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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?

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  • $\begingroup$ 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. $\endgroup$
    – Andrew
    Apr 3 '17 at 8:48
  • $\begingroup$ With a long enough lever, as small as you want though only in one dimension. $\endgroup$ Apr 3 '17 at 8:51
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    $\begingroup$ 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. $\endgroup$
    – alephzero
    Apr 3 '17 at 10:44
  • $\begingroup$ 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. $\endgroup$
    – Robin
    Apr 3 '17 at 12:22
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    $\begingroup$ 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? $\endgroup$ Apr 3 '17 at 13:32
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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.

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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.

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  • $\begingroup$ Additional engineering will be needed actually make the experiment happen, but I needed to know how fine of a moment I had available. $\endgroup$
    – Elenesski
    Apr 3 '17 at 17:35
  • $\begingroup$ Pricing is going to be the driving factor in that case. Nanometer is definitely possible, though difficult. You may want to consider a rougher movement, but higher accuracy measuring tools. I.e. less concerned with what position you've moved to but are highly accurate on measuring the exact position. You might find a tool that has +-0.001mm position precision, but could then measure the accuracy of that position to 10-9m if that makes sense $\endgroup$
    – Diesel
    Apr 3 '17 at 17:44
  • $\begingroup$ Micro meter precision isn't fine enough. I'll need 25nm precision. $\endgroup$
    – Elenesski
    Apr 3 '17 at 19:57

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