting displays for entertainment. Semiconductor lasers in the blue to near-UV have also been used in place of light-emitting diodes (LED's) to excite fluorescence as a white light source. This permits a much smaller emitting area due to the much greater radiance of a laser and avoids the droop suffered by LED's; such devices are already used in some car headlamps.

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  1. CDL

    Mean Frequency and Frequency Spread of a Laser Pulse

    Homework Statement Laser probes are being used to examine the states of atoms and molecules at high temporal resolution. A laser operating at a wavelength of 400 nm produces a 1 femtosecond pulse. Compute the mean frequency and frequency spread, ∆ν, of this laser pulse. Homework Equations c =...
  2. Adrian Tudini

    Power of a Quantum Cascade laser by theory

    hi Just a little question. How does one calculate the power of a QCL by theory? Is there any free software that allows one to calculate the power of a inputted laser medium for a qcl? Thanks. Adrian
  3. FelixLudi

    I Possibility of a quasar jet laser impacting Earth directly

    I understand quasars as black holes with an accretion disk and occassional jets of mass being shot out of the black hole from it's top and bottom. (Correct me if I'm wrong) If so, what is the actual possibility for that type of quasar to be rotated so heavily that it rotates on a horizontal...
  4. T

    Wavelength of a laser within an optical cavity

    1. The problem statement, all variables and given/known date Homework Equations $$\delta v=\frac{c}{2nL} \:[1]$$ $$N=\frac{\Delta v}{\delta v}=\frac{2nL\Delta v}{c} \:[2]$$ The Attempt at a Solution I am having trouble with question 5, but have come to realize I think my cavity length is...
  5. T

    Calculating Laser Power from Temperature Rise, Time, and Target Mass?

    Hi Everyone! There is a type of CO2 laser cutter power meter on the market (Product link removed) The meter uses a block of black anodized aluminum bonded to the end of basically a mechanical meat thermometer, and has a zero adjustment on the back of the face to set the base temperature to...
  6. LarryS

    I How can laser photons have the same precise energy?

    The photons generated by a conventional quantum laser are all in the same quantum state. Doesn't that mean that they all have the same exact energy? Yet, because of energy-time uncertainty, the exact energy of any particle can never be measured. Also, the Copenhagen Interpretation says that...
  7. Gowtam Chandra Pal

    Confirming Improved Nuclear Model with Laser Spectroscopy of Cadmium Isotopes

  8. F

    Optical How to Use a Laser Beam for Measuring Machine Guide Way Flatness?

    Hello all, I want to use a laser beam as a straightness standard for use in measuring flatness of a machine guide way which is about 2 meters long. I'm envisioning a low power laser pointed at the sensor of a digital camera which moves laterally along the imperfect guide way. The waviness...
  9. Krushnaraj Pandya

    Uncertainty in the energy of a laser beam

    Homework Statement The duration of a laser pulse is 10^(-8) s. The uncertainty in its energy will be? Homework Equations ## \delta x \delta p=\frac{h}{2\pi}## The Attempt at a Solution speed of laser beam=c, duration is given so distance can be calculated exactly-shouldn't that mean delta...
  10. Alianos

    Emission cross section and laser performance

    How does the emission cross section of an emitting atom (such as Yb atoms in glass) affect the laser performance, namely the slope efficiency (signal power vs absorbed pump power) and laser threshold? Thanks a lot
  11. R

    Intensity of a Gaussian laser beam

    I have two lasers with different intensity distributions (shown below) — one is Gaussian and the other one is rectangular (having the shape of a Fresnel diffraction pattern at the target). I am trying to compare the efficacy of the two lasers for burning a certain material (I am really...
  12. E

    China Develops Laser Gun Like Star Wars: Burns Through Skin

    China develops new laser gun similar to Star Wars. It can burn through skin to produce immense agony. Here...
  13. A

    Can I get different frequencies from He-Ne Laser ?

    Hi guys, can I get different frequencies from He-Ne Laser? if Not? why is it used in Infrared spectroscopy?
  14. Sebastiaan

    I Effect of Relativity on Laser Sail Acceleration

    Question, does general or special relativity have any effect on the acceleration of laser sail from an external observer? Let's say a laser-sail is first accelerated to 0.2c. Ignoring diffraction, Due to redshift, the incoming laser beam would get stretched by 20%, reducing the power by 20%...
  15. Zahid Iftikhar

    I Energy Transfer Mechanism in Helium Neon Gas Laser

    I need help to understand the energy transfer mechanism in Helium Neon Gas laser. When helium atom is excited and staying in its metastable state, it is said to have collision with neon atom and thus transfers its 20.61eV energy plus some of its kinetic energy 0.05eV to enable neon atom to reach...
  16. A

    B Observational Effects of "FTL" spotlight from laser pointer?

