Institute of Atomic-Scale Engineering


The "Optical Assembler," aka the "Food Replicator"

  Forrest Bishop

Interview of Forrest Bishop by Bill Spence

December 10, 1996

[[Note: This is a partial description of an idea I originally had several years ago. It has not

proceeded past the conceptual stage, and is offered only for your entertainment.

Forrest Bishop ]]

F = Forrest Bishop

B = Bill Spence of NanoTechnology Magazine

B: Forrest Bishop on a different kind of replicator, one that does not involve robot arms.

 F: Right.

B: What does it use to manipulate?

F: This is very similar to what was on the original Star Trek episodes. They called it the "Food Replicator". It was depicted as a box in which things would simply appear when you wanted them, and so I use that name because it has some of the same properties.

B: Is the food replicator...Earl Grey tea or ...general country doctor?

F: Yes, this is very speculative technology; itís not a for-sure thing; itís more out on the fringe. The central idea is ...

B: Well, first, let me ask you, what is a replicator? It manipulates atoms in foods and puts them in specific places where you want them to be?

 F: Yes, to build an object, you want to create an object thatís atomically precise. So, some kind of device to do this.

B: And one kind of system is basically robot arms that physically move things.

F: Yes, thatís the most popular version.

B: And this is completely different?

F: Yes, it uses electromagnetic energy in a structured electromagnetic field to do the same thing.

B: To move individual atom, more than one atom:?

F: Individual atoms, molecules, small structures.

B: Small structures?

F: Yes, possibly.

B: What does this device look like? How does it function? How does it work?

F: The central idea is to create a structured electromagnetic field that is variable in real time. The atoms are moved around by the electromagnetic field.

B: Atoms can be moved around by electromagnetic field?

F: Yes.

B: What frequency are we talking about?

F: Roughly, light, visible spectrum, about [600 nanometers] depending on the particular atom, depending on whether youíre trying to ionize it or not.

B: So youíre pushing atoms with light?

F: Yes. This is already being done now. Itís partially based on ...

B: Trapping an atom with lasers, right?

F: Yes. This has already been accomplished. In this environment, imagine a flat plate of emitters that are--each emitter is addressable; each emitter is very tiny. By changing the timing--you have a row of them--by changing the timing on them, you can create a wave front thatís steerable, just as in a phased array radar.

B: OK. Light frequency.

F: Yes. So, a planar array of these --

B: A whole plane.

F: A whole plane consisting of a grid of emitters can construct a beam of the frequency of your choice. The frequency can be varied over [time, space, and phase] also, and that way, youíre creating a beam that is coherent or different frequencies in different parts of it, thatís steerable over the half-sphere. Ideally, you want to use emitters as small as possible--quantum well lasers are one possibility.

B: Are they attainable?

F: They are.

B: In frequency?

F: Thereís already existing devices that are wholly suitable. These are also called artificial atoms for the reason that you have -- in them, you have an electron that is trapped in some kind of a potential well, which then [radiates] as the voltage varies the size of that potential well.

 B: Oh, itís [an] orbiting electron. Instant frequency of what itís going to throw off in radiation?

F: Thatís right.

B: Pretty clever.

F: Yes. These are existing devices. Currently, researchers are trying to make arrays of these which is going to be difficult, from the one emitter ________one its neighbor.

B: Why?

F: Because these are tiny [quantum] mechanical properties that youíre playing with.

B: So the radiation field of one would affect the other?

F: Yes, you could put it that way. The electric field of the voltage thatís being used to adjust the potential well in one is affecting its neighbor as well.

B: How would you overcome that?

F: In this idea, the way to overcome it, if you will, is simply through computation [of] the wave function [of the entire planar array].

B: Would it take into consideration how one field affects the other? And changing whatever parameters necessary?

F: Thatís right. It would take a massive amount of computer power.

B: OK, so you have a plate.

F: Yes, behind this plate, you have -- the equivalent of millions of supercomputers are needed to run this.

B: Oh, that much power?

F: Thatís right. Youíre running in real time, and in this case, real time means youíre obtaining a type of _________ range, so itís a huge computational problem that require nanocomputers in order to realize it.

B: I see. So youíve got one plate with a hemisphere thatís completely controllable where the wave is, and even what frequency it is. Then what?

