1

I am trying to design a science experiment involving lasers and want to know if what I am planning to build it technically feasible.

Part of the experiment requires that I make tiny nanometer changes to the apparatus in order to lengthen the time it takes for a beam of light to travel a particular distance. I need to be able to control the distance very accurately because I have to make calculations based on how far the light is travelling.

I'm guessing the weight of the apparatus is roughly a kilogram. What's the smallest reliable distance I can move the apparatus with the specifications I have?

Elenesski
  • 111
  • 2
  • Somewhere between 1cm and 1nm depending entirely on your budget. What's the smallest movement you have the equipment to measure? Because you're not going to be able to move less than that for a start. – Andrew Apr 03 '17 at 08:48
  • With a long enough lever, as small as you want though only in one dimension. – ratchet freak Apr 03 '17 at 08:51
  • 1
    You also need to consider how much the apparatus will move "on its own", because of air currents, temperature changes, random electromagnetic fields, random vibrations (anything from "people walking about in the lab" through "traffic on the road outside the building" to "earthquakes"), etc, etc. – alephzero Apr 03 '17 at 10:44
  • For small displacements have a look at piezo stacks or piezo actuators. Usually the manufacturers will give you a voltage vs. displacement chart or something similar. – Robin Apr 03 '17 at 12:22
  • One atom width. Take a look at magnetic traps and laser traps, etc. , tho' i suppose that answers your question but not your need. – Carl Witthoft Apr 03 '17 at 13:31
  • 2
    Don't move a 1-kg item. Figure out how to move just the reflector or whatever is actually changing the path length. But how are you going to measure the elapsed time -- attoseconds? – Carl Witthoft Apr 03 '17 at 13:32
  • you might want to add more details about your experiment. a "particular distance" can be meters when you discuss train travel, or dozens of kilometers in space travel. but for precision machining of medical or aerospace devices, millimeter accuracy isn't good enough – Mohammad Athar Apr 03 '17 at 15:01
  • @Mohammad, The total distance of the movement won't be more 3-4cm. – Elenesski Apr 03 '17 at 15:06
  • @Carl, distance of the laser is critical, it's not just an angle thing. As for the 1kg weight, it's the weight of the reflectors and the bracket that holds them. I used 1KG as the upper limit, but the actual weight is unknown, so I err'ed on the side of too much, than too little. The actual weight might only be 250mg. – Elenesski Apr 03 '17 at 15:09
  • Maybe this question will fair better on the Physics S.E., there might be more folks there with experience with such experimental apparatus? – J. Ari Apr 03 '17 at 15:13
  • @Andrew The distance to move is as small as I can reliably go. At least 1/20th of the wavelength of an argon laser (488 nm), so roughly 25nm. is my guess, but it's an experiment, so I might need a resolution finer than this. – Elenesski Apr 03 '17 at 15:17
  • @alephzero that's very interesting ... natural movements, I'll keep that in mind. – Elenesski Apr 03 '17 at 15:31

2 Answers2

1

Positioners with resolution on the order of 1-10 nm are totally doable. Here's one example: 3-Axis NanoMax Flexure Stages

When you buy this with the closed loop piezo option, 5 nm resolution is possible and it has a 1 kg load capacity. Only $3000 too. Getting down to 0.1 nm resolution is certainly possible, and is in fact routinely done in the world of atomic force microscopy. However, you may have to sacrifice total travel, load capacity, or cost in order to get there.

DiaperHands
  • 772
  • 1
  • 7
  • 22
Daniel K
  • 2,676
  • 9
  • 14
0

This will depend on the setup of your system and how easily you want to be able to make the movement. Off the top of my head though this sounds feasible.

The setup I would imagine, or start from is moving your mass laterally (parallel to the ground). Having it sit on low friction bearings or bushings of some sort. Then having that position controlled by a fine pitch lead screw. There several options available for nanometer precision lead screw type tools (I found Nano-Gauge off a quick google search, but there are several dozen others as well). Cost will likely not be that cheap.

You could design and control your own system which would be cheaper, but calibration and the time to build it will be much much higher than buying a COTS (COTS - commercial off the shelf) part.

Nanometer precision is difficult but doable. Verification and calibration will be tricky. Temperature control and air pressure of your system will be of a concern at this scale, doable, just tricky.

Diesel
  • 629
  • 7
  • 21