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"Polarization Controller Symbol A polarization controller is an optical device which allows one to modify the polarization state of light.E. Collett, "Polarized light in fiber optics",SPIE Press, p. 540 (2003) Types and operation Polarization controllers can be operated without feedback, typically by manual adjustment or by electrical signals from a generator, or with automatic feedback. The latter allows for fast polarization tracking. A polarization controller can have the task of transforming a fixed, known polarization into an arbitrary one. Since polarization states are defined by two degrees of freedom, for example azimuth angle and ellipticity angle of the polarization state, such a polarization controller needs two degrees of freedom. The same holds for the task of transforming an arbitrary polarization into a fixed, known one. More difficult is the transformation of an arbitrary polarization into another arbitrary polarization. Yet this requires just two degrees of freedom. Such a polarization controller can for example be obtained by placing on the optical path three rotatable waveplates in cascade: a first quarterwave plate, which is oriented to transform the incident elliptical polarization into linear polarization, a halfwave plate, which transforms this linear polarization into another linear polarization, and a second quarterwave plate, which transforms the other linear polarization into the desired elliptical output polarization. While the three rotatable waveplate positions present of course three degrees of freedom, one degree of freedom is consumed in the described case by the choice of linear polarizations before (and hence also behind) the halfwave plate. Polarization controllers can be implemented with free space optics, through a fiber pigtailed U-bench, for example. In that case, light exits the fiber, passes through the three waveplates, that can be freely rotated to allow polarization adjustment and then enters back into the fiber. Polarization controllers can also be implemented in an all- fiber solution. In that case, the polarization of light is changed through the application of a controlled stress to the fiber itself. For polarization controllers with automatic feedback, integrated optical lithium niobate (LiNbO3) devices are very suitableB. Koch, R. Noé, V. Mirvoda, H. Griesser, S. Bayer, H. Wernz, Record 59-krad/s Polarization Tracking in 112-Gb/s, 640-km, PDM-RZ-DQPSK Transmission, IEEE Photonics Technology Letters, 26 July 2010, DOI 10.1109/LPT.2010.2060719 and Vol. 22, No. 19, 2010, pp. 1407-1409B. Koch, R. Noé, V. Mirvoda, D. Sandel, 100-krad/s Endless Polarisation Tracking with Miniaturised Module Card, Electronics Letters, Vol. 47, No. 14, 2011, pp. 813-814. Polarization controllers with tracking speeds of up to 100 krad/s on the Poincaré sphere are commercially available (see external link at the bottom). If not only an arbitrary polarization is to be transformed into a desired one but also the phase shift between this polarization and its orthogonal is to be controlled then three degrees of freedom are necessary. An implementation with a tracking speed of 20 krad/s is described in B. Koch, R. Noé, V. Mirvoda, D. Sandel, First Endless Optical Polarization and Phase Tracker, Proc. OFC/NFOEC 2013, Anaheim, CA, Paper OTh3B.7, Mar. 17-21, 2013 https://www.novoptel.de/Control/Literature/OFC2013_3DOF_presentation_short_n06.pdf https://www.novoptel.eu/Control/Literature/OFC2013_3DOF_presentation_short_n06.pdf. This way the whole normalized Stokes space can be stabilized for implementation of the BB84 or similar quantum cryptography protocol. Another application scenario are phased arrays with coherent optical feeding. See also * Polarization scrambling * Fiber squeezer References External links Category:Fiber optics "
"Tucker with Lotte Lenya at Sadler's Wells Theatre, 1958 Norman Walter Gwynn Tucker (24 April 1910 – 10 August 1978) was an English musician, administrator and translator. Trained as a concert pianist, he was invited to join Sadler's Wells Opera in 1947 in an administrative role, and from 1948 to 1966 he was the managerial head of the company. His translations of operas new to the repertoire and fresh translations of repertoire works were performed by the company at Sadler's Wells Theatre and, after his retirement and the company's move, at the London Coliseum. Early years Tucker was born in the London suburb of Wembley, the son of Walter Edwin Tucker and his wife Agnes Janet."Tucker, Norman Walter Gwynn", Who Was Who, A & C Black, 1920–2008; online edition, Oxford University Press, December 2007, accessed 13 June 2011 He was educated at St Paul’s School, London, New College, Oxford, and the Royal College of Music.Rosenthal, Harold. "Tucker, Norman", The New Grove Dictionary of Opera, Grove Music Online, Oxford Music Online, accessed 13 June 2011 He graduated from the last with a performance of Brahms's Second Piano Concerto conducted by Sir Thomas Beecham. Piano career From 1935 until the Second World War he pursued a career as a concert pianist. During the war he served first as a stretcher-bearer in a hospital and then as private secretary to successive Chancellors of the Exchequer, Sir Kingsley Wood, Sir John Anderson and Hugh Dalton. After the war, Tucker resumed his career as a pianist, but in 1947 the conductor James Robertson invited him to join Sadler’s Wells Opera as joint director with himself and his co-conductor Michael Mudie. They were dubbed "the three Norns" by the company.Gilbert, p. 113 Administrative career The two conductors soon handed over all administrative responsibility to Tucker, who ran the company from 1948 until 1966.Gilbert, pp. 116 and 198 His experience at HM Treasury was valuable in the company's frequent negotiations with the Arts Council which dispensed the scarce public subsidies for the arts, and Tucker did much to secure the funding necessary for the survival of Sadler's Wells in the 1950s and 1960s.Gilbert, p. 117 For the company Tucker provided new translations to replace some of the stilted old ones, and translated other libretti into English for the first time. Prominent among the latter was Piave's libretto for Verdi's Simon Boccanegra of which Sadler's Wells gave the British premiere in 1948.Gilbert, p. 118 Other Verdi operas he translated were Luisa Miller and Don Carlos. Tucker was enthusiastic about the operas of Janáček (as was one of the company's rising young conductors, Charles Mackerras) and he translated Katya Kabanova, The Cunning Little Vixen and The Makropulos Affair for their Sadler’s Wells premieres. Tucker laid great emphasis on the dramatic side of opera, and was proud of attracting leading theatre directors to work at Sadler's Wells; they included Michel Saint-Denis, Glen Byam Shaw and George Devine. He introduced operetta to the company's repertoire. It proved a financial blessing. The success of The Merry Widow saved the company from financial crisis in 1958. That box-office hit, followed by another with Orpheus in the Underworld (1960), made him determined to stage Gilbert and Sullivan as soon the operas came out of copyright and the D'Oyly Carte Company's monopoly ceased at the end of 1961.Gilbert, p. 162 Iolanthe and The Mikado (both 1962) were box-office successes, and popular with the company, though less so with the higher-minded members of the Sadler's Wells board.Gilbert p. 176 Forced retirement Other tensions between Tucker and the board, combined with his great disappointment when a plan for a new opera house on the South Bank of the Thames was abandoned, badly affected his health. He began to drink excessively, and his contract was terminated by the board on 8 March 1966. He was succeeded by his deputy, Stephen Arlen. Death After his enforced retirement, Tucker continued to have ties with the company, making further translations including another Janáček opera, The Excursions of Mr. Brouček (1978)."Obituary – Mr Norman Tucker", The Times, 14 August 1978, p. 14 By the time the piece was staged, Tucker had died, aged 68; the first night was dedicated to his memory.Gilbert, p. 310 Notes References * Category:1910 births Category:1978 deaths Category:Opera managers "
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