F: Then what? Now, imagine two of these plates facing each other. A quantum well emitter is also a receiver. A wave that comes in will cause a electron or quantum well emitter to transition to a level, if it is the correct frequency, which it will be, because it is part of the same system to design that in. Therefore, you can create a standing between two plates. You can steer that wave; you can, by phase shifting between the two plates, you can cause the nodes, the standing of the nodes...

B: Where thereís energy and where thereís no energy.

F: Yes, it vibrates something down, kind of like a violin string, and there are certain points on it that where the field strengths donít change, called the nodes, and at those points is where you place an atom and have it stay. Itís kind of similar to, if you take a board and want to saw on it, sawdust will bounce up and down on the boards and collect in the nodes, which is the places on that board that arenít moving up and down. Some parts of the board move and some stand still, and thatís where the sawdust collects. Itís a little bit like that.

B: So you could have atoms that would stay in the low-energy spots.

 F: Yes, which is the nodes.

B: But you could move those nodes, is that correct?

F: Right, by phase shifting between the two plates, you could move the nodes back and forth, and the atoms, theoretically, will move with the nodes.

B: Aha! So, you can move atoms in one axis.

F: Yes, one axis.

B: So far.

F: So far. Now, make it six plates. Now you can construct a three-dimensional, fully specified, electromagnetic standing-wave field. You can move it, and the atoms that are in it can be moved, shifted, in space.

B: Relative to each other?

F: Relative to each other, and relative to the box.

B: A lot closer together, if need be, or want?

F: Youíd want it to be.

 B: Yes, I guess you would want it to be.

F: Yes, the idea is to inject an atom and have a wave front set up at that point that catches that atom, or small molecule, or what have you, perhaps you want to hit it with high energy to ionize it, to create a radical group, and then you use the standing waves to move it, in three dimensions, over to where you want it, and theoretically, cause a reaction.

B: Oh, in other words, bring it closer to another atom or molecule and cause a reaction.

F: Yes, [close to the structure] youíre building. Cause a reaction.

B: And because you have so much resolution, you could inject lots of atoms at one time in lots of places.

F: Because you have lots of computational power, you should be able to do that. Every time you place an atom in this electromagnetic field, its field interacts with that field and, in principle, you can deduce the location of that atom by...

B: By its shadow?

F: By its effect on the overall field.

B: OK, so you constantly know where the position of all the atoms are, in real time?

F: Yes, like I say, this is getting kind of far out there. Another problem is the wavelength is, say, 500 nanometers, which is much greater than the positional accuracy required for reactions. However, by time-averaging the position of that atom, you should be able to deduce its position to a small fraction of a wavelength, in other words, to the resolution required for positional chemistry.

B: All right. So, what weíve got here is a box that you can inject atoms into and grab them with standing, very complex lightwaves, and literally move them around independently and get them into position to go into place. As opposed to robot arms, youíre using lightwaves, energy. It sounds very exciting.

F: And the higher frequency lightwave can be used [to knock] an electron off an atom to create a radical group, and at the desired time.

B: Oh, so, itís more reactive; can jump into...

F: Remember, I was saying the plane consists of tuneable quantum well lasers that have a spatial frequency distribution so that you can address that atom with the UV ray you want.

B: Sounds pretty utilitarian to me. Itís very useful.

F: Yes, itís a lot of speculation. It may or may not happen. Thereís some research and ideas that are similar to this already being done, so...

B: Briefly, what is that research?

F: Well, I just learned of a fellow--I think heís simply conceived it--with what he calls an "optical crystal"--I think thatís what he calls it--and it is kind of the same idea, of having a three-dimensional standing wave and placing atoms in the nodes, but not shifting it, but placing atoms in the nodes such that they form a lattice structure thatís like a crystal, except the atoms are actually separated quite a distance, at least one wavelength of light apart, but theyíre in a lattice. Now, as Iíve said before, the presence of those atoms alters the field, alters the electromagnetic field in spots, and therefore, gives it a new optical property that it didnít have before those atoms were there.

B: And itís detectable.

F: Yes. For instance, the index of refraction would be different than if it was a box of [just] electromagnetic [energy]. And so by, for instance, changing the frequency, youíre changing the lattice spacing, youíre altering .. the [optical] properties of this volume ....

B: With this Optical Assembler...

F: Thatís a good name for it.

B: What do you feel like you could build? Anything? A cup of Earl Grey?

F: No, itís so speculative that Iím already out on a limb, and I donít know how much further I want to go. Conceivably, anything; practically, thereís a lot of unanswered questions. Somewhere between there.

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