Photonic Fiber Research Articles

Realization of all-optical multiplexer–demultiplexer in mid-IR wavelengths using triple-core photonic quasi-crystal fiber

We report a wide bandwidth and low crosstalk Ge11.5As24Se64.5 triple-core photonic quasi-crystal fiber (TPQF) for the multiplexing–demultiplexing (MUX–DEMUX) operation in mid-IR region. In this numerical investigation, we explore the various MUX–DEMUX parameters such as coupling length, coupling length ratio, separation length, crosstalk and bandwidth. Further, the proposed TPQF based MUX–DEMUX exhibits high bandwidth of 263, 252, 214, 129 and 134 nm for low crosstalk of -36.47, -34, -31, -30 and -31.3 dB at the wavelengths of 2, 2.3, 2.9, 3.5 and 4μm, respectively. The proposed MUX–DEMUX characteristics are realized first time in TPQF at mid-IR wavelengths. Besides, the bandwidth is improved as 310, 292, 286, 148 and 164 nm for the very low crosstalk level of -45.8, -44, -42.3, -42.35 and -49.93 dB for the separation lengths of 5.5, 6.1, 6.6 and 7.4 mm wavelengths of 2/4-μm, 2.3/4-μm 2.9/4-μm and 3.5/4-μm, respectively, when phase of core 1 is about 1.2π. Thus, the proposed TPQF-based MUX–DEMUX is a suitable candidate for the development of mid-IR photonic devices such as wavelength division multiplexing (WDM) couplers and power splitters.

Analysis of Natural Gas Using a Portable Hollow-Core Photonic Crystal Coupled Raman Spectrometer.

The low accessibility of natural gas fields and transporting pipelines requires portable online analyzers of the composition of natural gas, ensuring nearly chromatographic precision and capable of in situ analysis of a wide range of gases, including infrared-inactive ones (hydrogen, oxygen, nitrogen, chlorine). We have developed an express method of gas analysis meeting all the requirements for analysis of natural gas and its derivative mixtures using a portable 532 nm Raman spectrometer rigidly connected to a hollow-core crystal photonic fiber.

High-sensitivity SPR sensor based on the eightfold eccentric core PQF with locally coated indium tin oxide.

A highly sensitive surface plasmon resonance (SPR) sensor comprising an eccentric core photonic quasi-crystal fiber (PQF) coated with indium tin oxide is designed and numerically analyzed. The novel, to the best of our knowledge, structure with an eccentric core layout and local coating not only strengthens coupling between the core mode and surface plasmon polariton mode but also provides higher refractive index sensitivity in the near-infrared region. Analysis based on the finite element method to assess the performance of the sensor and optimize the structural parameters reveals that the maximum wavelength sensitivity and resolution are 96667 nm/RIU and 1.034×10-6RIU in the sensing range between 1.380 and 1.413, respectively. Meanwhile, the average sensitivity is enhanced to 25458 nm/RIU. The sensor is expected to have broad applications in environmental monitoring, biochemical sensing, food safety testing, and related applications due to the ultrahigh sensitivity and resolution.

Sensitivity enhancement of annular one dimensional photonic crystals temperature sensors with nematic liquid crystals

A novel design of one dimensional annular photonic crystals with a low birefringence nematic liquid crystal as a defect layer is introduced. The output field of the sensor structure is plotted after different optimization steps on all constituents such as thickness and core radius of the starting medium. The performance of the sensor was studied using different quality parameters such as sensitivity, figure of merit, detection limit and resolution. The designed sensor exhibits a sensitivity of about 0.224 nm °C−1 due to the presence of the liquid crystal material. The proposed sensor design can be used as a narrowband optical filter in the visible region around two wavelengths: 600 nm and 700 nm. As an optoelectronic device, this structure can serve as a temperature sensor with higher sensitivity than the conventional one dimensional photonic crystal structures and photonic crystals fibers.

