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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124 views

Lang-Kobayashi rate equation derivation

The Lang-Kobayashi rate equations of a semiconductor laser experiencing feedback are as follows: \begin{align*} \frac{d}{dt}\left(E(t)e^{i\omega t}\right) &= \left[\omega_N(n) + \frac{1}{2}(G(n) -...
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29 views

Coloring the clouds with lasers

What strength of laser would be needed to color or make projections of images upon clouds in the sky? I am assuming that this is possible, if not, please explain why. For the purposes of this ...
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196 views

Intersecting Lasers

What happens at the point of intersection of 2 lasers. If 2 lasers of different colour intersect, what will be happening at the point of intersection? Won't colour mixing happen?? Won't that point ...
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1answer
136 views

Simple derivation of the doppler limit and recoil limit

Im doing an essay on laser cooling, and I've got two questions about the derivation of the two limits. Firstly, in the derivation of the Doppler limit, it is stated in many places that the scattering ...
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28 views

Lower Threshold optical beam limiter?

We would like to implement a very fast beam limiting, so far google search shows that the common threshold ranges is in 1J/cm^2 or more, this could take seconds to activate as our laser ranges from 1 ...
2
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1answer
138 views

Why does the laser change colour? [duplicate]

In the first image, the laser colour is green. When it is shined on the plastic cap of the pink highlighter, the colour changes, why has this happened? Tech Details about the Laser Source are; Max ...
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1answer
281 views

Does laser beam expand along distance or not? [duplicate]

Why does laser dot become bigger at bigger distance? e.g: from millimeter to inches so that it distracts pilots in aircrafts. I knew that laser beam should't expand over distance, but remain stable. ...
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113 views

Gain clamping and threshold gain in quantum optics

We increase the pump power of a laser to the point where laser action starts, i.e. the threshold gain is reached. Now we increase the pump power even more, which increases the intensity of the cavity ...
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1answer
43 views

Can a laser class be lowered by lowering the input duty cycle? [closed]

According to this description, class II lasers have a power output of less than 1mW, class IIIa lasers have a power output of 1-5mW, and class IIIb have a power output of 5-500mW. Can a class IIIb ...
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73 views

Difference between steady state intensity and saturation intesity in laser

Can some one explain the diffrence between steady state intensity and saturation intensity in lasers. And diffrence between gain at threshold and gain at steady state,why are these two gain equal? ...
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47 views

How to classify laser output

What are the quantifiable criteria that are used to assign a safety classification to a laser? Googling finds me only vague subjective descriptions, like "safe to use under normal conditions" or "...
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26 views

How to read CO2 a laser line label?

A line emitted from a CO2 laser is often labelled as 9P36, 10R18(13C), 9R32, etc. What do these labels mean? For example, does 9P36 mean the line is 9.36um from the P-branch? What difference does it ...
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120 views

Could a civilisation contact us by laser from 50 light years away?

The Kepler Space Mission has discovered over 1,000 planets. These discoveries may increase the confidence of some people that other civilisations exist. That is an opinion issue, and not what I want ...
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30 views

What is Frequecy Pushing/ Pulling in Laser Physics

I heard the term "Frequency Pushing/Pulling" in combination with phenomena like in homogeneous broadening and hole burning but I didn't understand what Frequency Pushing/ Pulling is supposed to mean. ...
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18 views

Relaxation Times in Quantum Optics

I am studying laser physics and in in the lecture we defined the transversal and longitudinal relaxation times as the relaxation times of the coherent/ population states of the density matrix. The ...
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1answer
191 views

Spectral Line- Width

How does the spectral line-width of light source (let that be ordinary light, LED, LASER etc.) decides for which communication purpose it will be used for ? Is it like spectral line-width effects the ...
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38 views

Laser Energy Level Transitions

I am new to Laser Physics. While looking at the Energy Levels diagram for the Laser Transition of ND:YAG laser, I see energy levels labeled like 4F(3/2), 4I(15/2),.. I did not come across such energy ...
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1answer
203 views

Using a laser to overhear a room conversation

Movies with science based tricks and gimmicks are generally silly and sometimes even annoying. The science based trick that I don't know enough about to judge is the following (and I have seen it in a ...
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2answers
55 views

Creating nanosecond pulses from a CW laser source

Experimental setup question. If anyone aware of a technique to create pulses of several nanoseconds at a around 10Hz repetition rate from a CW laser source?
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1answer
53 views

Dissolving photoconductor (TiOPc) from Laser Printer drum possible?

When I was thinking of a Lab-On-a Chip Application which combines a lensless microscope and an optical tweezers I saw the ODEP-concept:(http://pubs.rsc.org/en/content/articlelanding/2013/lc/c3lc50351h#...
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2answers
70 views

Light (Laser) operated optical switch

I have searched the web and found that optical switches are activated either through mechanical or electro/magnetics. Making them sort of Optomechanical or optoelectronic switches. Lets exclude ...
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21 views

Limitation of Rytov approximation for turbulence

I have been working through the textbook "Laser Beam Propagation through Random Media" by Andrews and Phillips and have arrived at an interesting dilemma. For a second-order perturbation in the Born ...
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1answer
74 views

Effect of the refractive index of a transparent layer coating a particle?

I am modelling a cell as a particle coated by a layer of a material whose refraction index might change. This layer is to resemble the membrane. The purpose of the model is to simulate what happens ...
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146 views

How to calculate the Refractive index of a glass sheet

My question is how to find the $n$ of a glass sheet with just aiming a laser beam to that. I've got lot of ways that let me find the $n$ ( Refractive index ) but I need the whole part of the ...
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1answer
375 views

Are there naturally occurring lasers in nature?

