------is 90° υ ϑ () 2 s is zero and obtain we υ co 0 =⋅ II is the angle position between both υ birefringent material. Areas with same inten behaviour a quarter of plate. wave turns It out nally oriented . polarizer. oriented nally nally aligned to each other thevalue of rection the of optical axis, the material behaves results which is a fingerprint for the specific resulting in zero transmission. Placing a half means that the half plate wave turns the polari maximum transmission. In they are orthogo tal is used. In a conoscopic set-up impressive tardationdifferentfor voltage measuredis level tion thetransmission becomes maximum, that that such a plate converts linear light into circu laser beam in ordinary and extraordinary rays larisation stage the of incident light. The corre lar ones provided the optical axis the of plate is places of same . Conoscopy is a .In casethey are oriented to the Pockels cell containing a Lithium Niobate crys interference pattern are created when the high high the when created pattern are interference is measured by using therotary polarisation is aligned orthogonally to the first one. In di isotropic and there will be no change in the po increase in the transmission. In a certain posi sponding image on the screen remains dark. All such a way that a fraction can pass the orthogo sity (same retardation) are termed as isogyres, sation Inby 90°. the sameexamine way we the same angle the value of and the half voltage wave is determined. are observed. The these of rays analyser. As an example a biaxial of crystal a axis undergochangea to their polarisationin as quality control for LCD displays. Consequently, a typical intensity distribution wave platewave between the polarizers results in an other rays propagating inclined to the optical rawof crystals in optic manufacturing as well oriented with by 45° respect to the polarisation direction the of light. voltage is applied. Furthermore, the optical re very important method to find the optical axis Whereby Iceland Spar () Jones matrix - - - otodetector re em conic em ­nents in , for example as orier oriser irerinent teri irerinent mteri half and quarter plates, wave precision polar uniaxial and biaxal crystals principles which means a photodetector, of the transmitted in the polarization and optical activity, and Jean- ting a wavelength nm(green). 532 of Thelight the birefringentmaterial. Thesecond polarizer the two polarizer the famous Malus’ law can be tensity is measured as a function the of angle passes the first polarizer. Afocusing lens cre Baptiste Biot who defined the first principles of important compo izer to tune laser lines. The experiments may is directed to thecalcite and thesplitting the of start with the observation birefringence of shown by calcite crystal. The green probe laser , by differentiating in particular, arestill valid today. Birefringentmaterials are ates the“conical” light beam which traverses orientation either of the birefringent material or the polarizer. Without any material between verified.

Pockels Cell

Ordinary and Extraordinary beam Crystalline quartz

ptic xis optic xis - - - - ocusin ens orier oriser The optical axis the of birefringent material perpendicular to the light beam The optical axis the of birefringent material parallel to the light beam

Birefringence Quarter and half waveplate Conoscopic imaging

not the only crystal which shows double refrac markedness this of phenomenon. His discovery materials are arrangements where the optical tion, but a crystal with an extraordinary high to the light source. In such a case, the light is placed between two rotatable polarizers. By Huygens in 1674 markedHuygens the in beginning 1674 the of Fig. 2.2: Fig. 1: In 1669, Erasmus Bartholin was the first one In this experimentare we usinglaser a emit is oriented parallel to the incident light beam. studies onoptical crystal properties. More than sights through DominiqueArago, who studied and its first scientific explanation by Christian almost parallel. The birefringent material is axis the of crystal is perpendicularly oriented a birefringent material where the optical axis fraction. investigated He a crystal calcite: of who reported his observations on double re The creation an of conoscopic image requires

100 years100 later, crystal optics got further in Another method to characterise birefringent

PE-0100 Double Refraction of Light RefractionDouble of PE-0100

How it works it How Introduction Keywords 5 Optic Experiments Experiments Fig. 2.5: 2.5: Fig. 2.4: Fig. Fig. 2.3: 2.3: Fig. Fig. 2.6: 2.6: Fig. Item PE-0100 Double Refraction of Light consisting of: consisting of Light Double Refraction PE-0100 8 12 10 13 14 15 16 17 11 6 4 5 3 1 2 9 7 6 8 270 290 1 A 310

Option (orderOption separately) 330 MM-0020 MM-0420 MM-0430 OM-0800 UM-PE01 MM-0110 OC-0040 OC-0840 DC-0020 OC-0820 OC-0830 OC-0360 DC-0250 LQ-0020 MP-0150 OC-0710 DC-0358 Conoscopic Setup for a quartz crystal plate crystal aquartz for Setup Conoscopic Conoscopic Setup with a calcite crystal acalcite with Setup Conoscopic Setup to measure the phase retardation and Malus’ law Malus’ and retardation phase the measure to Setup Conoscopic Setup for a calcite crystal acalcite for Setup Conoscopic

Code 350 0

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0.6 30

0.8 1.0 50

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Qty.

