Photonic Crystal Cladding Research Articles

3D soft glass printing of preforms for microstructured optical fibers

We report on the development of a 3D printing process dedicated to the production of soft glass optical fibers. Direct printing with a miniaturized crucible for melting glass blocks with a pneumatic extrusion head was established. For 3D printing, a developed in-house heavy metal oxide glass was used. Contrary to previous studies on 3D printing of optical fiber preforms, the proposed process is based on the deposition of straight horizontally-oriented lines with a diameter of 300–500 µm to replace standard stack-and-draw manual assembly technique typically used in the development of microstructured optical fiber preforms. A test fiber preform composed of 2500 microrods with dimensions of 60x25x25 mm was printed. As a proof of concept, a photonic crystal fiber preform composed of a solid core and 3 rings of air holes in photonic crystal cladding was printed, and further processed into the optical fiber using a standard fiber drawing tower. We measured a single mode performance of fabricated fibers at 1.55 µm, and flat dispersion in the range of 1.6 – 2.2 µm with zero dispersion wavelength at 1.70 µm.

Negative capacitors and inductors enabling wideband waveguide metatronics

Waveguide metatronics, known as an advanced platform of metamaterial-inspired circuits, provides a promising paradigm for millimeter-wave and terahertz integrated circuits in future fifth/sixth generation (5/6G) communication systems. By exploiting the structural dispersion properties of waveguides, a lumped type of waveguide integrated elements and circuits could be developed in deep subwavelength scales with intrinsic low loss and low crosstalk. In this study, we focus on constructing negative capacitors and inductors for waveguide metatronics, effectively expanding the operating frequency range of waveguide integrated circuits. The incorporation of negative elements enables wideband impedance matching in waveguide, which have been both theoretically explored and experimentally validated within the waveguide metatronics paradigm. Furthermore, we have demonstrated that the negative elements can also be realized in the optical domain through the utilization of a silicon waveguide with photonic crystal cladding, indicating the feasibility and universality of wideband waveguide metatronics. The negative lumped elements could boost the progress of the waveguide metatronic technique, achieving superior performance on the conventional lumped circuits within waveguides that solely rely on positive elements.

The Effect of the Spin and Orbital Parts of the Poynting Vector on Light Localization in Solid-Core Micro-Structured Optical Fibers

The optical properties of solid-core micro-structured optical fibers (SC MOFs) have been studied for a long time. The process of the energy outflow of the core modes has always been associated with the process of constructive interference of the core modes fields under reflection from the photonic crystal cladding. In this paper, we want to offer a new look at the light localization in the core of SC MOFs related to the behavior of spin and orbital parts of the Poynting vector of these core modes and singularities arising in it. Such an approach can help in forming a better understanding of the process of the core modes energy leakage and also in the creation of SC MOFs with a simplified design and low losses.

Magnetic Field Sensing Based on Whispering Gallery Mode with Nanostructured Magnetic Fluid-Infiltrated Photonic Crystal Fiber.

A kind of novel and compact magnetic field sensor has been proposed and investigated experimentally. The proposed sensor consists of a tapered single mode fiber coupled with a nanostructured magnetic fluid-infiltrated photonic crystal fiber, which is easy to be fabricated. The response of magnetic fluid to magnetic field is used to measure the intensity of magnetic field via whispering gallery mode. The magnetic field-dependent shift in resonance wavelength is observed. The maximum magnetic field intensity sensitivity is 53 pm/mT. The sensor sensitivity is inversely proportional to the thickness of the photonic crystal fiber cladding.

Design and analysis of heptagonal cladding with rotated-hexa elliptical core based PCF for the applications of communication sectors in the THz region

Photonic crystal fiber-based heptagonal cladding with the elliptical rotated-Hexa core is reported in the terahertz waveguide for the applications of communication area in this paper. By utilizing the photonic crystal fiber concept, all numerical results have been obtained by the finite element method with perfectly matched layers based on the COMSOL Multiphysics computer software tool. This H-PCF fiber shows a low effective material loss of 0.0076 cm−1, with a larger effective area of 5.95 × 10–8 m2, power flows within the core area of 90%, confinement loss of 3.35 × 10–16 cm−1, and scattering loss of 1.24 × 10–10 cm−1 at 1 THz. Besides, other optical properties like confinement loss, scattering loss, power fraction, V-parameter, and effective area have also been considered briefly. So, it is expected that the mentioned H-PCF structure-based waveguide will significantly improve many kinds of communication fields of the THz technology.