Are there natural processes we've discovered which lead to laser light of some distinct wavelength?
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3answers
367 views

Why does shining a laser into an iPhone camera create these shapes?

When I shine a laser light into an iPhone 6 camera I get these weird shapes: The shapes are in no way in the background behind the laser. What causes these to appear? I know about typical lense ...
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1answer
37 views

Material that changes transparency when lased from side?

I am into photonics research, and have been searching about this topic in vain, but almost nothing from Google shows up. So i turned here for some light. Do you guys know any material that changes ...
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27 views

Inertial frames and Sagnac interferometers

Let's posit: I am in orbit around a large body, like a planet, and I am close enough to be tidally locked to the large body. Am I in an inertial frame? Even without looking at the stars, couldn't ...
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1answer
66 views

Laser: Looking for name for optical component

I'm currently planning a laser setup in which I want to send a (1mW) laser into the environment using a commercial scanning unit (made of two galvanometers). I would like to measure the reflectivity ...
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1answer
47 views

Meaning of “electrostatic” and “nonresonant laser” fields

I just read the following sentence: The molecule is subjected to an electrostatic field $E$ combined with a nonresonant laser field of intensity $I$, whose linear polarization is collinear with $...
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2answers
131 views

Is circular masking a laser beam an acceptable way to get the beam diameter you require?

I am wondering what are the down sides to just masking a laser to get the beam diameter you require? For example if you have a collimated eliptical beam of say 2mm width and 4mm height, but you ...
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48 views

Visible wavelengths of air fluorescence data - needed for school demo laser telephone design

I'm seeking information about fluorescence in visible wavelengths (390-700nm) of any of the main constituents of air ( $ N_2, O_2, CO_2, H_2O, CO, etc. $) that can be excited with a (hopefully low-...
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1answer
910 views

Why do we see brown light?

While researching about lasers (it's my hobby), it suddenly hit me: there are lasers for every color of the visible spectrum, but there are no brown lasers. Brown isn't even on the rainbow. How is it ...
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112 views

Stimulated emission in LASER

I have been reading about how lasers function : A photon is used for stimulated emission of electrons from the metastable state to a lower energy state. What I don't understand is : How can "giving" ...
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1answer
26 views

I'm looking for a formal definition of 'scintillations' in laser beam propagation

I'm trying to make a scintillometer, based on Rytov's method. I've understood the whole phenomenon, and gone through some of the research papers in the field. But, I haven't encountered any definition ...
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1answer
199 views

Can I catch a single photon with webcam's CMOS or CCD sensors?

I thought it would be nice to capturing single photons using a webcam's sensor due to simplicity. I've read that ccd and cmos sensors have a certain percent of quantum efficiency. What about webcam'...
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3answers
171 views

Diffuse laser light in a surface

Im building a laser target. It consists of a box, with a black plexiglass circle in the center of one of its sides, and a larger white circle around it. The black for the inside shots, and the white ...
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1answer
76 views

What could cause a diode laser to be emitting the half-harmonic of the fundamental frequency?

I have a 405nm laser which is seemingly outputting a small portion of 810nm light. I am wondering what mechanism this could be caused by. Is this a down-conversion phenomenon or perhaps just another ...
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1answer
35 views

Optical pumping without stimulated emission

If I want to pump Rubidium 87 atoms From fg = 2 to fe=1 level with a laser tuned to D1 transition and avoid stimulated emission then it is sufficient that I use a laser power which gives me an ...
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3answers
7k views

How to measure the wavelength of a laser pointer?

I'm working on something and I need to know the wavelength of the laser pointer that I'm using. Can you suggest me a way, using some optics formulae, or anything else to calculate the wavelength?
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38 views

Deconvoluting Raman spectras from different wavelengths

I am using a laser source that is wider than typical laser source for Raman spectroscopy. This mean that the full width at half maximum (FWHM) of the laser is about 5-10 nm, compared to the normal 1-3 ...
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24 views

How does an electron deexcites during stimulated emission? [duplicate]

During stimulated emission in laser,the electron de-excites by supplying energy,generally it must excite,right? My doubt is then why does it de-excites?
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36 views

Laser beam receiver

Problem: I have an object that can move in the $x,\,y,\,z$ direction. The goal is to measure the $x,y$ variation as the object travels along the $z$ axis. Typically the distance traveled is less than $...
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2answers
241 views

Using a transfer matrix to calculate beam width of off-axis Gaussian beam?

I have been reading a lot about ABCD matrices that are used for ray tracing. I can calculate the output offset $r_{o}$ (with respect to the optical axis) and the angle $\theta$ of the ray by $$ \...
2
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0answers
46 views

What causes this pattern in the reflection of a laser on a screen? [duplicate]

When I shine a red laser behind me at a wall I see a strange reflection occurring on my laptop screen Why does this happen? The pattern on my screen occurs exactly where the laser is hitting the wall. ...
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1answer
68 views

Gaussian beam shape

In this diagram of a Gaussian beam, why does the radius vary with z position? Is it assumed that a Gaussian beam is always being focus by a lense? Why can the beam not go any smaller than $w_0$ and ...
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1answer
65 views

Power of several focused laser beams on a small surface

After viewing this: My Homemade 40W Laser Shotgun Will the initial 40W power of the diodes beams be roughly transferred to the targeted surface where the 8 beams are focused, or will there be a power ...
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1answer
67 views

Can infrared lasers still do damage to things if they are powerful enough?

So I get that infrared light is not visible to the human eye without some sort of device to assist in helping you see it, but I was just wondering how that plays into things like lasers. I know you ...
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74 views

Laser output below, just above and way above threshold?

I've been reading up on lasers recently and learnt that within the cavity while the laser light is amplified by the gain coefficient, it loses power due to transmission and absorption. Suppose the ...