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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Spectrum of generic $\mathrm{CO_2}$ laser

It is often quoted, that it's emission is 10.6um. But we also know that CO2 lasers have huge number of possible emission lines in 2 main bands: 10.6um and 9.6/9.4um. But what is emission spectra of ...
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443 views

Gamma Ray LASER Theory and Technology

I am aware that a similar question has been asked by someone else in the past, but in a very general form. Due to the physics interest and technology, in this question I put emphasis on the detail of ...
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484 views

Will overlapping two different beams of coherent light cause interference?

I have two laser beams with same polarization running parallel to each other. Will they interfere? If yes, then what are the conditions (perpendicular distance etc) and how can I observe the ...
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1answer
131 views

What low-level process drives a frequency-doubling crystal?

I was reading about second-harmonic generation (SHG) crystals (or frequency-doubling crystals) used to produce green laser light from IR. What low-level process in the crystal is actually driving ...
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143 views

What theories allow for “Tractor Beams”?

NASA recently announced $100k grant to study the possibility of using laser tractor beams. What tractor beam concepts have been published but not been dis-proven?
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350 views

Laser frequency tripling

I've heard that common way to get 354nm laser is to triple 1064nm Nd:YAG one. But how to make non-linear crystal to do tripling instead of doubling? What are the best crystals for tripling and what's ...
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903 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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271 views

what is the probability distribution for the angle of an approximate laserbeam

I'm trying to simulate the light distribution characteristics from a Gaussian laser beam, but having difficulty with the angular distribution. I need to generate a large number of points on an x/y ...
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5k views

From power of a laser beam to electric field amplitude

In my experiment, I use a laser beam with wavelength $\lambda=894 \text{nm}$ for some magnetic resonance experiment. Right now, I'm doing some calculation using Quantum Mechanics, which requires the ...
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239 views

Proper and rigourous derivation of Gaussian beam?

Gaussian beams are known solutions to the Paraxial Wave Equation: $$ \frac{\partial^2 \Psi(x,y,t)}{\partial^2 x} + \frac{\partial^2 \Psi(x,y,t)}{\partial^2 y} = 2ik\frac{\partial ...
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295 views

Stimulated Emission

In the case of stimulated emission we always see that one photon goes into the gain medium and two photons come out. How can this conserve energy?
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3k 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 ...
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167 views

Why are laser pulses Sech Squared in temporal shape?

Ultrashort pulses from mode-locked lasers often have a temporal shape which can be described with a squared hyperbolic secant ($\mathrm{sech}^2$) function: $$ P(t)=P_0 \mathrm{sech}^2 \left( ...
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279 views

What makes a material a good lens for CO2 lasers?

I read on Wikipedia that zinc selenide and germanium make good lenses for $\mathrm{CO}_2$ lasers. My question is, Why?
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1k views

Beam splitters- Direction of use

There are two cases I'm asking about. The square in the middle is a cube beam splitter in the same orientation for both cases. We are looking at the beam splitter from the top. In the first case, ...
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1answer
1k views

Can a UV LED cause air ionization?

I am thinking of the high power LEDs at around 250nm wavelength and an output power of some 30mW optical, in continuous mode either divergent beam or focused.
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2answers
661 views

The most price-efficient experimental setup involving SPDC, single-photon counting etc

I would like a suggestion on a price-efficient way of experimenting with spontaneous down-conversion and single-photon counting. The simple dual-slit experiment could be one part of an application ...
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2answers
531 views

How we see laser light if it travels in a straight path? [duplicate]

Light travels in straight path, and our eyes detects an object's reflected light then we see the object. So if laser light is going in a straight path, how come we can see laser light?
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870 views

Is single photon perfectly monochromatic?

Now, we do have equipment to generate single photon at a time, and LASERs are nearly monochromatic. While typing the question, am realizing that successive photons in case of single photon ...
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448 views

Why there is a minimum lasing threshold?

Can someone help me understand why it is often mentioned that for certain lasing media there is a certain minimum lasing threshold without mentioning resonator design & doping concentration? As ...
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98 views

Can polarization effect the coherence length?

I'm taking an optics lab in which I'm required to construct an interferometer, and measure the wavelength of a laser, and the coherence length of the light emitted from a candle fire. Now, I've been ...
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41 views

What is crater's influence on laser ablation?

In many laser ablation experiments (especially Pulsed Laser Deposition), target is moving to avoid crater formation. But I can't find any source that says why it is needed to avoid it. So why is ...
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1answer
204 views

Laser diode spectrum vs LED spectrum, why so much difference in broadness?

I've been reading about how light is produced in both laser diodes (the most common types of lasers) and LED's. The mechanism seems very similar if not exactly the same: one applies a potential ...
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224 views

Stimulated emission and No cloning theorem

I have a little trouble with the simulated emission. I know of the no-cloning theorem which states that it is not possible to duplicate any state. One the other hand, I know about the stimulated ...
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2answers
286 views

Conservation of energy (or lack thereof) in Doppler cooling [duplicate]

I did not find my question answered elsewhere, so here it is. I'm doing a project in my first optics course, and we are reading a bit about Doppler cooling. I understand that a laser is tuned to a ...
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112 views

Simple Experimental Laser Characterization Parameters Ideas?

