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Photonic crystals

Shuhei Hatanaka, Kazuhiko Sugiyama, Masatoshi Mitaki, Masatoshi Misono, Sergey N Slyusarev, Masao Kitano
We phase lock an octave-spanning optical frequency comb, generated using a mode-locked titanium-sapphire laser and a photonic-crystal fiber, to a continuous-wave laser line-narrowed to a reference cavity. To phase lock the pulse-repetition frequency, the cavity length of the mode-locked laser is controlled by using a fast piezoelectric-actuated mirror of a servo bandwidth up to 80 kHz. The residual phase noise is 0.35 rad, and 89% of the power is concentrated to the carrier. To apply the system to optical frequency-ratio measurements and to evaluate the phase locking, a simultaneous frequency measurement of the beat between the other mode of the comb and another laser line-narrowed to a different resonance of the common reference cavity is demonstrated...
April 20, 2017: Applied Optics
Kawsar Ahmed, Sawrab Chowdhury, Bikash Kumar Paul, Md Shadidul Islam, Shuvo Sen, Md Ibadul Islam, Sayed Asaduzzaman
In this paper, a novel polarization-maintaining single-mode photonic crystal fiber (PCF) has been suggested for terahertz (THz) transmission applications. The reported PCF has five layers of hexagonal cladding with two layers of porous core. The cladding and core territory of the PCF are constituted by circular and elliptical air cavities, accordingly acting as a dielectric medium. Different geometrical parameters of the proposed PCF including pitches and diameters of circular air holes with the major and minor axes of elliptical air cavities being varied with the optimized structure...
April 20, 2017: Applied Optics
Bradley, S F Abdul Sani, A S Siti Shafiqah, S M Collins, R P Hugtenburg, H A Abdul Rashid, Nurul Najua Zulkepely, M J Maah
Using tailor-made sub-mm dimension doped-silica fibres, thermoluminescent dosimetric studies have been performed for α-emitting sources of (223)RaCl2 (the basis of the Bayer Healthcare product Xofigo®). The use of (223)RaCl2 in the palliative treatment of bone metastases resulting from late-stage castration-resistant prostate cancer focuses on its favourable uptake in metabolically active bone metastases. Such treatment benefits from the high linear energy transfer (LET) and associated short path length (<100µm) of the α-particles emitted by (223)Ra and its decay progeny...
April 14, 2017: Applied Radiation and Isotopes
Kuo Zhong, Ling Wang, Jiaqi Li, Stijn Van Cleuvenbergen, Carmen Bartic, Kai Song, Koen Clays
Hollow sphere colloidal photonic crystals (HSCPCs) exhibit the ability to maintain a high refractive index contrast after infiltration of water, leading to extremely high-quality photonic band gap effects, even in an aqueous (physiological) environment. Superhydrophilic pinning centers in a superhydrophobic environment can be used to strongly confine and concentrate water-soluble analytes. We report a strategy to realize real-time ultrasensitive fluorescence detection in patterned HSCPCs based on strongly enhanced fluorescence due to the photonic band edge effect combined with wettability differentiation in the superhydrophobic/superhydrophilic pattern...
April 21, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Carlos G Avendaño, Arturo Reyes
We theoretically study the dispersion relation for axially propagating electromagnetic waves throughout a one-dimensional helical structure whose pitch and dielectric and magnetic properties are spatial random functions with specific statistical characteristics. In the system of coordinates rotating with the helix, by using a matrix formalism, we write the set of differential equations that governs the expected value of the electromagnetic field amplitudes and we obtain the corresponding dispersion relation...
March 2017: Physical Review. E
Sergei Sokolov, Jin Lian, Sylvain Combrié, Alfredo De Rossi, Allard P Mosk
Ga<sub>0.51</sub>In<sub>0.49</sub>P is a promising candidate for thermally tunable nanophotonic devices due to its low thermal conductivity. In this work we study its thermo-optical response. We obtain the linear thermo-optical coefficient dn/dT=2.0±0.3·10<sup>-4</sup>  K<sup>-1</sup> by investigating the transmission properties of a single mode-gap photonic crystal nanocavity.
April 10, 2017: Applied Optics
J Mundry, J Lohrenz, M Betz
Up to 400 mW of near-IR (1370-1500 nm) femtosecond pulses are generated from an optical parametric amplifier directly driven by a Yb:fiber oscillator delivering 100 fs pulses at 1036 nm. The process is seeded by a stable supercontinuum obtained from a photonic crystal fiber. We use a single pass through a 3 mm, magnesium oxide-doped, periodically poled LiNbO<sub>3</sub> downconversion crystal to produce a near-IR pulse train with a remarkable power stability of 1.4% (RMS) during one hour. Tuning is achieved by the temperature and the poling period of the nonlinear crystal...
April 10, 2017: Applied Optics
Siqi Yan, Ziwei Cheng, Lars Hagedorn Frandsen, Yunhong Ding, Feng Zhou, Jianji Dong, Xinliang Zhang
A photonic differentiator (DIFF) plays a crucial role in photonic circuits. Despite the fact that a DIFF having a terahertz bandwidth has been reported, the practical bandwidth is limited to being a bandpass response. In this Letter, we propose the concept of a bandwidth-adaptable DIFF, which exploits the slow light effect in a photonic crystal waveguide (PhCW) to overcome the inherent bandwidth limitation of current photonic DIFFs. We fabricated a PhCW Mach-Zehnder interferometer (PhCW-MZI) on the silicon-on-isolator material platform to validate our concept...
April 15, 2017: Optics Letters
Lifeng Chen, Martin Lopez-Garcia, Mike P C Taverne, Xu Zheng, Ying-Lung D Ho, John Rarity
We propose a method to directly visualize the photonic band-structure of micrometer-sized photonic crystals using wide-angle spectroscopy. By extending Fourier imaging spectroscopy sensitivity into the infrared range, we have obtained accurate measurements of the band structures along the high-symmetry directions (X-W-K-L-U) of polymeric three-dimensional, rod-connected diamond photonic crystals. Our implementation also allows us to record single-wavelength reflectance far-field patterns showing very good agreement with simulations of the same designs...
April 15, 2017: Optics Letters
Wensheng Gao, Meng Xiao, Baojie Chen, Edwin Y B Pun, C T Chan, Wing Yim Tam
There is no known simple rule that assures the existence of interface states in photonic crystals (PCs). We show here that one can control the existence or absence of interface states in 1D PCs through engineering the bulk geometrical phase such that interface states can be guaranteed in some or all photonic bandgaps. We verify experimentally the interface state design paradigm in 1D multilayered PCs fabricated by electron beam vapor deposition. We obtain the geometrical phases by measuring the reflection phases at the bandgaps of the PCs and achieve good agreement with the theory...
April 15, 2017: Optics Letters
Jeremy D Witmer, Joseph A Valery, Patricio Arrangoiz-Arriola, Christopher J Sarabalis, Jeff T Hill, Amir H Safavi-Naeini
Future quantum networks, in which superconducting quantum processors are connected via optical links, will require microwave-to-optical photon converters that preserve entanglement. A doubly-resonant electro-optic modulator (EOM) is a promising platform to realize this conversion. Here, we present our progress towards building such a modulator by demonstrating the optically-resonant half of the device. We demonstrate high quality (Q) factor ring, disk and photonic crystal resonators using a hybrid silicon-on-lithium-niobate material system...
April 13, 2017: Scientific Reports
Gang Yeol Yoo, Jae-Seung Jeong, Soyoung Lee, Youngki Lee, Hee Chang Yoon, Van Ben Chu, Gi Soon Park, Yun Jeong Hwang, Woong Kim, Byoung Koun Min, Young Rag Do
There are four prerequisites when applying all types of thin-film solar cells to power-generating window photovoltaics (PVs): high power-generation efficiency, longevity and high durability, semitransparency or partial-light transmittance, and colorful and aesthetic value. Solid-type thin-film Cu(In,Ga)S2 (CIGS) or Cu(In,Ga)(S,Se)2 (CIGSSe) PVs nearly meet the first two criteria, making them promising candidates for power-generating window applications if they can transmit light to some degree and generate color with good aesthetic value...
April 20, 2017: ACS Applied Materials & Interfaces
Ji-Hwan Kang, Shin-Hyun Kim, Alberto Fernandez-Nieves, Elsa Reichmanis
As an effective platform to exploit triplet-triplet-annihilation-based photon upconversion (TTA-UC), microcapsules composed of a fluidic UC core and photonic shell are microfluidically prepared using a triple emulsion as the template. The photonic shell consists of cholesteric liquid crystals (CLCs) with a periodic helical structure, exhibiting a photonic band gap. Combined with planar anchoring at the boundaries, the shell serves as a resonance cavity for TTA-UC emission and enables spectral tuning of the UC under low-power-density excitation...
April 17, 2017: Journal of the American Chemical Society
Emilie Roncali, Mariele Stockhoff, Simon Cherry
Accurately modeling the light transport in scintillation detectors is essential to design new detectors for nuclear medicine or high energy physics. Optical models implemented in software such as Geant4 and GATE suffer from important limitations that we addressed by implementing a new approach in which the crystal reflectance was computed from 3D surface measurements. The reflectance was saved in a look-up-table (LUT) then used in Monte Carlo simulation to determine the fate of optical photons. Our previous work using this approach demonstrated excellent agreement with experimental characterization of crystal light output in a limited configuration, i...
