Questions tagged [laser]

Light Amplification by Stimulated Emission of Radiation. A means of creating coherent light by either driving an atomic or molecular transition in an optical cavity or firing a beam of electrons through an undulator.

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2answers
31 views

Effect of a cylindrical lens in front of a diffractive optical element (DOE) and 5mW red laser

I want to expand the image formed by a grid pattern diffractive optical element (DOE). I will be using a 5mW red (650nm) laser. I thought maybe putting a cylindrical lens in front might spread the ...
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What are critical differences between conventional lasers and matter lasers?

In what ways would a coherent stream of matter waves/De Broglie wavelength interacting with the environment differ from a conventional coherent stream of photons? What have been observed and what have ...
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Virtual Photon Laser [closed]

Can virtual photons such as a magnetic field have the potential, or be made to travel in a strait line such as photons in a laser. Or better yet, can a magnetic field be generated remotely so that a ...
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Can laser light be described by individual photons?

If laser light is described by a coherent state, a macroscopic quantum state, to what extent does it make sense to speak of individual photons in laser light? And if the laser is attenuated to be a ...
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1answer
55 views

Frequency “changed” on changing the medium

I have been taught in my school (and read on many internet sites too) that frequency of light doesn't change by changing the medium. Also I read that the colour we see depends on the energy of the ...
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Entangled Photon Sources: how to choose the pump wavelength in SPDC?

I found several papers dealing with entangled pairs of photons generated by means of a setup consisting in a pump laser and a nonlinear crystal, such as BBO or KTP and here the incoming photons ...
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Why does the light of this infrared laser become visible after reflection?

We use a 780 nm laser in our lab, and that makes it in the near infrared (IR) range. The majority of people can not see this wavelength of light. However, when the beam reflects off of an object (see ...
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Photon absorbtion and reemission in water vapor

The real question: Water vapor absorbs photons at 950nm -- does that mean that it reemits a photon at 950nm later, or does it heat up, emit photons at a longer wavelength, or what? The "I'm ...
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Orientation of KDP crystal to generate 4th harmonic using a Nd:YAG Q-switched laser and set temperature to stabilize crystal

I am setting up a 4th harmonic generator for a Q-switched Nd:Yag laser that will already have the second harmonic generator in place. I need to know how to orient the KDP crystal with respect to the ...
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1answer
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Does colliminating light with optics require monochromacity? Or coherency? Or both?

I've had it in my head for a while that collimation requires both monochromacity and coherency. However, lately I've started thinking about it and I can't really see why coherency is required for ...
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Selecting a pumping rate for a population inversion

I'm trying to make a plot (on mathematica) of population inversion vs time for a ruby laser including the time dependence in the formula given below. The pumping rate is given by r*exp(-(t-dt/[Delta]t)...
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For a two-level atom subject to a laser field, what is the rate of absorption followed by stimulated emission?

So the textbook I'm using (H.J. Metcalf and P. van der Straten. Laser Cooling and Trapping) derives the photon scattering rate of a laser close to a two-level transition starting from the Optical ...
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Do the electrons in metastable state jump to ground state simultaneously?

Do the electrons, jumped from excited state at different times to the metastable state of gain medium, jump from metastable state to the ground state simultaneously or at different times which can or ...
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Using an LED for Doppler cooling

Would it be possible to use an LED to perform Doppler cooling? I understand that the linewidth of lasers is around a tenth of LEDs. I feel that there should be a trivial reason that should explain the ...
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1answer
136 views

Would a lightsaber burn or blind a wielder? [closed]

This question got an off-topic slap on the Sci-Fi Stack because I asked about real-world physics, rather than fictional physics. I want to completely disregard the canon. Hypothetically put this into ...
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Does regulating a laser diode's power change the quality of the beam?

In machine vision, you can use linear lasers as sheets of light to infer an object's 3D position or shape. (AFAIK it's just a laser beam stretched in one direction using optics.) Those are usually ...
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Monochromaticity of laser [closed]

I am writing a paper on doppler cooling for the course of a laser in college. Doppler cooling is basically an application of the highly monochromatic nature of lasers (right?). I understand that the ...
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1answer
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Why does CW imaging not provide the same data as Pulsed imaging?

