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Questions tagged [optical-materials]

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For the high-frequency permittivity of a material, do I need to look beyond its value in the optical energies region?

I was trying to find $\varepsilon_\infty$ for InSb, and the value I found on Kittel p. 416 was 15.6. But in the literature, even at 6 eV, $\varepsilon (\omega )$ is still in the negative (at -3.835) ...
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1answer
18 views

Does optical density depend upon concentration of a solution?

Does optical density vary upon the amount of salts dissolved in water?
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8 views

Why the first ring's radius appears to be too little in newton's ring experiment?

In newton's ring experiment we should be going to see a large number of rings with their converging radius. But the ring right next to dark fringe is way nearer than 2nd or 3rd which appears to be an ...
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1answer
29 views

What materials allow $12\,\mathrm{\mu m}$ LWIR to pass?

What commonly available materials will allow Infrared Radiation with wavelength of $12\,\mathrm{\mu m}$ to pass through? Commonly available is something that can be obtained easily for manufacturing....
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2answers
43 views

Why is it important to measure permittivity and permeability complex of materials?

I know that in general, $\epsilon(r,\omega)$ and $\mu(r,\omega)$ are complex tensors, so now how do you resolve maxwell equations? I don't understand why there are techniques to measure them if you ...
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2answers
41 views

Polarised glasses for high astigmatism and myopia [closed]

So I have -4 for both of them, which results in -8 in total (same for left and right eye). At my optician, I have to choose the best package they have to make sure my sunglasses can be as light as ...
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0answers
10 views

Semiconductors with low thermal conductivity (lattice matched to GaAs)

What are the semiconductors with lowest thermal conductivity that can be grown on GaAs with the least possible incorporated strain (i.e. lattice-matched or close to it)? GaAs has thermal conductivity ...
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1answer
69 views

Can light in a medium travel faster than speed of light $c$ in vacuum?

Refractive index of medium $m$, $n_m$, is given by $$n_m = \sqrt{\mu_r\epsilon_r}$$where $\mu_r$ and $\epsilon_r$ are permittivity and permeability of the medium respectively. And, velocity of light ...
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1answer
27 views

Cooling photons to a solid state

Can we cool photons so the stop moving completely? So they can behave like particles in a solid.
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0answers
36 views

A simple thin-film transmittance calculation problem

I am trying to reproduce results of thin-film transmittance given in this article by using this online thin-film calculator tool (www.filmetrics.com). I would like to use the calculator later for more ...
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1answer
27 views

Why does certain clear plastic have an inner glow?

A type of plastic used in packaging for tamper resistant seals appears to have (what I can best describe as) a purplish inner glow under sunlight, and perhaps other bright light. In the image below, ...
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13 views

Spectrum of Dielectric Function along Energy

What do the peaks and troughs in the spectrum of the dielectric function (real and imaginary parts) along energy indicate? I understand that the real part represents the polarization and the imaginary ...
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1answer
32 views

Why air spacing for high power beam splitters?

Ordinary glass cube beam splitters are constructed with a dielectric or hybrid coating on the hypotenuse of a right angle prism which is then cemented to another right angle prism. These fail in ...
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1answer
47 views

How to calculate the dispersion parameter of a Fiber?

I am writing a presentation about DCF Fibers. From many articles i am reading, the dispersion parameter of Fibers are given. But it is not shown how it has been calculated. For example ,in this ...
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1answer
30 views

What is the gain control technique used in optics?

In optics, it is said that The gain bandwidth and gain flatness of Amplifiers are enhanced utilizing gain control techniques.What techniques are they referring to ? I know the automatic volume ...
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1answer
36 views

What is a pump reflector?

I understand the meaning of laser pumping. But i don't understand what is a pump reflector. As a clear definition does not appear online. In the paper,DESIGN AND DEVELOPMENT OF WIDEBAND HYBRID RAMAN/...
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2answers
109 views

Magnifying power of a microscope for a farsighted person

I was doing some problems on optical instruments and in one of the questions it was asked that if a simple microscope(magnifying glass) has a magnifying power 5X for a normal relaxed eye.. what will ...
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1answer
27 views

Which transparent material alters light the least?