Study on Physical Effects of Optical Fiber Transmission Characteristics Under Nonlinear Optical Effects

Photonic crystal fiber has a special light guiding mechanism and structural tunability, which can produce singular dispersion characteristics and high nonlinearity, which provides new conditions for the research in the field of nonlinear fiber optics. Due to the combined action of a variety of nonlinear optical effects, photonic crystal fibres with different structural parameters and transmission characteristics can produce rich nonlinear spectra under different pump light pulse parameters. We use the photonic crystal fiber cladding section to conduct nonlinear optical experimental research, and obtain the broadband spectral output of soliton wave and dispersive wave. The theoretical analysis and experimentally measured spectra include blue-shifted dispersion waves in the visible light band near 0.5 μm, residual pump light in the 0.82 μm band, soliton waves in the 1.1 μm band, and red-shifted broadband dispersive waves near 2 μm. Corresponding to this, the formation and redshift of solitons can be clearly seen in the time domain, and there is no more oscillation secondary peak in the femtosecond transmission pulse.

Frequency dependence of electric field tunability in a photonic liquid crystal fiber based on gold nanoparticles-doped 6CHBT nematic liquid crystal

In this paper, we investigate an external electric field frequency influence on a photonic liquid crystal fiber (PLCF) based on a gold nanoparticles (NPs)-doped nematic liquid crystal (LC) and its response to the external electric field. We used a 6CHBT nematic LC doped with 2-nm gold NPs in a weight concentration of 0.1%, 0.2%, 0.3%, and 0.5%. Full Text: PDF ReferencesJ. C. Knight, T. A. Birks, P. St. J. Russell, and D. M. Atkin, "All-silica single-mode optical fiber with photonic crystal cladding," Opt. Lett. 21, 1547-1549 (1996) CrossRef J. C. Knight,T. A. Birks, P. S. J.Russell, , and J. P. De Sandro, "Properties of photonic crystal fiber and the effective index model", JOSA A, 15(3), 748-752, (1998) CrossRef S. A. Cerqueira,F. Luan, C. M. B. Cordeiro, A. K. George, and J. C. Knight, "Hybrid photonic crystal fiber", "Optics Express", 14(2), 926-931,(2006) CrossRef W. Bragg, "Liquid Crystals", Nature 133, 445-456, (1934) https://doi.org/10.1038/133445a0 CrossRef J. Kędzierski, K. Garbat, Z. Raszewski, M. Kojdecki, K. Kowiorski, L. Jaroszewicz, and W. Piecek, "Optical properties of a liquid crystal with small ordinary and extraordinary refractive indices and small optical anisotropy", Opto-Electronics Review, 22(3), 162-165, (2014) CrossRef Y. Li, and S. T. Wu, "Polarization independent adaptive microlens with a blue-phase liquid crystal", Optics express, 19(9), 8045-8050, (2011) CrossRef T. Woliński, S. Ertman, K. Rutkowska, D. Budaszewski, M. Sala-Tefelska, M. Chychłowski, K. Orzechowski, K. Bednarska, P. Lesiak, "Photonic Liquid Crystal Fibers - 15 years of research activities at Warsaw University of Technology", Phot. Lett. Pol., (11), (2), 22-24, (2019) https://doi.org/10.4302/plp.v11i2.907. CrossRef T.T. Larsen, A. Bjraklev, D.S. Hermann, J. Broeng, Opt. Expr. 11(20), 2589, (2003) CrossRef T.R. Woliński, K. Szaniawska, K. Bondarczuk, P. Lesiak, A.W. Domański, R. Dąbrowski, E. Nowinowski-Kruszelnicki, J. Wójcik, "Propagation properties of photonic crystal fibers filled with nematic liquid crystals", Opto-Electron. Rev. 13(2), 59 (2005) DirectLink L. Scolari, S. Gauza, H. Xianyu, L. Zhai, L. Eskildsen, T. T. Alkeskjold, S.-T. Wu, and A. Bjarklev, "Frequency tunability of solid-core photonic crystal fibers filled with nanoparticle-doped liquid crystals," Opt. Express 17(5), 3754-3764 (2009). CrossRef A. Siarkowska, M. Chychłowski, D. Budaszewski, B. Jankiewicz, B. Bartosewicz, and T. R. Woliński, "Thermo-and electro-optical properties of photonic liquid crystal fibers doped with gold nanoparticles", Beilstein Journal of Nanotechnology, 8(1), 2790-2801, (2017) CrossRef D. Budaszewski, M. Chychłowski, A. Budaszewska, B. Bartosewicz, B. Jankiewicz, and T. R. Woliński, "Enhanced efficiency of electric field tunability in photonic liquid crystal fibers doped with gold nanoparticles", Optics express, 27(10), 14260-14269, (2019) CrossRef D. Budaszewski, A. Siarkowska, M. Chychłowski, B. Jankiewicz, B. Bartosewicz, R. Dąbrowski, T. R. Woliński, "Nanoparticles-enhanced photonic liquid crystal fibers", Journal of Molecular Liquids, 267, 271-278, (2018) CrossRef

