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. A

    Cannot lock reference signal on lock-in amplifier

    Hello everyone, I am using a lock-in amplifier SR860 with the aim of reading an optical pulse from a laser break-out board operating at 30 kHz as the reference. The reference signal is not being picked up by the lock-in amplifier. However, it is being read by the oscilloscope. I have used a...
  2. Bilan

    Laser to burn insect

    What would be the ideal wavelength and power of a laser to kill an insect on human skin without burning the skin ?
  3. Shealen Fairchild

    I Why was a HAM radio license required to operate early lasers?

    In a lecture (at 10:24) on the birth of the laser printer, Gary Starkweather mentions that a HAM radio license was required to use early lasers (he finished undergrad in '60). Why was this? (All the following questions are just filling out the primary question.) What were the...
  4. S

    I Original HBT experiment with mercury isotope lamp

    From "Boffin : a personal story of the early days of radar, radio astronomy, and quantum optics", by R Hanbury Brown... If it had been truly coherent (e.g. laser light), wouldn't the detection events have been uncorrelated? That is, two independent Poisson processes?
  5. davidjoe

    I Battery life on VERY fast moving object

    Accepted thinking is that time slows as speed increases, relative to a non-moving reference frame. But supposing that the object approaching C is a ship in rotation around the earth, and on that ship is a laser mounted on a gimbal such that the laser is always pivoting and trained on exactly...
  6. dedesperado

    Dangerous Area of a Hair Removal Laser

    From what distance does the diffuse radiation of a „hair removal laser“ cease to be a threat? I apologize for the peculiar question, but I'm curious about the following matter: I walked past the window of a hair removal studio about 50 meters away earlier, and I noticed repeated bright red...
  7. elou

    B How to build a simple polarization filter

    For that we will need a laser pen and two square pieces of opaque, non reflecting material. In both these squares a slit will be cut, wide enough to let a beam of the laser pass through without any refraction effects. First, after the laser has been turned on, one of the squares is placed in...
  8. K

    A ABCD matrix formalism for real laser

    Hello! I have an optical setup and a laser producing a gaussian beam and I would like to get the waist of the beam at the end of the setup (i actually want to know what focal length to use for some lenses, such that I get a certain beam waist in the end). Getting the ABCD matrix for my setup is...
  9. T

    How Does Britain's New £140m 'DragonFire' Laser Transform Air Defense?

    New British LASER is one heck of an anti-aircraft gun! LIGHT-SAVER Britain blows up drones with £140m LASER dubbed ‘DragonFire’ in incredible first – with each shot costing just a tenner The futuristic laser can destroy a target from miles away with pin point accuracy... The highly focused...
  10. James_AA

    I Laser and nano-holes experiment

    Hi everyone, let me propose an experiment to see if you agree with my points. There is a 1cm2 1-micron thick aluminum substrate with a matrix of 100x100 nano-holes each with 100x100nanometers cross section separated by 100nanometers. Then, we focus a 1W laser with visible wavelength: 1-...
  11. D

    Why won't my laser fire to the left of screen? (game design)

    Hi everyone I'm making a shoot 'em up like Fantasy Zone, i.e. the player can face either left or right (as opposed to only facing one direction while moving forwards and backwards). I've made separate scenes for the laser that fires left and the laser that fires right. The player should...
  12. D

    How do I stop my laser from destroying two items with one shot? (game design)

    Hi everyone I'm making a game in which a player's laser can destroy enemies and cancel out enemy lasers. My code for the player laser executes queue_free() when it enters the collisionshape for the enemy laser and enemy. The player laser is only supposed to destroy one item per shot...
  13. rbjjj

    Light Transmission Through Half-Hollow Sphere

    Homework Statement: hw Relevant Equations: hw I am looking for a light source, preferably a laser, for a specific optical experiment. The experiment involves a spherical object positioned 6 meters away from this light source. My goal is to shine the laser through the sphere, specifically...
  14. S

    How to show light from laser pointer is plane polarised?

    The answer key is the light is directed through one polarising filter then filter is rotated and the light changes intensity. I don't understand how that proves that the light is plane polarised. I think if the light is unpolarised, the intensity will also change when it passes through...
  15. K

    Converting oscilloscope voltage to laser power

    Hello! I have this photodiode which I connect to an oscilloscope using a normal BNC cable to an oscilloscope, terminated with a 50 Ohm resistor. I measure the output from an optical cavity (which is basically laser light), which in my case looks like a flat signal close to zero, and regular...
  16. H

    How Many Bright Spots Are Visible When Laser Shines Through Slits?