I am making a spectrometer as my school project. It's main application will be analyzing the light emitted by various light sources. It measures visible, near IR and UVA/UVB radiation. I need it to be ...
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1answer
71 views

Why glass is considered as an opaque body…? [closed]

We know that the transmissivity of glass is 0 then also in general conditions it is taken as an opaque body and also in some books, it is taken as an opaque body.
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1answer
1k views

How can the refractive index be below 1 in a dielectric?

Upon checking the optical properties of different dielectrics, I found the interesting case of $Al_2O_3$. It seems to be reported with a refractive index below 1 in the infrared range of $10 - 12~\mu ...
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1answer
47 views

Is it possible to have an optical version of a greenhouse? With optical fibers?

Optical fibers transport light within them using internal reflection, but the light only enters from one end of the fiber. Is it possible to somehow have light entering from the sides of the fiber (...
2
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2answers
104 views

Is there such a material that only emits, or “sends out” the same color light that was “taken in” (absorbed)?

For example, glow-in-the-dark materials (photoluminescent) only emit a green hue regardless of the color of the light shone on the material. Is there such a material that emits the color of the light ...
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2answers
123 views

Star Trek - Transparent Metals Possible?

Is the concept of transparent metals (like the transparent aluminum in Star Trek IV - Voyage Home) a real-life concept? Or is it far-fetched movie fiction? Thus my main question then is: could we ...
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1answer
58 views

Is there a material that allows light to pass perpendicular to the surface, but reflects at an angle?

This is inspired by Michael Steven's new video about optics. He shows off Selenite, which has the property that light entering on one side travels perpendicularly down the crystal until it exits the ...
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2answers
46 views

Using of optical slit for different spectrum

Here below the 3 spectrum currently used in astrophysics and illustrating Kirchhoff's laws (emission, absorption and continuous spectrums),: I just want to know : what's the utility of the optical ...
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2answers
135 views

Can you burn invisible jelly balls with a laser?

Suppose you have some jelly balls with similar refractive index as that of water, like in this video. You put them in water, making it invisible. So, the optical behavior of the balls should be ...
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1answer
192 views

Why does the definition of angular magnification relative to the substended angle of least distence that the eye can see

The angular magnification defined as, angle subtended by image of object /angle subtended by object when 25 cm from the naked eye Consider this. An object is placing 50cm in front of a convex ...
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1answer
50 views

How reflectivity of metals depends on the condition of the surface?

Does it depends on the flatness and pureness of surface. does it change when dust or oxides settle on it.
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2answers
313 views

Is there a way to make infrared pass through metals?

I am curious to know a way that will make infrared pass through metals. Metals are good reflectors of infrared,can we manipulate the wave in order to make them pass through metals?.
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0answers
131 views

Change of refractive index using semiconductor

I was wondering, if it is possible to change the refractive index of a semiconductor using an electric field or current? I have heard about injecting charges to tune the refractive index. How/Why does ...
2
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1answer
2k views

What plastic-like materials allow IR to pass through them?

What plastic-like materials allow IR to pass through them? Material should be solid and plastic like. Does't care if it is transparent to light or not. IR ray is emitted by Sharp distance center so it ...
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3answers
60 views

See through material for IR camera

I have an IR camera that I'm trying to hide behind an opaque or fine meshed material (plastic?). Any idea? Thanks!
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0answers
23 views

How to theoretically determine thermal emissivity of thin polymeric films?

Maybe someone could help with determining gray-body emissivity of thin films such as polyethylene. There is a lot of conflicting data online with some sources stating polyethylene's epsilon value as 0....
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0answers
67 views

Identifying diagrams for optical processes

I was reading some papers on the study of the optical properties of some metals and came upon these conference proceedings by Hopfield from 1972. They are on the study of the infrared properties of ...
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0answers
60 views

Where can I purchase a funnel reflector? [closed]

I am designing a testing apparatus to contain the light emitted from a 40mm dia. xenon bulb and concentrate it at a 35mm dia. target. My apparatus consists of a large funnel reflector: large hole dia....
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1answer
299 views

Why is liquid fat transparent and solid fat opaque?

