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Questions tagged [laser-cavity]

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Cavity mode counting

I am reading the book "Laser Fundamentals" by William T. Silvast and he mentioned that the number of cavity modes can be calculated as an octant of a spherical volume, i.e. $M=\frac{1}{8}\frac{4\pi}{...
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Gain Coefficient of lasers and intensity paradox?

It can easily be shown that the intensity of a laser is $$I = I_0e^{z\gamma} \,, \tag{1}$$ where $\gamma$ is the gain coefficient. It can also be shown that $$\gamma = \frac{\gamma_0}{1+I/I_{\text{...
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Finding intensity of laser after round trip in cavity with single mirror [closed]

I came across a question in a text book today, and was wondering if someone could maybe check to see if my physics and workings are correct, as I am getting a intensity value greater the what going ...
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1answer
34 views

How to decrease the Q-factor of a resonator?

I was trying to create a mode-locked laser in order to create high-intensity light pulses, this experiment was done a while ago and with someone else, and in our notes says that the laser cavity's q-...
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Can a laser ever run single mode without active stabilization?

So when we talk about the emission wavelength of a laser, what we actually mean most of the time is the central, brightest emission wavelength, e.g. 852 nm on some diode laser. When we look at this ...
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Transverse modes in optical resonators

Im struggling with understanding transverse modes in an optical resonator or laser. Hopefully you can solve this mystery for me. Thank you very much! As far as I know, there are two types of modes: (...
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1answer
22 views

How do I calculate a loss rate from the reflectivity?

If I have a laser cavity that is contained between two mirrors and I know the reflectivity, R1 and R2, of each mirror, is there an easy way to calculate the photon loss rate through each of the ...
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Beam waist size inside a hemispherical cavity

I would like to know if the beam waist inside a laser cavity depends on the pump beam size. For example, for a hemispherical cavity with a plane pump mirror adjacent to the laser crystal, and a plano ...
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How to calculate laser parameters for drilling 30um holes?

To drill such small holes around 30 micro-meter in Cu(used in Printed Circuit Boards), what type of laser should be selected? How to calculate the parameters of laser like its wavelength, pulse ...
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30 views

Fundamental questions on resonators and modes

Im struggling with a quiz to resonators and modes. Consider a gaussian beam which excites the fundamental mode of a optical resonator. Which parameter of the Laser beam do matter? How do you have to ...
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38 views

Why do we use detuned lasers?

One often comes across optical systems like cavities, where detuned lasers are used. Why does one need a detuned lasers? What can we do with a detuned laser that we can't do with a "non-detuned" laser?...
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1answer
161 views

How does one calculate the stability of a ring cavity?

When discussing whether or not a cavity is stable, i.e., if a beam stays inside the cavity, one can either employ the ABCD-matrix approach, in which case the cavity is stable if $$ 0 \leq \frac{A+D+2}{...
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Eigenvalues of the Hamiltonian in quantum optics [closed]

I have the following Hamiltonian (non-Hermitian) $$ H=-(iM_1 +N)A^\dagger A + (iM_2 - N) B^\dagger B - L(A^\dagger B + A B^\dagger), $$ where $A$ and $B$ are the annihilation operators for two ...
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advantages or disadvantages of pulsed laser vs continuous-wave (CW) laser

What are the advantages and disadvantages of pulsed vs CW laser? Does pulsed laser have more power compared to CW laser, or it is vice versa? If I have to guess, for long distance communication, ...
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1answer
91 views

Is confocal resonator consisted of spherical or parabolic mirrors?

When talking about optical resonators for lasers I found on several places that confocal resonator is defined as "two spherical mirrors of the same radius of curvature R and separated by a distance L ...
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Dependence of Rabi oscillations on laser power

Is there an expression for the dependence of the Rabi oscillations of a system on the laser power? The system I'm considering is an electron spin in a quantum dot.
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Pease explain why does the phase bw two sidebands in PDH method changes from pi (when laser is at perfect resonance with cavity) due to dithering?

since, this signal is compared with the original modulating signal and the net phase shift gives the error signal which is fed to the servo for control. Hence, knowledge of phase deviation due to ...
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What is the difference between “normal mode” and just “mode”?

So in the oscillation problems, is there difference between "mode" and "normal mode"? I know that "normal modes" are independent and orthogonal, so one doesn't affect the other. Now I am not sure when ...
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1answer
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Qualitative description of how an inhomogeneous broadening mechanism can lead to multimode oscillation in a laser cavity

I understand that when there is inhomogeneous broadening in a laser cavity, the resultant gain profile is a Gaussian (as opposed to a Lorentzian profile for homogeneous broadening). Due to the wider ...
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109 views

Why does a Gaussian beam shrink in diameter when approaching a focal point?

I'm basing my question on the above graphic. I've been trying to research this, but I'm having trouble getting it into my head. The caption says it follows the $\frac{1}{e^2}$ point on beam intensity, ...
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1answer
272 views

What if the optical length of a cavity is not a half integer scalar of the standing wave wavelength?

Pardon the confusing title, but I'll try and rephrase what I'm asking. Longitudinal modes in a wavelength of light require the optical length of the cavity to be such that the wavelengths need to form ...
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83 views

What exactly is Q-switching?

Some questions of mine spawned upon reading my lecture notes about Q-switching: "In a Q-switched laser we stop the laser from oscillating by altering some property of the laser cavity (otherwise ...
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How does Gain-switching produce intensity spikes?

Gain switching is described in my lecture notes as "we simply control how long we supply energy to the laser for, and thus how long the laser remains above threshold for. As the laser only emits ...
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Are some wavelengths 'longer' than others spatially, and as such explain things such as longitudinal modes?

I'm currently learning lasers. In my research of mode-locking, I've stumbled across something called a longitudinal mode. The allowed modes of the cavity are those where the mirror separation ...
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How can you work out the FWHM of the gain profile for a longitudinal laser cavity?

Consider a longitudinal cavity with a gain medium. Assuming knowledge of the geometry of the cavity (i.e. its length) and the free spectral range of the modes, as well as the frequency of the light ...