# Questions tagged [non-linear-optics]

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### Photon-wise justification of chosen compensation crystal length in SPDC

I know a compensation crystal in SPDC schemas serves the temporal walk-off erasment purpose. However, I am not sure why half the length of the original crystal is opted for. I read an article that ...
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### How can we generalize the definition a non-linear media?

According to the definition: Nonlinear media are dielectric materials whose polarization density changes nonlinearly if a strong field is applied to them. If the field is small the nonlinear terms ...
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### Why are pulsed lasers are the main tool used in nonlinear optics applications, instead of CW sources?

Why we often use pulsed lasers for nonlinear optics applications (such as SHG) instead of continuous wave lasers?
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### Phase matching for second harmonic generation

I am solving an application about angle phase matching for type I second harmonic generation in a negative uniaxial crystal (taken from the book Nonlinear Optics 4th ed. by Robert W. Boyd section 2.3)....
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Quick question regarding non-linear optics: A nanoparticle, either dielectric or metallic present second harmonic generation. The dielectric, following the simplest modelization as: $$E(2\omega)\... • 41 0 votes 0 answers 22 views ### How do Pockel's cells rotate linearly polarized light? My partner and I are doing a nonlinear optics experiment with a Pockel's cell. What we want to do is to hook the Pockel's cell up to a wavefunction generator that inputs a gaussian pulse. What goes ... 0 votes 2 answers 39 views ### Complex electric field in second order polarization I am reading an introductory article on nonlinear optics. Here is what the part that's troubling me says:$$\tilde E(t) = Ee^{-i\omega t} + \text{c.c} $$When this electric field is incident on a ... • 452 1 vote 2 answers 63 views ### Four-wave mixing and modulation transfer spectroscopy: why do sidebands appear on the probe? I'm trying to understand modulation transfer spectroscopy in simple terms. For those unfamiliar with it, this article gives a very good summary. To sum it up, two counterpropagating beams, a pump and ... • 143 1 vote 0 answers 24 views ### Second harmonic generation (SHG) in centrosymmetry material I know SHG in centrosymmetry material is not possible as "E(t)\rightarrow -E(t)" and "P(t) \rightarrow -P(t)" one should get the same P(t). I am confused why E(t) and P(t)... 0 votes 1 answer 55 views ### What do the subindices jkl... represent in the nonlinear polarization equation? After studying this article on non-linear polarization, I have two main questions: The first was which is the origin of nth order susceptibilities; this was mainly already answered by a previous ... 5 votes 1 answer 163 views ### QED vacuum as a classical dielectric medium? I have heard this analogy a few times, particularly in the context of vacuum polarization. To what extent can the QED vacuum be modeled as a classical dielectric medium? Can one compute effective ... • 606 1 vote 1 answer 69 views ### Physical origin of Kerr effect I was wondering if someone could explain to me the physical (not mathematical) origin behind the Kerr effect and why it results in birefringence in materials. Also, can the birefringence be introduced ... 2 votes 0 answers 56 views ### Why do we get rings in the Spontaneous Parametric Down conversion (SPDC) process? In the SPDC process, the phase-matching conditions between the o-rays and/or e-rays have to hold for the down-conversion process to take place. Say we have a non-collinear phase-matching at the plane ... 1 vote 1 answer 27 views ### Requirements for Z-scan or I-scan measurements of nonlinear optical materials I am looking to understand what requirements there are for any version of Z-Scan technique or the I-scan technique. These techniques are used for measuring nonlinear absorption and nonlinear ... • 21 1 vote 0 answers 62 views ### What are the factors that decide which type of SPDC (Type I or II) occurs in a Non-Linear Crystal? I have been reading through some literature on the theory of Spontaneous Parametric Down conversion (SPDC), their types, the phase-matching condition, etc. To my understanding, the downconverted ... 0 votes 1 answer 94 views ### Can we predict harmonic generation from Maxwell's equations? One typical experimental setup to generate harmonics from a laser pulse is to irradiate some plasma stab with a laser, register both reflected and transmitted waves, and the spectrum of those waves ... 