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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Coherence in stimulated emission

Laser light shows the unique property of coherence. This is due to the stimulated emission process of photons. But why is it that stimulated emission leads to coherence?
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What is the dependence of size of Nd:YAG crystal for making Nd:YAG lasers?

Assume that we are able to grow a 1 meter long and 5 cm thick Nd:YAG crystal using best possible growth facility. Is it possible to generate a high power Nd:YAG laser using this big crystal?
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In carbon dioxide laser,during the laser excitation, do the carbon and oxygen atoms get excited in their electronic levels? [closed]

I read about CO2 lasers. It says we add a fraction of nitrogen in CO2, that nitrogen gets excited and it transfer the excitation to CO2. So, in CO2 lasers, during the laser excitation, do the ...
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Electrical energy consumed by a laser beam [closed]

How much electrical energy (KWH) is consumed while drilling a hole of 0.01 mm dia and 10mm deep by a laser beam of red colour? Could you please help me out with this one, thanks in advance.
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Can a soap bubble bounce off a laser?

Clip; I presume some momentum transfer's at play, but can't put a full picture together. What's going on - why does the laser 'repel' the bubble? ... or is it fake?
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Marginal theorem in frequency-resolved optical gating (FROG)

In ultrashort laser physics, frequency-resolved optical gating (FROG) has been a standard method since a few decades to measure the temporal profile of an unknown pulse's electric field $E(t)$ via a ...
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Probability of an atom wanting to Excite/Deexcite in the state of Population Inversion

I know that population inversion is achieved when the probability of stimulated emissions is greater than the probability of absorptions. But after the state is achieved, if $E_1 < E_2$ then what ...
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Calculating the transparency current of a laser?

I'm stuck trying to solve analytically the transparency current of a laser, Itr. I've calculated the transparency carrier density N, and I know the area of the active region A, but simply going Itr=...
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Does Heisenberg uncertainty affect Snells law?

Assuming an ideal single frequency plane wave, we can determine the angle of retraction for the light beam. But the more I make my pulse shorter, the less certain I am in the frequency and thus the ...
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What is the minimal equipment required to observe the Apollo lunar retroreflectors?

It's rather well known that the Apollo lunar landings installed retroreflectors on the Moon, and that these can be used to reflect laser beams back at Earth, to measure the Earth-Moon distance to ...
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Pointing a laser to a mirror on the moon in spite of refraction by earth's atmosphere

I was reading that the Apollo missions left a laser reflector (Mirror) on the moon for scientific use. Having read some of the controversy here and elsewhere about lasers being affected by refraction ...
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How can you determine if the high harmonic supercontinuum is coherent or not?

With the development of suitable mid-IR ultrafast sources to drive High Harmonic Generation (HHG), researchers have reported the development of high harmonic X-ray supercontinuum sources. But how can ...
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Why can we eliminate the Doppler-broadened background by chopping the pump beam?

In Wolfgang Demtröder (auth.) - Atoms, Molecules and Photons we have this laser spectroscopic setup. Without any explanation he claims the chopper can fix the Doppler broadening background shown on ...
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Can any material be used as a laser medium in principle?

Reading up on how lasers work, I found out that there are lots of different materials that can be used as laser medium, from noble gas ions and halogens to metal atoms to organic dyes. So far I have ...
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Is a three level pumping scheme possible in a LASER only when exactly three energy states are present in it? [closed]

I'm brushing up my concepts on LASER's and I was just curious about this. Does a three level pumping scheme necessarily imply that exactly three energy states have to be present? Or can more or or ...
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If you were to fire a laser or maser into space, how much of its energy would be lost to the atmosphere?

I'm very interested in knowing about how much energy would be lost to the atmosphere if you fired a laser or maser into space. I know the laser would probably diverge quite a bit over that distance, ...
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Do chemical and gas-dynamic lasers scale down to milliwatt sizes?

Chemical (e.g. COIL or hydrogen fluoride) and gas-dynamic type lasers are usually in the kilowatt to megawatt output range, because getting lasers of such power ratings powered electrically can be ...
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Laser flux power density and Raman scattered radiation

I am currently studying the textbook Infrared and Raman Spectroscopy, 2nd edition, by Peter Larkin. In a section entitled The Raman Scattering Process, the author says the following: The intensity of ...
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Is there a upper limit to the intensity of a laser

Is there a upper limit to how intenset a laser can be? If so what is it?
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What's the value of the Mourou limit?

What's the specific value of the Mourou limit here. https://en.wikipedia.org/wiki/File:History_of_laser_intensity.svg I can't find an exact value.
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Aren't sounds made by sinusoidal plane vibrations sound-lasers or SASERs?

I read the first sound laser (or SASER) was made in 2010 here. But if we're talking about the state of the phonons emitted then we could say that any sound created by a planar vibration has a unique ...
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Does modulating a laser source change its color?

Hopefully you guys can solve this hypothetical for me. Suppose I have a laser which emits light at frequency $530\mathrm{THz}$ with a very narrow spectral width $1\mathrm{Hz}$. From signal theory, ...
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Explanation of ruby laser behaviour

One of the reason why He-Ne (Helium Neon laser) is better than Ruby Laser is that, He-Ne laser produces light as a continuous beam unlike Ruby laser which produces light in short pulses. But why is ...
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Can an infrared laser be made visible with another type of laser?

I was wondering, if you had an infrared(or ultraviolet) laser, is there any way that you could make it visible by intersecting it with another type of laser? For example, uv with uv, infrared with ...
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Would a perfectly collimated laser beam have a flat intensity distribution?

