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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42 views
Photon pumping in Laser
Let's consider a ring laser where the laser must pass through the gain material before it is sent toward a partially reflective surface $\ R=1-T $. The other mirrors are perfect reflectors with $\ ...
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0answers
237 views
Turn-on delay time for Laser diode
Do you know any simple explanation on the reason why the turn-on delay time on a laser diode is reducing while we increase the bias current?
Turn on delay,is the time that the laser needs from the ...
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3answers
3k views
How do laser rangefinders work when the object surface is not perpendicular to the laser beam?
I find the functioning of a laser rangefinder confusing.
The explanation usually goes like this: "you shine a laser beam onto the object, the laser beam gets reflected and gets back to the device and ...
2
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2answers
82 views
Spot of my light on the moon
This is a funny question, but worth answering. The distance between the moon and the Earth is 384,400 km. The speed of light is 299792.458 km/s. It will take 1.3 seconds (Approx.) for my laser beam to ...
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3answers
192 views
Material resistency to lasers beam
Keeping the average power constant, why some materials are more eager to be damaged by pulsed laser with respect of C.W. lasers, or viceversa?
When i talk about pulsed lasers i think for examples of ...
2
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2answers
126 views
Would a laser with four possible energy levels be better than three?
I'm wondering about achieving population inversion for a laser. I learned that without an active medium, it's not possible to create a laser with only two energy levels, but it would be possible with ...
2
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2answers
650 views
Can you use a laser to measure the speed of light with a rotating mirror?
I have learned that the classical measurement of the speed of light with a rotating mirror does not work with a laser (as opposed to, say, a mercury-vapor lamp).
Can you tell me if and how coherency ...
2
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1answer
307 views
Generated wavelength of free electron laser
Could you please help me understand how one can measure output frequency of free electron laser (provided that we know size of magnetic domains and electron energy)? This should be a function of ...
2
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3answers
484 views
Recently publicized experiment on destructive interference between two laser beams
Recently I've had several non-physicist friends ask me, independently of each other, about an experiment where two collinear laser beams destructively interfere along a certain length. Everybody wants ...
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2answers
57 views
Optical trapping problem
Can we make light slower by applying optical trapping (I mean applying laser beam to lower the speed of light)?
2
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1answer
104 views
How would one generate Brownian light? What would it look like?
When light is an equal mix of all visible frequencies, we call it white light.
By analogy, sound that is a mix of all audible frequencies is called white noise.
For sound, there is an additional ...
2
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1answer
82 views
Factors that make beam divergence worse after refocusing
A beam of light of width $W$ and wavelength $\lambda$ with divergence that is diffraction-limited is refocused with an optical element placed at a distance $D$ from the beam source. Will the refocused ...
2
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1answer
161 views
Validity of Einstein Coefficient Derivations
Consider a two-level energy gap with electronic energy states $E_1$ & $E_2$ and associated population densities $n_1$ and $n_2$ with $E_2>E_1$.
In the derivation of the Einstein coefficients ...
2
votes
1answer
250 views
What's the big deal with Nd:YAG rods?
I see the prices of Nd:YAG rods for lasers, and could someone explain why they are so expensive?
Do they need to be mono-crystalline or something?
Will Nd:YAG laser work with ...
2
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0answers
86 views
Macroscopic chromodynamics
Lately I've been reading about gamma ray lasing phenomena, and I've been wondering about the applications of this.
More concretely, the above fantastic question led me to wonder if we could somehow ...
2
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1answer
125 views
Consistently oscillating micron sized particles in a liquid
I have an idea that would involve the measurement of an oscillating substance whilst the substance is immersed in a liquid. However, the method that I would use to measure the frequency of these ...
2
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1answer
337 views
Can energy be extracted from clouds?
Can cloud charge imbalance be used as an energy source?
First off quite some energy must be present in clouds: a lightning path is quite long, and electrical breakdown of air requires about 1MV/m. ...