All-Optical Directional Control of Emission in a Photonic Liquid Crystal Fiber Laser

This study investigates the all-optical directional control of emission in a cholesteric liquid crystal (CLC)-infiltrated photonic crystal fiber (PCF) laser. A laser dye-doped CLC (LD-CLC) and an azobenzene LC-doped CLC (ALC-CLC), which are selectively infiltrated into the hollow core and holey-matrix cladding of the PCF, function as an optically active cavity and an all-optical emission direction-controllable light valve, respectively, in the photonic LC fiber (PLCF) laser. Experimental results show that the PLCF has a low energy threshold (approximately 63 nJ/pulse) and a large circular polarization anisotropy (g ≅ 2) in lasing output. The lasing output from the LD-CLC-filled core of the PLCF can be all-optical controlled to emit omni- or semi-directionally or to off-emit by controlling the isothermal phase transition of the CLC between the scattering focal conic state and the transparent isotropic state by the all-optical-induced reversible photoisomerization of the doped ALCs in the cladding region. The emission direction-controllable PLCF laser has significant potential in various applications, such as bio-image, photo-therapy, wearable devices, displays, sensors, and lighting.

Dispersion-flattened photonic quasicrystal optofluidic fiber for telecom C band operation

Photonic quasicrystals are of particular interest for waveguiding applications because of their beneficial advantages over conventional photonic crystals, such as higher-order rotational symmetry and more isotropic Brillouin zone. In this work, by use of a 12-fold symmetric photonic quasicrystal lattice and an optofluidic infiltration approach, we sought to design a hollow-core fiber for telecom C band operation. The simulation results demonstrate a wide flat dispersion range around the zero-dispersion wavelength of 1550 nm and an ultralow confinement loss of 2.6 × 10-7 dB/m, whereas the maximum effective mode area attained in the simulations is approximately 5.5 μm2.

Fabrication and characterization of femtosecond laser induced microwave frequency photonic fiber grating.

We proposed and fabricated a microwave-frequency photonic fiber grating (MPFG) by femtosecond laser micromachining on optical fibers. Illuminated by low coherent light source, the MPFG can be interrogated using proposed microwave photonic system to show the resonant peaks in microwave frequency domain. We studied the working principle and characteristics of this device. After that, we discussed the influence of fiber type, apodization and light source coherence lengths on this device. The device can also respond to ambient temperature change like fiber optic sensors.

Soft Photonic Fibers for Colorimetric Solvent Vapor Sensing

AbstractStimuli‐responsive elastomers are promising material systems for the development of optical sensors with visual outputs that can be easily assessed by the human eye. These materials, when shaped into alternating layers, form distributed Bragg reflectors (DBRs) that feature a high spectrally selective reflectivity. The adsorption of vapor molecules into these photonic structures leads to partial swelling in the constituent materials that can induce pronounced color changes. Here, it is demonstrated that soft photonic fibers with a DBR‐cladding can selectively sense and quantify different organic vapors. It is found that fibers with a multilayer cladding assembled of films of polydimethylsiloxane (PDMS) and a polystyrene‐polyisoprene block‐copolymer (PSPI) change color sensitively depending on the concentration of toluene, benzene, tetrahydrofuran, or chloroform vapors. It is shown that this is a direct consequence of a selective swelling of the constituent polymer layers due to vapor adsorption. With wavelength variations as small as 5 nm being noticeable to the human eye, such photonic fibers are interesting materials for optical sensors. Modifications of their building blocks and their structural morphology make these vapor‐sensing fibers a versatile platform for standalone and textile‐integrated solvent sensing systems applied in industrial and lab‐scale manufacturing processes.

Advantages and Disadvantages of Using New Types of Photonic Fibers in Fiber-Optic Gyros

In this paper, two new types of optical fibers are considered that can be used for design of a fiber optic gyroscope with improved characteristics. A fiber optic gyroscope is relatively novel type of sensors for measuring orientation and angular velocity. Characteristics of fiber optic gyroscopes significantly depend on type and quality a light source and a photonic fiber. There are also a number of effects that have a significant influence on the performance of FOG. Some of these effects can be eliminated or minimized by design. Currently, two novel types of optical fibers have been developed - microstructured fibers and multicore fibers. The use of these type of fibers can significantly reduce the effect of temperature influence on the gyroscope. In the paper the advantages and disadvantages of using of microstructured fibers and multicore fibers were discussed.

편광 유지 광자 결정 광섬유에 제작한 장주기 광섬유 격자를 이용한 광섬유 비틀림 센서

In this paper, we demonstrated a fiber-optic torsion sensor capable of discriminating twist direction using a long-period fiber grating(LPFG) inscribed on polarization-maintaining photonic cystal fiber(PMPCF) by CO₂ laser pulses. The LPFG written on PMPCF, referred to as the PMPC-LPFG, has a polarization-dependent resonance dip, and two resonance dips are obtained for orthogonal input polarization states designated here as linear horizontal polarization(LHP) and linear vertical polarization(LVP). The torsion responses of these two resonance dips were investigated in a twist angle range from -160° to 160°. When the transmittance of the fabricated PMPC-LPFG, measured on a logarithmic scale, was converted to the transmittance represented on a linear scale, the torsion responses of both dips showed high linearity with an adjusted R<SUP>2</SUP> value greater than 0.99596 in a twist angle range from -160° to 160°. In addition, the temperature response was also examined in a temperature range from 40 to 80℃. The experimental results show that our PMPC-LPFG-based torsion sensor can distinguish torsion direction with excellent linearity and can also offer temperature-insensitive torsion measurement.

Interfacial Engineering for Gradient Optical Fiber

AbstractGradient functionalization is a widely applied process in materials science that involves generating gradient distribution of composition or structure to yield materials with new functions or improved properties. Here an interfacial engineering is described for construction of gradient fiber, which exhibits gradient distribution of active centers, bonding configuration, and the resultant optical response. It is shown that the interfacial diffusion of protype niobium (Nb) in the core and cladding region of the fiber can be tuned via rational control of the viscosity of melt and the subsequent thermal activation. This leads to gradient distribution of Nb species and active [NbO6]7− centers within 10–20 µm region. As a result, unique optical properties including the tunable energy transfer between active centers and special annular emission beam can be obtained. These results highlight a fundamental principle to develop novel photonic fibers and provide a great step in expanding the scope of gradient materials.

Vector rational and semi-rational rogue waves for the coupled cubic-quintic nonlinear Schrödinger system in a non-Kerr medium

Non-Kerr media possess certain applications in photonic lattices and optical fibers. Studied in this paper are the vector rational and semi-rational rogue waves in a non-Kerr medium, through the coupled cubic-quintic nonlinear Schrödinger system, which describes the effects of quintic nonlinearity on the ultrashort optical pulse propagation in the medium. Applying the gauge transformations, we derive the Nth-order Darboux transformation and Nth-order vector rational and semi-rational rogue wave solutions, where N is a positive integer. With such solutions, we present three types of the second-order rogue waves with the triangle structure: the one with each component containing three four-petaled rogue waves, the one with each component containing three eye-shaped rogue waves, and the other with one component containing three anti-eye-shaped rogue waves and the other component containing three eye-shaped rogue waves. We exhibit the third-order vector rogue waves with the merged, triangle and pentagon structures in each component. Moreover, we show the first- and second-order vector semi-rational rogue waves which display the coexistence of the rogue waves and the breathers.