While frying some chicken I was wondering why the fat becomes transparent when melting. As far as I know, transparency is caused by the fact that the substance can't absorb photons of visible light (...
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3answers
51 views

What are the other ways to pass particular wavelength of light without using optical band pass filters?

I'm working on an experiment that have visible spectrum light source (RGB LED at e.g. 495–570 nm wavelength), holder with sample, narrow bandpass filter (eg: CWL:520nm, FWHM:5nm) and a photodiode to ...
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1answer
62 views

Parameters for custom lens design

First, problem background: I'm attempting to source lenses for use in eyeglasses to deal with extreme sensitivity to chromatic aberration, and likely need either achromatic doublets or single lenses ...
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2answers
1k views

Does temperature affect the index of refraction?

I would like to know the physical reasoning behind the fact that temperature indeed does change the index of refraction of a certain medium. (Is there an easy experiment for me to try this at home?)
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1answer
44 views

Relating to IR rays [duplicate]

I am working on a project where I am putting an IR sensor similar to what we use IR module for Arduino.I just want a material that can pass the IR rays but it should be opaque to visible eyes .Like ...
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1answer
22 views

What photoconducting materials/metamaterials reach full conductivity within 1/30th of a picosecond

I'm doing research on photoconducting materials/metamaterials but I'm having a hard time finding confirming how fast they reach full conuctivity, What photoconductors reach full conductivity and back ...
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0answers
45 views

How to decide between sizes of particles for maximum light intensity for scintillation?

Are nanoparticles or microparticles or quantum dots better suited as scintillation materials as far as light yield intensity is concerned? I was unable to find literature that compares micro vs ...
4
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1answer
94 views

Periodic multi-layer scattering of neutrons

I am trying to understand the reflectivity plot on slide 26 of Neutron optics,Soldner lecture. 1.Is the peak from $\theta$=0.0 to 0.4 due to total external reflection from the first upper surface?. ...
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1answer
36 views

Semireflectivity of a material (acrylic)

I am using acrylic for a project due to its semi-reflectivity (as well as the fact its easily laser cut, and is in great supply where I am). However, I was wondering about the factors that determine ...
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1answer
60 views

How can I make a Telescope with the lenses I have

List of lenses I have Convex - 200mm F.L - 50mm Dia Convex - 50mm F.L - 50mm Dia Convex - 40mm F.L - 40mm Dia Convex - 45mm F.L - 25mm Dia Concave - 200mm F.L - 50mm Di I tried to make a ...
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0answers
136 views

optical scattering cross section and polarization tensor

The optical scattering and absorption cross sections are well known to be $$ C_{sca} = \frac{k^4}{6\pi}|\alpha|^2 \qquad C_{abs} = k\Im (\alpha) $$ where $k$ is the wavevector and $\alpha$ is the ...
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1answer
38 views

Beam Profile Through an Optical System

I am curious about how to counteract the effect different optical elements have on a beam profile. I know a good rule of thumb with lenses is that you should balance positive and negative ones to ...
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1answer
394 views

What does the refractive index for e.g. alpha mean?

When I look for some materials like https://en.wikipedia.org/wiki/Barium_sulfate and want to extract the refractive index then there is written: (nD)=1.636 (alpha). And sometimes also for beta and ...
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0answers
288 views

What are eclipse glasses made of? [closed]

What is the principle of eclipse glasses? Are they just high optical density plastic, or do they do something fancier? Could I make my own by taping ND filters into cardboard? I tried Googling ...
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1answer
492 views

Minimum deviation position in prism [duplicate]

Why does deviation become minimum at minimum deviation position? What is its importance in practical applications?