70 3 3 90 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 Active SiPIN Photodetector SiPIN Active Translucent screen on carrier MG20 carrier on screen Translucent Calcite crystal on rod and carrier and rod on crystal Calcite Quarter wave plate in C25 mount C25 in wave plate Quarter mount C25 in plate quartz Optical mm 500 MG-65, Bench Optical (532 housing ø25 Green DPSSL in nm) LED and PD Conroller and LED Rotary mount on carrier MG20 carrier on mount Rotary Pockels’s cell assembly on C30 on Pockels’s assembly cell DQ21 Driver Cell Pockels of Light Refraction Manual mount C25 in Polariser housing ø25 x6 in Expander Beam mount C25 in mm f=40 lens Plano-convex MG20 carrier on mount kinematic axes Four MG20 carrier on C25 plate Mounting Description 270 290 B 310

330 10 4

350 11 0

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0.6 30 14 7 0.8 13

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1.0 50

70 90 9 11

270 290 C 310 7

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350 7 5 2 0

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70 90 4 A Pockels cell is placed in the focal plane of a polarized and a conoscopic a conoscopic and of a polarized plane focal the in placed is cell A Pockels A green laser pointer (3) is used as light source. In a first experimentthe With a value of avalue With Conoscopy withacalcitecrystal Conoscopy withaquartz Characterising aPockelsCell of the half wave voltage. At the lowest applicable voltage the polarisation polarisation the voltage applicable lowest At the wave voltage. half of the determination the is example measurement Another of symmetry. lower To make sure that the laser light is linearly polarized, one polar one polarized, linearly is light laser the that To sure make when the phase retardation of the cell is is cell of the retardation phase the when ence can be observed on a screen and need to be interpreted. When the the When interpreted. be to need and ascreen on observed be can ence one polarizer (11) is used. The laser beam is expanded (10) and passes the the (10) passes expanded and is beam (11) laser The polarizer used. one is axis lies perpendicular to the surface of the plate The divergent beam beam divergent The plate of the surface the to perpendicular lies axis (13) the plate in placed is quartz refractive a“cone”. Adouble forms and analyser is turned to maximum intensity. The cell voltage is increased increased is voltage cell The intensity. maximum to turned is analyser can be interpreted as a bunch of rays with different propagation angle angle propagation different with rays of bunch a as interpreted be can corner to the other. Such a crystal is mounted to a post holder to permit permit to holder apost to mounted is acrystal Such other. the to corner stronger double refraction than a quartz crystal with has a value of 0.0091. avalue has with crystal aquartz than refraction double stronger optical the that amanner such in cut is crystal The plane. focal created so in the distance of its focal length and subsequently it becomes divergent divergent itbecomes subsequently and length focal of its distance the in ial and shows other interference patterns, characteristic for such crystals crystals such for characteristic patterns, interference other shows and ial aelt w wl gt litcl B o crua plrzd ih (C). light polarized circular or (B) elliptical get will we waveplate controller (1). For different angles of the polarizer the intensity is drawn drawn is intensity the polarizer the of angles (1). different For controller By adding the lens (9) in the beam path, the laser beam creates a focus afocus creates beam laser the path, beam (9) the lens in the adding By should expect a graph like (A). like agraph expect should passing the quartz crystal. All those rays which are retarded by by retarded are which rays those All crystal. quartz the passing izer is placed behind the beam expander and turned to maximum in maximum to turned and expander beam the behind placed is izer we polarized linearly is laser the If coordinates. polar with agraph into the study of the much stronger conoscopic pattern on the screen. the on pattern conoscopic stronger much of the study the until the transmitted intensity becomes almost zero which is the case case the is which zero almost becomes intensity transmitted the until placed between the polarizer. Depending on the orientation of the of the orientation the on Depending polarizer. the between placed light of the (2) intensity the (11). photodetector of the polarizer means By only purpose For this (3) determined. laser is probe of the polarisation bright areas on the screen (5). screen the on areas bright and of dark pattern a beautiful creating polarizer next the by blocked be beam. By inserting a polarization analyser, beautiful patterns of interfer patterns beautiful analyser, apolarization inserting By beam. Double RefractionandMalus’ Law transmitted intensity is almost zero. The quarter waveplate (14) waveplate is quarter The zero. almost is intensity transmitted the For (A). law Malus’ the of verification the yield will intensity the plot of Aangular analyser. as used is polarizer second The tensity. next experiment the polarizers are oriented in such a way that the the that away such in oriented are polarizers the experiment next half waveplate. waveplate. half biax becomes crystal the on, switched is cell Pockels the to voltage high behind the second polarizer is detected and the value is displayed on the the on displayed is value the and detected is polarizer second the behind Details page Δn=0.172 Conoscopy suitable for live demonstration suitable Conoscopy Basic experiment Basic calcite crystal has a more than 100 times 100 times than amore has crystal calcite The optical axis of the calcite crystal goes goes crystal calcite of the axis optical The of the crystal as shown in the picture on the the on picture the in shown as crystal of the from the upper left to the lower right corner corner right lower the to left upper the from such a way that a beam can travel from one one from travel can abeam that away such left. Therefore we need to cut the crystal in in crystal the cut to we need Therefore left. Intended institutions and users: and institutions Intended Electronic department Electronic department Engineering Physics education in Medicine in education Physics department Biophotonics Laboratory Physics iits λ/2 . In this case the cell acts as as acts cell the case this . In λ/2 will will - - - - 6

Optic Experiments