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| {{Redirect|Étalon|the ''commune'' in [[Somme]], [[France]]|Étalon, Somme}}
| | Because you can eat because much fruit as we like, we wont be affected by hunger. There is equally enough variation of different types of fruit, making the fruit diet not boring at all.<br><br>[http://safedietplans.com diets] actually have the above mentioned reported criteria plus let the dieter to consume what they need at certain certain periods. This would confirm which the dieter does not get into binge eating and refuses to drop away within the diet.<br><br>There are three major items a individual should remember on her diet plans losing weight. One is that calories are enemies, 2nd is that fiber is a advantageous friend plus 3rd is the fact that water may fill one up.<br><br>Take a great deal of vegetables: take about 6 serving of fresh veggies daily. If greens are from your reach, you are able to replace them with multivitamins. Make a meticulous choice when selecting the many adequate multivitamin, many over the counter multivitamins cause a lot of hunger pangs. Take varieties of veggies per day to enhance the vitamins, minerals, and phyto-chemicals your body need. Vegetables like pumpkin and green leaves are many adequate when you are inside a fat loss system. Additionally if you need to eat salad, blend it with sandwiches instead of butter.<br><br>To be extremely honest with you is the fact that the diets that are promoted are all trash. Yes. Garbage. None of those fad diet do not work. I guess it may start creating sense to you why you can not lose fat. Additionally we should understand that all those diets are the cause of we Yo-Yo Dieting, losing fat and gaining more in couple of weeks, being cranky and stressful etc.<br><br>The Cabbage Diet. Lose weight rapidly with all the cabbage diet. This diet consists of making a soup with cabbage, which you'll eat during the 7-day length of the diet. The diet is low in fat, and significant in fiber that can assist you lose weight quickly. During this diet you'll rotate between eating cabbage soup and fruit with eating greens plus meat on each different day. This diet might help you lose fat because it happens to be low in calories. Some people find it hard to maintain this diet due to the limited food options it allows.<br><br>We have considered all of the above citations to choose diet medications which function. Our goal is to guide we through acquiring carefully selected high quality fat reduction supplements, prepared from natural resources plus clinically proven to bring you the best results possible. Choose from the right and lose fat with self-confidence. The trim and appealing you're possible. Make the analysis and slim down the healthy way with top quality diet supplements. |
| [[File:Fabry Perot Etalon Rings Fringes.png|right|thumb|200px|Interference fringes, showing [[fine structure]], from a Fabry–Pérot etalon. The source is a cooled [[deuterium]] lamp.]]
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| In [[optics]], a '''Fabry–Pérot interferometer''' or '''etalon''' is typically made of a transparent plate with two [[Reflection (physics)|reflecting]] surfaces, or two parallel highly reflecting mirrors. (Technically the former is an etalon and the latter is an [[interferometer]], but the terminology is often used inconsistently.) Its transmission [[optical spectrum|spectrum]] as a function of [[wavelength]] exhibits peaks of large transmission corresponding to resonances of the etalon. It is named after [[Charles Fabry]] and [[Alfred Perot]].<ref>Perot frequently spelled his name with an accent—Pérot—in scientific publications, and so the name of the interferometer is commonly written with the accent. {{cite journal
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| | first=Françoise |last=Métivier
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| |title=Jean-Baptiste Alfred Perot
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| |date=September–October 2006
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| | journal=Photoniques |issue= 25| language=French
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| |url=http://www.sabix.org/documents/perot.pdf |format=pdf
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| |accessdate=2007-10-02}} Page 2: "Pérot ou Perot?"</ref> "Etalon" is from the French ''étalon'', meaning "measuring gauge" or "standard".<ref>''[[Oxford English Dictionary]]''</ref>
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| Etalons are widely used in [[telecommunication]]s, [[laser]]s and [[spectroscopy]] to control and measure the [[wavelength]]s of light. Recent advances in fabrication technique allow the creation of very precise tunable Fabry–Pérot interferometers.
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| == Basic description ==
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| [[File:Fabry Perot Interferometer - diagram.png|thumb|300px|Fabry–Pérot interferometer, using a pair of partially reflective, slightly wedged optical flats. The wedge angle is highly exaggerated in this illustration; only a fraction of a degree is actually necessary. Low-finesse versus high-finesse images correspond to mirror reflectivities of 4% (bare glass) and 95%.]]
