Questions tagged [non-linear-optics]

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What are the reasons of why PG-FROG is not as popular as SHG-FROG?

One of the most popular techniques for ultrashort pulse characterization is titled as Frequency-Resolved Optical Gating (FROG), of which there are several variants. Amongst them, one of the most ...
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Can waste heat in specific environments be collected into photons and converted to electricity? [closed]

Crossposted on Engineering SE Here and here show possibility to combine photons of lower energy to one higher. Thinking of an application, it could be used to dissipate heat from laptop. Liquid ...
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Is it possible to create a mirror that redshifts light?

Mirrors are able to reflect light but are not perfect and after a number of reflections, light loses intensity. However I wonder, during the reflection by a different type of mirror, could the light ...
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14 views

Quantum Dot Surface Area to Volume Relationship

Do the properties off quantum dots depend more on their surface area rather than the volume they occupy? Depending on the case, then would quantum dots of different shapes show different properties?
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ugly beam profile in noncollinear optical parametric amplifier

I am currently (re)building a noncollinear optical parametric amplifier (NOPA). Such NOPA is seeded with supercontinuum white light (SWL), generated in a sapphire window, by ~100 fs, 795 nm centred ...
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Do laser filaments propagate in a straight line over long distances?

In so-called filament propagation, a powerful laser beam can propagate through a medium without diffraction. This occurs because the beam focuses itself through non-linear optical effects. Self-...
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1answer
15 views

Multiple Cones in SPDC output

I have seen a picture very similar to this one where it shows the different ouputs for photons during an SPDC process, but the only part (c) makes sense in this diagram. The photon pairs exiting ...
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1answer
37 views

Is there a nonlinear optical material that absorbs visible light stronger with increasing intensity independent of its wavelength?

One of the main shortcomings of digital image sensors is the quite "unnatural" behaviour for rendering highlights compared to film (and the human eye, I guess). Typically, with increasing ...
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1answer
21 views

Is there a frequency converting amplifier? [closed]

Frequency conversion means output of the amplifier is at a frequency different from that of the input.
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Time Response of Nonlinear Optical Materials

When reading about optical nonlinearities (and the nonlinear materials), a response time is often reported. I have been reading to try and understand the response time what these times mean. I ...
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The mechanism behind the second order non-linear injection current

In this paper the mechanism of second order non-linear injection current is defined as Injection currents are produced by quantum interference between different polarization components or between one ...
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1answer
86 views

Self-focusing of laser beam

I have exam of „Nonlinear Optics“ tomorrow and I don't understand one thing. In the book it is said, that self-focusing occurs when power of beam reaches so called critical focusing power $P_{cr}≈\...
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In Quantum imaging with undetected photons, why is the idler photon sent through a second non-linear crystal if it is then discarded?

I've been reading up on quantum ghost imaging and other similar approaches. In particular, I'm reading a paper Quantum Imaging with Undetected Photons by Gabriela B. Lemos et al and trying to ...
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59 views

Microscopic origin of non-linear optical effect

I know that a non linear optical medium is a medium in which the optical response for example polarisation vector varies as \begin{equation} \vec{P}=\epsilon_0\chi^{(1)}\vec{E}+\epsilon_0\chi^{(2)}\...
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Why linear optical response is absent in a non-centrosymmetric system with time reversal symmetry?

In this paper, it is mentioned that a non-centrosymmetric system with time-reversal symmetry doesn't have a linear response. It is actually a consequence of the Onsager reciprocal theorem. But I didn'...
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How is type I and type II phase matching formally defined for non-critical phase matching?

