laser Definition and Topics - 126 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. R

    I Qualitative description of stimulated emission & population inversion

    I'm having trouble understanding stimulated emission and population inversion, and how they work together to make a laser work. I pretty much need this explained completely. 1. Spontaneous emission, they say, is when an atom absorbs and then later emits a photon. Isn't that just regular...
  2. small physicist

    Spectrum of laser light absorbed and re-emitted by a white object

    Hello, If I shine a red laser onto a white surface, I assume that: some of the red light will be nearly instantly reflected, some will be absorbed and converted into phonons and some will be absorbed and re-emitted. Is that correct? I know that my laser has this extremely narrow spectrum...
  3. S

    Does the ruby laser (the first invented laser) have nonlinear behavior?

    Hello Everyone! I read about the function of the ruby laser which made from ruby crystal and has three energy levels. There is radiationless transition to what so called metastable level and then the electrons there stimulated to transit to ground energy state. The question is: does this...
  4. person123

    Optical Compact Device For Measuring Speed of Light

    Hi. This is an idea which I just happened to think of, and I was curious if it would be at all feasible. Here's a quick sketch I drew: The two curved mirrors should have a laser attached on one end and a video camera attached on the other. The laser would be tilted very slightly above...
  5. Muthumanimaran

    I Is a LASER a classical light source or a coherent state in quantum mechanics only?

    My question is the physics behind the LASER such as stimulated emission can be only explained by quantum mechanics only. We can represent LASER as coherent state in quantum mechanics only. Then how can we say LASER can be thought of a classical light source?
  6. W

    B Gamma rays over very large areas

    According to this link, HERMES III at Sandia National Labs can generate very large area gamma rays by converting the electron beam into bremsstrahlung radiations after hitting the tantalum target. As we can see in the isodose contours in the...
  7. S

    A Laser Ablation of a fused silica surface

    I read in couple of articles, like this one: that regions of fused silica surface can be ablated by laser... I have two questions: 1- Why does the ablation occur? 2- does the ablation happens when the laser waist point is under the...
  8. Cheesycheese213

    What is the meaning of polarization ratio?

    I was trying to research about polarizing lasers for an experiment, and there were some things that were confusing? A website said, I was wondering if the polarization ratio was the same as the extinction ratio? Also, I was curious because I thought 100:1 would be a lot, and not much light...
  9. hagopbul

    I Photon induced magnetic effects

    Hello all: Reading about HB-11 start up and they mentioned laser induced magnetic field : How is that created and the size of the magnetic field is in kilo Tesla range any one heard of that Best Hagop
  10. M

    Optical Laser to refract/reflect water vapor and smoke... angles?

    Building visibiity sensor.... What is best angle to detect water vapor reflection from laser, and refraction? I plan to have two open cylindrical containers painted flat black and put inside eachother so the overlap is about 0.5-1" (adj to limit ambient light vs airflow). Laser is cheap red...
  11. Behrouz

    Surface temperature-laser radiation

    Hello, I'm looking for the governing equations for the laser radiation on a surface. I understand there are several types and methods. I was wondering if there is an equation to show all the parameters in calculating a surface temperature after laser radiation for a specific time. Some of the...
  12. angela6884

    Misc. How can I enlarge the light produced by a laser?

    I need to enlarge the light produced by a small laser beam that I have for a science project. I can't buy a larger laser because they're too expensive and not in the right color. Any suggestions? Thanks!
  13. K

    Measuring the Distance between the Fringes of a Diffraction Grating

    I have been preparing for a physics practical on diffraction. More specifically, we will use a CD as a transmission grating (by peeling off the reflective layer), and measure the distance between the fringes for a specific distance between the CD and the viewing wall. However, it is unclear...
  14. J

    Why is milk smoother and flatter than water?

