Questions tagged [non-linear-optics]

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1answer
112 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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1answer
40 views

Why we use $i\hbar(\hat A -\hat A^\dagger)$ in Parametric Down-Conversion?

When we descirbe the degenerate parametric oscillator or the Parametric Down-Conversion, we can use the hamitonian: $$\hat{H}=\hat H_0+\hat H_{int}+\hat H_{irr}$$ \begin{array}{l} \hat H_0=\hbar\omega ...
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21 views

What is the Holo-Exchange symmetry of the tensor $\chi^{(2)}$?

In a paper by Lu-Ming Duan and Guang-Can Guo, they develop an alternative approach to quantising the EM field in a nonlinear and inhomogeneous media. In this derivation, they use the holo-exchange ...
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2answers
38 views

Do the results of this laser experiment demonstrate nonlinear optical phenomenon?

In my photonics class, we conducted an experiment to observe the Beer-Lambert law and the effects of filters(absorption, transmittance, and reflection). We shined a red(632nm) 5mW Helium-Neon laser ...
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23 views

Derivation of Yurke-Stoler state

The evolution of a coherent state $\vert\alpha\rangle$ in a Kerr-nonlinear medium $H=\Omega (a^\dagger a)^2$ is given by $$ \vert \psi(t) \rangle = e^{-\vert\alpha\vert^2/2}\sum_{n=0}^{\infty} \dfrac{\...
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51 views

Phase Matching in a Non linear crystal

I am working with Second Harmonic Generation using a LBO crystal. My pump beam is 795nm and I want to generate blue light using Collinear SHG in LBO. I have perused a lot of resources on the internet ...
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27 views

Pump Probe Spectroscopy Zero Delay

I am setting up a Non Degenerate Pump Probe Experimental Setup, in my lab, as part of my Master's Project. Due to the constraints of the way the lasers have been set up in the lab, I am unable to ...
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1answer
67 views

Coherent state under Kerr evolution

I have a bosonic mode associated to the usual operators $a$, $a^\dagger$. I'm interested in knowing the evolution of a coherent state $\vert \alpha \rangle = e^{\alpha a^\dagger - \alpha^\ast a}\vert ...
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2answers
93 views

Maxwell's equations, nonlinear media, and dynamic response

Maxwell's equations in the vacuum with electric permittivity $\epsilon_0$ and magnetic permeability $\mu_0$ are given as: $$\nabla \cdot \vec E = \frac{\rho}{ \epsilon_0}$$ $$\nabla \cdot \vec B = 0$...
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1answer
71 views

Optimal pump wavelength for frequency doubling in periodically poled media

Background I am currently working on achieving second harmonic generation (SHG) in periodically poled lithium niobate (PPLN) using a 1560 nm pump laser. PPLN makes use of quasi-phase-matching of the ...
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15 views

What is the relationship between the nonlinear susceptibility and the effective nonlinear coefficient?

Oftentimes, I see equations for non-linear optics expressed in terms of the non-linear susceptibility tensor. Other times, however, I see these same equations expressed in terms of an effective non-...
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1answer
29 views

What are the material restrictions for a $\chi^{3}$ non-linear optical material?

For instance, I know that $\chi^{2}$ materials need to lack inversion symmetry, but what about $\chi^{3}$ materials?
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1answer
88 views

Furry's theorem and spontaneous parametric down-conversion

In spontaneous parametric down-conversion, a single photon interacts with a nonlinear medium to produce a pair of lower energy photons. It is observed that energy, momentum, and orbital-angular-...
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1answer
45 views

Non-linear optics - solve differential equations coupled with the finite difference method [closed]

I have these three differential equations in which I need to solve numerically: $$ \frac{dn_0}{dt}= -n_0(t)W_{01}(t) + n_1(t)K_{10} $$ $$ \frac{dn_1}{dt}= -n_1(t)W_{12}(t) - n_1(t)K_{10} + n_2(t)K_{...
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1answer
69 views

Spin conservation in spontaneous parametric down-conversion (SPDC)

If one pump photon "decays" through the process of spontaneous parametric down-conversion into two photons how can the spin be conserved?
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20 views

Phase matching and the index ellipsoid

I've seen analytically all the process that brings to the condition for the phase matching (after I'll use PM) in an isotropic crystal, which is $n(\omega)=n(2\omega)$. My teacher hasn't shown it ...
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1answer
53 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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75 views

When is the permittivity tensor not Hermitian?