    So from what I understand, it's possible to have a very powerful laser pointer where you point at an arbitrarily large and far away surface and make the spotlight appear to move at faster than light. E.g. you can be holding the laser in your hand and you simply flick your wrist. My question is...
  17. Marisa5

    Coherence pattern of HeNe laser in interferometer

    Hello, i hope i posted this in the correct forum! When measuring coherence of a HeNe laser using a Michelson interferometer, there are key points along the moving interferometer arm where coherence is highest. The distance between each of these peaks corresponds with the length of the laser...
  18. N

    On board a laser powered solar sail

    Can an on board laser be used to propel a solar sail spacecraft if the laser is pointed at the sails ? Would Newtons third law affect the laser and maybe prevent the ship from moving ? Thank you for answering my very ignorant questions. NineNinjas911
  19. L

    Intensity characterization of laser pulses

    754/5000 I am using the fluroescence spectroscopy technique to obtain the fluorescence spectrum of exposed neuroblasts to uv radiation (355 nm) from a Nd:YAG source and I need to characterize the radiation pulses of the laser. Specifically, I use a spectrometer (Avantes brand) with integration...
  20. R

    Light Reflection: Understand How Light Interacts with Materials

    Hello, I have a question or perhaps a few questions regarding light and mirrors. When we point light at a mirror, it gets reflected back. But we can see the point light (assuming that it is a laser for the sake of simplicity) at a surface opposite to the reflective surface of the mirror. What...
  21. T

    B Gravitational Redshift: Will Two Lasers Operate Differently?

    If we run two identical lasers and put one at sea level and one on top of a high mountain, will they operate at different frequencies?
  22. S

    Young's double slit experiment green laser

    Homework Statement If a green laser is (wavelength = 532nm) sent through two slits with a separation of 127 um, how wide (in total) would the 11 green dots formed be if they were projected onto a screen 1.25m away from the slits? Refer to this diagram sorry for bad quality...
  23. ephphatha16

    Find λ of light using a laser beam and a diffraction grating

    1. What is the advantage of using class 2 laser light? I would really appreciate if reference source is also given!Homework Equations Not needed.[/B]The Attempt at a Solution Well, I thought that using monochromatic light would made it easier to measure the distance between fringes. And also...
  24. X

    Laser pumping: further increasing injection above threshold?

    Above the threshold, the stimulation emission becomes dominant for lasing. If increasing the pumping, what will be the change of spontaneous emission and its contribution to the output power and FWHM of the signal, based on the threshold carrier density clamping and the threshold gain clamping...
  25. HappyBlue

    Mirror: refractive index and thickness

    Homework Statement Hello everyone ! I hope this is the correct place to ask. Here is my probem: I have to measure the refractive index and the thickness of the glass part of a mirror. The idea that I have, and that has been approved by my teachers, is the following: In order to measure the...
  26. D

    Possible to make speckles without a Laser?

    Hello, it is possibile to make speckles on a surface with a LED or something else? With a Michelson Interferometer you can get interferences with an LED -> are this already speckles? regards, Hans
  27. C

    Laser safety / measuring errors question

    Homework Statement a) If you were using a hands –on activity to verify your predictions and use measurements to determine the wavelength of the laser being used, describe any safety precautions you would have to take and sources of error that you might encounter. Be sure to explain how you...
  28. Q

    I Why can't there be a 2-level laser with Non-Optical Pumping

    Hi everyone, I would like to understand the answer to the question in the title. I got that when we use optical pumping of a laser, the probability, given an incoming photon of adequate energy, for an atom to absorb it and for an other to produce some stimulated emission out of it are equal...
  29. S

    3D subsurface laser engraving for translucent minerals?

    3D Subsurface Laser Engraving works for clear glasses like Schott BK7 and B9 Borosilicate Glass. How does one do the same for relatively translucent minerals? I have read research papers on using lasers for tattoo removal and cancer radiation therapy. However, I want to know how the laser's...
  30. R

    Laser induced damage and irradiation time

    We want to examine the thermal effects of irradiating a given material with a laser. The material under consideration can either be homogeneous and isotropic or a diffusive turbid material (e.g. biological tissues). Suppose we decrease the power by a certain factor. Will we still get the same...
  31. fishin_kitten

    Laser Gravity: Can a Laser Pull Gently?

    Would the beam of a powerful laser have any gravitational tug?
  32. K

    Conservation of energy of a perfectly decoherent laser

    The energy and momentum of a closed system is always conserved. If a laser can emit perfectly parallel and perfectly superimposed light waves (occupy the exact same space) that are perfectly 180° out of phase and of the same frequency, what can be said about the energy and momentum of the...
  33. D

    Understanding Laser Safety Glasses: Wavelengths, Frequency, and Protection

    Hello all. I am buying a laser engraver for my business. The company I'm getting it from and the "industry" in general doesn't think I need safety glasses when operating it (most say cause the light isn't visible to the eye) . I don't personally feel safe with that assumption for my eyes or my...
  34. T

    Why parts of the laser ray seem brighter than other parts

    Hi. When we see a laser ray, it seems that part of the ray are brighter than the other parts and they seem like they’re vibrating and moving. It also seems there are fractures in its path. I want to know why do we see like this? For example see this picture (it is from wikipedia). I circled...
  35. Gamma

    Laser Safety Glasses for Class II

    Hello, Community college teacher here. I was instructed to employ a laser safety program in my intro physics lab. We mainly use Class II lasers that came with the PASCO Optics table and Laser Ray boxes. One of my adjunct faculty uses Purple and green laser pointers which is classified as Class...
  36. rnbguy

    Can a Laser Beam be Repeated Across Multiple Points?