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| The heart of the Fabry–Pérot interferometer is a pair of partially reflective glass [[optical flat]]s spaced millimeters to centimeters apart, with the reflective surfaces facing each other. (Alternatively, a Fabry–Pérot ''etalon'' uses a single plate with two parallel reflecting surfaces.) The flats in an interferometer are often made in a wedge shape to prevent the rear surfaces from producing interference fringes; the rear surfaces often also have an [[anti-reflective coating]].
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| In a typical system, illumination is provided by a diffuse source set at the [[focal plane]] of a [[collimating lens]]. A focusing lens after the pair of flats would produce an inverted image of the source if the flats were not present; all light emitted from a point on the source is focused to a single point in the system's image plane. In the accompanying illustration, only one ray emitted from point A on the source is traced. As the ray passes through the paired flats, it is multiply reflected to produce multiple transmitted rays which are collected by the focusing lens and brought to point A' on the screen. The complete interference pattern takes the appearance of a set of concentric rings. The sharpness of the rings depends on the reflectivity of the flats. If the reflectivity is high, resulting in a high [[Q factor]], [[monochromatic light]] produces a set of narrow bright rings against a dark background. A Fabry–Pérot interferometer with high Q is said to have high ''finesse''.
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| == Applications ==
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| [[Image:LASCO C1a.png|thumb|right|A picture of the solar corona taken with the [[Large Angle and Spectrometric Coronagraph|LASCO]] C1 coronagraph which employed a tunable Fabry–Pérot interferometer to recover scans of the solar corona at a number of wavelengths near the FeXIV green line at 5308 Å. The picture is a color-coded image of the [[Doppler effect|doppler shift]] of the line, which may be associated with the [[Corona|coronal plasma]] velocity towards or away from the satellite camera. In calculating the velocity, the velocity due to [[solar rotation]] has been subtracted.]]
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| [[File:Dispositif Fabry-Perot .jpg|thumb|A commercial Fabry-Perot device]]
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| * Telecommunications networks employing [[wavelength division multiplexing]] have [[add-drop multiplexer]]s with banks of miniature tuned [[fused silica]] or [[diamond]] etalons. These are small iridescent cubes about 2 mm on a side, mounted in small high-precision racks. The materials are chosen to maintain stable mirror-to-mirror distances, and to keep stable frequencies even when the temperature varies. Diamond is preferred because it has greater heat conduction and still has a low coefficient of expansion. In 2005, some telecommunications equipment companies began using solid etalons that are themselves optical fibers. This eliminates most mounting, alignment and cooling difficulties.
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| * [[Dichroic filter]]s are made by depositing a series of etalonic layers on an optical surface by [[Vacuum deposition|vapor deposition]]. These [[optical filter]]s usually have more exact reflective and pass bands than absorptive filters. When properly designed, they run cooler than absorptive filters because they can reflect unwanted wavelengths. Dichroic filters are widely used in optical equipment such as light sources, cameras, astronomical equipment, and laser systems.
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| * Optical [[wavemeter]]s use Fabry–Pérot interferometers with different free spectral ranges to determine the wavelength of light with great precision.
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| *[[Optical cavity|Laser resonators]] are often described as Fabry–Pérot resonators, although for many types of laser the reflectivity of one mirror is close to 100%, making it more similar to a [[Gires–Tournois interferometer]]. Semiconductor [[diode laser]]s sometimes use a true Fabry–Pérot geometry, due to the difficulty of coating the end facets of the chip.
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| *Etalons are often placed inside the laser resonator when constructing single-mode lasers. Without an etalon, a laser will generally produce light over a wavelength range corresponding to a number of [[Optical cavity|cavity]] modes, which are similar to Fabry–Pérot modes. Inserting an etalon into the laser cavity, with well-chosen finesse and free-spectral range, can suppress all cavity modes except for one, thus changing the operation of the [[laser]] from multi-mode to single-mode.
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| *Fabry–Pérot etalons can be used to prolong the interaction length in [[laser absorption spectrometry]], particularly [[cavity ring-down spectroscopy|cavity ring-down]], techniques.
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| *A Fabry–Pérot etalon can be used to make a [[spectrometer]] capable of observing the [[Zeeman effect]], where the [[spectral lines]] are far too close together to distinguish with a normal spectrometer.
