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Apr
15
comment Non-semiconductor CW laser types for 445-465nm
Don't know much about rp-photonics.com/upconversion_lasers.html . But apparently they come in blue. Usually longer wavelength than your range, but sometimes in range, e.g. ncbi.nlm.nih.gov/pubmed/19855716
Mar
18
comment Obtaining a Positive Hall Coefficient for Electrons Near the Top of a Valence Band
Related: physics.stackexchange.com/questions/10800/…
Mar
15
comment What is an absolute frequency reference (Frequency combs)?
I was referring to calibration for the purpose of timekeeping. Then there's no need to adjust the frequency. The only thing you need to do is measure its absolute frequency and write it down. If it's a clock with output in seconds, it probably has control software where you can say what the exact oscillator frequency is.
Feb
10
comment Is Planck’s proof of Kirchhoff’s Law of Thermal Emission false; and if it is not false why is it not false?
I believe Planck's proof because I never saw any reason to doubt it. And having read the linked paper, I still do not see any reason to doubt it. Additionally, I know that the result is right because I know several airtight proofs from reading modern textbooks, often crediting Planck. Admittedly, it is possible that Planck stated a true result but gave a false proof. But it suggests that is proof is probably by-and-large correct. Considering all these things, that is why I believe Planck's proof is not false. My belief is not an especially strong belief, but there you have it.
Feb
10
comment Why is the Pythagorean Theorem used for error calculation?
@LeonardoCastro - Sorry I was speaking loosely and leaving out steps. Thanks for your comments, I just edited, I hope it's better now.
Feb
6
comment Selection rule used in singlet/triplet recombination in LEDs
@user5419 - No. Nothing in my answer is based on the assumption that light has zero angular momentum. I also never said light "does not couple", only that it couples very weakly.
Jan
29
comment How Special Relativity causes magnetism
@ChrisWhite -- For what it's worth, most serious theoretical physicists believe that magnetic monopoles exist in the universe, but that they're very very rare. I don't think it matters for the issue under discussion though.
Jan
29
comment How Special Relativity causes magnetism
I didn't say that electricity and magnetism were "symmetric" in the sense that you're using the term. (Please re-read my answer, I was discussing asymmetry of pedagogical emphasis.) Any 6-year-old can tell them apart. I only said that the relationship between electricity and magnetism is not cause-and-effect: They are equally fundamental parts of physics.
Dec
30
comment Translating Electronic Bands back to first Brilluoin Zone
I recently put an explanation and image on wikipedia on this topic: See en.wikipedia.org/w/… and the red+blue graphs on the right.
Dec
22
comment Temperature of fusion in the Sun vs. fusion in controlled experiments on Earth
You should also add that fusion reactions on earth have an extremely low duty cycle (the reactor is turned on for a tiny fraction of a second, off for a long time, ...), whereas the sun keeps it going continuously.
Dec
4
comment How can I change the angle of a laser without mechanical aid
ditto a spatial light modulator with phase control
Oct
31
comment Magnetic monopole bound state
You can say "there might be multiple different particle species with magnetic charge, but having different mass, spin, lepton number, etc."---and you can say that without discussing duality transformations. In fact, I just did so! And incidentally, this fact, while true, doesn't mean that the original question is unanswerable. Physicists have pretty specific ideas about what magnetic monopoles particles are likely to look like, for example 't Hooft–Polyakov monopoles etc.
Oct
31
comment Magnetic monopole bound state
I think you're being pedantic by discussing duality transformations. There is no actual ambiguity in what we call "electricity" and "magnetism", because there is a universally-accepted convention that resolves the ambiguity. Every physicist agrees: Electrons have an electric charge, and my refrigerator has magnets on it, not the other way around.
Oct
29
comment Polarization of Light Without Reducing Intensity
I don't get that paper. If the two polarizations get sent to the same direction, then it violates thermodynamics and the paper is wrong. If they get sent to different directions, why not just use a beamsplitter cube and a half-wave-plate and some mirrors to accomplish the same thing with >99% efficiency? I don't see a clear discussion of this in the paper.
Oct
16
comment Non-uniqueness of the k-vector in Bloch state
I made a wikipedia image on this topic: commons.wikimedia.org/wiki/File:BlochWaves1D.svg See the caption too. Does that help? If not, what's confusing about it?
Oct
9
comment Polarization of Light Without Reducing Intensity
If you combine a horizontally and vertically polarized beam using a beamsplitter, you can with linear polarization, or circular ... or unpolarized! How do you propose to avoid winding up in the same unpolarized situation you started in?
Oct
2
comment Polarization of Light Without Reducing Intensity
Yes, that's exactly right!
Sep
29
comment Do photons emitted from a LED show bunching?
Yes, if you have a giant LED but you ONLY look at the 0.1% of photons that are coming out from a particular part of the chip and/or coming out in a particular direction ... then that subset of the photons can have bunching or anti-bunching.
Sep
17
comment How does DC current work in Cathodic Protection?
I would say that the important thing is the DC voltage, not the DC current. The voltage prevents corrosion, the current is an inevitable side effect of applying a voltage.
Sep
13
comment What is the pressure of a charged gas?
@BlackbodyBlacklight - The "novelty glass globes filled with fluorescent plasma" is not an example. Even if it were completely ionized, it would be a mixture of positive and negative ions.