Optical Free-Form Couplers for High-density Integrated Photonics (OFFCHIP): A Universal Optical Interface

Coupling of light between different photonic devices, for example on-chip waveguides, fibers, and free-space optical elements, is an essential function enabling integrated optical systems. Efficient optical coupling demands matching the optical mode profiles and effective indices between two devices, and often changing propagation direction of the light. To date, such coupling is pre-dominantly accomplished via direct butt coupling of two devices, or meticulously optimized diffraction gratings. In this article, we present a new coupling scheme based on microfabricated free-form optical reflectors. The free-form reflector simultaneously achieves the functions of light beam re-directing and shaping (for mode matching), and can be versatilely adapted for coupling between photonic chips, fibers, and free-space surface-incident devices. We show that this technology uniquely fulfills all key performance requirements for optical interfaces with exceptionally low coupling loss (0.2–0.3 dB per coupler), large bandwidth (over half an octave), high density (large 2-D coupler arrays), polarization diversity, and superior alignment tolerance commensurate with passive alignment techniques. Preliminary experimental validation demonstrates waveguide-to-fiber coupling with a low insertion loss (IL) of 0.9 dB. We foresee that the technology will become a promising solution to the chip-level photonic interconnection and packaging challenges plaguing integrated photonics.

Hollow-core photonic quasicrystal fiber with high birefringence and ultra-low nonlinearity

A hollow-core fiber based on photonic quasicrystal arrays is theoretically proposed for high-quality light wave propagation with high polarization maintaining performance and low nonlinearity. This fiber, called hollow-core photonic quasicrystal fiber (HC-PQF), can simultaneously realize a high birefringence that reaches 1.345 × 10−2 and a small nonlinear coefficient of 1.63 × 10−3 W−1·km−1 at a communication wavelength of 1.55 μm due to the air-filled core and unique quasiperiodic fiber structure. To further demonstrate the controllability of the nonlinear coefficient and the application of sensor and polarization-maintaining fiber, the nonlinearity is investigated by filling different inert gases in the fiber core while the birefringence keeps a high order of 10−2. In the wavelength range λ ∈ [1.53 μm, 1.57 μm], the dispersion is near zero and flattened. The HC-PQF is expected to be used for applications in optical communication, high power pulse transmission, polarization beam splitters, etc.

Fabrication for Polymer Optical Waveguide Using the Mosquito Method and Its Application to Adiabatic Coupling Between Silicon Photonics Chip and Fiber

Fabrication for Polymer Optical Waveguide Using the Mosquito Method and Its Application to Adiabatic Coupling Between Silicon Photonics Chip and Fiber

Integrated Microstructured Photonic Fiber as a Bifunctional Robust Frit and Efficient Electrospray Emitter of a Packed Column for Capillary Liquid Chromatography-Tandem Mass Spectrometry Analysis of Complex Biological Samples.

Although capillary liquid chromatography married with tandem mass spectrometry (cLC-MS/MS) has become a powerful technique for proteomics and metabolomics research, it is still a great challenge to fabricate durable capillary-based analytical columns coupling continuous nanoflow (<1 000 nL/min) electrospray ionization (ESI) with MS, owing to the issue of clogging and fragile of emitters. Here, we proposed a simple approach to integrate microstructured photonic fibers (MPFs) into wide bore capillaries with 150 μm i.d., serving as an integral bifunctional frit or/and ESI emitter of packed columns. Two kinds of MPFs containing 126 homogeneous microchannels with different inner diameter, 3.2 μm for MPF-1 and 2.6 μm for MPF-2, were explored for preparation. The octadecylsilicate (ODS) silica-packed column using MPF-1 as a frit exhibited the lowest plate heights of 14.2-19.7 μm for five alkylbenzenes at the velocity of 1.5 mm/s, which were slightly lower than those of packed column with porous polymer monolith (PPM)-based frit by cLC coupling with ultraviolet (UV) detection. Additionally, the packed columns with integral MPF frit-emitters were further applied in analysis of a complex biological sample of digest of Hela cells by cLC-MS. An average of 7109 unique peptides could be identified in a single analysis by using MPF-1 emitter, and 7110 unique peptides were identified by using the MPF-2 emitter, which were superior to the identified result of packed column with an integral tapered tip emitter (6894 peptides). It is obvious that this novel integral MPF-based frit-emitter does not easily suffer from the issues of cracking owing to the silica cladding around independent microchannels (>100), which always encumbers both independent and integral tapered tip emitters for cLC-MS.

