Questions tagged [optical-materials]
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286 questions
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Ideal refractive index of a thin film coating
My professor wrote that the refractive index of a thin film when we do a coating of it (say on glass to make them non reflective or anything) should be
$n_f = \sqrt{n_1 \cdot n_3}
$
Why should it be ...
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How does an optical interrogator work?
Could someone explain the principles behind an optical interrogator?
I know that it is currently used to demodulate signals from FBG sensors, however, I am curious about the intrinsic workings and ...
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Can invisibility be achieved through physics? [closed]
I’ve been reading about the concept of invisibility in physics and am curious about its feasibility. We often see references to invisibility cloaks in science fiction, but what does physics say about ...
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An object's colour and its relation to light
I know that an object (say, a block of red colour) appears red because white light from the light bulb or sun shines on it, and the block absorbs all the other wavelengths of light except that ...
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Effect of sugar on the refractive index of water
I'm investigating the effects of sugar on the refractive index of a water and sugar solution. I'm wondering if the explanation behind why sugar changes the refractive index of water is similar as to ...
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Why are no metals green or blue?
Copper is orange; gold is yellow; silver, platinum and lead are white (chromatically speaking).
Why are there no metals that are blue or green?
Why do the colours of cold metals follow, more or less, ...
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Acoustic diffraction grating
Is it possible for diffraction grating to make similar scattering pattern as how it can for light?
If no please say why in detail
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Linear-array diffraction beam splitter
This question is composed of two parts. The first is about the grating equation. The second is about a particular software used for diffraction gratings.
The grating equation is
$$
\sin(\theta_m) = \...
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Thin Lens in different media
I have been given an equiconvex lens (of given focal length), placed on a plane mirror, with water between the lens and the mirror.
An object has been placed at a certain distance and I have been ...
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Is X-Ray-Emission-Containing Phosphorescence possible or is it limited to Immediate-Emission XRF?
This was a random thought that I wanted to follow up on. I know some materials can take in and kick out X-Rays in XRF (Though most x-ray scintillators tend to emit mostly visible light, not x-rays). ...
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What is meant by optical density?
I’m trying to research about optical density for a school task, but the definitions online are confusing me.
From what I’ve gotten, optical density is:
how much the intensity of light is increased or ...
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Material that Increases Angle of Incoming Light
Snell's law states that light refracts when entering a substance and refracts back to its original angle upon exit. This is shown in the diagram below from this webpage.
I was wondering if there are ...
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Deriving dispersion relation of hyperbolic material
I am trying to derive the following form of the dispersion relation for hyperbolic material:
From the literature, this dispersion relation is achieved by setting the determinant of the below matrix ...
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Could a transparent frequency-altering material be possible?
I would imagine a material that is transparent but a electromagnetic wave going out will have a lower frequency than when going in (and maintaining it's direction). You could build glasses to see UV-...
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Can an optical medium be lossless and dispersive?
Occasionally, I come across the phrase "lossless dispersive linear optical medium". How can such a medium be possible mathematically? I mean the real and imaginary parts of the electric ...
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Second Harmonic Generation on chiral surfaces
I try to recreate a fit in this paper on SHG on chiral surfaces.
I guess the question itself is too specific to get an answer, so I state these questions that are a bit more to the point (and leave my ...
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What percentage of light gets scattered by a mirror?
Sunlight strikes a mirror at a 45 degree angle. The vast majority of light will be reflected about the normal. Some light will be absorbed by the mirror. Some light will be transmitted through the ...
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Light splitting plastic film in phone display screen
I was recently taking apart a button-press phone (like this one) and right under the glass protective screen was a thin plastic film.
This is what happens when I place it over a single dot:
As far ...
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Mixed configuration of magneto-optical kerr effect
Typically there are three types of magneto-optical Kerr effect experiments: Polar, longitudinal, and transverse. These three geometries yield very different results regarding what is measured (...
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How are 3 Principle Sections possible in a crystal even when there is only one optical axis and all must contain it?
While studying polarization in calcite crystals, I came across that there are 3 possible principle sections in the rhombohedral crystal. But the conditions are that each section must be perpendicular ...
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How can a greater than 1 reflectance coefficient be explained in $\rm SiC$-$\rm SiO_2$ interface?
I ran a simulation using the Transfer Matrix Method to plot the R,T and A curves for a SiC->SiO2 interface. There's a region of incident energies where the |r|^2 I get is higher than 1 and the ...
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Why can you not create a LED equivalent by illuminating a colored plastic casing?
I would first like to apologize if this is a dumb question.
I understand the physics of color sufficiently well. You have an incoming photon that intercepts an electron on the atom, the electron gets ...
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Imaginary part of permittivity tensor
For a general permittivity tensor, why is the imaginary part of the off-diagonal component, e.g.:
$$\epsilon_{xy}$$
equal to:
$$\frac{\epsilon_{xy} + \epsilon_{yx}^*}{2i}$$
instead of:
$$(\epsilon_{xy}...
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Refraction and Snell's law at $\rm SiN$ inverse taper facet
For an optical inverse taper, for example, for a $\rm SiN$ taper, material of core is $\rm Si_3N_4$ while cladding is oxide. At the facet, there is a polish angle theta to reduce the backreflection. ...
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$\rm InP$ Mach-Zender modulator
I know how a Mach-Zender electro-optical modulator (MZM) works when based on non-linear crystals like LN. On-chip realization of MZMs is often done with $\rm InP$ that is a semiconductor. What is the ...
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Knowing the optical path difference, how do I calculate the resulting image?
