cylindrical lens pair vs anamorphic prisms?

[planters]

It occurs to me, that your rather "unconventional" use of a right angle prism, might (by total fluke) have arranged for the incident angle, to be close to Brewsters angle (for red) on the way into the prism, thereby neatly obviating the need for an AR coating on the incident face of the prism.

If you rotate this prism so the beam exits in an upward direction........do the losses (reflected beam power) increase drastically.

Interesting point and worth a test just for the benefit of answering this question.

and also does it make a difference if one of the beams goes through a waveplate...is that not polarization?

This is also a good point. A wave plate will have no effect if the beam is not polarized. I am not aware of any diode laser that is unpolarized. They may exist, but I don't think so. The polarization comes from the extreme asymmetry of the emitting region. You can visualize it as laser light being emitted from the thin edge of a piece of paper. The P-N junction can be broad and wide, but it can't be thick.

Ok I need to ask you a question before giving an answer....because my lasers are combined by a PBS cube...does that not make it polarized?

The fact that you can combine them at all proves that the diodes that went into the cube were polarized. The combined output is then no longer polarized. It is now a mix of two orthogonal, polarized beams.

I wish i had a power meter to confirm the exact results

Oh boy! Stop right here. You NEED a power meter. It is the single most important piece of equipment you will use after a volt/ohm meter.

[planters]

Planters would it be ok if I sent you one of these prisms to test?

What are you wanting to test for?

If you can, try to place all the things you want to say in one or two posts. It is more difficult to read when you spread the messages you are sending over so many posts.

Keep looking for power meters. Most of what you are doing is experimenting and this is very impractical and largely guess work when you have no means of quantifying what you are doing. You are talking about losses for one system vs losses for another system and you have no way of measuring this.

[planters]

You see what I meant about the importance of removing the hot side...heat?

Take a look at this video. At about 4 min I discuss the type of box that I routinely use. This can be done with hand tools if you work carefully. Stay away from wood if you can. It is porous. A forstner bit in a hand drill can partially drill through the side to help secure the window, but you could simply use RTV silicone to glue the window directly to the side. The "O" rings are very useful to provide a seal that still allows you to easily access the diode for adjustment.

Another thing that you need to consider is that the diode mounted collimator lens will change its best focus position as the temperature is lowered. At very low temperatures you will need to trial and error adjust this a couple of times. This is a bit of a hassle because whenever you open the box you have to wait until the diode reaches near room temperature in order to avoid condensation.

https://www.youtube.com/watch?v=RDfwJw7S_CE

P.S. You can speed the process considerably be temporarily, reverse biasing the TECs.

[kecked]

Do you think adding a humidity sensor would help? This way the drive stops cooling before the condensation? KISS comes to mind here.

[planters]

KISS comes to mind here.

I like to KISS a lot. What I mean is that first I engineer something, then I work out the bugs, then I build it, then I modify...modify...modify. It is never really done. Rather, I asymptotically improve until I loose interest or move on. But, and this is important, I would never come up with really good and effective solutions without burning through some less practical ones. Luck is a poor design strategy.

With that said, I would not do that. Condensation is a progressive thing. As the item cools condensation will begin before it begins to become grossly obvious and will increase in speed as you cool further. It would be difficult to draw the line. If you are using large, two stage TECS with water cooling, you will be wasting a lot of potential if you only cool to the point of free air condensation.

The box works really well. It does not have to look sexy, just be air tight. Even when cooled to -35C it prevents condensation on the diode. You will see a small amount on the coldest part of the TEC surface, but this is a good thing because this coldest surface is acting as a getter, capturing and holding all the residual moisture within the box.

[kecked]

For clarity I was referring to myself in regards to kiss! Thanks for the reply as always.

[planters]

For clarity I was referring to myself in regards to kiss!

I knew that. I couldn't resist. Despite what some may think, I read carefully and I'm pretty subtle.

But now, the Devil is claiming payment.

Try something new. Really new and exciting. It doesn't have to be expensive, it's much better if it isn't. It is even valuable if it doesn't work, because it will save others wasted time.

Then share it.

[catalanjo]

@ "If I turn the prism in a certain way I can get the beam to expand so much that it has a negative mrad or very long focal point but it will be impractical to use with scanners " ......

I still can't figure out how "king4quarter" manages to "focus" a beam using a prism!

Cheers

[planters]

Exactly like the red line Click image for larger version. Name: Untitled.png Views: 4 Size: 11.1 KB ID: 51376

You cannot focus light with a prism. The flat surfaces will not redirect the ray paths that pass through it, differently, based on their location across the diameter of the beam. A curved lens is actually an infinite assembly of infinitesimal prism segments, each with a varying angle of incidence relative to the incoming beam.

The increase in the diameter of the beam as it passes through a prism comes from the greater distance the bottom of the beam (in your image) travels through the glass after the first refraction, relative to the top of the beam before each encounters the second surface. The angles are the same.

[acheter]

Laser beams are different, depending on the type of a laser (diode vs. DPSS), laser power, the methid of collimation, and homogenization applied. Not all applications require a perfect beam, but those with high focusability requirements need either a beam from a DPSS laser or a well filtered beam from an SM laser diode.

At Integrated Optics we offer several types of beam collimation. For demanding applications we always recommend SM/PM fiber coupled lasers, wheras fiber coupling is offered at very competitive rates, as compared to competition and provides much higher flexibility and virtually perfect beam quality.

DPSS lasers have better beam quality is most aspects, as compared to diode lasers but are more expensive.