Why no green focus lens?

[tsteele93]

I understand greens are a whole different animal of laser. I have read and understand this page.

Dissection of Green Laser Pointer

That said, many of the 532's we have include a "focus lens."

Why aren't there any "G-1's" for green in this scenario?

Would it be beneficial to have a better lens with good coatings of green here?

P.S. After reading that article, I'm a lot more inclined to try and combine some parts from some greens and see if I can build one from a dead laser. I'm amazed at how imprecise it seems he could be and still have it work!

 

[RA_pierce]

I understand greens are a whole different animal of laser. I have read and understand this page.

Dissection of Green Laser Pointer

That said, many of the 532's we have include a "focus lens."

Why aren't there any "G-1's" for green in this scenario?

Would it be beneficial to have a better lens with good coatings of green here?

P.S. After reading that article, I'm a lot more inclined to try and combine some parts from some greens and see if I can build one from a dead laser. I'm amazed at how imprecise it seems he could be and still have it work!

The "G-1" lenses are designed for two purposes:
1. Moar power
2. Thinner beam

More power is accomplished by using a lens that captures more light (it sits closer to the diode and has a high NA).
Thinner beam is accomplished by using a lens with a short focal length.

G-1 lenses are not needed for green lasers because:
1. Green laser modules are pre-assembled with all the necessary optics. That is, green lasers are not made in Aixiz modules that require an additional focusing lens.
2. DPSS lasers have different beam characteristics that require more than one optic to get the beam typical of green laser modules. Straight from the crystals, the green beam is much less divergent than the beam straight from a diode, so it calls for a different method of collimation. That is why green lasers typically use at least two lenses: 1. a bi-concave lens to expand the beam, 2. a convex lens to force the light into a parallel beam.
3. Not all green lasers are designed the same, so creating a "one-size-fits-all" lens for greenies may be difficult if not impossible.
4. Custom glass can get expensive and may not be worth the extra cost for most people.

When/if green diodes become common you can expect a G-1 lens for green wavelengths or maybe a broadband coated lens for 400-660nm

 

[tsteele93]

Thanks for the thoughtful response. The only thing that I am not sure on is that there are some greens with adjustable optics as the last lens in the system. I have one that I bought here used...

Actually, it is this laser...

LZMN - 532nm 200mW Focusable Green Laser Pointer

The last lens in the system moves closer to or farther from the diode to focus the beam.

I guess that based on the reviews of the various G-1 lenses out there, it is very possible that the 405 would be fine in one of these.

I may have to order a bare lens assembly from Jayrob and test it.

:thanks:

 

[Sigurthr]

Green DPSS topology is usually:

Pump Diode -> focusing lens(es) -> MCA -> negative lens (or short FL positive) -> positive lens.

The last two lenses form a beam expander, by moving the last lens closer or farther away you can vary the focus of the laser.

 

[DTR]

The G-1/G-2's should work very well with green as the coatings which I am pretty sure it is the same on the G-1 but the G-2 datasheet shows it is coated for 400nm-600nm which is one of the reasons they work well with the 635's. So if the green diodes start becoming available I can see them being used commonly.

 

[jayrob]

Second that...

But about the DPSS green modules, I have had them in focus-able hosts before, and personally did not like it.

If you remove the final lens from the front of a green module, you can mount it so that it can focus the beam.

But I found that messing with the focus only took away from the quality of the output. Because the thin beam and good divergence of a DPSS module is so nice, that trying to focus it will result in less than desired results... (IMO)

 

[InfinitusEquitas]

I haven't tried with a g2, but a 405 g1 lens works great with everything I have on hand, up to ~660nm.

Obviously the 650 g1 is better for the reds, but g1 is a huge improvement over the standard lenses.

 

[jayrob]

Agreed! :beer:

I was just talking about whether you want to make a DPSS thin beamed green 'focus-able'...

Some people want to try and focus it for burning maybe, but personally, I choose a fixed focus for DPSS. (I'm guessing that most would agree)

 

[InfinitusEquitas]

Some people want to try and focus it for burning maybe, but personally, I choose a fixed focus for DPSS. (I'm guessing that most would agree)

Yup, I always leave my lasers focused to infinity, especially with dpss... much easier to burn with a 445nm if that's what you're after.