2
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0answers
194 views
Levitation rotation speed involving laser acceleration, pyrolytic graphite and a vacuum
The experment would involve a small NIB magnet levitating between or on the diamagnetic material pyrolytic graphite, unlike other forms of levitation this doesn't require power to run such as ...
2
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1answer
133 views
Optical element is heated by laser: is it possible to get oscillating heat distribution?
Imagine that we have thin optical element, which is irradiated by laser. Laser heats element, so there is some heat distribution in element. There is a heat sink through upper and lower element faces ...
2
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0answers
186 views
How is the “negative dispersion” derived?
I'm looking at Kopfermann H., Ladenburg R., Nature, 122, 338-339 (1928) and it appears Ladenburg in Ladenburg R., Z.Physik, 4, 451-468 (1921) was the first to discover the phenomenon of "negative ...
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3answers
5k views
What makes some laser beams visible and other laser beams invisible?
What makes the beam of some lasers:
1-visible?
such as the ones used in clubs or such as the laser pointers sold at amazon which if pointed to the sky look like a solid visible beam of light ...
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4answers
857 views
How can a laser pointer have range of several kilometers in atmosphere?
Laser pointers manufacturers claim that some pointers have range of several kilometers.
Okay, they use a powerful laser, but that powerful laser usually has power less than one watt. Okay, the laser ...
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2answers
50 views
Selectively visible laser beam with a controllable means
How can parts of a laser beam be made visible while others left invisible using something electronically controllable (for example, another laser beam crossing it, or a magnetic field, or heat, etc).
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2answers
329 views
laser pointer class III and potential eye damage
we just bought a green laser pointer on Ebay and had a discussion about the safety. The laser is low end chinese one (5 USD, free shipping :-) ) and the seller says this:
Green Laser Pointer Point ...
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1answer
76 views
Ideal four-level Gain Medium (or just any old gain medium)
What exactly is happening in a laser's gain cell when the irradiance is greater than the saturation irradiance?
Also can someone offer a clear conceptual treatment of the gain-coefficient and its ...
1
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1answer
104 views
Does Combining Lasers Add to Their Power?
For example... If I had a 2W green laser, a 2W red laser, and a 2W blue laser, could I combine them using crystals to form a 6W white laser? Or is that now how it works? If not what would be the ...
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1answer
146 views
What is 'tilt locking' of a laser cavity?
In another question, jasonh mentions a scheme for locking a laser to a resonant cavity called 'tilt locking':
The signal is used for locking the frequency of a laser to a high finesse cavity. The ...
1
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1answer
58 views
how laser interact with atoms?
I am reading a book introducing basic concept of laser. It is pretty shocking to me that people can generate beam with almost all photons in the same state. In the book, it said that a two-level atoms ...
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2answers
82 views
Quantum yield and spontaneous decay
I'm trying to figure out how many atoms are decaying spontaneously in a span of 2 seconds. Let's say that the quantum yield is 0.45, and that the lifetime "τ" (tau) is 10 microseconds.
Then I found ...
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1answer
125 views
What is the optical power level of common fiber optics lasers?
In the book Nonlinear Optics, it is stated that the nonlinear effects start to become a problem in WDM systems (around 1550 nm) after about 1 mW of optical power. However, I measured the optical power ...
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1answer
130 views
Why does a coulomb explosion induce fusion?
If you strip the valence electrons apart with a very short intense electromagnetic field the remaining core explodes in a so called coulomb explosion.
But experiments have shown that under certain ...
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2answers
175 views
Why we don't see long range airborne CO2 lasers?
I wonder, why http://en.wikipedia.org/wiki/Boeing_YAL-1 is not CO2 one?
Are the issues with air transparency at 10um? Or it's impossible to focus on large distances due to diffraction?
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1answer
92 views
Demonstrating Quantum effects with home experiments using green diode laser [closed]
I would like to preform home experiments to demonstrate quantum effects to my kids. I need a list of experiments on Laser photons that could be easily conducted at home to demonstrate quantum ...
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0answers
29 views
What methods exist for us to measure the position and momentum of atoms that make up molecules?