    The angular position of t)he first diffraction minimum is θ≈sinθ= λ/a, and dsinθ=mλ, so m = (dsinθ) /=[d(λ/a)]/λ =d/a = (2.4 x 10-4 m)/(8.0 x 10-5 m) =3. Since both bright and dark pots separated on both sides of central bright region, so the smaller bright spots observable within the central...
  17. M

    I Laser linewidth in a STIRAP process

    Hello! In a STIRAP process, for the right parameters (assuming a ##\Lambda##-type transition), the lifetime of the excited state doesn't come into play, so one can achieve very narrow linewidths of the measured transition of interest, regardless of the linewidth of the intermediate, excited...
  18. benswitala

    Laser cooling of Earth's climate

    Hi, I am worried about climate change. I want to cool the earth. Would it work to build solar panels to provide shade, and then to blast the captured light energy out into space via lasers? I think only certain frequencies will go through the ozone. Could solar powered lasers help cool the...
  19. Sciencemaster

    I Can a pulse from a laser be treated as a Gaussian?

    I know a laser is generally treated as a coherent state (i.e. a plane wave). However, if a laser turns on and back off quickly, can the resulting light be treated as a gaussian multiplied by the plane wave that would have been emitted if the laser were continually active?
  20. M

    Optics for High Resolution Laser Imaging: Finding the Best Path

    Objectives: - best path for optics needed to focus and "draw"/project a high resolution image onto a workspace around 500mm square (for a Laser Direct Imaging machine) - where to cost effectively purchase or make the optics necessary to build a prototype The problem: I need to project a high...
  21. M

    I Grating Resolving Power of Laser Beams with Gaussian Distribution

    All resources I’ve found for grating resolving power assume uniform distribution on the grating and produce airy disks. Resolvance is determined by the Rayleigh criterion where the peak of one wavelength is at the minima of the adjacent one. This definition doesn’t seem applicable for Gaussian...
  22. A

    Can lasers modify the threshold voltage of power-off transistors?

    Hi, I am a phd student in hardware security, I want to know what is the effect of the laser on power-off transistors and can it modify the threshold voltage of these transistors? And is there an equation that links the laser and the threshold voltage degradation? Sincerely
  23. R

    B Can lasers really cause explosions? Let's use a silly hypothetical to find out!

    The context behind my question is quite silly, but I've encountered some people who believe lasers cannot produce explosions, even at insane levels of energy. Now, I'm not big on physics nor will I pretend I am, I think they could but I came here to get a more knowledgable opinion(using a silly...
  24. anorlunda

    Can lasers guide lightning strikes to a safe target?

    I like this idea. Very creative, but in retrospect it sounds obvious. Just create a path of ionized atoms.
  25. S

    I Laser and hair - scattering or destructive interference?

    There is a video, where the author shows the interference of laser beam on a strand of human’s hair: I bought a laser pointer and reproduced this experiment. Indeed, when a single hair is placed on the way of the laser beam, I see the “scattering” picture (a series of points with intervals of...
  26. skaiser

    I Issues collimating my laser with 4f system

    I am using 2 lenses in a 4f configuration. The input is a large collimated beam (632nm). After passage through the 2 lenses the beams vertical dimension remains constant, however, the horizontal dimension get smaller, as if it is being focused only in the horizontal direction. Does anyone have...
  27. S

    I IR Laser makes glowing spot on radiometer vane

    Is the explanation at the end of the video correct?
  28. redirmigician

    I About Direct Laser Acceleration

    How does this Lawson–Woodward theorem work. I read on the wiki that the particles cannot be accelerated by lasers. But I do see acceleration of electrons with free space. I wonder how this is done. https://rdcu.be/c0fRw http://dx.doi.org/10.1103/PhysRevAccelBeams.19.021303 In addition, I have...
  29. redirmigician

    I Acceleration in an electron field

    I read something about accelerators using nanotubes. I am a little concerned about the design mentioned in the "High Density with Perpendicular Carbon Nanotubes" part of this paper(https://doi.org/10.3390/photonics8060216). Can wakefield acceleration be done in an electron field? Or maybe I...
  30. redirmigician

    I Can surface plasmons be used to build GeV gamma-ray lasers?

    I read a paper about coherent surface plasmon amplification by free electron pumping in an article a few days ago. It seems to work as some kind of free electron laser-like light source, and I wonder how high the energy of photons can go in this way. Also I read in another paper about...
  31. J

    I Exploring Entanglement Through Laser Light Mixing Experiments

    https://quantum.phys.lsu.edu/old-website/seminars/abstracts/Kaushik10.pdf I have discovered an experiment in the link above where you get NOON entangled states by mixing classical laser light with quantum light from SPDC. But I cannot understand the mathematics behind it. Can you explain it to...
  32. gggnano

    I Negative energy when a laser goes through lithium niobate crystal?