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| *In [[astronomy]] an etalon is used to select a single [[atomic transition]] for imaging. The most common is the [[H-alpha]] line of the [[sun]]. The [[Calcium#H_and_K_lines|Ca-K]] line from the sun is also commonly imaged using etalons.
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| *In [[gravitational wave]] detection, a Fabry–Pérot cavity is used to ''store'' [[photon]]s for almost a millisecond while they bounce up and down between the mirrors. This increases the time a gravitational wave can interact with the light, which results in a better sensitivity at low frequencies. This principle is used by detectors such as [[LIGO]] and [[Virgo interferometer|Virgo]], which consist of a [[Michelson interferometer]] with a Fabry–Pérot cavity with a length of several kilometers in both arms. Smaller cavities, usually called ''mode cleaners'', are used for [[spatial filter]]ing and frequency stabilization of the main laser.
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| == Theory ==
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| [[File:Etalon-2.svg|frame|right|A Fabry–Pérot etalon. Light enters the etalon and undergoes multiple internal reflections.]]
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| The varying transmission function of an etalon is caused by [[Interference (wave propagation)|interference]] between the multiple reflections of light between the two reflecting surfaces. Constructive interference occurs if the transmitted beams are in [[phase (waves)|phase]], and this corresponds to a high-transmission peak of the etalon. If the transmitted beams are out-of-phase, destructive interference occurs and this corresponds to a transmission minimum. Whether the multiply<!--YES THIS IS CORRECT--> reflected beams are in phase or not depends on the wavelength (λ) of the light (in vacuum), the angle the light travels through the etalon (θ), the thickness of the etalon (''ℓ'') and the [[refractive index]] of the material between the reflecting surfaces (''n'').
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| The phase difference between each successive transmitted pair (i.e. T2 - T1 in the diagram) is given by δ:<ref name="Lipson, Optical Physics" >{{cite book
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| |first=S.G. |last=Lipson |first2=H. |last2=Lipson |first3=D.S. |last3=Tannhauser
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| |year=1995
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| |title=Optical Physics
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| |edition=3rd
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| |pages=248
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| |ref=Lipson, Optical Physics
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| |isbn=0-521-06926-2
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| |publisher=Cambridge U.P.
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| |location=London
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| }}</ref>
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| :<math>\delta = \left( \frac{2 \pi}{\lambda} \right) 2 n \ell \cos\theta. </math>
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| If both surfaces have a [[reflectance]] ''R'', the [[transmission coefficient|transmittance function]] of the etalon is given by
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| :<math>T_e = \frac{(1-R)^2}{1+R^2-2R\cos\delta}=\frac{1}{1+F\sin^2(\delta/2)},</math>
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| where
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| :<math> F = \frac{4R}{{(1-R)^2}}</math>
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| is the ''coefficient of finesse''.
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| [[Image:Etalon-2.png|frame|right|The transmission of an etalon as a function of wavelength. A high-finesse etalon (red line) shows sharper peaks and lower transmission minima than a low-finesse etalon (blue).]]
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| Maximum transmission (<math>T_e=1</math>) occurs when the [[optical path length]] difference (<math>2 n l \cos\theta</math>) between each transmitted beam is an integer multiple of the wavelength. In the absence of absorption, the reflectance of the etalon ''R''<sub>e</sub> is the complement of the transmittance, such that <math>T_e+R_e=1</math>. The maximum reflectivity is given by:
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| :<math>R_\max = 1-\frac{1}{1+F}= \frac {4R}{(1+R)^2} </math>
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| and this occurs when the path-length difference is equal to half an odd multiple of the wavelength.
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| [[File:Etalon-finesse-vs-reflectivity-2012-May-15.svg|thumb|400px|right|Finesse as a function of reflectivity. Very high finesse factors require highly reflective mirrors.]]
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| The wavelength separation between adjacent transmission peaks is called the [[free spectral range]] (FSR) of the etalon, Δλ, and is given by: | |
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| :<math>\Delta\lambda = \frac{ \lambda_0^2}{2n\ell \cos\theta + \lambda_0 } \approx \frac{ \lambda_0^2}{2n\ell \cos\theta } </math>
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| where λ<sub>0</sub> is the central wavelength of the nearest transmission peak. The FSR is related to the full-width half-maximum, δλ, of any one transmission band by a quantity known as the ''finesse'':
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| :<math> \mathcal{F} = \frac{\Delta\lambda}{\delta\lambda}=\frac{\pi}{2 \arcsin(1/\sqrt F)}</math>.
