Questions tagged [laser-cavity]
92 questions
14
votes
3 answers
What happens to the non-axial photons of a laser cavity?
When a laser cavity is pumped, the axial photons are reflected back and forth by the cavity mirrors and so contribute to stimulated emission, but the non-axial photons do not have this opportunity. What happens to these non-axial photons?…
The Pointer
- 939
8
votes
3 answers
Can you make a laser without cavity, if you have a pump strong enough? I think no, but is my reasoning correct?
I've found an SE question (Laser without a cavity) about that, but it isn't exactly the same as mine.
My thinking is: no, you can't, because without the cavity, there wouldn't be possibility for one dominant phase to take over and create stimulated…
user46147
- 3,114
5
votes
1 answer
Homogeneous gain saturation and single-longitudinal-mode lasing
I am currently studying Laser Systems Engineering by Keith Kasunic. Chapter 1.2.1 Temporal Coherence says the following:
Whether or not multiple axial modes will lase depends, in part, on the cavity-mode spacing $\Delta \nu_a$ in comparison with…
The Pointer
- 939
4
votes
1 answer
Optical or Geometrical length in ABCD Matrix?
I'm trying to obtain the correct expression of the waist of a gaussian beam with respect to the ABCD Matrix coefficients in a bow-tie ring cavity, where one places a non-linear crystal of index $n$ and length $l_c$.
For an homogenous medium of…
Chris Ze Third
- 415
4
votes
1 answer
Physical meaning of Cavity Finesse
I was wondering what does the term cavity finesse mean, physically? I understand that it is defined by—
$$F = \frac{ \text{Free Spectral Range (FSR)}}{\text{Linewidth}},$$
where FSR is the frequency separation of the cavity modes given by the…
4
votes
2 answers
What exactly do we mean by 'Free spectral range'?
While reading about Fabry perot interferometers, we conclude that transmission can only happen when twice optical length of the cavity is equal to an integer multiple of the wavelength of the incident light. Elaborating further, the source converts…
Sanika Khadkikar
- 195
4
votes
1 answer
Sidebands, cavity tuning and detection in interferometric gravitational wave detectors
I know the basics of gravitational wave detection but struggle to put things together and view the whole picture of the signal path. Most of my knowledge refers to second generation gravitational wave detectors.
What I understand:
Gravitational…
Another S.
- 41
3
votes
1 answer
Purcell effect for large cavities
The model of interest is a 2-level system (e.g. an atomic transition) inside a damped single-mode cavity.
The purcell effect states that the atomic decay rate inside the cavity $\Gamma_{cav}$, on resonance, is enhanced compared to the free-space…
DLosc1
- 43
3
votes
1 answer
Half-wavelengths of the electric field fit in the cavity length $L$: $m \frac{\lambda}{2n} = L$
I am currently studying Laser Systems Engineering by Keith Kasunic. Chapter 1.2.1 Temporal Coherence says the following:
Axial (or longitudinal) modes are determined by the geometrical fit (or resonance) of a given wavelength in the laser cavity.…
The Pointer
- 939
3
votes
2 answers
What are the losses in a laser cavity?
I studied that to get the lasing conditions gain must overcome the losses. But what are the losses? Thanks a lot
Luigi2405
- 153
3
votes
1 answer
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
$$
0 \leq \frac{A+D+2}{4} \leq 1
$$
In a cavity with two perfectly…
John Doe
- 1,389
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3
votes
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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 one says just "mode" is it meant on "normal…
matori82
- 943
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2
votes
1 answer
Why some laser diodes have angled window?
Why some laser diodes have angled window? Here is an example
Jimski
- 234
2
votes
1 answer
Reflection spectrum of a triangular cavity
I am struggling to find the expected reflection spectrum of a triangular cavity, both with and without round-trip losses.
This is a simple scheme:
Laser light is being coupled in the cavity through mirror M1, which has a reflectivity R1 lower than…
2
votes
0 answers
How are frequency combs obeying the energy conservation?
The operational principle of frequency combs is that you generate very short pulses (in time domain), and that in the frequency domain (due to Fourier's transform) the spectrum of such pulses is a comb.
But this is just maths. And how it works from…
user46147
- 3,114