    A screenshot from a book which describes it: So I am trying to picture this one: 1. A laser is "pumped" through a cylinder made from lithium niobate which is placed at 90 degrees, perpendicularly...so that the laser passes through the body of the cylinder (and not through the 2 round ends)...
  33. S

    I Analytical proof of LASER production

    Is there analytical proof that a photon Pe will be emitted by an excited atom Ae when another photon Pp of the same frequency is passing by Ae in LASER production? I tried using Feynman diagram to show a high probability of this event. I failed (most likely because I am not an expert in QFT)...
  34. Astronuc

    I Multi-GeV Electron Bunches from All-Optical Laser Wakefield Accelerator

    Compact electron accelerator reaches new speeds with nothing but light https://phys.org/news/2022-09-compact-electron.html Multi-GeV Electron Bunches from an All-Optical Laser Wakefield Accelerator Abstract We present the first demonstration of multi-GeV laser...
  35. sergiokapone

    I Mathematics for dancing laser beam

    Is there a math that describes these shapes at least one frequency?
  36. H

    A Realizing EIT with Pulsed Laser: Intensity, Duration & Frequency

    I have realized EIT with continuous laser. What are the requirements for the intensity, duration and repetition frequency if EIT is realized with pulsed laser? you can attach any reference:biggrin:thanks a lot!
  37. bmihalik

    I Using Lenses with Laser Diode Microscope to Reduce Aberrations

    I would like to build a microscope witch can be used with different monochromatic light sources (laser diodes), and this system should has small astigmatic and coma aberration, but keep the chromatic aberration property. Can I use two spherical or ashperical lenses (facing with convex side to...
  38. J3J33J333

    I Can you put out a fuse (fire) with a laser?

    I was wondering you if you could use a laser to put out a fuse or to stop combustion? Could you use some form of laser/laser cooling to put out an explosion mid-explosion?
  39. peetm

    I Russia Claims Laser Weapon Can Destroy Drones: Is it Possible?

    The Telegraph is running this story with little detail. https://www.telegraph.co.uk/world-news/2022/05/18/russia-claims-laser-weapon-can-destroy-drones-1500km-earth But, is such a laser possible? Wouldn't it scatter, and how much energy would be absorbed by the atmosphere?
  40. K

    A Laser signal input for PDH lock

    Hello! I have a laser with only one input for external signals. Currently I use that to send the error feedback signal when I measure the power transmission from my cavity (not using PDH). If I want to use PDH, I would need to modulate the laser frequency, which means that I need to send to the...
  41. F

    Finding Total Number of Optical Field Modes for Visible Light

    ρ_kdk = k^2/π^2 dk is the density of field modes (what we are trying to solve for here), and as ρ_kdk = ρ_λdλ, and k=2π/λ, we can rearrange this to get ρ_λdλ = 8π/λ^4dλ This is where my confusion lies. I am not sure what to do next. I know this equation physically means the number of modes per...
  42. D

    What is the Purpose of This Aluminum Laser with No Markings?

    Hello smart folks! I recently discovered this item in the estate of a former space shuttle engineer. He was responsible for replacing major components on the space shuttles as well as the crawler. It has no property markings…only the laser warning sticker. My curiosity has me here to...
  43. K

    I Optimizing PID Parameters for Laser Servo Locking

    Hello! I am a bit confused about locking a laser to a stable cavity in practice. I understand there are 2 stages. In the first one you scan the laser frequency and the signal you see on an oscilloscope is made of peaks corresponding to when the laser is on resonance with the cavity. In this step...
  44. sbrothy

    Could Aliens Use a Star to Forge the Ultimate Cosmic Weapon?

    This is pretty out there so bear with me. Imagine a brunch of aliens having gravity under fine-grained control. So much so, in fact, that they'd bend space around a star so all the light would be forced around to exit from a circular aperture.No Loss. Furthermore they could bend space in front...
  45. yglo98

    Optics. A laser beam is refracted in a piece of glass.

    A red laser with the diameter of 3mm is directed towards a piece of glass. It has the effect, P of 1mW. The angle of incidence is 90 degrees. The glass has refraction index n2= 1,5 and thickness 2 cm. Its front side is convex with a convergence radius,R, of 11 cm. The back side is plane. Whats...
  46. A

    B Wavelength of a laser beam emerging from a prism

    Summary:: If you send a laser beam through a prism, can you measure any shift in wavelength at the other side of it? This sounds like a high school experiment and the concept is simple. I feel the laser should emerge monochromatic and at the same wavelength it went in. Do you get this result...
  47. Aymangh994

    According to which criteria should I choose a laser diode?

    Hello everyone, I don't know which laserdiode and lens system should I choose for my Project. It is all about AFM Microscopy with a cantilever ( Length= 450 um, width = 50 um and thickness= 2um). So as you see it is not a small cantilever. As far as I Know, the larger the cantilever is, a larger...
  48. L

    Intensity of a laser beam at a certain distance

    I haven't been able to pinpoint a definition of "angular divergence" of a laser so by pure intuition I assumed it would be something like ##\theta=\frac{2R}{D}## and with that I have that the radius of the lase beam is ##R=\frac{D\theta}{2}=90\cdot 5 \cdot 10^{-6} m=450\ \mu m## so...