I'm trying to simulate a collimated laser beam in some FORTRAN and am wondering about the intensity distribution of a perfectly collimated beam: would it be a flat distribution (equal intensity across ...
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Speckles max intensity paradox

Wikipedia says (link) that in the limit of many interfering waves the distribution of intensities (which go as the square of the vector's length) becomes exponential $${\textstyle P(I)={\frac {1}{\...
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Does the light pulse broadens in time when passing bandpass filter?

What I don't understand about relationship between laser pulse width in time and frequency, is where these rules apply, namely rules of Bandwidth-limited pulses. Say, I have a femtosecond laser ...
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How to calculate the intensity profile of a pulsed laser beam given its pulse energy?

I am trying to calculate the intensity profile of a pulsed laser given that the intensity envelope is Gaussian. I also know the full width half maximum and pulse energy of the pulse. What are the ...
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Why wouldn't I observe Poisson's spot in Fresnel regime when the disc blocking half-period zones is not circular?

In an experiment, a black circular disc is placed in front of, and orthogonal to a plane wave light source, in order to observe Poisson's spot. Details of the wavelength, radius of disc, distance to ...
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Light confinement in homojunction laser diode

Why is light confined to the depletion region in a simple homojunction Fabry-Perot laser diode, like the one schematically illustrated below? Does this region for some reason have a higher refractive ...
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How to calculate the Rabi frequency of a pulsed laser?

I read that the Rabi frequency $\Omega$ for a constant intensity laser with intensity $I$ is given by $$\Omega=9.95 \times10^7 \sqrt I$$ from Equation 3 in this paper. For a pulsed laser, how does ...
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What are some of the applications of Helium-Neon lasers?

I've worked with them in the lab and while they have a very nice Gaussian beam profile, they are tedious to say the least to align(2 hours to align a HeNe laser compared with 5 minutes to align a ...
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How to explain light beams in terms of wave theory?

How can we explain the formation of light beams in terms of wave theory? According to wave theory, shouldn't the source point of beams emit radiation omnidirectionally, rather than a concentrated ...
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Surface plasmon polaritons in quantum cascade laser waveguides

i am doing my 3rd year electrical and electronic project on simulating quantum cascade laser waveguides. Surface plasmon polaritons are used as a optical confinement mechanism inside the waveguide but ...
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Light Hamiltonian contains a mass, is this normal?

I am reading about the coherent states of light (Glauber States), where the starting point is the solution of the stationary Schrödinger equation is solved using analytical and algebraic methods for ...
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Does diffraction of a coherent laser beam affect its polarization state?

Suppose I have a collimated laser beam with an arbitrary polarization state - linear, circular, or elliptical. The beam encounters an obstacle, such as a pinhole. Diffraction occurs as photons ...
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How can all the information that we, humans, generate be carried by a single laser beam?

In the book of How the laser happended, by C.H.Townes, at page 5 the author states that Lasers provide an unsurpassed medium for communication. One laser beam can, in principle, carry all the ...
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Is it possible to cause condensation in air using low energy pulsed lasers?

I read here that femtosecond pulsed lasers can cause condensation in the air. They primarily work by ionizing air, thereby creating charged hot spots around which water particles condense. But the ...
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Solid-state lasers: The peak power of each pulse is at least three orders of magnitude above the average output power?

My textbook, Solid-State Laser Engineering, 6th edition, by Walter Koechner, says the following: Average Output Power. The majority of solid-state lasers available commercially have output powers ...
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Can you make a laser without cavity, if you have a pump strong enough? I think no, but is my reasoning correct?

I've found an SE question (Laser without a cavity) about that, but it isn't exactly the same as mine. My thinking is: no, you can't, because without the cavity, there wouldn't be possibility for one ...
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Velocity distribution for Molecular beam vs. gas

In the book: https://g.co/kgs/JRBLeA (Atomic Physics by C.J. Foot) on page 152 there's a table in the end that compares gas' velocity distribution and that for a molecular beam. I am unable to account ...
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Semiconductor structure confinement modes

Today, I would like to simulate the field intensity in an emitting structure such as a laser diode. With this field, I will be able to calculate the confinement factor of my device. I put an ...
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How can laser diffusion be reduced?

So, a laser works by bouncing photons back and forth between two mirrors until they straighten each other out and exit a small hole, like this: The problem is that no matter how much the photons ...
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Need for laser handbook with overview of different types of semiconductor lasers [closed]

I have already some books about lasers, but none of them has an overview of many different laser types. At the same time while reading different papers, I have learned about existence of five various ...
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Is there a graphical summary of which modulation technique to use in communication systems using Visible Light Communication techniques?

I am currently looking at various papers written (some listed at the bottom) that discuss how laser pulses can be modulated to send encoded messages to a receiver for communication systems. The more I ...
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Uncertainty in laser beam width

I have voltage vs position data for the cross-sectional profile of a laser beam, acquired from a photodiode, and I'm trying to find the beam's width and the uncertainty in the width. I was planning to ...
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Can an electromagnetic wave be pulsated at the same frequency of the wave itself?

This is a thought experiment that's been bugging me for some time and I haven't been able to find any literature on this topic. I am not a physicist, please bear with me :). Suppose I have a 500nm ...
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Are monochromaticity and coherence in the context of lasers two sides of the same coin?

We know that monochromatic lasers produce monochromatic light, i.e., all photons have the same wavelength $\lambda$ (ideally). Coherence, on the other hand, states that the phases of photons are in ...
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Stark level manifold

In this figure from https://www.rp-photonics.com/effective_transition_cross_sections.html: When a high energy photon (920nm) is absorbed followed by phonon emission to lower energy level in the ...
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Does a laser's listed wattage or joules include the frequency? Or just the amplitude?

In other words, if the number of photons in two different lasers is the same, but the second laser has a higher wavelength, does the second one have more 'wattage' or more total joules? (Since higher-...

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