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| This is commonly approximated (for ''R'' > 0.5) by
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| :<math> \mathcal{F} \approx \frac{\pi \sqrt{F}}{2}=\frac{\pi R^{1/2} }{1-R} </math>
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| Etalons with high finesse show sharper transmission peaks with lower minimum transmission coefficients. In the oblique incidence case, the finesse will depend on the polarization state of the beam, since the value of "R", given by the [[Fresnel equations]], is generally different for p and s polarizations.
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| A Fabry–Pérot interferometer differs from a Fabry–Pérot etalon in the fact that the distance ''ℓ'' between the plates can be tuned in order to change the wavelengths at which transmission peaks occur in the interferometer. Due to the angle dependence of the transmission, the peaks can also be shifted by rotating the etalon with respect to the beam.
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| Fabry–Pérot interferometers or etalons are used in [[optics|optical]] [[modem]]s, [[spectroscopy]], [[laser]]s, and [[astronomy]].
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| A related device is the [[Gires–Tournois etalon]].
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| {{clear}}
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| === Detailed analysis ===
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| {{Unreferenced section|date=October 2011}}
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| [[Image:Fabry Perot Diagram1.svg|320px|right]]
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| Two beams are shown in the diagram at the right, one of which (T<sub>0</sub><!--NOT A VARIABLE-->) is transmitted through the etalon, and the other of which (T<sub>1</sub><!--NOT A VARIABLE-->) is reflected twice before being transmitted. At each reflection, the amplitude is reduced by <math>\sqrt R</math>, while at each transmission through an interface the amplitude is reduced by <math>\sqrt T</math>. Assuming no absorption, [[conservation of energy]] requires ''T'' + ''R'' = 1. In the derivation below, ''n'' is the index of refraction inside the etalon, and ''n''<sub>0</sub> is that outside the etalon. It is presumed that ''n'' > ''n''<sub>0</sub>. The incident amplitude at point a is taken to be one, and [[phasor]]s are used to represent the amplitude of the radiation. The transmitted amplitude at point b will then be
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| :<math>t_0 = T\,e^{ik\ell/\cos\theta}</math>,
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| where <math>k=2\pi n/\lambda</math> is the wavenumber inside the etalon and λ is the vacuum wavelength. At point c the transmitted amplitude will be
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| :<math>t'_1 = TR\,e^{3ik\ell/\cos\theta}</math>.
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| The total amplitude of both beams will be the sum of the amplitudes of the two beams measured along a line perpendicular to the direction of the beam. The amplitude ''t''<sub>0</sub> at point b can therefore be added to ''t'''<sub>1</sub> retarded in phase by an amount <math>k_0 \ell_0</math> where <math>k_0=2\pi n_0/\lambda</math> is the wavenumber outside of the etalon. Thus
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| :<math>t_1 = TR\,e^{3ik\ell/\cos\theta-ik_0 \ell_0}</math>,
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| where ℓ<sub>0</sub> is
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| :<math>\ell_0=2\ell\tan\theta\sin\theta_0\,</math>.
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| The phase difference between the two beams is
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| :<math>\delta={2k\ell\over\cos\theta} - k_0 \ell_0\,</math>.
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| The relationship between ''θ'' and ''θ''<sub>0</sub> is given by [[Snell's law]]: | |
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| :<math>n\sin\theta=n_0\sin\theta_0\,</math>,
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| so that the phase difference may be written:
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| :<math>\delta=2k\ell\,\cos\theta\,</math>.
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| To within a constant multiplicative phase factor, the amplitude of the ''m''th transmitted beam can be written as:
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| :<math>t_m=TR^m e^{im\delta}\,</math>.
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| The total transmitted amplitude is the sum of all individual beams' amplitudes:
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| :<math>t=\sum_{m=0}^\infty t_m=T\sum_{m=0}^\infty R^m\,e^{im\delta}</math>
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| The series is a [[geometric series]] whose sum can be expressed analytically. The amplitude can be rewritten as
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| :<math>t=\frac{T}{1-Re^{i\delta}}</math>.
