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5

Yes there are. All you really need is for energy to be injected into a system, and for the particles to linger for relatively long periods of time in some excited state. For example, if you have states $A$, $B$, and $C$ in order of increasing energy, natural pumping might work well for $A \to C$ and poorly for $B \to C$. Suppose $C \to B$ occurs rapidly via ...


4

The underlying principle is to use interferometry and the Doppler effect to remotely measure the velocity of a reflecting surface. When a moving object is illuminated with coherent light it reflects it with a wavelength shift proportional to its velocity. This is the well-known Doppler effect. The frequency shift relates to the source's velocity as ...


3

The divergence of the signal is closely related to the angular resolution of the "antenna" (lens, reflector, ...) you use. This will in turn be a function of the size of the source in relation to the size of the lens - or in the limit, the ratio of dish diameter and wavelength (the familiar $\frac{1.22\lambda}{d}$ relationship) Typically this means it is ...


3

The diagram you want to use looks something like this: Depending on how much attenuation there is in the membrane, you need to consider the potential of multiple reflections (or not). I actually analyzed this problem in some depth - considering not only the intensity of reflections on the different surfaces, but also multiple reflections and even the ...


3

Just a guess, but those rings look to me like Haidinger fringes. When monochromatic light falls on a thin, transparent plate or film, some of the light is transmitted and some gets reflected back, then reflected forward again, from the two surfaces. The reflected light interferes with the transmitted light. Whether the interference is constructive or ...


2

Depending on wavelength, just with an aperture diffraction will kick in few cm after the aperture, and you'll get rings opening up with further propagation. For some applications that could be ok, especially if you use the beam right after the aperture. Practically, the way I would change the beam shape from elliptical 2x4mm to circular 1.5mm is putting in ...


2

We'll need a bit more info about your tach. Is it pulsed? Any idea about the coherence length? But in the meantime, you don't need a slit one wavelength wide. A couple of razor blades (use 'em because their edges are clean and sharp) mounted edge-to-edge, as close to parallel as you can get, will produce a diffraction pattern once they are maybe 1/4 ...


2

In fiber optic communications, the linewidth of the source often affects the bandwidth of the transmission medium (fiber). This is because the glass of the fiber is at least somewhat dispersive, meaning that different wavelengths of light propagate at different speeds along the fiber. Because of this, if you launch a narrow pulse of light (representing a ...


2

I can identify the "rings of a tree" as a typical Airy function corresponding to a diffraction on an edge. In this case the edge is circular, as is the aperture of your camera. You can best observe the same Airy-like "ringing" when you focus the laser and put some obstacle to the beam near the focus. Multiple internal reflections in the lens can generate ...


1

When you say "laser", I'm guessing that you mean visible or near-visible light. The problem is, where are they going to build their laser? If they build it on their home planet, then it's going to be so close to their sun, that our telescopes won't be able to distinguish the one from the other. We won't even be able to tell that it's there unless it is a ...


1

Does this mean that there are two different fields, one static field and one induced by a laser? Yes, that is exactly right. There is a static (meaning not time dependent) electric field $\vec{E}_\text{static}$ $(*)$ and there is also a time-varying electric field $\vec{E}_\text{laser}$ from the laser. Since we are told the laser field is linearly ...


1

That component is a "Faraday rotator" or "optical isolator" or "optical diode", but that is almost certainly not what you want. Those are used mainly to prevent back-reflections from entering your laser cavity. The quality of an optical isolator is therefore usually not precise enough for optical measurements, and the beam is not usually deflected at a ...


1

Can you define "side"? Are you looking for a material which changes its absorptivity in one axis only when illuminated from a different axis? I tend to doubt that even hyperboic, aka metamaterials, can demonstrate such a behavior. As you may know, there a variety of organic dyes which are used as either saturable absorbers or saturable transmitters. ...


1

I'll try my best to explain each part of the photo. Everything that's red in the photo should be from the laser itself. The nearly center white part of the photo comes from camera sensory overload. Lasers are extremely powerful concentrations of light, so when they directly hit the eye or an aperture they temporarily "blind" the source. In addition, ...


1

Laser Mirrors are used for beam-steering in demanding laser applications. Laser Mirrors are Optical Mirrors that have been designed for specific laser types or wavelengths.Optics’ Laser Mirrors feature dielectric coatings that have been optimized for high reflectance at specific laser wavelengths. Edmund Optics’ dielectric coatings typically feature greater ...


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A sum-frequency system with a "hot" mirror could act something like an optical switch: Unlike a switch, the output frequency will be different from either of the inputs. Edit: For an example of sum-frequency generation crystals see: Thorlabs Introduction To Periodically Poled Lithium Niobate (PPLN) (PDF) Thorlabs also sells hot mirrors.



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