Elliptical Air Holes Research Articles

Mid-infrared polarization beam splitter based on square/circular hybrid air holes with wide bandwidth and ultrashort length

A novel mid-infrared polarization beam splitter (PBS) based on GaS is proposed. The high birefringence is achieved by using the cladding structure of alternating arrangement of square and circular air holes as well as introducing double elliptical air holes. The finite element method (FEM) is utilized to investigate the mode coupling characteristics in the proposed PBS. The results show that the highest extinction ratio of 115 dB and shortest length of only 40 μm can be realized at a wavelength of 4 μm. A wide bandwidth of 200 nm ranging from 3.9 to 4.1 μm is obtained.

Lower index liquid chemical detection by using photonic crystal fiber sensor

In this paper a novel hollow core photonic crystal fiber (PCF) sensor is presented which provides extremely high sensitivity and low confinement loss for liquid and chemical sensing applications. We examined the efficiency of the proposed PCF structure for liquids with wide range of refractive indices i.e., 1.484–1.534. The numerical investigation of the PCF is executed by the finite element method (FEM).The structure is designed by considering circular airhole in the core instead of an elliptical airhole to decrease the fabrication complexity. The investigation is carried out for a wide wavelength range from 0.8 to1.8 µm. In the simulation results based on FEM, we observed that the constructed PCF offers a high sensitivity of 95.64%, 96.20%, and 98% while low confinement loss of 1.13 × 10-16 dB/m, 8.5 × 10-17 dB/m and 5.3 × 10-17 dB/m respectively for n = 1.484, n = 1.5 and n = 1.534 at 1.3 µm operating wavelength. Thus, the proposed PCF can be used widely for liquid chemical detection in biosensing and commercial applications.

D-shape photonic crystal fiber for optical coherence tomography: design and analysis

A simple D-shaped photonic crystal fiber (D-PCF) with silicon-nano-crystal enrichment is proposed, with substantial nonlinearity, ultrahigh birefringence, and a higher degree of transverse resolution. To scrutinize the optical properties of the suggested D-PCF, the full vector finite-element method has been employed with an anisotropic perfect matched layer added around the designed model as a boundary condition. An elliptical air hole is being used as the core region of this simple structure, and thus it can achieve the most desirable property birefringence in the order of 10 − 2. Tight mode confinement inside the core region benefits the large Kerr nonlinearity (γ) of 2.8 × 105 and 2.3 × 105 W − 1 km − 1 for X and Y polarization modes, respectively, at a wavelength of λ = 1.55 μm. Meanwhile, the numerical aperture is extraordinarily high, exceeding 0.60, with many applications in optical coherence tomography and other related fields. Due to the simple design and low air filling fraction, the D-PCF is feasible for practical realizations in many sectors.

Design of biochemical biosensor based on transmission, absorbance and refractive index

The paper presents novel research related to biosensors based on “photonic crystal fiber (PCF)” and works on the “surface plasmon resonance (SPR)” phenomenon. Real-time analysis of biochemicals is presented in this article through an advanced spectroscopy sensing setup which provides information about the transmission (%) and absorbance (AU) from the biochemicals. The biochemicals are distinguished based on physical appearance and chemical composition. Besides, they possess a distinguish refractive index (RI) value. This research explores the possibility of a correlation between the “transmission (%),” “absorbance (AU),” and RI of the biochemicals. Biochemical having RI varying from 1.340 to 1.380RIU are analyzed in this work. Later analysis of a sensitive PCFSPRRI biosensor having a combination of circular and elliptical air holes and operating in the RI range of 1.340 to 1.380RIU is presented as supplementary information. The maximum value of the sensor parameters is obtained for the biochemical having RI1.345.