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| The intensity of the beam will be just ''t'' times its [[complex conjugate]]. Since the incident beam was assumed to have an intensity of one, this will also give the transmission function:
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| :<math>T_e=tt^*=\frac{T^2}{1+R^2-2R\cos\delta}</math>
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| ===Another expression for the transmission function===
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| Defining <math>\gamma=\ln(1/R)</math> the above expression may be written as:
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| :<math>T_e=\frac{T^2}{1-R^2}\left(\frac{\sinh\gamma}{\cosh\gamma-\cos\delta}\right)</math>
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| The second term is proportional to a [[wrapped Cauchy distribution|wrapped Lorentzian distribution]] so that the transmission function may be written as a series of [[Cauchy distribution|Lorentzian functions]]:
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| :<math>T_e=\frac{2\pi\,T^2}{1-R^2}\,\sum_{\ell=-\infty}^\infty L(\delta-2\pi\ell;\gamma)</math>
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| where
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| :<math>L(x;\gamma) = \frac{\gamma}{\pi(x^2+\gamma^2)}</math>
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| == See also ==
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| * [[Lummer–Gehrcke interferometer]]
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| * [[Atomic line filter]]
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| * [[ARROW waveguide]]
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| * [[Distributed Bragg reflector]]
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| * [[Fiber Bragg grating]]
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| * [[Optical microcavity]]
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| * [[Thin-film interference]]
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| ==Notes and references==
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| {{reflist}}
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| *{{cite book
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| | first = G. | last = Hernandez
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| | year = 1986
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| | title = Fabry–Pérot Interferometers
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| | publisher = Cambridge University Press | location = Cambridge
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| | isbn = 0-521-32238-3
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| }}
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| ==External links==
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| * [http://www.infratec.de/fileadmin/media/Sensorik/pdf/Appl_Notes/Application_note_FP_detectors.pdf Compact FP interferometer for gas analysis]
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| *[http://www.precisionphotonics.com/technology/EtalonAdvanced.pdf Advanced Design of Etalons]- by Precision Photonics Corporation
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| {{DEFAULTSORT:Fabry Perot Interferometer}}
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| [[Category:Interferometers]]
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Because you can eat because much fruit as we like, we wont be affected by hunger. There is equally enough variation of different types of fruit, making the fruit diet not boring at all.
diets actually have the above mentioned reported criteria plus let the dieter to consume what they need at certain certain periods. This would confirm which the dieter does not get into binge eating and refuses to drop away within the diet.
There are three major items a individual should remember on her diet plans losing weight. One is that calories are enemies, 2nd is that fiber is a advantageous friend plus 3rd is the fact that water may fill one up.
Take a great deal of vegetables: take about 6 serving of fresh veggies daily. If greens are from your reach, you are able to replace them with multivitamins. Make a meticulous choice when selecting the many adequate multivitamin, many over the counter multivitamins cause a lot of hunger pangs. Take varieties of veggies per day to enhance the vitamins, minerals, and phyto-chemicals your body need. Vegetables like pumpkin and green leaves are many adequate when you are inside a fat loss system. Additionally if you need to eat salad, blend it with sandwiches instead of butter.
To be extremely honest with you is the fact that the diets that are promoted are all trash. Yes. Garbage. None of those fad diet do not work. I guess it may start creating sense to you why you can not lose fat. Additionally we should understand that all those diets are the cause of we Yo-Yo Dieting, losing fat and gaining more in couple of weeks, being cranky and stressful etc.
The Cabbage Diet. Lose weight rapidly with all the cabbage diet. This diet consists of making a soup with cabbage, which you'll eat during the 7-day length of the diet. The diet is low in fat, and significant in fiber that can assist you lose weight quickly. During this diet you'll rotate between eating cabbage soup and fruit with eating greens plus meat on each different day. This diet might help you lose fat because it happens to be low in calories. Some people find it hard to maintain this diet due to the limited food options it allows.
We have considered all of the above citations to choose diet medications which function. Our goal is to guide we through acquiring carefully selected high quality fat reduction supplements, prepared from natural resources plus clinically proven to bring you the best results possible. Choose from the right and lose fat with self-confidence. The trim and appealing you're possible. Make the analysis and slim down the healthy way with top quality diet supplements.