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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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Laser power and coherent state amplitude

How it is possible to relate the power $P$ of a laser light with frequency $\omega$, to the amplitude $\alpha$ of its description as a coherent state $\vert \alpha \rangle$ ? For a massive particle in ...
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Why do thermal currents affect light but wind does not?

I notice if I put heat under a laser beam it will cause the beam to shimmer. The heated air is causing a disturbance in the air which affects the light. Yet, I can blast a stream of air from a ...
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Curved Light stream?

I was wondering, a while ago, i asked if there is a way to bend light someway, which I got the answer is index of refraction. In this question I wish to know if this mention when applied with a dense ...
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23 views

What is a pump reflector?

I understand the meaning of laser pumping. But i don't understand what is a pump reflector. As a clear definition does not appear online. In the paper,DESIGN AND DEVELOPMENT OF WIDEBAND HYBRID RAMAN/...
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Difference in spectrum of green laser and green LED

In an experiment I conducted I used a spectrometer to find the spectrum of green laser and green led. this is what I found: LED spectrum: Laser spectrum: why is the spectral width of the LED is ...
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41 views

Are photons in laser entangled?

When energy is pumped into the atom, photon is being emitted which would then get absorbed by another already excited atom causing the atom to emits 2 similar photon. Soon more photons are produced in ...
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What are laser achromats?

I came across "we used Nd:YAG laser achromats" in a paper, and I was wondering what exactly is the purpose of achromats here. The paper in question is "Dynamics of laser-induced cavitation bubbles ...
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Where does laser reflection (1) come from?

I have the above experiment setup where a triangulation-based laser scanner projects a laser (line) towards a transparent glass material. I then took a picture using my phone (indicated in the above ...
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48 views

How does a dielectric interact with a laser beam? [on hold]

A nano-ball made of latex, which is insulating, has no net electrical charge, and is much smaller than the wavelength of the light. The ball is compact, homogeneous with spherical shape. It has ...
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Higher-order dispersion in non-linear optics

In many cases, dispersion of an optical medium is presented by saying that the dependence of the wavenumber $k$ on the (angular) frequency $\omega$ can be expanded in Taylor series as: $$ k(\omega) = ...
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Are the bandwidths of a laser pointer and a sodium-vapor lamp comparable?

The question is not about the slightly differing wavelength of the devices caused by manufacturing processes or the shift from changing temperature. A German source says that the spectral width with ...
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Heating a chamber of air with laser

If I want to heat compressed air stored in a cylindrical chamber to extremely high temperatures in the order of 3000 degree celcius using lasers, in what way should I focus the laser (because laser ...
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How is the laser frequency for doppler cooling determined?

How is the laser frequency for doppler cooling determined for a certain element? Will any frequency from the absorption lines of that element work? How is the amount of redshift in the laser ...
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High intensity laser and neutrino pair production

Given the very small rest mass of the neutrino, visible photons have plenty energy for neutrino pair creation. What would be the probability of $\gamma \to \nu + \bar\nu$? Would the neutrinos be ...
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How to check the sensitivity of a mini spectrometer?

I want to be able to see the spectrum of bioluminescence(400-500nm) and the data sheet for the mini spectrometer I want to use says that it has a relative sensitivity of more than 90% between 400-...
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Calculating Laser Focal Power & Focused Beam Waist

If I focus a 1 watt, 405nm laser with a 25mm fl lens what is the power at the waist. I see calculators online but none that make sense. Rather than just telling me can you put your equations you use ...
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Do solid-state lasers emit hadrons at some exitation state? [closed]

Given an observation at a solid-state emitter at it's current limit where the device creates more photons than the crystal dissipates (reflected and thermally); thus making photons to impact over ...
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68 views

How to reduce edge diffraction?

I have a simple setup with a diode laser and an object placed in front of it. I want to observe the edge's shadow clearly. However, I get this very annoying effect of diffraction and interference ...
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What does taking the sum over all optical modes mean?

I'm doing a project where I take the spectrum of a VCSEL using a spectrometer and then analyse the data to retrieve the modes. I need to do several parts to the analysis, and one thing I need to do is ...
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Why all laser photons are in the same direction?

The lasing process begins when just one photon is accidently emitted. This explains why the photons on the line between the two mirrors are in phase. But what about the neighboring atoms or even ...
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MOLE - interferometers of PTB and NMIJ

For the definition of the mole, two interferometers were used: the first is a Fizeau spherical interferometer belonging to the PTB (Germany) and the second is the NMIJ interferometer, in order to ...
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the effects of wind on particles trapped in a laser beam

First off I have done a few experiments with trapping of particles in a laser beam using a red 100mW laser and a 532nm 20mW laser. The Setup to achieve the two is seen below. Now in real life you can ...
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Observation of Strange Pattern with He-Ne Laser passing through a sample of Chlorophyll

We Designed in our lab an experiment with 5mW He-Ne laser, passing through Chlorophyll, which was extracted from Hibiscus rosa-sinensis leaves dipped in Ethanol. The resultant pattern we observed on ...
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Can shining a laser pointer on an Ice Cube melt it?

I heard in videos that if you use a laser pointer (Green if I recall) and point it on a ice cube, that it would cause it to start melting, is that true?
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Spacing of resonant modes in a (laser) cavity

I don't see why the frequency spacing between resonant cavity modes should decrease with higher frequency. Here's what I have: For a laser cavity of length $L$, from the condition of constructive ...
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1answer
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How to measure width of a very narrow spectral peak without expensive instruments?

