Laser Definition and 1000 Threads

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. M

    Setting up a circuit to drive a Laser Diode

    Hello fellow physics friends (alliteration: always a strong opener). I am writing today because I find myself struggling to complete something which ostensibly doesn't seem that difficult to the average physics undergrad working in a lab. However, electronics and circuits are definitely a...
  2. F

    How to get a 30um (micrometer) laser diameter?

    Greetings everyone. I am a mechanical engineering student whose professor challenged him to a project that requires some optics knowledge. After years of quietly reading the physics forums I am finally making my first post. If this question ends up in the wrong forum, feel free to move it to the...
  3. B

    Understanding Laser Safety: Choosing the Right Laser Level for Eye Protection

    https://www.amazon.com/dp/B003JH8Q98/?tag=pfamazon01-20 I plan to purchase the above laser level tool that can project laser in lines.. it has included goggles for safety. There are many devices with lasers now. May I know what is the safe laser level for the eyes and what range or values...
  4. S

    Can a laser be effective in a sandstorm or through ash?

    Could a laser be effective through ash or sand? Could a powerful enough laser burn through sand or ash and work effectively?
  5. L

    Laser Beam Diameter which Minimizes Volume?

    Homework Statement Consider a 10 meter long gas column. We interrogate the gas molecules with a HeNe laser (lambda=633nm) at the minimum possible gas volume. If we focus the beam tightly, it will eventually diverge and the sampled gas volume will increase. Consider a minimum beam diameter D...
  6. Basov

    A How a laser resonator generates the standing wave?

    Hi, guys. I'm interrest in the question about how optical (laser) resonator can generates the standing wave? As i know, there is a condition that the resonator base (lenght between two mirrors) should be multiple to the length of the wave. (L=k*(lamda/2)). But in practice no one never measures...
  7. Antraxius

    Designing a planocovex PMMA lens

    As an electrical engineer, I am an amateur on optics, but I really could use some help. I am making a lens of PMMA, 2D. To 'convert' a rotary movement into a sweep. The lens needs to be 120mm long, with its focus at a max distance of 80mm the light traveling out of the lens needs to be parallel...
  8. P

    Understanding laser power terminology

    I see that many LIDAR systems use power in the millijoule range in atmospheric research. A typical number is 25 millijoules. 25 millijoules is equal to 25 milliwatt/seconds. This means 25 milliwatts for one second. This seems like a tiny amount of power, yet a 25 millijoule laser costs many...
  9. P

    Combining two DC voltages for laser locking

    I need to combine two DC voltages to scan and lock a laser. The scanning will be 0-100 V and the locking will be performed with a small correcting voltage, +/- 1 V. Both of these will be fed into a PZT driver. My advisor suggested using an opto isolator, however I am not sure how that would...
  10. Lord Crc

    Observation of laser pulse propagation in optical fibers

    Just wanted to share this, mainly because I really liked the videos (found in the supplementary section at the end). Moderators, feel free to move it to a more appropriate place. Observation of laser pulse propagation in optical fibers with a SPAD camera Recording processes and events that...
  11. donavi

    I The spin of the photon -- a weird experiment with a laser

    Hello everybody, I'm playing with a ne -ne laser And i conducted an interesting experiment I did colliding beams the type of interferometer Fabry Pero between the mirrors I put the cuvette with different substances I tried to detect changes of polarization of the laser beam with the help of a...
  12. A

    Software for laser simulations

    Hello everyone, I'm searching for a software for simulating laser beams, their intensity, power, reflections, arrangement of mirrors, etc. I searched for a while but I couldn't find what I need. Any suggestions would be appreciated.
  13. W

    Exploring the Mysteries of Laser Physics

    Hi! I am currently self-learning laser right now, and I have some questions about it.. 1. We know that water moves from higher to lower altitude, air moves from higher to lower pressure, electrons move from higher to lower potential. What about photons? Where would it go? 2. Why would only...
  14. Daniel Petka

    Red laser erases on glow in the dark surfaces?

    Hey guys, So recently I came across a weird phenomenon... Basically, I shined a red laser on a glow in dark surface and the laser could erase it. The fun fact is that before the laser erases the are, it makes it glow for a short time. You need good goggles to see the glow despite the intense...
  15. Daniel Petka

    B Quantum Tunneling and Heat Distribution in Laser Cavities?

    What if I replaced the half transparent mirror in a laser cavity with a 100% reflective mirror? -would all photons escape due to the quantum tunneling effect? -would the mirrors melt? Thanks :biggrin:
  16. Karolus

    B What is the fundamental principle behind the operation of a laser?

    The principle of operation of the laser is based on stimulated emission concept. In short, if a suitable energy photon hits the electron of an atom, in which the electron is in the excited state, there is a probability that the electron returns to the ground state. The photon emitted has the...
  17. L

    A laser emitting light with a wavelength of 560 nm (Single slit).

