Making a 50 um collimated beam on a budget

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In summary, the conversation discusses the need for a low-cost solution to produce a circular, collimated 405nm beam with specific diameter and output power requirements. The suggested method involves using a 405nm laser with single-mode pigtail coupled into a lens tube with an aspheric lens and plano-convex lenses. However, this method may be more expensive and there is a need for a translation axis to keep the image in focus for 3D objects. Suggestions for a long focal length lens and borrowing a 405nm laser are also mentioned. Another solution is a standard 4f lens configuration to telescope the beam, but this may have limitations due to diffraction.
  • #1
Mike_In_Plano
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Hello again,

My handy optics engineer has left the country leaving me with a problem that's over my head. I need a low cost (i.e. $500.00) solution to produce a circular, collimated, 405nm beam. My beam needs to be within the target diameter (+/-20%) from 0 - 4" from the output lens and have an output power of about 6.5 mW +/-2mw.

My first thought is to take a 405nm laser with single-mode pigtail coupled into a lens tube with an aspheric lens to collimate it and a couple of plano- convex lenses to reduce the collimation to .002".
This method is more expensive than I like, but it avoids having a pinhole / alignment fixture, which is also expensive.

Any ideas?

Thanks in advance,

Mike
 
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  • #2
It's been a while since I tried something similar, but if the laser is already fiber coupled, there should be a reasonably simple way to do this (but to be fair, your spec may be unrealistic). Maybe a ball or GRIN lens at the fiber output?
 
  • #3
Conceptual adjustment.

It appears that any efforts to re-collimate down to 50um is unrealistic.

Thus, I perceive my best option as focusing a circular image at some distance from my optics. This is unfortunate in that I'm attempting to expose 3D objects, and my current mechanical system lacks a translation axis to keep the image in focus as the object's distance varies from about 1-4 inches.

Given the need still achieve a 100um spot with roughly 6.5mw at 405nm, do I have any suggestions on how to achieve this on a $500.00 budget and what optical configuration would be most appropriate?

Thanks in advance,

- Mike
 
  • #4
Use a really long focal length lens; but then the focal spot will be bigger.

Also note that the nominal focal length is usually based on green light (~530 nm); it will be in the lens specification. So you will have to recompute the focal length for the 405 nm light Be sure to buy a lens that has good transmission for that wavelength! Fused silica has higher transmission as you near the UV than does BK7; but it costs a bit more.

Also a long focal length will increase the focal spot size, as well as the Rayleigh range. For a 2 meter focal length with UV light I got a 200 um spot size.

PS: Why not email your former optics guy, and ask his advice?
PPS: Or call tech sales support at one of the optics supply houses - they are very knowledgeable, and know all of the gadgets and their costs
PPPS: And the cheapest way is to borrow the 405 nm laser ...
 
  • #6
Provided your beam is collimated to begin with, a standard 4f lens configuration should be able to telescope the beam to whatever diameter you require, within the bounds allowed by diffraction.

Note that the narrower you attempt to focus/collimate a spot, the more it will diffract. This is a standard trade off that has no cheap solution unfortunately.

Claude.
 

FAQ: Making a 50 um collimated beam on a budget

1. How can I make a 50 um collimated beam on a budget?

There are several ways to achieve this, depending on the specific materials and equipment you have available. One method is to use a cylindrical lens to focus a diverging beam of light onto a pinhole aperture, which can then be collimated by another cylindrical lens placed at a specific distance. Another option is to use a diffraction grating to produce a parallel beam of light.

2. What materials do I need to make a 50 um collimated beam?

You will need a laser source, a cylindrical lens, a pinhole aperture, and another cylindrical lens or a diffraction grating. You may also need mounting equipment such as lens holders and mounts, as well as any necessary tools for adjusting and aligning the components.

3. Can I make a 50 um collimated beam without expensive equipment?

Yes, it is possible to make a collimated beam on a budget using alternative methods and materials. For example, instead of a specialized cylindrical lens, you can use a simple convex lens and adjust its position to achieve the desired collimation. Other techniques, such as using a lens and a mirror to collimate a beam, can also be effective and cost-effective.

4. What are the potential challenges when making a 50 um collimated beam on a budget?

The main challenge is ensuring precise alignment and positioning of the components to achieve the desired collimation. This may require patience, skill, and the use of additional tools such as laser alignment systems. Another challenge may be finding suitable materials or alternative methods that can produce the desired results without breaking the budget.

5. Are there any safety precautions to consider when making a 50 um collimated beam?

Yes, it is important to take proper precautions when working with laser equipment and potentially hazardous materials such as diffraction gratings. This may include wearing protective eyewear, working in a well-ventilated area, and following proper handling and disposal procedures. It is also important to carefully read and follow any safety guidelines provided by the equipment manufacturer.

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