"Unlike pulsed THz imaging, the CW imaging (...) only yields intensity data and does not provide any depth, frequency-domain or time-domain information (...)." [1] Why does a pulsed signal ...
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Effects of Non-Linear Atomic Laser

As "lasers" formed from the stimulated emission of Bose-Einsten condensates do not follow Maxwell's linear equation's which are normally used when calculating current lasers, how would this ...
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1answer
30 views

What happens to the power of the beam passing through a lens?

Sorry for the fundamental and basic question, Does the power of the beam that is falling on lens is equal to the power of the beam after passing through lens. Suppose If I used convex lens to converge ...
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Why don't we directly excite atom to the meta-stable state in laser physics?

I started reading about laser physics, in various cases (online as well as in books) the atoms are first excited to an "excited" state which is less stable and decays into a more stable &...
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Visible Interference of Two Lasers [duplicate]

If 2 Lasers collide in the air, could they interfere with one another? Given 2 lasers with a max reach of 10 meters (beyond 10 meters they´re not visible with human eyes) If those two lasers meet at ...
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1answer
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Why is the spontaneous decay rate $A_{21} \propto \omega_0^3$?

I have seen the Einstein thermal equilibrium derivation that $\frac{A_{21}}{B_{21}}= \frac{\hbar \omega_0^3}{\pi^2 c^3}$, but intuitively I would expect the spontaneous decay rate $A_{21} = \frac{1}{\...
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Transform limited pulse duration from emission cross section spectrum

Hi there, I was wondering if anyone could give me some advice for a calculation in Python to model the minimum pulse length achievable with the emission spectra below. As an example in Ti:Sapphire one ...
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1answer
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How do fillings change their state once they are put in mouth? (possibly related with lasers)

I recently seen a dentist for my filling, I for the first time paid attention to what he was doing I guess, because the material he used for my filling was easily deformable before he put it on my ...
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1answer
47 views

How does a light source / laser transfer energy to a material?

I am trying to understand the physics of how a laser is able to heat a solid. My understanding so far is that when photons are incident upon a body (e.g. a metal) the momentum of the photons is ...
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How is the phase gain of a Fabry-Perot resonator for gravitational wave detection derived?

I am trying to understand the use of the Fabry-Perot (FP) resonator in the arms of a gravitational wave detector. A typical explanation is that the gain in power in the arms is equal to $\sqrt{F}$ (...
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1answer
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Soft magnetic induced magnetization through radiation

Is it possible to induce temporary magnetism upon a soft magnet, such as a soft ferrite, alongside the parallel axis of a laser beam fired at the material? Would the soft magnet need to be ...
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2answers
55 views

Is it possible to laser cool without using spatially-varying magnetic fields and above zero degrees?

As the title says, is it possible to laser cool without generating a weak quadrupolar magnetic field? Also, if I wasn't trying to achieve extremely low temperatures is it possible to use laser cooling ...
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Unexpected frequencies on the Fourier spectrum. Are them due to aliasing from Shannon-Nyquist Theorem?

I have recently performed an experiment in which the light produced by a pulsed Ti-Sa Laser is detected. The detection can be consider in this simply way: the laser is turned on and when the first ...
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5answers
145 views

How does diffraction cause laser beam divergence, and why will a laser beam always diverge, due to diffraction?

I have seen it said that diffraction causes laser beam divergence, or that a laser beam will always diverge, due to diffraction, or some variation of these statements. I understand diffraction in ...
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Is it true that longer laser cavities generally produce more collimated beams?

I read that longer laser cavities generally produce more collimated beams. Is this true? And, if so, then why? The closest source of information that I could find is this Wikipedia article on ...
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Why does a laser cavity being finite imply that beam divergence occurs?

I recently read that one of the reasons laser beam divergence occurs is because the radius of the cylindrical cavity is finite, and so the stimulated emission with amplification also occurs for ...
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1answer
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Why 16/84 clip levels are chosen for determining laser beam diameter by knife edge technique (ISO 11146)? [closed]

In ISO 11146 pt.3 (https://www.iso.org/obp/ui/#iso:std:iso:tr:11146:-3:ed-1:v1:en) - the standard committee determines the clip level at 16% and 84% power levels but, unfortunately, I wasn't able to ...
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How is it that having a laser cavity geometry with one flat mirror and one curved mirror produces a more divergent beam?