I understand that a permittivity tensor is symmetric if there is no absorption. On the other hand is it always Hermitian? Under what cases would that not be the case?
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25 views

What is the Brillouin Stokes power?

I know what is the brillouin scattering and i also know what is the Stokes power. Do someome knows what is the Brillouin Stokes power ?
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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
86 views

Difference-frequency generation: physical interpretation

Sum-frequency generation is easy for my to understand. Two photons combine their energies in a nonlinear medium and out comes one photon with the sum of both energies. But Difference-frequency ...
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85 views

Do radio beams self-focus in the interstellar medium?

Summary: In a plasma, electromagnetic waves create a ponderomotive force that pushes electrons and ions out of the way. Thus, in an intense laser beam, electrons tends to move away from the areas ...
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2answers
101 views

Higher-order dispersion in non-linear optics

In many cases, dispersion of an optical medium is presented by saying that the dependence of the wavenumber $k$ on the (angular) frequency $\omega$ can be expanded in Taylor series as: $$ k(\omega) = ...
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1answer
60 views

Paraxial approximation in nonlinear optics [closed]

I have a question about the paraxial approximation in nonlinear optics, it is different from the one in linear optics. and i'm confused about the difference between them, can anyone clarify this ...
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3answers
151 views

Frequency Chirp, Instantaneous Frequency and Photons

I understand ideas coming from Optics, such as the concept of frequency chirp and instantaneous frequency, and their use in nonlinear optics. However, I am struggling in giving them an intuitive ...
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2answers
65 views

Is second harmonic generation a special case of high harmonic generation?

That might be a strange question, but while I was researching for these topics, I never found an explicit statement that would answer that question. (That might be because of the different ...
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2answers
40 views

Observation of Strange Pattern with He-Ne Laser passing through a sample of Chlorophyll

We Designed in our lab an experiment with 5mW He-Ne laser, passing through Chlorophyll, which was extracted from Hibiscus rosa-sinensis leaves dipped in Ethanol. The resultant pattern we observed on ...
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1answer
122 views

Refractive index of Noble Gases at high pressure

How/where can I find(estimate) the refractive index of noble gases like argon and krypton? How does the refractive index of argon and krypton depend on the pressure, specifically high pressures of up ...
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1answer
66 views

Problem in derivation of nonlinear optics wave equation

Consider Maxwell's equations in a general medium without free charges or currents: $$\nabla\cdot\vec{D} = 0 \tag{1}$$ $$\nabla\cdot\vec{B} = 0 \tag{2}$$ $$\nabla\times\vec{E} = -\frac{\partial \vec{B}...
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42 views

Can light of different frequencies interfere with each other?

In principle I'm aware of superposition and how it works. Nevertheless I'm not really able to answer the following: Will two light beams of different frequencies interfere with each other? More ...
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1answer
109 views

Why non-linear fiber capacity limit decrease for higher signal-noise ratios?

In fiber optics communication, there is the concept of nonlinear Shannon limit (see e.g. this article), implying that the communication capacity of an optical fiber decreases for high SNR. I don’t ...
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1answer
77 views

What is difference between transmission and transparency?

I learned about the spectral hole burning. On Wikipedia, it said Spectral hole burning is the frequency-selective bleaching of the absorption spectrum of a material, which leads to an increased ...
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1answer
65 views

How does “coherence” contribute to inverting a two-level system?