Microstructured optical fibers for terahertz waveguiding regime by using an analytical field model

Abstract Microstructured optical fibres (MOFs) are seen as novel optical waveguide for the potential applications in the terahertz (THz) band as they provide a flexible route towards THz waveguiding. Using the analytical field model (Sharma et al., 2014) developed for index-guiding MOFs with hexagonal lattice of circular air-holes in the photonic crystal cladding; we aim to study the propagation characteristics such as effective index, near and the far-field radiation patterns and its evolution from near-to-far-field domain, spot size, effective mode area, and the numerical aperture at the THz regime. Further, we present an analytical field expression for the next higher-order mode of the MOF for studying the modal properties at terahertz frequencies. Also, we investigate the mode cut-off conditions for identifying the single-mode operation range at THz frequencies. Emphasis is put on studying the coupling characteristics of MOF geometries for efficient mode coupling. Comparisons with available experimental and numerical simulation results, e.g., those based on the full-vector finite element method (FEM) and the finite-difference frequency-domain (FDFD) method have been included.

High-sensitivity photonic crystal fiber long-period grating methane sensor with cryptophane-A-6Me absorbed on a PAA-CNTs/PAH nanofilm.

A high-sensitivity photonic crystal fiber long-period grating (PCF-LPG) methane sensor with cryptophane-A-6Me absorbed on a poly(acrylic acid)-carbon nanotubes/ polypropylene amine hydrochloride (PAA-CNTs/PAH) nanofilm was investigated. The sensing film was coated onto the internal surface of a photonic crystal fiber cladding air holes by an electrostatic self-assembly technique. Based on a finite element method and the coupled local-mode theory, the effects of the sensing film's refractive index (RI) and thickness on the resonant wavelength were theoretically and numerically analyzed. When the sensing film RI decreases from 1.55 to 1.53, and the thickness increases from 100 nm to 200 nm, the resonant wavelength has a blue shift. A higher RI sensitivity with 1.075 × 103 nm RIU-1 is observed for the film thickness of 200 nm. The PCF-LPG methane sensor was fabricated by a pressurized injection method. The sensing experimental result shows that the resonant wavelength of the transmission spectra has a blue shift when the methane concentration increases from 0.0% to 3.5% by volume. The sensor has a good sensitivity of 1.078 nm%-1 and a low detection limit of 0.18% for a film thickness of 210 nm.

Characteristics of solid-core square-lattice microstructured optical fibers using an analytical field model

The excellent propagation properties of square-lattice microstructured optical fibers (MOFs) have been widely recognized. We generalized our recently developed analytical field model (Sharma and Sharma, 2016), for index-guiding MOFs with square-lattice of circular air-holes in the photonic crystal cladding. Using the field model, we have studied the propagation properties of the fundamental mode of index-guiding square-lattice MOFs with different hole-to-hole spacing and the air-hole diameter. Results for the modal effective index, near and the far-field patterns and the group-velocity dispersion have been included. The evolution of the mode shape has been investigated in transition from the near to the far-field domain. We have also studied the splice losses between two identical square-lattice MOFs and also between an MOF and a traditional step-index single-mode fiber. Comparisons with available numerical simulation results, e.g., those based on the full-vector finite element method have also been included.

Femtosecond-laser-written Tm:KLu(WO4)2 waveguide lasers.