I recently asked this question about the non-axial photons of a laser cavity. While doing further research on the subject, I read that exploiting the paraxial photons by having one mirror of the laser ...
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1answer
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In Helium-Neon Laser, why Helium atoms don't decay via photon emission after excited to higher state?

I have some difficulty in understanding physics in the Laser(He-Ne). In a He-Ne Laser gas chamber, Why only 'Helium' atoms are ionises when electrical discharge created by strong electric fields. &...
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Pulsed laser data sheets: “repetition frequency” in Hertz and “repetition rate” in “pps” (assuming pulse(s) per second) are equivalent concepts?

When I read the data sheets for pulsed lasers, some specify "repetition frequency" in Hertz, and others specify "repetition rate" in "pps" (assuming pulse(s) per second). ...
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29 views

Is it possible to combine laser beams using a telescope?

I'm trying to understand how to combine a square array of laser diodes of the same wavelength and polarisation into a single beam. It seems like there are only two options (beam splitter cubes and ...
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1answer
44 views

What shape lens will focus parallel laser beams to the smallest point?

I'm playing with Algodoo optics. I'm trying to focus parallel lasers using refraction. I thought an ellipse or parabola would work, but not precisely. As you can see in this picture, the ellipse ...
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What happens to the non-axial photons of a laser cavity?

When a laser cavity is pumped, the axial photons are reflected back and forth by the cavity mirrors and so contribute to stimulated emission, but the non-axial photons do not have this opportunity. ...
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Does laser coherence length impact phase noise?

I am trying to simulate laser phase noise numerically by creating a random phase $\phi(t) = \sqrt{2\pi\Delta\nu_L} \int_{0}^{t} dW(t)$, where $\Delta\nu_L$ is the laser linewidth in Hz and $\int_{0}^{...
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ugly beam profile in noncollinear optical parametric amplifier

I am currently (re)building a noncollinear optical parametric amplifier (NOPA). Such NOPA is seeded with supercontinuum white light (SWL), generated in a sapphire window, by ~100 fs, 795 nm centred ...
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The single active electron model (SAE)

The single active electron model (SAE) is an approximate solution to the interactions of multiple electrons with a laser field. The approximation assumes that only one electron interacts with the ...
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1answer
236 views

Bandwidth vs linewidth

Regarding to lasers sources, what is the difference between bandwidth and linewidth, I know that a lot of people use linewidth when you have monochromatic source, but is there any difference between ...
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1answer
54 views

Why must interplanetary visible-light-wavelength laser communication beams be transmitted at very low power levels?

From the March 2021 Scientific American: Optics. Traveling Photons. A laser-based system could boost deep-space data transfer. 'Laser communication could work with receivers about 20 centimeters ...
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“Anomalous” Interference Maxima from a Diffraction Grating

When shining a red diode laser ($\lambda = 635$ nm) laser through a diffraction grating (5276 lines/cm), I'm observing what I consider to be anomalous maxima near each of the expected maxima for the ...
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1answer
28 views

Rate Equations for Simulation

I would like to simulate a passively Q-switched laser with MATLAB. Do you have any suggestions - or link to literature/paper - which rate equations I should use? It would be nice if the equations ...
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28 views

Fringe movement analysis to extract displacement

I am using a Michelson interferometer with the interferogram recorded on a CMOS sensor. I have taken a video of the fringes moving when a displacement of 50 $\mu m$ is imposed to one of the mirrors. ...
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1answer
29 views

Must the distance between the reflectors of a coherent laser be a multitude of its intended wavelength?

Must the distance (aka cavity length $L$) between the two reflective mirrors of a spatial and temporal coherent laser be a multitude of the lasers intended wavelength? If no, why not? If yes, how does ...
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Help finding a laser that will pulse with my signal generator

When I connect my 5mW red laser to my signal generator the laser fails to deliver clear square wave pulses once I go below the 2000ns mark. The signal generator is capable of producing pulses as low ...

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