I did not find any good reference for this (simple) question.
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70 views

Difference between photogalvanic effect and Photovoltaic effect

What is the difference between the two phenomena, photovoltaic and photogalvanic effect? I can't find any difference between them. Both are generation of current when a material is illuminated with ...
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1answer
40 views

Question on the creation of an entangled photon pair in a specific realization of the EPR-Bohm Experiment

In a student experiment the following assembly is used to create an entangled photon pair. From the left, a laser beam polarized along $\frac{\hat{x}+\hat{y}}{\sqrt{2}}$ is incident on a pair of BBO ...
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2answers
34 views

Why the optic axis of an crystal should has a proper direction; why it cannot be a single line? [closed]

In many books it is written that the optic axis of a crystal is a direction rather than a single line! I really cannot understand what is the necessity of the direction and why I cannot say that it ...
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1answer
19 views

Solutions in Bi-stable Regime

I am trying to plot the Bi-stable behavior governed by the equation: Here the parameters have given numerical values. For a certain range of $x$ there exists three roots. Ideally two of these should ...
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1answer
15 views

Is it possible to optimally transmit solar radiation by a system of multiple optical fibers?

As we all know, if an optical fiber is designed with the right material and properly bent, light can be transmitted along the fiber with very little attenuation. Figure 1 shows the interaction of ...
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1answer
72 views

Why the Divergence of Electric field is Zero?

I am studying nonlinear optics, specifically the wave equation of nonlinear optical media. During the derivation I came across a point where the divergence of electric field was zero for a linear ...
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1answer
29 views

Does self-phase modulation generate new frequency components?

Not a physicist. Hope to clarify some conceptual issues I have with non-linear propagation of light through a medium, since I seem to be mixing up some very fundamental concepts. Specifically, I am ...
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67 views

Good books on electromagnetism for nonlinear optics

While reading books on nonlinear optics, I often come across concepts such as second-order susceptibility which is not covered in undergraduate E&M books like Griffiths. Are there any good E&M ...
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Derivatives of the propagation constant in optical fibers

In many books on nonlinear fiber optics, the Taylor series expansion of the mode-propagation constant $\beta$ is performed about a frequency $\omega_0$ at which a pulse's spectrum is to be centered. $\...
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Free Spectral Range versus Axial Mode Spacing?

I am doing research on micro cavity frequency combs and I've been trying to understand things like dispersion, Free Spectral range, resonance, and modes. I am looking at the definition of free ...
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16 views

Treatment of a light pulse moving from linear material A into non-linear material B

When I simulate the propagation of a pulse through a material without non-linear effects, I can use the non-linear schrödinger equation $$\partial_tE=\frac{i}{2k_0}\nabla^2E$$ with $k_0$ the wave ...
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Spiral waveguide for single-photon generation

I would like to ask about the advantage of a spiral waveguide for single-photon generation(using SFWM) compared to the SPDC process using bulk optics.
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Resources to learn about spontaneous parametric down conversion

I have recently begun working on a project where I will be modeling some experiment that uses SPDC to generate entanglement. However, I have not formally studied SPDC in any capacity. Is there any ...
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1answer
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How to calclate Drude dielectric function vs probe energy from time resolve spectroscopy?

How can I calculate drude dielectric function vs probe energy (in eV) form differential transmittance vs delay time plots.
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How can I easily generate $\rm GaAs$ band structure?

Is there a program where I can easily generate $\rm GaAs$ band structure that shows lowest conduction band valleys?
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1answer
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Definition of the polarization of a light beam due to the Kerr effect in fourier- and real space

During my literature review of linear and non-linear optics I found the linear polarization acting on light usually defined as $$\hat{P}=\varepsilon_0\chi^{(1)}\hat{E}$$ with $\hat{E}$ the electric ...
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Calculating the response function depending on the wavelength for a pulse propagation in time

When solving the non-paraxial pulse propagation $$\partial_z\hat{E}(\omega, z)=ik_z\hat{E}(\omega, z)+\frac{i\omega^2}{2\varepsilon_0c^2k_z}\hat{P}(\omega, z)$$ with $$E_0 = E_0(r, t, z)$$ the initial ...
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What is the typical efficiency/probability of success of producing a pair of photons in SPDC?