Let's say I'm taking a picture through a cube of some material where the index of refraction varies in a known way, such as a GRIN lens. I can calculate the optical path difference as a function of ...
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Exactly which objects should we considered as colorless? [duplicate]
My question is which objects are considered as colorless?
In chemistry we sometimes consider white object as colorless,Many times we use the word colorless for transparent substances like water, glass,...
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Understanding the differences in dielectric functions derived from various methods
I am currently investigating the response of a specific system to an external electric field and have encountered a question that has puzzled me for a long time.
Consider a system subjected to ...
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Transmittance of one material through a multilayer
Good morning,
I have the transmittance and the reflectance spectrum of PET (Polyethylene terephthalate) and I also have the transmittance and the reflectance spectrum of PET + Copper (50 nm). I would ...
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Why does this toy color mixing cube exhibit asymmetrical behavior?
I have this "color mixing cube" desk toy; when looked through, each axis filters a different primary color of light.
It seems to be made of a cube of transparent material (refraction index ...
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Do there exist materials whose Opacity varies with temperature?
Do there exist materials whose Opacity varies with temperature?
E.g a Material that becomes more Opaque as it gets hotter?
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What is a true delay line and is there possibly a false delay line?
I'm reading "Silicon nitride passive and active photonic integrated circuits: trends and prospects" and one of discussed application of $\rm SiN$ is "true delay line". All the ...
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Why are the total and free EM fields mixed together?
For calculating the work done on a medium by an electric field: $đW = \vec{E} \cdot d\vec{P}$ but for magnetic fields: $đW = \mu_0 \vec{H} \cdot d\vec{M}$. For impedance, $Z = \frac{E}{H}$. Why is the ...
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Do mirrors (with metal surfaces) show TIR (Total Internal Reflection)?
[Not a duplicate! Also, the answer to a similar question was unsatisfactory]
I was digging into why we don't use mirrors in place of fibre optics cables. Majorly, the answers were as follows:
It's ...
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How do optical fibres work with high critical angles?
The critical angle is given by:
c = arcsin(n2 - n1)
For a typical optical fibre, it says on the web that refractive index (n2) for cladding is higher than that of the glass core (n1) but it's only a ...
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What are some liquids with high ranges of refractive index with change in temperature?
I need to run an experiment on the effect of temperature on refractive index of a liquid, and in order to make the change most visible and have the lowest percent uncertainty I need the change in ...
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In a uniaxial crystal, what determines the optical axis, extraordinary axis, and ordinary axis?
In a uniaxial crystal there is an optic axis, an extraordinary axis, and an ordinary axis. The optic axis is not the direction in which we plan to propagate light. The light is propagating in a ...
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What happens when screen is not placed where Image is focused but elsewhere?
When we try to form a real image on a screen by a convex lens, we place the screen at a distance where the image is focused. But if we try to place the screen at a distance less than the distance ...
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Why are things reflective, absorbent, transparent etc? [duplicate]
What determines whether a material reflects, absorbs or transmits a certain wavelength of light? Just a layman's question.
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Why can't we create a laser with wavelength of 13.5nm?
I was reading about EUV and the extraordinary process of firing two different lasers as tin droplet to collect 13.5nm wavelength light and I was wondering why this is required and we can't just create ...
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Why does light either get reflected, absorbed, or passes through a surface or obstacle?
For each of these 3 cases, I'm having trouble understanding...
If light is reflected, does that mean that there was not sufficient energy by the photons to excite the electrons of the surface to ...
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Why does (oxidized) aluminum have a diffuse optical appearance?
Unoxidized aluminum has a shiny appearance like typical metals. However in air aluminum rapidly oxidizes, giving it a more diffuse appearance (or bidirectional reflectance distribution function). ...
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What difference between metallic reflection and polished/mirror reflection [closed]
At the moment I am studying materials in raytracing (I am writing my own personal project)
I found out that there are several types of reflections.
I read this article from wikipedia:
https://en....
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Laser confocal microscope filter
I wanted to mount a narrow bandpass filter which allows to transmit 405 nm wave, i. e. the laser wavelength. I wanted to cut off other light, cause my detector is also sensitive to other wavelengths.
...
user256423
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Recording Analog Data in Optical Disc Using Laser Beam Mechanism [closed]
Is it possible to storing/writing any Analog Audio Signal (i.e. Vinyl Record & etc) into a little bigger and thicker Optical Disc as compared to the other conventional Compact Disc while using the ...
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Are there everyday materials that change color, depending on illumination spectrum?
Initially I wanted to ask this exact question about color change due to "white" light source spectrum change, and the accepted answer satisfies me fully.
However the answer says that most of ...
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Why do non-linear optical effects occur?
Why do non-linear optical effects occur? Why do the materials respond differently at high intensities and at some resonant frequencies?
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Classical EM wave: Wavelength dependence of modelling material as Lorentz oscillator vs Bragg diffraction?
For convenience, consider a classical EM wave within a perfect crystal.
The Lorentz oscillator seems a good way to model material characteristics.
Yet in introductions to eg. X-Ray Crystallography, we ...
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Size of metal domain needed to reflect light ; are small graphene sheets shiny?
I remembered that shininess of a material is because of reflection, ie surface current responding to light. Mathematically, one can solve Maxwell equations under a relevant boundary condition, with ...
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What is difference between Electromagnetically induced transparency (EIT) and Coherent population trapping (CPT)?
EIT: Electromagnetically induced transparency
CPT: Coherent population trapping
When two resonant light fields (probe field and strong coupling field) are incident on an opaque material whose atoms ...
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