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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1answer
14 views

Relationship between refractive index and concentration [on hold]

what does the gradient of the graph of refractive index against solution concentration mean
0
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14 views

How do laser triangulation sensor reflection obeys law of reflection?

I find it hard to understand how laser triangulation sensor work considering this image The laser beam form the angle of $90^o$ with the surface so how can the reflection beam form the different ...
0
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1answer
28 views

Near perfect reflectors and LASERs

What would happen in a hypothetical scenario in which a LASER strikes a near perfect reflector (like the ones made by Jason Valentine at Vanderbilt, which reflect 99.7% of visible infrared light). I ...
66
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5answers
6k views

How do laser “tape measures” work?

There is a device available for about $\$40$, which fits in the palm of the hand, runs on two AA batteries, and can measure distances up to $50\,{\rm ft}$ to an accuracy of $\sim \frac{1}{8}''$ ($\sim ...
0
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0answers
22 views

How is the conversion from an operator equation to a c-number stocastic differential equation justified?

In many papers on laser dynamics theory, quantum Langevin equation of operators is converted to c-number stocastic differential equations, which is analyzed to obtain results. However, why this ...
5
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2answers
78 views

7 W medical laser without any precautions?

Today I got some medical laser treatment to treat some tendon irritation. The doctor used a red or IR laser with 7 W of power. He casually applied the laser onto the knee and was panning over the ...
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2answers
44 views

Interference or something beyond?

I have an experiment with He-Ne laser in my practical syllabus. In curiosity I took a photo of the incoming radiation directly from the laser with my mobile camera. Some strange pattern is observed. ...
0
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0answers
21 views

Zero group refractive index within laser cavity

I am considering a uniform plane wave propagating within a laser cavity with $$ \frac{2\omega n L}{c} = 2m\pi $$ where $\omega$ is the angular frequency, $n$ is the effective refractive index of the ...
0
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1answer
32 views

Sech laser pulse time-bandwidth product calculation

Find the time bandwidth product for a $\operatorname{sech}$ shaped pulse. Attempt: I know that the time bandwidth product $\Delta t \Delta \omega$ for a $\operatorname{sech}$ shaped pulse must ...
1
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0answers
20 views

How to estimate the heat generation and the power per square cm provided the resistance and the current of a laser diode?

Laser Diodes are very tiny. So, it is making me confused in its calculation. In laboratory, the resistance of a laser diode is 10-15 ohm and the current is 80-100 mA. How could I estimate the heat ...
5
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1answer
52 views

Laser resonator analytic formula for sum of modes

For a sum of N modes in a resonator with identical phases, find an analytic formula for the pulse shape in the limit of many modes. Use the analytic expression for the sum of a geometric series. ...
0
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1answer
39 views

Laser resonator modes

For a resonator, plot the intensity as a function of time for (i) when the modes have identical phases, and (ii) when the modes have random phases. Attempt Here is the equation for intensity (p. ...
0
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0answers
22 views

Interesting question regarding stimulated emission

why is outgoing photon emitted during stimulated emission in phase with the incoming photon? I can't see why this is so because the two photons may be out of phase yet conserving momentum and energy. ...
3
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1answer
24 views

Orbital Velocity & LLR

As I understand it, light that is emitted from a source is not imparted with the motion of the source and so always follows a "straight line". If this is correct, I am having a difficult time ...
0
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1answer
40 views

What is the divergence of a beam from the output of a laser?

Diffraction through an aperture gives a half-angle divergence of $1.22\lambda/a$ where a is the aperture diameter. The half-angle divergence of a Gaussian beam is $\lambda/\pi w_0$ where $w_0$ is the ...
1
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0answers
31 views

Spinning black hole laser?

Is a laser that uses a rotating black hole's ergosphere as the gain medium possible? The idea is that the coherent light feeds off of the black hole's rotation. Assume that the black hole is ...
1
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1answer
21 views

How is it guaranteed that electrical connections could be made without destroying a diode laser?

