Laserbtb 515nm 5mw

[Cyparagon]

Since the diode output is polarized, you would be able to employ a transparent "window" optic properly oriented in the beam of your 520 at/near Brewster's angle, changing the angle of incidence until you get a beam of the same power as your other laser, for visual comparison

Let's not be silly. A window isn't going to block >60% of the beam.

 

[svdr]

Let's not be silly. A window isn't going to block >60% of the beam.

THat's not what he meant. He talks about Brewster's Angle. It's not about the window blocking light, it's about the part that gets reflected by it.

 

[Cyparagon]

Okay, but a window isn't going to reflect 40% either. You would also have multiple beams from the multiple reflections.

edit: I bought one. Should be here in 3 weeks or so.

 

[Teslanium]

FYI all, polarized laser beams are very efficiently reflected or refracted at transparent optical window surfaces depending on the polarization angle of incidence. See here:

Brewster's angle - Wikipedia, the free encyclopedia

If you have a laser with a polarized output it is relatively easy to find the polarization direction by aiming the laser at a piece of flat clear glass at an angle, say 45-60 degrees. As you rotate the laser on axis you will notice that the beam is more or less reflected from the surface. By increasing/decreasing the angle of incidence of the laser and repeating the rotation, you can find Brewster's angle for that wavelength, at which as the laser is rotated, the beam will alternately totally refract through, or be totally reflected from, the window surface. Try it yourself, it is a fascinating thing to see. You can then mark the polarization direction on your laser for future reference if needed.

This is also how a polarized output is obtained in gas lasers. You may have seen those funny angled windows on the ends of gas laser tubes? They preferentially pass light of a single polarization direction with almost no loss, while light at other polarization angles is more or less reflected out of the resonator cavity. This ensures that only polarized light passes back into the cavity and is further amplified, giving rise to a polarized output beam.

This is why I made the suggestion to Pman of simply using an optical window at/near Brewster's angle to adjust the measured beam power for visual comparison with another laser of lesser power. It is a very easy and elegant solution.

T.

 

[Cyparagon]

Wow. Just tried it - That worked a lot better than I expected it to. I'm familiar with brewster's angle, but I guess it never occurred to me it could be variable. Thanks for the explanation. +4.

 

[Pman]

I will have to try this as it sounds fascinating.
Thanks for the info. Tes
+REP

 

[Cyparagon]

It's good. Review here.

 

[LASER66]

The 515nm is a lower grade diode of the PL520. These is a 30mW version (50 MAX) vs. the 50mW (80mW MAx) of PL520. It was a stepping stone diode, still available from OSRAM. Sold in higher volumes likely in China for low cost products like pointers, etc.

 

[offroadfreak8582]

The 515nm is a lower grade diode of the PL520. These is a 30mW version (50 MAX) vs. the 50mW (80mW MAx) of PL520. It was a stepping stone diode, still available from OSRAM. Sold in higher volumes likely in China for low cost products like pointers, etc.

The output is just less. I would not call that a lower grade diode? I would call it lower grade if it would die sooner or something.

greetings,, :san: