Polarization-independent bidirectional 4×4 optical switch in free space

Abstract. Liquid crystals are nowadays widely used in all types of display applications. However their unique electro-optic properties also make them a suitable material for nondisplay applications. We will focus on the use of liquid crystals in different photonic components: optical filters and switches, beam-steering devices, spatial light modulators, integrated devices based on optical waveguiding, lasers, and optical nonlinear components. Both the basic operating principles as well as the recent state-of-the art are discussed. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).[ DOI: 10.1117/1.3565046] Subject terms: liquid crystals; photonic applications; review; liquid-crystal lasers; spatial light modulators; tunable lenses; nematicons; optical nonlinearity.Paper 100913SSR received Nov. 5, 2010; revised manuscript received Jan. 11, 2011; accepted for publication Jan. 13, 2011; published online Jun. 14, 2011. IntroductionLiquid crystals (LCs) are organic materials that are liquid but that show a certain degree of ordering (positional and/or orientational). With this definition, many materials can be classified as liquid crystals, but the majority of liquid crystals that are used in photonic applications are of the thermotropic type. Thermotropic means that the liquid-crystal phase exists within a certain temperature interval (in contrast to lyotropic materials for which the material is liquid-crystal within a certain concentration range). Various types of thermotropic liquid-crystal materials exist, and many different mesophases have been discovered in the last decades: nematic, smectic A, smectic C, columnar, blue phases, and many many more. The diversity of liquid-crystal materials is huge, but this diversity is even overshadowed by the number of applications in which liquid crystals are used nowadays. The majority of applications are related to informationdisplay applications. Liquid crystals have conquered the major market share in different display application areas: television screens, laptop screens, screens in mobile phones, etc. Only in projection displays does a tough competitor exist, namely microelectromechanical systems or licenced by Texas Instruments: Digital light processing. Organic light emitting diodes (OLEDs) are the obvious next generation technology that could overtake the LC domination, but today OLED displays have not penetrated the market and only the future will tell if they will. In this review article, we will focus on nondisplay applications, but because we cannot go too broad, we restrict ourselves to photonic applications in which the light is actively manipulated by the LC. In this review article, a certain external influence (surface anchoring, electric fields, optical fields) is used to (re)orient the LC in a certain way. In turn, the LC then changes the light that is propagating through it. Of course, as in every review article, it is impossible to list all the fascinating new scientific results or breakthroughs. Therefore, the authors apologize for not i...

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“…[36][37][38] However, most of the promising free-space LC switches are based on a different principle, which is shown in Fig. 7.…”

Section: Optical Switches In Free Spacementioning

confidence: 99%

Liquid-crystal photonic applications

2011

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“…It consists of two physically distinct detection bases and a mirror which directs all incoming light to one and only one base under the control of a local and private QRNG. This switching mechanism is allowed by the laws of quantum mechanics and could be implemented, for example, via the use of a motorized mirror, a MEMS router [25,26], a mechanical switch inside optical fibers [27], or an electro-optically controlled Mach-Zehnder interferometer (MZI) 2 × 2 port switch [28]. While micromechanical mirror switches offer switching times as low as a microsecond, an MZI offers sub-nanosecond switching times and is suitable for photonic integration.…”

Section: Improved Setup With a Fully Active Base Selectionmentioning

confidence: 99%

Enhancing the Security of the BB84 Quantum Key Distribution Protocol against Detector-Blinding Attacks via the Use of an Active Quantum Entropy Source in the Receiving Station

Stipčević

2023

Entropy

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True randomness is necessary for the security of any cryptographic protocol, including quantum key distribution (QKD). In QKD transceivers, randomness is supplied by one or more local, private entropy sources of quantum origin which can be either passive (e.g., a beam splitter) or active (e.g., an electronic quantum random number generator). In order to better understand the role of randomness in QKD, I revisit the well-known “detector blinding” attack on the BB84 QKD protocol, which utilizes strong light to achieve undetectable and complete recovery of the secret key. I present two findings. First, I show that the detector-blinding attack was in fact an attack on the receiver’s local entropy source. Second, based on this insight, I propose a modified receiver station and a statistical criterion which together enable the robust detection of any bright-light attack and thus restore security.

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“…Among them, electro‐optic switches‐based silica by materials has low coupling coefficient and insertion loss. However, its switching time is larger than millisecond order because of its low heat transfer coefficient [23]. Silicon‐on‐insulator thermo‐optic switch also suffers greater insertion loss (>1.5 dB) and higher power consumption (∼600 mW) [24].…”

Section: Introductionmentioning

confidence: 99%

Optical data shifting using polarisation properties of light

Chattopadhyay

2015

IET Optoelectronics

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Polarization-independent bidirectional 4×4 optical switch in free space

Cited by 14 publications

References 50 publications

Liquid-crystal photonic applications

Liquid-crystal photonic applications

Enhancing the Security of the BB84 Quantum Key Distribution Protocol against Detector-Blinding Attacks via the Use of an Active Quantum Entropy Source in the Receiving Station

Optical data shifting using polarisation properties of light

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