Depressed-index channel waveguides with a circular and photonic crystal cladding structures are prepared in a bulk monoclinic Tm:KLu(WO4)2 crystal by 3D direct femtosecond laser writing. The channel waveguide structures are characterized and laser operation is achieved using external mirrors. In the continuous-wave mode, the maximum output power of 46 mW is achieved at 1912 nm corresponding to a slope efficiency of 15.2% and a laser threshold of only 21 mW. Passive Q-switching of a waveguide with a circular cladding is realized using single-walled carbon nanotubes. Stable 7 nJ/50 ns pulses are achieved at a repetition rate of 1.48 MHz. This first demonstration of ∼2 μm fs-laser-written waveguide lasers based on monoclinic double tungstates is promising for further lasers of this type doped with Tm3+ and Ho3+ ions.

Metal-Coated Silicon Nanowire Embedded Plasmonic Photonic Crystal Fiber: Kerr Nonlinearity and Two-Photon Absorption

In silicon, the presence of two photon absorption (TPA) and the generated free carriers can strongly perturb any Kerr-related nonlinear performance. Special consideration about the geometry and applied input power is needed to reduce undesirable free carrier effects (FCE). In our study, a plasmonic photonic crystal structure consisting of a central metal-coated silicon nanowire is proposed. The photonic crystal cladding and plasmonic nature of the guided modes provide the efficient wave propagation in the subwavelength core radius size of 150 nm, well beyond the diffraction limit at λ = 1.55 μm. Considerable increase of the threshold powers (approximate increment of 42d B W and 12d B W for the free carrier absorption and dispersion threshold powers at r S i = 500 nm) for the observation of FCE is a distinguished feature of the proposed structure which guarantee the safe launch of high input powers for full development of Kerr-based phenomena. An excellent agreement between the numerical solution of the nonlinear schrodinger equation and the calculated threshold powers confirms the obtained results. The proposed structure has potential applications in the areas regarding the Kerr-related nonlinear performance especially with relative high powers utility.

All-silica, large mode area, single mode photonic bandgap fibre with Fabry–Perot resonant structures

Abstract All-silica, photonic crystal fibres consisting of a low index, silica core surrounded by higher index inclusions embedded in a silica matrix to form a photonic bandgap cladding were numerically analysed. The aim of the investigations was to modify the guiding properties of the fibre by introducing resonant structural entities. These structural modifications are realised by altering the refractive index of certain high index inclusions in the photonic crystal cladding resulting in mode coupling between the core mode and the mode propagated in the modified index region. This results in an increased effective core area of the fundamental core mode and consequently decreased nonlinearity as well as modified effective index compared to the effective index of the unmodified structure and resonant dispersion profile that can be used for pulse compression or optical delay purposes.

Analysis of single polarization single mode photonic crystal cladding with hexagonal and rectangular lattice

Single-polarization single-mode (SPSM) operation of highly birefringent (HB) photonic crystal fibers (PCF) with rectangular and hexagonal lattice is investigated in detail by using a full-vector finite-element method (FEM) with anisotropic perfectly matched layers (PMLs). The position of the region of single polarization can be tuned freely by adjusting the size of the central enlarged air holes. The confinement loss and dispersion losses for standard single-mode fiber for particular SPSM PCFs are calculated and optimized. The proposed fibers are nonlinear SPSM, which may be useful for nonlinear optical applications or applications with a wide SPSM operating bandwidth requirement.

Negative Curvature Hollow-core Fibers: Dispersion Properties and Femtosecond Pulse Delivery

In this work a comparative analysis of dispersion properties of hollow core photonic crystal fibers (HC PCFs) and negative curvature hollow core fibers (NCHCFs) was carried out. It was shown that the main reason for the low dispersion slope of NCHCFs is a strong light localization in the air core in comparison with HC PCFs. The strong light localization in NCHCFs allows not to use the complicated photonic crystal cladding and to reduce the air mode interaction with silica glass elements of the cladding. This conclusion was confirmed by experimental measurement of the group velocity dispersion and femtosecond pulse transmission for the NCHCF.

Highly sensitive octagonal photonic crystal fiber based sensor

In this study, a number of propagation characteristics of hexagonal and octagonal photonic crystal fiber (H-PCF and O-PCF) structures, where both core and cladding are microstructured have been investigated by employing the full vectorial finite element method (FEM). The confinement loss, the effective refractive index and the relative sensitivity coefficient behaviors of the O-PCF and the standard H-PCF are numerically investigated and compared. It is found that under the same design parameters O-PCF structure has significantly lower losses and higher relative sensitivity coefficient compared with H-PCF structure.