Advances in hydrogel photonics and their applications

Hydrogels are three-dimensional, hydrophilic networks of cross-linked polymers that can retain water molecules in the structures and respond to physical/chemical stimulus by changing their phase and volume. Recent progress shows hydrogels with optical clarity and good processability to construct various microstructures/nanostructures, which are attractive for photonics-based environmental and biological sensing applications. Moreover, hydrogel-based photonic structures formed by biocompatible and biodegradable polymers are capable of delivering light into living tissues for diagnosis, therapy, and stimulus. We introduce recent studies of hydrogel-based photonic structures, including waveguides, optical fibers, photonic crystals, and plasmonic structures. Optically active photonic devices have been reported by doping luminescent agents into the hydrogel. In addition to introducing important demonstrations of the photonic components, the recent progress in new applications using the hydrogel-based photonic platforms is discussed. Development in the technology of hydrogel photonics will provide a solution to the convergence of scientific fields where the use of conventional photonic devices has been limited.

Supercontinuum Generation in Highly Nonlinear PQF with Two Zero Dispersion Wavelength

An optical input pulse with a duration of nanosecond to femtosecond propagates through a dispersive nonlinear medium, it is subject to an extreme spectral broadening termed as white light supercontinuum (SC). In PCF, dispersion characteristics can be modified by the waveguide geometric parameters and thereby the nonlinear dynamics can be altered. In this article, the fiber parameters like core diameter, doping percentage, and pitch are varied and analyzed to achieve a conclusive zero-dispersion wavelength (ZDW) and a high nonlinearity. The numerical study presents different designs of solid-core photonic quasi-crystal fiber (PQF) and selection of highly nonlinear fiber with an effective area of 1.14 mm2 and nonlinearity of 196 W-1-km-1 at 780 nm exhibiting two-zero dispersion wavelength for supercontinuum generation in different regimes. The results exhibit a significant pulse broadening effect when the pump pulse (FWHM) was varied from 25 fs to 100 fs. Similarly, the influences of the pulse energy and peak average power on the bandwidth of the generated SC are studied

Numerical analysis of a high-birefringent photonic quasi-crystal fiber with circular air holes

A high-birefringence(HB) photonic quasi-crystal fiber(PQF) with all-circular air holes is designed and ZrF4-BaF2-LaF3-AlF3-NaF(ZBLAN) is used to increase the birefringence and reduce confinement loss of the PQF in the infrared region. The structure of the PQF is analyzed and optimized numerically using the full-vector finite element method by adopting the perfectly matched layer boundary conditions. The PQF possesses higher birefringence in the wavelength range between 1.3 and 1.8μm and the maximum birefringence value of 4.1×10−2 is achieved at 1.55μm. This is the highest birefringence value reported from all-circular-hole PQFs so far suggesting that the novel structure has great potential in high-performance optical devices.

Mode- and wavelength-multiplexed transmission with crosstalk mitigation using a single amplified spontaneous emission source

We propose to use the low-coherence property of amplified spontaneous emission (ASE) noise to mitigate optical crosstalk, such as spatial, polarization, and modal crosstalk, which currently limits the density of photonic integration and fibers for dense space-division multiplexing. High optical crosstalk tolerance can be achieved by ASE-based low-coherence matched detection, which avoids dedicated optical lasers and uses spectrally filtered ASE noise as the signal carrier and as a matched local oscillator. We experimentally demonstrate spatial and modal crosstalk reduction in multimode fiber (MMF) and realize mode- and wavelength-multiplexed transmission over 1.5-km MMF supporting three spatial modes using a single ASE source. Performance degradation due to model dispersion over MMF is experimentally investigated.