    Homework Statement Homework EquationsThe Attempt at a Solution a) see attached. b)[/B] i) Decreasing the width of the slit will cause less interference fringes to be seen, increases the distance amongst fringes and the fringes become wider. ii) If the screen was moved further away, fewer...
  18. Q

    I Temperature impact on laser emission

    Hi everyone, I'm trying to understand why laser diodes need a stronger input current to start lasing when their temperature increases. If I tried to add thermal transitions to the rate equations governing the evolutions of an atom quantum level populations (let's say ##n_{up}## and...
  19. A

    Imagine that you are conducting an activity with a laser....

    Homework Statement Imagine that you are conducting an activity with laser to create an interference pattern. Use the appropriate equations to predict two ways to change the interference pattern in order to have closer fringes. Explain your predictions. Change in X = L(Lambda) / d Homework...
  20. J

    B Laser Pointer at Speed of Light: Does It Point Ahead?

    This is just kind of an odd question that has to do more with concept than practice but if you were going 1m/s slower than the speed of light and were holding a laser pointer would the laser only point one meter ahead of you? I know that light doesn't add like normal vectors but this is...
  21. AdrianMachin

    Laser Pointer Troubleshooting: Solving Incoherence in a Red 650nm <5mW Beam

    I have a red 650nm and <5mW LASER pointer, but the beam is not very coherent. Actually, when I point to a wall at an approximately 300 meters away, the red point gets very large (about a meter in diameter). I wonder how a LASER could act like this?
  22. F

    Ti:sapphire: laser propagation

    Hello :) I have 2 questions about the beam propagation of an Ti:sapphire-laser: Picture 1: The cw argon ion laser brings the beam to mirror (1). Then...? Then the beam (100% of it), go to the birefringent plate (4), gets then reflectet to the first mirror again (1) , which reflects it to the...
  23. G

    I Ratio between spontaneous/stimulated emission

    Hi. In thermodynamic equilibrium, the ratio between spontaneous and stimulated emission is $$\frac{A_{21}\cdot N_2}{B_{21}\cdot N_2\cdot u(f)}=e^{\frac{hf}{k_B T}}-1$$ where ##A_{21}## and ##B_{21}## are Einstein coefficients. This means, that there's always much more spontaneous than...
  24. N

    Beam Divergence from non-circular laser beam

    Homework Statement The laser beam is not a point source. It is known that it has a rectangular shape with a divergence of 30 mrad x 1 mrad. I would like to know how large my laser lobe will be at a distance of 250 mm from the laser source. Homework Equations I think you can use trigonometri...
  25. D

    Determining hole size using laser interference

    Homework Statement Lisa makes a hole in aluminum foil. She wants to know the diameter of the hole. She points a laser through the hole. That picture is what appears on the wall that is 1,25 meters behind the aluminum. the distance between every circle is 8mm. the wave length is 633nm...
  26. N

    Is it possible to collimate monochromatic light with a taper?

    I am ignorant about laser physics, but i have this idea of collimating monochromatic light with an optical fiber/cable that is cone shaped: at inlet the cone has a wide diameter (several hundred microns - like an ordinary optical fiber, which might be used as a light source), on the other end it...
  27. bluejay27

    I Laser Gain Location - Where is it?

    Where is the laser gain located when we discuss about the laser-pumping light source?
  28. D

    Extreme Fiber Coupled Laser Diode Power Loss

    What could cause a laser source with fiber coupled laser diodes to have extreme loss of power? The laser diodes have a wavelength of 658nm and have an output rated at 60mW but it seems as though the optical channels actually output ranges between 58 to 70mW. During some troubleshooting I...
  29. P

    I Can a circularly Polarized Laser impart momentum to air?

    Does a circularly polarized laser beam, (say, 1 watt or so at visible wavelengths), impart linear or rotational momentum to air molecules.?? I'm not talking of ionization of air...which I know it doesn't, ...but rather momentum, in particular due to its Left or right CIRCULAR polarization...
  30. M

    Temperature of Plexiglass due to laser strike

    Hello, Any hep is appreciated. In the lab we want to use a 0.3mm sheet of plexi to reduce the intensity of the UV KrF laser. We want to determine the temperature of the plexi sheet after the laser beam strikes it. We have all the information about the laser... Is there a specific formula...
  31. G

    Is laser light polarised? In which direction?

    Hello. I want to know about the polarisation of lasers and I've been reading basically two kinds of answers for the question 'Is laser light polarised?' The first one is 'yes' and the second one 'not necessarily'. Let's consider a gaussian laser. Ideally its light is monochromatic and coherent...
  32. F

    I Laser Beam through Calcite crystal = Photon Entanglement?

    If I shine a laser beam through a calcite crystal, the beam is split in two, as shown below. Are the photons in the split beams in an entangled state?
  33. K

    I About creating standing wave with laser

    Hi all, I remember the standing wave is introduced in a chapter of mechanical wave in my undergraduate physics times ago. It is said that two waves of the same frequency propagating the opposite directions will form a standing wave in space. I wonder if it is possible to produce the standing...
  34. Tiny Rick

    I Is a One-Time Use Pulse Laser Possible?