    I have conducted an experiment involving projecting a laser beam onto a surface and observing speckles that move relative to us. Those speckles become less visible (maybe smaller?) when the surface is smooth and that is especially the case with milk. I have dyed milk and water to see whether in...
  15. S

    I Trying to Generate Entangled Photons

    I've been trying to generate entangled photons using KTP laser pointer that normally produces green light at 532 nm. I was hoping that after removing the IR filter, I could add a reflective coating (right now the coating I have is a glittery metallic green nail polish) to reflect the green light...
  16. Uchida

    I Minimum number of cycles in a short pulse laser

    Hello to all, In a short pulse laser emission setup, can a pulse be emmited with beam lenght shorter than one wavelenght? (can a pulse have a duration shorter than its period?) Lets say a laser emmiter shoots a quarter cycle pulse, what would happen to this short beam? (lets supose the...
  17. CptXray

    Laser cavity

    I guess the resonator will be stable when both focal lengths of lens and curved mirror meet. The curved mirror is fixed and it's focal length: $$f_{curved} = \frac{R_{2}}{2} = 50 \, mm.$$ Then the d should be: $$d=f_{lens}+f_{curved} = 100 \, mm.$$ I think that's also the distance for which the...
  18. Daniel Petka

    B Poisson spot madness

    Recently, I started to experiment with a laser and a coin used as a lens, being inspired by an old Cody's Lab video. My initial assumption was that through diffraction, the laser will be focused onto a spot on when the coin is a certain distance away from the wall. In a way, I imagined it as an...
  19. D

    Laser Linewidth Calculation

    Hi guys, It's one of the questions I'm asking myself needlessly but I really wonder about this ;) Say I have a laser at a wavelength λ. I can calculate the frequency by ν=c/λ. Then the linewidth Δν=cΔλ/λ2 that can be found through differentiation of two sides of the equation. The question is...
  20. U

    Laser gain and the saturation effects

    Hello, I study laser physics, using "Laser Physics" by Eberly and Milloni. I am confused regarding the notion of gain and the saturation effect. According to the book, the gain is defined as ## g(v) = \dfrac{g_o(v)}{1+I_v/I^{sat}_{v}} ## where ## I^{sat}_{v}## is the saturation intensity and...
  21. T

    What is the difference between 1/2 wavelength and 2 overlapped wavelength? (pulsed laser autocorrelation)

    So, I was working on autocorrelation for my pulse laser system and I started to wonder what is the difference between single wave with 400nm of wavelength and two 800nm waves overlapped. In the knowledge, I know of, is that wavelength is the length between two picks. And when it is pulse laser...
  22. S

    Modes and Q-factor(s) of a random laser

    Many papers about random lasers mention the Q-factor of random lasers. Since a random laser has multiple peaks close to each other like shown in the figure. Does each of these peaks correspond to a unique random lasing mode, or is it just a single mode? Similarly what is the right way to...
  23. M

    Controlling light diffraction angle with a holographic "lens"

    I'm a physics student, and working on a class project that requires coming up with a method to control the exit angle (diffraction angle) of a monochromatic light source. For example, taking a laser (monochromatic, coherent light source), spreading the beam, and directing the light at a piece...
  24. alaa_nasef

    What is the effect of a Laser on gravity

    Hi everyone, I have this topic ,and I searched all over the internet without any results what is the affect of Laser Beam on cancelling the Gravity or reducing it if anyone can refer to a reference that can help me I will appreciate it
  25. iVenky

    I Single-mode vs multi-mode fiber coupling

    Hi, Is coupling light from a laser into a single-mode fiber (transverse electric) more difficult than coupling to a multi-mode fiber? If so, is it due to the geometry? Does the laser light have multiple modes to begin with or it can be designed to have just one mode? Thanks
  26. P

    What exactly is the thermal lens effect?

    Hello, i just wanted to ask if you can explain to me what thermal lens effect is? I am supposed to answer why laser beam passing through ink or soy sauce creates this effect and i can't find any information on what actually this thermal lens is. I know of course that it is a lens, but why does...
  27. A

    What is meant by Spectral and Spatial Shaping of a laser

    Hi, I am new to the forum so apologies if I placed this in the wrong subforum though I think the subject is classical enough to be here. I was hoping to get a concise answer to what is meant by spectral and spatial shaping of a laser. My intuition says that we are modifying the amplitude of the...
  28. B

    Relation of laser pulse length and the Output Coupler trasmissivity

    Dear all, I'm within my Ph.D. studies in laser engineering and most of the details are rather new to me. Working on short pulse systems, my advisor told me some times about the relation of the output coupler transmissivity and the outcoupled pulse length, but more as a rule of thumb. According...
  29. R

    Reflected Light Beam

    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...
  30. T

    B Gravitational Redshift of a laser

    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?