In laser physics I am told that inverting a two-level system is not possible, since it will become transparent once the inversion reaches 50% and no longer be able to absorb more photons. This makes ...
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1answer
68 views

Plasma in solids

One way to create plasma is to focus a very powerful laser pulse to a small beam waist. In gaseous atoms, ionization will occur, yielding a soup of ions and electrons, which we call a plasma. But ...
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2answers
75 views

Pockels Cell reverse propagation

Pockels Cells are called "voltage controlled waveplates", since the voltage changes the birefringence of the material, leading to the same birefringence induced change of total polarisation plane than ...
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1answer
107 views

Purity of a quantum state in the Heisenberg picture

The purity of a quantum state is defined as $$ \gamma = \mathrm{Tr}(\rho^2) $$ In the Schrödinger picture, it's easy to use this formula to see how the purity of the system changes as the system ...
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1answer
40 views

Footage of SHG in smoke/fog

I am looking for a footage of second harmonic generation performed with laser and a non-linear crystal in which infrared light is converted to visible light. But I also want that to be performed in ...
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1answer
67 views

How is 'nonlinear optics' related to 'nonequilibrium'?

According to what I found, nonlinear optical process is related to nonequilibrium physics - nonequilibrium green's function (Keldysh green's function/formalism) appears in nonlinear optics. However, ...
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1answer
90 views

Is it possible to build a “DIY” quantum memory?

I am currently working on a home project which is a computer which will be capable of doing basic quantum computations (my first goal is a random-number generator) based on optical devices. Nowadays I ...
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5answers
125 views

Is it possible to divert light and/or wave by light or wave?

Is there a way to divert (deviate, deflect) light (photons) by another light (such as laser) or ...
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1answer
79 views

Why there are no periodically poled BBO crystals?

I am researching the topic of quasi-phase matching and I was wondering why it is not possible to periodically pole beta barium borate crystal? (I haven't seen any papers on this topic at least) ...
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2answers
470 views

Why is two-photon absorption a third-order non-linear process?

I've just started learning about non-linear optics where I could not understand why the two photon absorption is a $\chi^{(3)}$ process. The way I understand susceptibility is that the order of $\chi$ ...
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0answers
125 views

Complex part of second-order susceptibility in nonlinear optics

In optics, the absorption of photons by a material can be described by considering the material's susceptibility. For linear absorption (involving a single photon), we think about the imaginary part ...
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1answer
41 views

How to treat complex conjugates in a wave equation for EM wave?

In a class of nonlinear optics, the professor said that the E fields are always real and that for an EM wave we write $\vec{E}(\vec{r},t) = \vec{E}(\vec{r})\cdot e^{-i\omega t } + c.c.$ to ensure the ...
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1answer
151 views

Seeding Optical Parametric Amplifier (OPA) with Signal and Idler

Optical Parametric Amplifiers (OPAs) usually have two inputs: a more or less weak seed $\omega_s$ and a more or less strong pump $\omega_s$ where (ideally) each pump photon is converted into a seed ...
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1answer
47 views

Laser filamentation in air

For the non-linear optical process of filamentation in the atmosphere propagated by intense laser pulses (1TW) of ps-fs pulsewidths, what is the optimum method, through lens set-ups (or otherwise) to ...
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0answers
34 views

Where does the relation $\theta =(\theta_\mathrm{sf}^2-\theta_\mathrm{dif}^2)^{1/2}$, for combining self-focusing and diffraction effects, come from?

I have some troubles understanding one statement in the book "Nonlinear Optics" by R.Boyd. In chapter 7.1, it is derived that in a nonlinear material a light beam undergoes self-focusing due to the ...
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1answer
36 views

How to determine the laser duration in high harmonic generation?

In high harmonic generation, how can we determine the laser width (duration)? Say, I have a Gaussian laser pulse with intensity $10^{14} \:\rm W/cm^2$ centered at 800 nm wavelength, interacting with ...
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148 views

Scattering, absorption, emission and virtual photons

From reading many questions on this site I have the following conclusions: Interaction of a photon and a free electron is an instantaneous process of scattering (transfer of momentum) between said ...
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1answer
172 views

Finding four-wave-mixing terms in photon-atom interaction (by adding for fields to EIT)

The Problem I'm interested in solving for the four-wave-mixing terms in Electromagnetically Induced Transparency (EIT) when additional fields are added (while maintaining 3 atomic levels). Normally ...