A diode laser is a tiny diode and requires a microscope to see it. Since a laser generates a good amount of heat, the diode should be destroyed with the produced heat. But it does not happen. but why ...
4
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4answers
100 views

Intensity fluctuations at the output of a single mode fiber coupled to a He Ne laser

I have coupled a Thorlabs HNL050L-EC - HeNe, 632.8 nm, 5 mW, Polarized Laser to a 2 meter long single mode fiber patch chord using a Thorlabs F230-FC-B aspheric lens. While I am certainly able to ...
-1
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0answers
17 views

Sharp spot with laser diode

Hope this is the right forum. What components are required for optic system to project a sharp spot with laser diode on a target 10mm-30mm away of the light source? Sharp- means that the transition ...
-3
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1answer
42 views

stimulated emission in lasers [closed]

In LASERS, when the initial stimulated photon gets emitted, it stimulates other photons to get emitted. Now my question is: Does the wave of this photon interfere with other waves and makes a bigger ...
0
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1answer
35 views

What kind of other light sources can disturb the detection of LASER [closed]

My project objective is to detect different lasers , for example Laser Range Finder: pulse width 10ns and repetition rate is ...
4
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2answers
406 views

Is gravity the current limitation to laser cooling?

This is something I've been wondering for a while. I've read about the experiment with NASA to reach unprecedented cold temperatures in space because of the microgravity environment not being such a ...
4
votes
3answers
115 views

Why can't incoherent light be collimated as well as laser light (e.g. in a laser pointer)?

Why does a laser pointer contain a laser diode, and not just an LED? A laser pointer contains a laser diode, which essentially shines coherent light over a large angle, and a collimating lens, to ...
0
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2answers
29 views

Reason behind heating the substrate in Pulsed Laser Deposition

Why do we need to supply a constant heat to the substrate while depositing thin films in Pulsed Laser Deposition technique?
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0answers
11 views

Parameters for modelling 4 level 2 electron gain medium for laser

I have an EM simulator that can model laser gain medium by a 4 level 2 electron system. However the model requires pumping wavelength, lasing wavelength, pumping linewidth, lasing linewidth, decay ...
3
votes
1answer
41 views

How is a result of no time variation in the gravitational constant $G$ related to a measurement of no local expansion?

In this answer @PhillS linked to the paper Progress in Lunar Laser Ranging Tests of Relativistic Gravity which has given me a great start. While its main focus is on the Equivalence Principle (EP) ...
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3answers
104 views

Create a laser from sun light

I have read on wikipedia the basic theory behind laser. A photon passes through an excited electron which then produces the exact same photon. Light is bounced off mirrors to create more photons. Is ...
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1answer
23 views

Is possible to excite semiconductor with attosecond laser pulse [closed]

Is possible to excite semiconductor with attosecond laser pulse for generation THz wave?
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1answer
39 views

What is the theoretical maximum data transmission rate of an optical laser at 400nm and at 800nm, with optimal pulse width? [closed]

I want to know what the highest possible data transfer is for visible light with regards to the frequency, disregarding noise. Using the shannon-hartley formula wasn't of much use, as it operates ...
2
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2answers
31 views

How do I find uncertainties in an intensity plot created from a photograph?

I have a photo of a laser beam (taken by sending the laser into a CCD). I then took the image and ran it through an image reader that gave an intensity surface plot. I then took a single cut from that ...
0
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1answer
37 views

Focal Length Calculation [closed]

Although I research in the internet, I couldn't find detailed answer. I have a question and I want to make sure from the answer. The ligth is coming from a fiber laser source and focused on a ...
3
votes
1answer
32 views

Master equation approach only suitable for good cavity laser?

As I understand, master equation and quantum Langevin equation are equivalent formalisms. However, in a Review of Modern Physics article titled sub-Poissonian processes in quantum optics, the author ...
0
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1answer
46 views

How can a Satellite's position/orbit be calculated using only range measurements from ground stations?