I have 2 months to do a project on characterization of a laser parameter. We have typical optics lab equipment (DFB Lasers, oscilloscopes, random number generator, etc.). I was told to choose a laser ...
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1answer
139 views

Polarisation of light is a wave concept or applicable to photons as well?

I have a very fundamental question. We explain polarisation of light assuming wave nature of light. Is it still valid if we assume light as photons? Or in other words, polarisation is a wave concept ...
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374 views

What happens if an already excited electron gets hit by another photon (lasers)?

Slightly vague title but it is the best I can do. My question stems from some interest in how 3 stage lasers function. A photon from the pumping source comes in and strikes a atom in the active ...
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425 views

Redirecting light beams from beam splitters

I'm doing a project where I am taking a laser beam and sending it through a beam splitter. As I understand, approximately 50% of the light will go pass through and 50% will be reflected. So this means ...
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Propagation of light in transparent media: absorption and reemission or scattering?

In the two Phys.SE questions What is the mechanism behind the slowdown of light/photons in a transparent medium? and Why glass is transparent? transparent media were discussed. But I'd like to clarify ...
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49 views

Does laser light with less than the work function still ionise some atoms?

If a gas is illuminated with a laser of a frequency less than (but more than half of) the work function of the atoms in the gas, the atoms will be excited into Rydberg atoms. Is there a finite chance ...
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1answer
151 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 ...
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1answer
159 views

How powerful would a laser need to be to make a hole in snow?

How strong would a laser beam have to be (and what frequency would be optimal) for it to be able to make a hole in snow? Here I am looking for a laser beam that could make the hole after less than 2 ...
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1answer
218 views

What determines the form of the intensity curves in Laser-Induced Fluorescence (LIF) measurements?

What determines the form of the intensity spectra of different particle species in Laser-Induced Fluorescence (LIF) measurements? See e.g. I figure that bigger particles have more ways to get ...
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229 views

Laser Transverse/Longitudnal Modes

When we say Laser transverse modes. Is that mean what we will get at the output spot of laser beam ? secondly In practice , what TEM01 or TEMnm means ?
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2k views

Doppler cooling limit vs recoil limit

I was discussing laser cooling in class today and I understood that the main principle of the process is to tune a laser to a frequency lower than the absorbtion frequency of the atom and so only the ...
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1answer
368 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
344 views

How I can launch light into PM fiber

A polarization maintaining fiber preserves the linear polarization of the light at the output, the light at the input must be linear polarized to see signal at the photodetector... However I can't see ...
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1answer
2k views

Michelson interferometry - is a compensator plate necessary?

I am studying the Michelson interferometer shown in figure 2 (similar design shown below) of the AMRITA vlabs tutorial. There it is stated that Since the reflecting surface of the beam splitter ...
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117 views

Michelson interferometer interference pattern [duplicate]

My friend and I recently did an experiment on Lasers where we shot a laser beam through a Michelson interferometer and observed the interference pattern on the wall. Here is the basic setup: One ...
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1answer
296 views

Laser Cutter Power/Wavelength to Cut Paper

I've been reading up on laser cutting and it seems that 808nm at around 2 watts is typical to cut paper. How would one calculate the wavelength and power required to cut an arbitrary material?
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1answer
276 views

Phase noise and linewidth of laser

I learned that the linewidth of a single frequency laser is closely related to the phase noise. But this sentence from a book completely confuses me: "A quantum-limited beam in a so-called coherent ...
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1answer
196 views

How to create a barrier for sound waves?

Is there a way to create a barrier so that sound waves cannot pass through? Does laser light have this ability to act as a barrier or bounce sound waves back? This came to my mind when I was ...
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1answer
145 views

Low-cost 532nm DPSS laser modulation

Could anyone suggest modern means of modulating 100mW CW 532nm DPSS laser? This should be low-cost(<50$) in high volume. Frequency bandwidth is 10Mhz, so modulation of pumping diode would ...
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1answer
246 views

Laser beam position using galvanometer

In 3D printing techniques like SLA and SLS use lasers for solidifying a cross section / layer of the model that is printed. These machines, as far as I know, use XY laser scanners to project the laser ...
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246 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 ...
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1answer
109 views

What methods exist for us to measure the position and momentum of atoms that make up molecules?

In this paper, Localization of an atom by homodyne measurement. A. M. Herkommer et al. Quantum Semiclass. Opt. 8 no. 1, p. 189 (1996) (paywalled). the authors are able to localize atoms using ...
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2answers
28 views

Frequency modulation in laser locking - what frequency?

In laser locking, e.g. using the PDH technique, the light (say of frequency $f$) is modulated so as to add two symmetric sidebands of frequency $\Omega$. I know the maths, I understand how this leads ...
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3answers
153 views

Shining a laser onto a mirror

Theoretically, if I shined a laser at a mirror at an angle of 0 degrees so that the light was perfectly reflected back to the light source, then I should not be able to see the light because it is not ...
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2answers
157 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 $$ ...