Fiber optic nanotechnology: a new frontier of fiber optics

Nanophotonics is an exciting new field of nano-science that deals with the interaction of light with matter on a micro/nanometer size scale. It is a field in which photonics merges with nanoscience and nanotechnology, providing challenges for fundamental research and creating opportunities for new technologies and applications. Nanotechnology has spawned new areas of research for fiber optics, namely fiber optic nanophotonics. When we think of optical fibers, we typically think of optical propagation through waveguides of dimensions greater than or similar to the optical wavelength. Conventionally, little attention need be given to sub-wavelength or nano meter size features. However, when nano-features are intentionally incorporated into optical fibers, many interesting phenomena may arise. For example, with nano-features of sufficient refractive index contrast, a properly designed optical fiber can do more than simply guide light from one point to another. Such features can be used to create different types of waveguiding phenomena as well as enabling capabilities for manipulation of light that go beyond conventional optical transport. This additional functionality offers great potential of fiber-based nanotechnology for applications in communications, computation, sensing, biology and chemistry for both waveguides and waveguide-based devices. Nanotechnology can be exploited in multiple ways. In perhaps the most widely recognized form, nano-features provide an additional mechanism for confinement of light in so-called photonic crystal fiber. The concept of using air-glass structures to guide light was proposed in 1974 as a possible design for low-loss optical fiber. However, the field saw little activity until 1996. A major reason for this was because conventional fibers were so successful commercially that most research efforts were focused on exploiting more conventional fibers. Demonstrations of fibers with photonic crystal cladding, and later photonic band-gaps, in the late 1990s reinvigorated the field and attracted new research interest because air-glass microstructures offer a number of interesting physical effects that do not exist in conventional fibers. Microand later nano-structured optical fibers became an extremely active research area while miniaturization pushed toward micro/nanophotonic devices, such as tapers, resonators and interferometer for a wide range of telecommunications and specialty applications.

Widely tunable broadband deep-ultraviolet to visible wavelength generation by the cross phase modulation in a hollow-core photonic crystal fiber cladding

The deep-ultraviolet (UV) to visible wavelengths are efficiently generated for the first time by the cross phase modulation (XPM) between the red-shifted solitons and the blue-shifted dispersive waves (DWs) in the fundamental guided mode of the multi-knots of a hollow-core photonic crystal fiber cladding (HC-PCFC). When the femtosecond pulses with a wavelength of 850 nm and average power of 300 mW are coupled into the knots 1–3, the conversion efficiency ηuv−v of 11% and bandwidth Buv−v of 100 nm in the deep-UV region are experimentally obtained. The multi-milliwatt ultrashort pulses are tunable over the deep-UV (below 200 nm) to visible spectral region by adjusting the wavelengths of the pump pulses in different knots. It is expected that these widely tunable broadband ultrashort deep-UV–visible pulse sources could have important applications in ultrafast photonics, femtochemisty, photobiology, and UV–visible resonant Raman scattering.

Robust Optical Fiber Using Single Negative Metamaterial Cladding

We introduce the idea of optical fibers made up of single negative metamaterial photonic crystal cladding with zero effective phase bandgap. Fiber characteristics are analyzed both at sub-wavelength and non sub-wavelength crystal dimension by varying cladding thickness and core radius. We find that in both cases they are robust with respect to incident angle, polarization of the light, crystal constant, and cladding irregularities. The fiber is found to behave like a step index fiber but the guided modes are leaky like Bragg fiber. It is shown that a fixed cladding thickness produces fixed loss around impedance matching frequency irrespective of crystal constant.

Polarization-dependent efficient Cherenkov radiation at visible wavelengths in hollow-core photonic crystal fiber cladding

Efficient Cherenkov radiation (CR) is experimentally generated by a soliton self-frequency shift (SSFS) in a knot of hollow-core photonic crystal fiber (HC-PCF). When the angle of the half-wave plate is rotated from 0° to 45°, the Raman soliton shifts from 2227 to 2300 nm, the output power of the CR increases 8.15 times, and the maximum output power ratio of the CR at 556 nm to the residual pump is estimated to be 20:1. The width of the output optical spectrum at visible wavelengths broadens from 25 to 45 nm, and the conversion efficiency of the CR can be above 28%. Moreover, the influences of the pump polarization and wavelength on the CR are studied, and the corresponding nonlinear processes are discussed.