Lasers typically have very narrow peaks in their spectrum, much narrower than 1 nm. It would require quite a high-resolution spectrometer to measure such a peak precisely. But if I simply need to find ...
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46 views

Is this possible to focus common light (not laser) to a small point in the wall and control it with mirrors?

I want to make something like a laser projector for an experiment but with common light. My question is: is this possible to focus a small point of common light to the wall and control it with ...
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Lissajous of a laser

What is the physical meaning of the Lissajous of a laser that has hit a grating and been diffracted? I.e. if I had some kind of laser source that hits a diffraction grating, what am I seeing if I look ...
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Two-level laser rate equation

I am stuck on what I assume is a very basic rearranging of terms in Siegman's Lasers, Page 204. Here, the saturation of a laser medium is introduced. The change of the populations of two energy levels ...
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Can amateurs use the retroreflector on the moon? [duplicate]

There is a retroreflector on the moon, placed there, I believe, by astronauts in the 1970s. I think there is at least one station (in France?) that continuously beams a laser at it to measure the ...
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1answer
41 views

Laser spot size change through a beam expander

In a laser guided through a fiber, the beam is divergent upon exit. What normally is done is to put the fiber on the focus of a lens in order to achieve a collimated beam. This beam is then guided ...
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What is the distance the polarization of light is maintained in a single mode fiber?

I am currently working on a project that involves a fiber laser system with fiber optic cable parts more than 2 kilometers each. I know that in standard single-mode fibers, the polarization of light ...
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2answers
25 views

How can the repetition rate of mode-locked lasers be tuned?

In my job there is a femtosecond mode locked laser. It is able to operate at a range of repetition rates. I understand the principle behind mode locking of a laser, but I do not know how it would be ...
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What bounds does Femto photography of light pulses put on photon length?

The question What are the dimensions, width and length, of a photon?, and similar posts, repeat the assertion that photons do not have a defined length. Yet femto-photography appears to contradict ...
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How to derive the equation for sinusoidal fringe pattern?

I have this equation for the sinusoidal fringe pattern: $I_1(x,y)=I'(x,y)+I''(x,y)\cos\phi(x,y)$ and want to know the derivation of this equation. Thanks!
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Requirements for a fluorescent medium to provide optical gain

I have seen fluorescent material such as Rhodamine 6G being used as a gain medium in dye lasers. My understanding is that by pumping the medium with energy, we can make stimulated emission happen ...
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Hydrogen atom in laser pulse

Recently I asked the related question but this one is more complicated. If one has a hydrogen atom interacting with a laser pulse with the hamiltonian: $$H = \frac{1}{2}{\left[ {\hat p - \frac{1}{c}\...
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Spectral full width at half max of a Gaussian light pulse [closed]

I need to calculate the spectral full width at half max (FWHM) of a Gaussian light pulse. The frequency spectrum of a Gaussian light pulse is $$ \tilde{E}(\omega)\propto \exp{-\frac{(\omega-\omega_0)...
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What if we shine a laser to east and another to west, will they arrive at the same time?

If we have two lasers based at the equator and we direct one of them east and the other west on to two screens each 10 km away, will light emitted synchronously at the lasers arrive at the same time ...
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Can two semi-infinite plane waves undergo perfectly constructive interference?

This is building off of a question I asked here. When discussing the linked problem with some friends, the consensus seemed to be that the reason two identical semi-infinite plane waves cannot ...
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Why is silicon used in laser ablation experiments?

I have recently began reading into papers regarding laser ablation, and more often than not, silicon-based products seem to be the basis of the inquiry. What properties or uses does silicon present ...
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Energy conservation in the combination of two coherent beams

I was asked a question today by a student that I couldn't find a satisfactory answer to. Imagine we have two identical laser beams with average electric field strength $E$. Upon combining these beams ...
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1answer
47 views

Trapping particles in a laser beam (photophoretic trapping)

so to make a long story short this topic to me is very confusing but I would really like to achieve the effect. Basically in photophoretic trapping from what I understand it is the lowest density ...
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Wavelength importance in Pulsed Laser Deposition (PLD)

I found that in most ceases of complex oxide/cuprate deposition, used PLD has laser wavelength $\lambda$=248 nm. Is it any special reason to have this wavelength in order to make ablation of this ...
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Is a GASER a theoretical possibility? [closed]

This question (basically an analogy ) is inspired by several questions and answers that appeared on stackexchange.  We first define GASER, for the purpose of this question. GASER - gravitational (...
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2answers
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Frequencies of photons in spontaneous and stimulated emission

A Textbook of Engineering Physics by Avadhanulu, Kshirsagar says the following about Spontaneous Emission: Photons of slightly different frequencies are generated. As a result, the light is not ...
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Are there Lasers in wavelenght of UHF or radio frequency?

how exists lasers in many wavelength in electromagnetic spectrum, like UV, VIS and IR. I don't know nothing about others wavelength as X-ray or radio frequency.
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What is Chirped Pulse Amplification, and why is it important enough to warrant a Nobel Prize?

The 2018 Nobel Prize in Physics was awarded recently, with half going to Arthur Ashkin for his work on optical tweezers and half going to Gérard Mourou and Donna Strickland for developing a technique ...
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How to make light beam to be super narrow?

I am doing a project to use a regular laser beam to be super narrow (25um diameter). I am thinking to use some lens setup to do that. Does any lens setup can make a 5mm diameter laser light source to ...
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Metastable state

I know that in a metastable state the electrons can stay for a longer period than an exicted state. How? What is the difference between a normal excited state and a metastable state?