In reference to this paper, http://iopscience.iop.org/1355-5111/8/1/014, we are able to localize atoms using homodyne measurement. Would it be too naive to consider we can measure the position of ...
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1answer
112 views
Why does heterodyne laser Doppler vibrometry require a modulating frequency shift?
On the wikipedia article (and other texts such as Optical Inspections of Microsystems) for laser Doppler vibrometry, it states that a modulating frequency must be added such that the detector can ...
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0answers
99 views
What narrow-linewidth laser system runs at 2100nm with 1W of power?
For an experiment at our university we need a laser that runs at about 2.1 μm (about 20nm higher or lower would be fine too.
We have found a multitude of lasers that achieve this (typically Thulium- ...
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0answers
242 views
Maxwell's Demon - laser cooling
There’s an interesting article on Scientific American
that tells how to cool individual atoms can bee cooled to within a very tiny fraction of Absolute Zero.
It uses two laser beams acting on a very ...
0
votes
1answer
38 views
The units of gain and number of atoms in population inversion in a laser
I am following my university course notes on amplification in laser media, and have come across expressions for the gain of a medium, but the notes are not exactly rigorous... The expression given for ...
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2answers
191 views
New infrared laser weapon made by the USA - How does it work? [closed]
I have seen this post:
New infrared laser weapon, the Laser Weapons System, could shoot down drones or disable ships: US Navy
You can watch the video as well. that exhibits a laser weapon which can ...
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2answers
79 views
Image contrast as function of exposure for a CCD detector
In a laser interferometry experiment, we project a pattern of interference fringes onto a CCD sensor. For best results, we want good contrast between the bright and dark fringes, and we carefully ...
0
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1answer
105 views
Can the inverse of a laser exist?
Speaking as a layman, I understand a laser works by exciting an electron so it returns to rest by emitting a photon. Is it feasible to 'damp' the energy level/s of an electron so it absorbs energy ...
0
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1answer
42 views
I want some information about population inversion in graphene & build laser with this theory
I have read the paper
Theoretical Study of Population Inversion in Graphene under Pulse Excitation. A. Satou, T. Otsuji and V. Ryzhii. Jpn. J. Appl. Phys. 50 no. 7, pp. 070116-070116-4 (2011).
...
0
votes
2answers
210 views
about waveplate and polarization
I have a throlabs half- and quarter-wave plate with rotation plate. There shown the angle scales and a line denotes the fast axis. But what does the angle mean? I do some research and someone said the ...
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2answers
2k views
Free Optics Simulation Programs
I'm having an extremely difficult time finding an optics program that is easy to use and offers accurate physics simulations. I'm not asking for much, I just want to be able to simulate a laser going ...
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1answer
2k views
laser spectral width vs. linewidth
I have been racking my brains over the differences between laser spectral width and something called the linewidth. The linewidth was written about in detail by Henry in 1982. The spectral width is ...
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0answers
12 views
How does optical phase modulation produce photons with different frequencies?
The classical description of electro-optic modulators is an index of refraction that depends on the applied voltage. For example, for a sine modulation $\sin(\Omega t)$, a monochromatic laser of ...
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0answers
36 views
Time reversed laser
Recently, I read an article on time reversed laser. I don't know why they call it a time reversed. I have a doubt that why they use two laser in the device. And what is an anti-laser?
The device ...
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0answers
21 views
Calculating population ratio for radiative transmissions in lasers
I'm trying to understand how the ratio of population is related to the energy gap between two energy levels. If an emission of a wavelength at 550nm is given off at room temperature (293K), then what ...
0
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1answer
149 views
Calculating laser wavelength/power to cause emission of light in a gas?
It's been a long, long time since I've had to worry about electron excitation levels and band gaps. Please forgive (and correct!) my terminology and misconceptions. I've also posted this in the ...
0
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1answer
74 views
Density and statistical models for visible air dust
If a laser beam is looked at from the side versus a dark background, a sparkling effect can be seen caused by dust particles in the air hit by the beam.
Is there any simple model or coarse ...
