Single beam gradient force optical traps, or tweezers, are a powerful tool for a wide variety of experiments in physics, chemistry, and biology. We describe how to build an optical tweezer with a total cost of ≈$6500 using only commercially available optics and mounts. We also suggest measurements that could be made using the apparatus.

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In this discussion we characterize the laser beam with a definite diameter. Typical laser beams propagating in the z direction have an intensity profile I(x,y)=I0exp[−2(x2+y2)/w02]. Best trapping is obtained when the waist w0 is approximately dobj/2.
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