    Hi All, I'm new here and forgive me if I've posted in the wrong section, I'm more of a computer engineering/architect guy asking a physics question. Is it possible to have a projected laser beam repeated across multiple points? between the range of 600nm-900nm ? Example, a pad that takes in...
  37. N

    Why Raman spectroscope doesn't use 532nm laser ?.

    Most of the commercial Raman spectrometer uses 785nm or IR laser as excitation source. Though we could use visible lasers like 532 nm in this place, which can reduce the overall cost of the device by 1. Using less power laser( since intensity of raman signal is inversly propotional to the 4th...
  38. H

    Number of Photons inside a Laser Cavity

    << Mentor Note -- thread moved from the technical forums, so no Homework Help Template is shown >> Let's say you have a laser cavity with two mirrors at either end, one is considered 100% reflective, the other 99.9%, so that a wave beam is emitted through this lower reflectivity mirror. I know...
  39. The Extreme World of Ultra Intense Lasers - with Kate Lancaster

    The Extreme World of Ultra Intense Lasers - with Kate Lancaster

    The largest and most powerful lasers in the world can be used to make some of the most extreme conditions possible on earth. Scientists around the globe are using these lasers to try to miniaturise particle accelerators, make astrophysical conditions in the lab, and create fusion energy.
    • Wrichik Basu
    • Media item
    • laser
    • Comments: 0
    • Category: Optics
  40. N

    Plano-convex lens, which side should face the laser source

    I have two measurement cases in my setup. An divergating laser beam (not an gaussian) is measured at two locations from lens , at nearby i.e. 400 mm, and far away, > 2000 mm away. My lens is an plano-convex lens. Which side should face the laser in these two cases? I know that the...
  41. F

    Predicting Changes in Interference Patterns using Laser Interference Equations

    Homework Statement Imagine that you are conducting an activity with a laser to create an interference pattern. Use the appropriate equations to predict two ways (other than the way described in the following example) to change the interference pattern in order to have closer fringes. Explain...
  42. L

    To measure the energy density of a (brief) laser pulse

    I have the problem of making "at home" or almost, a measure of a laser's pulse energy for unit area of the target: those kinds lasts for ~ tens of milliseconds, up to some hundreds of ms and I should be able to verify that this energy "density" doesn't go beyond 40 J/cm^2 for a single pulse...
  43. Rigel84

    Is laser beam visible in vacuum?

    This is what I understand about light. Light is electromagnetic wave, it comes from the source, bounces from the objects and we see reflected light. Let's imagine next situation. We are in a dark room and we got only one light source, a toy laser. When we turn it on, we can clearly see beam...
  44. J

    Distance Traveled by a Laser Pointer in Outer Space

    Homework Statement A 50 g, 420 mw laser pointer is floating in outer space (don’t ask how it got there) at rest with respect to an observer. The laser pointer is turned on and let go. If the battery runs continuously for 250 hours before dying, what is the final speed achieved by the laser...
  45. Pattarasak

    I How to calculate the photons/pulse of Laser diode?

    Hello everyone, I'm an Undergrad and I'm trying to set the Quantum key distribution experiment by using weak laser pulses(the laser diode with attenuated filter). but I don't know how to calculate the photon number per pulse. Can anyone tell me how to calculate the photon number per pulse...
  46. B

    A Laser beam represented with complex conjugate?

    Boyd - Nonlinear Optics page 5, there says 'Here a laser beam whose electric field strength is represented as $$\widetilde{E}(t) = Ee^{-iwt} + c.c$$But why is it written like this? Is it because the strength is the real part of the complex electric field? Then why doesn't he divide it by 2 after...
  47. SchroedingersLion

    Laser pulse: spectral width vs time

    Hi guys, I am learning for an optics examination and found a picture that is supposed to show the duration of a light pulse with respect to the spectral bandwidth (appended). At this point in the lecture, we have not gone through modelocking yet, so I assume one should understand the picture...
  48. U

    Direct Modulation and Photon Lifetime - Laser

    Hello, There is a thing I struggle to understand on laser physics. There is a modulation method called direct modulation for semiconductor lasers where by changing the current we modulate the light which is emitted form the laser cavity. There is a picture below It is stated in...
  49. phyzguy

    Can laser-driven H-B fusion be a viable alternative with no neutron output?

    I'm interested in comments on the attached paper. The authors are advocating laser drive proton-boron fusion as an attractive option, given the lack of neutron output. They describe a laser driven method for achieving ignition in a solid target. Any thoughts? Is this even remotely feasible?
  50. E

    Can Quantum Laser Sintering Revolutionize 3D Printing?

    Hi. Me personally was touched by one patented technology "light engine with the ability to multiplex a single laser beam into several million microlasers". This technology use a sacral term "quantum". I try to understand how it is possible with 3kW. Thank to yours ideas and attention. Have a...
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