    I've been thinking... Is there any way that there could be sort of a one-time use pulse laser that uses something like a mini atomic bomb to create a super high energy laser? I found stuff about a Nuclear pumped laser and "Project Excalibur", but I wanted to ask actual people who know a lot...
  35. senobim

    Laser Spectroscopy: Calculating Transmitted Intensity

    Homework Statement Unpolarized light of intensity I0 is transmitted through a dichroic polarizer with thickness 1mm. Calculate the transmitted intensity when the absorption coefficients for the two polarizations are α|| = 100cm −1 and α ⊥ = 5cm −1 Homework Equations Is it possible to say what...
  36. hackhard

    Can a Rotating Coherent Laser Beam Create a Persistent Light Dot for Holography?

    if a coherent laser beam rotates about an axis at very high angular frequency can a light dot with radiant glow (of short radius) be obtained due to persistence of vision ?
  37. A

    A Problem in continuous function of Excimer laser

    I am student of MS and working in the field of laser. I am trying to run an old Excimer laser system (XeCl) having output energy 400mJ, pulse width 30ns and frequency 1-100Hz. The laser works only for less than one hours after filling with new gases and the energy continuously decreases within...
  38. A

    Logarithmic scale for the Laser Intensity.

    I drawed a relation between the growth rate of the material to the laser intensity. After drawing, My professor told me that I must convert both values of the growth rate and the laser intensity to their values in the logarithmic scale. I don't know how. May I get a help.
  39. P

    Laser beam in oil/water, why is it easier to see beam in oil

    Hi there I have a general question. I understand the process of light through a optically denser material, slower speed etc... but why would a laser beam in oil be easier to "see" than a laser beam through water. Cheers
  40. E

    Hair/wire laser diffraction interference pattern

    Hair/wire laser diffraction interference pattern - does it follow single-slit or double-slit? for single-slit interference, the equation nλ = d (y/D), (d is the width of the single-slit, y is the distance between central BRIGHT fringe to the nth DARK fringe, D is the distance from slit to...
  41. Ivor Denham

    Einstein Coefficients - Laser Beams

    Homework Statement Assume a two level laser system with no degeneracy (g1 = g2 = 1). If [tex]N_2 + N1 = \text{constant}[\tex], show that [tex]B12 = B21[\tex]. Homework Equations [tex]\frac{\partial N_1}{\partial t}=-B_{12}\rho(v_{21}N_1[\tex] [tex]\frac{\partial N_2}{\partial...
  42. Tareq Naushad

    When I lit a laser ray for 10 seconds from a distant planet

    I am on Alpha 4 light years away from earth. On 1st Jan, 2016 I lit a powerful laser light towards Earth for 10 seconds and then switched it off. My friend on Earth knows that he has to detect that light after 4 years on the night of 1st Jan, 2020 from a space station using a very powerful...
  43. H

    I Is it possible to image individual air molecules?

    I was wondering if it is possible to image the motion of individual air molecules? What I am picturing is using a laser to illuminate a volume of air, and using scattered light to measure the velocity of individual air molecules through the doppler shift of the scattered light. It seems that...
  44. M

    Practical scenario: NIR laser, black light marker and lamp.

    ...and my high-school buddies said you'll never use this stuff in real life. Hello, my name is Matt and once in a while I deal with the practical application of Physics in a wide range of real-life settings. Most of the time I'm capable of researching the given topic myself. This time, I need...
  45. whitsona

    Class Making a T.E.A. Laser-- we have questions....

    I run a Maker group for teens in Florida at the Pensacola MESS Hall. We are building a T.E.A. Laser powered by a Wimshurst machine along the lines of a Rimstar project we found on YouTube. But, we have some questions about the laser it will produce: (1) I read that the TEA Laser has high...
  46. P

    Fast Q-switching of flash pumped Nd:YLF laser

    Hi friends! I solved the problem 8.3 of ``Problems in Lasers Physics'' book (by Cerullo, Longhi, Nisoli, Stagira and Svelto) but I think there's a mistake on the solution presented in this book in page 196. This is a problem book with problems and solutions that follows closely the laser...
  47. E

    I Planck formula and density of photons

    Hello! Let's consider again a system of atoms with only two permitted energy levels E_1 and E_2 > E_1. When electrons decay from E_2 level to E_1, they generate a photon of energy E_{21} = E_2 - E_1 = h \nu. The number of photons (per unit frequency, per unit volume) emitted by such a system in...
  48. T

    Please explain this laser phenomena

    So I'm sitting at my dest playing with my greeen laser pointer pointing it at different things. In all cases I see a green dot and its reflection off other objects. Except when I point it at a pink hilighter standing upright on my desk. Instead of a green dot I see a yellow dot. That dot...
  49. Kg91

    Question regarding using existing technologies to make 3-D laser display

    I want to start off with an IR viewing plate to get the initial material of this post across. This is UV backlit screen that allows IR laser point to be tracked The screens are a mixture of: Zinc Cadmium Sulfide, Silver, Nickel Doped (Yellow) Zinc Sulfide, Copper Chloride Doped (Green) ^ I...
  50. LightHero

    NIR modulated laser system - Need advice

    I'd like to perform experiment on NIR laser (around 800nm) with modulated signal (varying duty cycle), with peak power around 1000mW, the output is desired to be connected to fiber optic. I am new to laser technology, and have googling around but can't find suitable laser module (complete set)...
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