Attending a laser show recently, I wondered how the effects were achieved.
Obviously, mirrors and lenses can manipulate light to produce animation.
But those are “mechanical” devices and they use moving parts to create their effect.
For example, electrons can be manipulated via magnetism which doesn’t necessarily require moving parts.
Is there any way to achieve the same effect for photons via magnetism (or some other non-mechanical mechanism that doesn’t require moving parts)?
You can manipulate the devices that reflect light with things like liquid crystals, which switch much faster than mechanical devices. You can also control when you emit light precisely - a lot of the lasers are driven with LED diodes which can change state rapidly, at least in terms of human perception.
There are also mirror arrays that use micromachined mirrors that can change states in milliseconds. Such as these : http://en.wikipedia.org/wiki/Digital_Light_Processing
If you want to affect photons while they are in motion, well, only gravity affects them in the same way that electric fields do.
Phased array optics is probably the technology you’re looking for, though it doesn’t exist quite yet (for visible light–it’s in widespread use for radio).
You may also be interested in the various non-linear optical processes.
There’s been some work on electrically variable index of refraction using liquid crystals. That link goes to lens research, but one could use the same tech for beam steering.
Manipulating electrons with a magnetic field is arguably manipulating electrons with photons. Therein is the clue. You manipulate photons with electrons. An appropriate plane composed of electrons will reflect photons. A different geometry of electrons will diffract them, and a body of electrons in the right configuration can slow them down. These are respectively - mirrors, diffraction gratings and lenses. If you can dynamically alter the nature of the electron configuration without gross movement you can get what you desire. The above examples are good ones of these systems.
That was fun chacoguy. Thanks!
I think I understand what the OP is asking about, but the thought of mirrors and lenses being “moving parts” is making my brain tilt.
The OP is talking about mirror galvanometers, which do indeed physically move. Lenses are also typically moved (as in a camera lens) when the configuration needs to change. That said, there are ways (for lenses at least) to change optical properties without movement.
Not in the way you are thinking. When you influence an electron with an H field you are still physically affecting the same electron as it moves. When you transmit photons they do not traverse the glass of a lense. It transfers the properties of the photon into another photon that emits from the glass itself (kind of like a quantum Newton’s Cradle). The only force that will do that with a photon AFAIK is gravity so you would need to be able to make controllable local gravity wells. If you can do that, you are definitely eligible for a Nobel and I really want to see the lab…
Keep in mind I only pursue QP as a hobby; I’m not a Theoretical Physicist but have seen them on TV…
It’s not really well-defined whether it’s “the same photon” or “a new photon”. Photons are all interchangeable.
I think you use Photonshop… or iPhoton?
Interesting name/thread title combination.
There are LOTYS of ways to manipulate light. Mechanical means, with mirrors attached to motors, translation stages, galvanometers, and the like care among the easiest and cheapest, which is why they continue to be used. In our optics teaching lab when I was a grad student, the professor had built a cheap “laserium” by bouncing the beam from an inexpensive HeNe laser off of two mirrors, each attached to the shaft of a variable-speed motor. Nowadays you can go even cheaper with a diode laser.
I believe that Laserium, by the way, uses piezoelectrically-driven mounts. It’s mechanical motion, but on a small scale.
There are lots of ways to msnipulate light using electrical or magnetic fields, although what you’re really doing is manipulating the medium through which the beam passes. These effects generally affect the polarization state of the light, rather than the direction. But look up
Kerr Effect
Magnet-optic Kerr Effect
Pockels Cell
Faraday Effect
Voigt Effect
Zeemen Effect
A way to alter the direction of a beam without (large) mechanical effects is Acousto-Optics, in which you cause standing waves (or slowly varying ones) in a medium that forms a diffraction grating (due to changes in index with density or temperature or some other property) that diffracts the beam into different directions. The directional shifts generally aren’t large, though.
There are other methods, such as using two interfering high-coherence beams to “write” a grating in a block of material by altering refractive index, or inducing defect centers, or some such, and your beam of interest then gets defected by the grating. It’s all done with light. But the way you vary the grating frequency will often be controlled by a mechanically mounted mirror that alters the angle of incidence.
So, yeah, there are other ways to control the beam using ultrasound, electric fields, magnetic fields, and the like. But for large swings, it’s generally easier to alter things mechanically.*
*And that need not be simply moving a mirror. You can electrically change the charge on a film boundary that changes the curvature of a lens, altering its power. There are at least two manufacturers of such liquid lenses making such thinhgs commercially – it’s small-scale mechanical. A professor I knew made similar variable mirrors usinf tiny drops of mercury. There are lots of nano-scale MEMS mirrors that don’t move at all, to the naked eye, but which will redirect your light. Mechanically, but on a small scale. And so forth. Even among older technology there are liquid lenses that you alter the curvature of by adjusting the pressure of the liquid, or gas-filled curved mirrors
I should amend my earlier statement as I realized last night that even using gravity you would be, as CalMeacham succinctly put it, ‘manipulating the medium’. Gravitational lensing is a result of altering the space around the light, not the light itself.
With a sufficiently strong magnetic field, you could control light even in a vacuum. That’s because extremely high-energy photons can interact directly with each other through virtual electron-positron pair creation.
One might argue, though, that if you have such a sufficiently-strong magnetic field, it isn’t really a vacuum any more, but an electron-positron plasma.