April 11, 2017: Physics in Medicine and Biology
Daniel Navarro-Urrios, Néstor E Capuj, Martín F Colombano, P David García, Marianna Sledzinska, Francesc Alzina, Amadeu Griol, Alejandro Martínez, Clivia M Sotomayor-Torres
Optical nonlinearities, such as thermo-optic mechanisms and free-carrier dispersion, are often considered unwelcome effects in silicon-based resonators and, more specifically, optomechanical cavities, since they affect, for instance, the relative detuning between an optical resonance and the excitation laser. Here, we exploit these nonlinearities and their intercoupling with the mechanical degrees of freedom of a silicon optomechanical nanobeam to unveil a rich set of fundamentally different complex dynamics...
April 11, 2017: Nature Communications
Julian Schneider, Wanlong Zhang, Abhishek K Srivastava, Vladimir G Chigrinov, Hoi S Kwok, Andrey L Rogach
Photo-alignment technology provides high alignment quality with an exceptional control over the local director of liquid crystals. Due to the reorientation ability of sulfonic azo dye molecules, they offer high azimuthal and polar anchoring energy with a low pretilt angle for the orientation of liquid crystals and liquid crystal composites. In this work, we make use of this approach to align thin film composites of light-emitting semiconductor nanorods dispersed in a liquid crystal polymer into both one-dimensional and two-dimensional micro-scale patterns...
April 10, 2017: Nano Letters
Imtiyaz Ahmad Bhat, Ruchi Jain, Mujahuddin M Siddiqui, Deepak K Saini, Partha Sarathi Mukherjee
A tetrafacial water-soluble molecular barrel (1) was synthesized by coordination driven self-assembly of a symmetrical tetrapyridyl donor (L) with a cis-blocked 90° acceptor [cis-(en)Pd(NO3)2] (en = ethane-1,2-diamine). The open barrel structure of (1) was confirmed by single crystal X-ray diffraction. The presence of a hydrophobic cavity with large windows makes it an ideal candidate for encapsulation and carrying hydrophobic drug like curcumin in an aqueous medium. The barrel (1) encapsulates curcumin inside its molecular cavity and protects highly photosensitive curcumin from photodegradation...
April 10, 2017: Inorganic Chemistry
Benjamin Doppagne, Michael C Chong, Etienne Lorchat, Stéphane Berciaud, Michelangelo Romeo, Hervé Bulou, Alex Boeglin, Fabrice Scheurer, Guillaume Schull
A scanning tunneling microscope is used to generate the electroluminescence of phthalocyanine molecules deposited on NaCl/Ag(111). Photon spectra reveal an intense emission line at ≈1.9  eV that corresponds to the fluorescence of the molecules, and a series of weaker redshifted lines. Based on a comparison with Raman spectra acquired on macroscopic molecular crystals, these spectroscopic features can be associated with the vibrational modes of the molecules and provide a detailed chemical fingerprint of the probed species...
March 24, 2017: Physical Review Letters
Murphy Yuezhen Niu, Barry C Sanders, Franco N C Wong, Jeffrey H Shapiro
We propose an optical scheme, employing optical parametric down-converters interlaced with nonlinear sign gates (NSGs), that completely converts an n-photon Fock-state pump to n signal-idler photon pairs when the down-converters' crystal lengths are chosen appropriately. The proof of this assertion relies on amplitude amplification, analogous to that employed in Grover search, applied to the full quantum dynamics of single-mode parametric down-conversion. When we require that all Grover iterations use the same crystal, and account for potential experimental limitations on crystal-length precision, our optimized conversion efficiencies reach unity for 1≤n≤5, after which they decrease monotonically for n values up to 50, which is the upper limit of our numerical dynamics evaluations...
March 24, 2017: Physical Review Letters
Yunjung Oh, Wooseok Yang, Jimin Kim, Sunho Jeong, Jooho Moon
Efficient sunlight-driven water-splitting devices can be achieved by using an optically and energetically well-matched pair of photoelectrodes in a tandem configuration. The key for maximizing the photoelectrochemical efficiency is the use of a highly transparent front photoelectrode with a band gap below 2.0 eV. Herein, we propose two-dimensional (2D) photonic crystal (PC) structures consisting of a CuFeO2-decorated microsphere monolayer, which serve as self-light-harvesting architectures allowing for amplified light absorption and high transparency...
April 13, 2017: ACS Applied Materials & Interfaces
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