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.
Questions tagged [laser]
1603 questions
16
votes
1 answer
Is the time reversed laser really a laser?
I'm looking at the time reversed laser and I was having trouble understanding why we call this device a laser. To me this device is more like the absorbers found in FDTD codes, something like a CPML.
I am having trouble finding the analogs to the…
Mikhail
- 878
13
votes
2 answers
In what sense the laser radiation is monochromatic?
In what sense the laser beam is monochromatic if there are multiple laser transitions happening in the active medium? For example, The two main argon laser transitions are at visible wavelengths:
Blue 0.488 [μm],
green 0.5145 [μm],
And still, it…
Jack
- 835
11
votes
2 answers
Why does stimulated emission happen?
In stimulated emission, why don't electrons just jump to a higher energy level instead of a lower one when they absorb a photon for the second time? Isn't that counter intuitive?
Karim mohie
- 371
10
votes
4 answers
How to build a laser in the garage?
So I wonder if it is any how possible to build laser at home. A powerful one to melt brick.
user2251
9
votes
5 answers
What causes the specific pattern of sparkly light from a laser pointer
I have a fairly cheap green laser pointer that produces a fairly big spot of light (actually two spots most of the time!). I'd guess the size of the spot is about 1/100th of the distance from the end of the pointer to the surface it hits (e.g. after…
CJ Dennis
- 860
7
votes
2 answers
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?
Kashif
- 173
7
votes
2 answers
How is the phase of the stimulated emission in a laser first "chosen"?
As I understand, once you have a population inversion and the excited atoms decay they will emit in random directions, and the ones that emit along the axis of the medium will cause stimulated emission.
Suppose an atom decays and starts the process…
4nt
- 341
7
votes
2 answers
What makes excimer lasers so complex, rare and expensive?
We all can agree that UV lasers are extremely useful, but we (poor majority) are still struggling with 355nm DPSS ones, while excimer lasers being prohibitively expensive (let's say at 1-10W average power, or 100Hz @ 0.1J pulse).
What is the reason…
BarsMonster
- 2,371
6
votes
2 answers
Laser cutting/drilling of copper
In industry, it's common to cut steel using 50-200 W $\mathrm{CO}_2$ laser.
Meanwhile, for making holes in PCB (35 $\mu$m of Cu), DPSS 355 nm laser is usually used and secondary $\mathrm{CO}_2$ to drill through glass.
Why $CO_2$ cuts steel easily,…
BarsMonster
- 2,371
6
votes
2 answers
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 cavity, the laser will by itself generate pulse. I…
StarBucK
- 1,350
6
votes
3 answers
Line width of green DPSS laser
Could someone suggest what is the line width/mode stability/coherence length of generic cheapo green (532nm) DPSS laser?
I've found lots of nice info here: http://redlum.xohp.pagesperso-orange.fr/laser/modeanalysis.html but there are no any DPSS…
BarsMonster
- 2,371
6
votes
2 answers
Why not just pump directly to the $3^\mathrm{rd}$ level directly in a $4$-level laser system?
In a 4-level laser system, the pumping is usually from level 1 (the ground state) to level 4 (the highest-energy state).
Image source
Why do such schemes not pump directly to the third level? Will this decrease the output intensity?
user56802
- 61
5
votes
3 answers
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 far as I see it - it should be possible to lower lasing…
BarsMonster
- 2,371
5
votes
1 answer
Need help understanding lasing threshold
I’m currently studying laser systems and doing some experimental work with a Nd:YAG laser that has a laser diode as the pump source. I think I understand the concept of lasing threshold, but there’s an experimental result I’ve been struggling with…
5
votes
1 answer
Optical laser pumping and reflectors
Let's say we are building Nd:YAG laser.
It is optically pumped by some linear xenon flash lamps, it absorbs light around 750nm and 800nm, and emitted light is at 1064nm.
The question is why doesn't 1064nm emission from the flash lamps interfere with…
BarsMonster
- 2,371