In Spontaneous Parametric Down Conversion process pump photons are broken up into pairs of photons. What is the typical probability of success or the efficiency of this process in practice?
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Marginal theorem in frequency-resolved optical gating (FROG)

In ultrashort laser physics, frequency-resolved optical gating (FROG) has been a standard method since a few decades to measure the temporal profile of an unknown pulse's electric field $E(t)$ via a ...
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Small values and Negative nonlinear susceptibility of a degenerate parametric amplifier

The quantum Hamiltonian of a degenerative parametric amplifier (DPA) is given by (taking $\hbar=1$ $$ \hat{H}=\omega\hat{a}^{\dagger}\hat{a}+2\omega\hat{b}^{\dagger}\hat{b}+\kappa\left(\hat{a}^{\...
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Optical Impedance Matching

Suppose you want to match optical impedances between a region of refractive index $n_1$ and a region of index $n_2$ and you want to expend a total distance $L$ in the impedance matching transition ...
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1answer
63 views

Differences in crystals used for SHG and OPO

SHG: second harmonic generation OPO: optical parametric oscillator As we know these are non linear cavities (optical cavities with non linear crystals in them along a part of light beam's path) used ...
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Maximum delay between n photons for multi-photon ionization

Given an IR laser with intensities that allow for a Keldysh parameter smaller than 1 in a given sample. I was wondering, what is the allowed timely separation distance between two IR photons such that ...
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Refractive index values of the solution less than that of the solvent. Why does that happen?

I have been doing an experiment for finding the third-order nonlinear susceptibilties of organic molecules using Degenerate Four-Wave Mixing (DFWM) at femtosecond regime. For the calculation of the ...
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66 views

Is it possible to solve those differential equations (with complex numbers)?

I'm trying to solve this equation, I don't know where to begin with. Is it feasible ? If so how should I solve it ? https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-20-7-7454&id=230426 https:/...
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What causes this high frequency “noise” in HHG spectra?

Looking at high harmonic spectra, one can often see that peaks corresponding to higher harmonics look more and more noisy and seem to be drowned out by the noise. For example, one such spectrum is ...
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1answer
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Numerical simulation for spontaneous parametric down conversion

I want to numerically simulate the SPDC (spontaneous parametric down conversion) process. I have a basic background on nonlinear and quantum optics — I am a graduate student and just took a few ...
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Calculating the absorption cross-section for Helium in a strong oscillating external IR field -> AC Stark Shift (Autler-Townes Splitting)

I try to obtain the absorption cross-section for atomic helium, in a strong and oscillating IR field, for when a second - XUV - pulse is probing the system. I think the only way of doing this is to ...
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3answers
501 views

Why are there only odd harmonics at High Harmonic Generation?

I'm trying to understand why in High Harmonic Generation (HHG) the spectrum only consist out of odd multiples of the driving frequency. Many sources state "because of symmetry" but they do not clearly ...
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1answer
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What is the difference between classical nonlinear optics and multiphoton physics?

Nonlinear optics is usually looked at through a classical lens for most purposes. I do a Taylor expansion of the material polarization in terms of light-field strengths and we can derive all the ...
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122 views

Electromagnetic energy density in a nonlinear medium

The energy density associated with the electric field in a linear medium of permitivity $ \epsilon $ is given as $$ U = \frac{1}{2}\epsilon\left | E \right |^{2} $$ As Robert Boyd mentions in the ...
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Derivation of Hamiltonian in non-linear optics

Update 2: one half of the answer to this question can be found here and the other half in the second half of this post. I asked this question a few hours ago, but decided to re-post it because I ...
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1answer
120 views

Focusing a Gaussian beam into a nonlinear crystal

Boyd analyzes in his book (Boyd's book), section 2.10.3, the case of harmonic generation using a focused Gaussian beam and he mentions that an analytic solution can be evaluated for certain special ...
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179 views

How does optical “self-torque” make sense in terms of Maxwell's equations?

I saw an article in Science (arXiv:1901.10942) that describes "self-torque" of light. My understanding is that a series of ultrafast optical pulses with different angular momenta combine in some ...

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