This task is often done in a process known as Satellite Laser Ranging (SLR). SLR stations (of known coordinates) track satellites, recording range measurements to the satellite at known times. I would ...
0
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0answers
18 views

What is the Reach distance of a laser beam? [duplicate]

How far can an uninterrupted beam of laser travel? And on what factors does it depend on?
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2answers
30 views

Projects to undertake Using Lasers [closed]

I need an economically feasible physics project that would use lasers in any manner preferably with respect to optics for a school projects class XII . Any suggestions are welcome no matter how crazy ...
9
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95 views

Stimulated Emission in QED

The explanations of stimulated emission which I have found all describe the phenomenon in terms of non-relativistic quantum mechanics. How might you describe it in a field theory such as QED? In ...
0
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1answer
29 views

What medium could I use for a laser pointer to hit and illuminate an entire area behind it?

I'm in the planning stages of making a fun project for my nephew which will allow a wood gun with a laser pointer attached to 'shoot' at a target area. The target area will most likely be a piece of ...
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0answers
25 views

why atoms can't be directly excited to meta stable state? [duplicate]

IN LASERS,Why is it necessary to excite atoms at higher energy level than meta stable state, why can't we just excite it to meta stable state and obtain the condition of population inversion. Don't ...
1
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1answer
45 views

Why does generating EUV frequency combs require femtosecond enhanced cavities?

When generating extreme UV (EUV) frequency combs using high-order harmonic generation, why does the harmonic generation step need to be inside a femtosecond enhanced cavity for the comb to work? More ...
3
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1answer
52 views
+50

How to find Intensity from field of train of pulses?

Lets say there is process that emits a field $E$ every half cycle of a driving laser pulse (in particular, high harmonic generation). The total field is $$ E_{tot}(t) = \cdots + ...
5
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2answers
110 views

Laser mode locking

I don't understand why we need to do mode locking in laser to generate short impulse ? Indeed, If I see this picture from wikipedia : By using multiple frequencies and the limit conditions of my ...
3
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2answers
54 views

Optics to correct focal distance across a plane

I have a laser beam which is focused to a point at a certain distance. I'm then going to use a galvanometer to scan that beam across a plane. Obviously, as the beam scans across the plane, the ...
19
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4answers
7k views

Can lasers lift objects?

I have been fascinated by a very intriguing question - Can lasers push objects up? I have done the below math to find out Lets say we have a $1000~\text{mW}$ laser and we would like to lift an ...
0
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0answers
39 views

Finding the appropriate fitting function for a coherence length measurement

I'm studying Coherent Optics in Experimental Physics, and I intend to determine the coherence length of a two beam interference. To do that, I used an He-Ne laser, a Michelson interferometer and a ...
1
vote
1answer
100 views

Does this length refer to wavelength or length? [closed]

In this question: A He-Ne laser emits red light of the wave length $\lambda = 632.8\ \mathrm{nm}$ with a beam diameter of $2.0\ \mathrm{mm}$ and a power output of $1.0\ \mathrm{mW}$ [...] (d) How ...
1
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0answers
27 views

How can I find out allowed quantum transitions?

My active element is fluorine(F), I have an energy level diagram: So, i must choose the pump's channel and find out what quantum transitions are allowed. How can i do it?
0
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1answer
35 views

Why must we use mode locked lasers?

Quick question: If I have a laser cavity with a bunch of harmonics under the gain curve: Why do I not always get a pulsed laser? EG: I mean since these harmonics exist in the cavity arn't they ...
0
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0answers
54 views

Why is a two level laser impossible to make? [duplicate]

I would like to know why it is impossible to have a two level laser ? Indeed if I write the equations (I neglect here the spontaneous emission), I have : $\frac{dN_2}{dt}=W(\omega).B.(N1-N2)$ and ...
1
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1answer
24 views

Timekeeping , optical clocks, and precision

I am having trouble understanding something: The concept of time measurement. So I want to simply this as much as possible to get an intuitive understanding: We define the second by the time it ...
0
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0answers
33 views

How would a BEC respond to the gravitional force of a small mass so sensitively?

Recently I watched a BBC programme on anti-gravity, most of which was wishful thinking by NASA and BAe Systems 20 years ago. At the end of the program through, they did show what appeared to be a ...