2 votes 1 answer 73 views ### Squeezed quantum states of light I am a beginner in quantum optics and started from reading the Fox's book. I got to Ch.7, where there is a discussion about the amplitude-squeezed states. I am really puzzled by the effect of phase ... • 1,095 1 vote 0 answers 37 views ### Nonlinear polarization? I am studying quantum optics by Mark Fox and in the review part he speaks about non linear optics. We can write the relationship between the polarization and electric field in this way: P = \... • 305 2 votes 0 answers 40 views ### Entangled Photon Sources: how to choose the pump wavelength in SPDC? I found several papers dealing with entangled pairs of photons generated by means of a setup consisting in a pump laser and a nonlinear crystal, such as BBO or KTP and here the incoming photons ... • 51 1 vote 1 answer 60 views ### Restoring force of electron-nucleus spring model (Lorentz oscillator model) The restoring force should fulfill at least two criterion Experience repulsive force when it is compressed and attractive force when it is extended The restoring force always increases with distance ... 0 votes 1 answer 30 views ### One-half factor representing power or energy In a book on optical solitons, the following is said- When loss or gain is taken into account, the equation - -i\frac{\partial u}{\partial z} = \frac{1}{2}\frac{\partial^2u}{\partial t^2} + |u|^2u ... • 452 0 votes 1 answer 19 views ### Where can I find some typical nonlinear optical materials SHG working region? Some example materials are KDP, LiNbO_3 and BaTiO_3. Where to find their SHG working region? Like some of them perfroming their SHG best in red light region. I've looked dozens of papers but ... 1 vote 1 answer 46 views ### Nonlinear Optics: SHG and OPO I am new to nonlinear optics, and recently I started studying about the second harmonic generation (SHG) and the optical parametric oscillation (OPO) where these two nonlinear interactions are ... • 327 0 votes 0 answers 45 views ### Why can't gases produce second harmonic generation (ie, why is \chi^{(2)} always zero)? To quote wikipedia on second-harmonic generation: Since media with inversion symmetry are forbidden from generating second-harmonic light via the leading-order electric dipole contribution (unlike ... • 1,600 0 votes 0 answers 64 views ### Inversion symmetry for Second Harmonic Generation I read this question "Lack of inversion symmetry" in crystal?, but it is not quite clear to me how to clearly define the symmetry. Let me explain with a simple example. In the image below ... • 307 1 vote 0 answers 38 views ### 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 ... • 129 13 votes 8 answers 3k views ### 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 ... • 3,179 1 vote 0 answers 19 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? • 351 1 vote 0 answers 28 views ### 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 ... 3 votes 0 answers 55 views ### 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-... • 3,888 0 votes 1 answer 52 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 ... 1 vote 1 answer 39 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 ... • 11 0 votes 1 answer 23 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. 3 votes 1 answer 182 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}≈\... 1 vote 0 answers 23 views ### 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 ... 1 vote 3 answers 87 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 \vec{P}=\epsilon_0\chi^{(1)}\vec{E}+\epsilon_0\chi^{(2)}\... • 1,187 1 vote 0 answers 29 views ### 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'... • 1,187 1 vote 1 answer 55 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 ... • 118 1 vote 2 answers 55 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 ... 0 votes 1 answer 21 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 ... • 1,273 1 vote 1 answer 16 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 ... 0 votes 1 answer 177 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 ... 0 votes 1 answer 57 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 ... 0 votes 1 answer 115 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 ... 0 votes 1 answer 227 views ### 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. \... • 452 2 votes 1 answer 62 views ### 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 ... 0 votes 1 answer 21 views ### 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. 0 votes 0 answers 29 views ### 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? 1 vote 1 answer 20 views ### 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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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 ...