Need waterproof 1.5mw laser built

>>Wouldn't the fiber ruin the beams collimation?<<

Been thinking about that, too. It comes to me that it may be possible to focus the beam at the fiber's business end. A bit of construction work may be needed.

This is how I see it; a laser emits coherent light that can be collimated into producing a beam of light that can, unless scattered by outside forces stay as a beam forever. When you run it through a fiber the photons would bounce around ruining their coherency and it isn't possible to reverse that so now amount of optics could turn the light back into a laser beam. The light exiting the fiber would basically be a single wavelength LED.

Someone correct me if I am off on this.

Hmm, I would consider maybe trying one of these:

Amazon.com: DicaPac WP410 (10.5x16.0cm) Small Zoom Alfa Waterproof Digital Camera Case with Optical Lens (Clear): Camera & Photo

Otherwise, underwater flashlights do tend to be kind of larger.

That would work great but it would also insulate the laser so you would be relying entirely on the heat capacity of the heatsink.

I still think using a small metal project box to house the diode and heatsink and driver and the power supply be kept out of the tank would work best for size and duty cycle.

Maybe, but then you're messing around with a wire to the power source outside the tank...

A beefy copper heatsink would work to have the laser on for a while, and if the heatsink/host made direct contact with the bag, some heat would still dissipate to water.

If the goal is to run a laser for a long time... larger host, or your solution would work best. If the goal is to be able to use a laser underwater for 2-3 minutes... the bag is nice and cheap.

Its quite easy to waterproof wires and the power source could easily be kept above water level when in use so it would be pretty safe especially if you put the wires themselves inside surgical tubing.

The box would mean a small heatsink and a small unit inside the tank and near infinite duty cycle(if made well enough) but would require more designing and build work but cost wouldn't really be much higher. Its a tradeoff. The bag idea would mean less time and money but you would have to be careful with duty cycles and NEVER allowing the beam to touch the bag itself.

Wow!! You guys are really getting into this! Thanks for all the great ideas. I just plan to use the laser to kill one aiptasia at a time. I don't want to have my arm in the tank for more than a minute at a time since I will be standing on a step ladder and leaning over into the tank. Also, a couple fish are semi poisonous, so I am just fine with the short cycle times of a minute on and a minute off. I still think my best bet will be to order a waterproof laser from O-Like. Thanks for all your input!!

I agree, but he needs no coherence, he needs high powered focusd light to kill anemones or so. Medical lasers are focused also after they emerge the fiber

exactly
also why would you use Glass Fibre if it would just destroy the laser beam...

svdr said:

I agree, but he needs no coherence, he needs high powered focusd light to kill anemones or so. Medical lasers are focused also after they emerge the fiber

Click to expand...

Um, the point of coherence is the whole reason to using a laser in the first place.

No offense bro but, medical lasers are many thousands of times as expensive and using parts with tolerances and grades incomparable to what we use thus irrelevant.

IMO, fiber is just out so it goes down to designing a laser to fit inside a camera bag or the system I mentioned or buying a "waterproof" laser from o-like that odds are will be sadly underpowered and may not even be fully waterproof to begin with.

Side note on part of why I dislike o-like, I am now on about 5 months waiting for my laser that was delayed due to an error on their part and supposedly reshipped over 2 months ago. That and most of what I hear about them is similarly disappointing and includes lots of dead lasers.

If you build the laser in a project box with a window, you can focus the laser to a certain point before sealing the box, and then just move the laser backwards and forwards in the water to focus the dot correctly on the pest. That way you don't need to build a focusing mechanism outside of the laser, making the build a lot simpler.

So long for the pests:

:lasergun:

Others are working with fiber, though.

from photonlexicon :

I can get my hands on some 3mm fiber. Is it possible to focus the beam down and at the focal point, inject the light into the fiber, at the other end, collimate the output from the fiber? Please correct me if I am wrong, but would this not give you a near TEM00 beam?

and :

...the fiber does not improve the beam. It can't alter the mode of a beam already generated. Even though what happens in a fiber is too small to see there is no magic occurring within the fiber. To help visualize this draw this out at a highly enlarged scale and trace a few rays from a diverging diode through a positive lens and into a fiber. The zig-zag rays will reflect due to total internal reflection as they pass through the fiber and as they exit a second collimnating lens will return the beam back to it's original diverging profile. The small entrance aperture of a fiber is used to act as a spatial filter to remove splash and non-uniformity

>>medical lasers are many thousands of times as expensive and using parts with tolerances and grades incomparable to what we use thus irrelevant.<<

I was just playing with the idea. Essentially, a medical laser is about a laser source, a glass fiber and a focussing unit. Can't see why a low tech 'copy' wouldn't work.

I think it is doable if you put the diode at the entrance side of the fiber, and the lens at the other side. That way you collimate the beam when it leaves the fiber.

@svdr Please do not double post, it is frowned upon in this forum, you could have put everything in the second post in the first one!

Yeah, I Know, happened accidental. Sorry for that

I would like to see it actually done. From my understanding the beam would lose its laser like properties due to the internal reflection as mentioned by the second quote and as far as I know the lenses could produce a laser like output but at the expense of most of the input power. Think of it this way, the photons start off going fairly straight all parallel to eahother but then you force them into a tube with reflective sides so they end up hitting the sides and bouncing off the walls and down the tube. The light exiting the tube would be scattered and would have lost all the uniformity it began with. Then you put it through some lenses but here is the thing, would lenses be capable of redirecting all of the infinite possible angles that the photons are going to be exiting from the tube in? Wouldn't this mean we could use the same lenses to turn any monochromatic light source into a beam that's just like what we get from a laser diode?

I might be off on some things since this is all just theory and I am very over tired from working all day. I really would like to see this tested or it actually in use because I could think of near infinite uses for such a thing if it is true.