Ultrabroadband polarization filter based on gold-coated PCF with high birefringence

Ultrabroadband polarization filter based on gold-coated photonic crystal fiber with high birefringence is proposed and analyzed by using the finite-element method. An elliptical central air hole is designed for high birefringence and shifting the wavelength of the loss peak. The gold layers are selectively coated on the inner surface of two elliptical air holes to support the surface plasmon resonance, which contributes to the filtering characteristics. By optimizing the structural parameters, a high extinction ra2tio is obtained of about 290.56 dB at a communication wavelength of 1310 nm when the length of L = 400 µ m , and its bandwidth is ∼ 530 n m . In addition, the birefringence can reach near 0.004 at 1310 nm.

A hybrid structured PCF for fuel adulteration detection in terahertz regime

An elliptical core based hybrid structured photonic crystal fiber (PCF) is proposed and analyzed in order to identify the fuel adulteration level using the terahertz spectrum. The performance of the proposed sensor is assessed by COMSOL software which uses the finite element method as a solver. At 2.8 THz, the proposed sensor shows an extremely high relative sensitivity of 102% with a very small confinement loss of 3.46× 10−11 cm−1 and a high numerical aperture of 0.45. Moreover, the proposed sensor also shows a large effective area of 1.715× 10−8 m2 with a low effective material loss of 0.0105 cm−1 at optimum structural conditions. Except for one elliptical air hole in cladding, the optical sensor contains circular air holes which ensure less complexity during fabrication. The sensor's excellent sensing and guiding properties will make it a competitive candidate in chemical sensing applications.

Design and analysis of the effect of Zeonex based octagonal photonic crystal fiber for different types of communication applications

In this present work, a novel structure of octagonal cladding with two elliptical air holes based on photonic crystal fiber (O-PCF) has been presented for the application of different types of communication areas within the terahertz (THz) wave propagation. There are five layers of octagonal design shape of circular air holes in cladding region with elliptical design shape of two air holes in core area has been reported in this research work. This O-PCF fiber has been investigated by the perfectly matched layers with the finite element method. After the simulation process, our proposed O-PCF fiber shows a low effective material loss of 0.0162 cm−1, the larger effective area of 5.88 × 10–8 m2, the core power fraction of 80%, the scattering loss of 1.22 × 10–10 dB/km, and the confinement loss of 3.33 × 10–14 dB/m at the controlling region of 1 terahertz (THz). Due to its excellent characteristics, this proposed O-PCF fiber gives proficient transmission of broadband terahertz waves of signals. Moreover, for different kinds of optical communication applications and biomedical signals, our suggested O-PCF fiber will be highly perfect in the terahertz (THz) regions.

Design and analysis of low loss porous-core photonic crystal fiber for terahertz wave transmission

We present a low loss hexagonal-core porous Photonic Crystal Fiber (PCF) for wave propagation in terahertz (THz) range. The cladding contains circular air holes whereas the core consists of elliptical air holes. As background material, Cyclo-Olefin Copolymer (COC) (also known as TOPAS) was used because in the terahertz range (0.1–2 THz), it shows a constant refractive index. The design has been analysed by using FEM-based COMSOL software for a particular frequency range and by varying radius along the x-axis. We observed that at radius of 8 µm and an operating frequency of 0.9 THz, the proposed fiber exhibits low effective material loss of 0.0697 cm−1 and low confinement loss in the order of 10−3 cm−1. Moreover, we did a complete analysis of the transition of core air holes from elliptical to circular.

Design and analysis of a gold-coated dual-core photonic crystal fiber bio-sensor using surface plasmon resonance

In this work, a simple gold-glazed dual-core photonic crystal fiber (PCF) is inspected by using surface plasmon resonance for biochemical sensing. Based on high sensing performance and chemical substantiality, gold (Au) is selected as plasmonic material to coat the external surface of the design. The target analyte and gold layer are placed on the outer surface of the PCF to offer fabrication simplicity. A central elliptical air hole is embellished to increase structural asymmetry between both cores hence the sensor came out with improved sensing performances. The numerical analysis of the proposed design is investigated employing the finite element method (FEM). The maximum optimized value of wavelength sensitivity is recorded at about 8000 nm/RIU with a resolution of 12.5×10−6 and amplitude sensitivity is achieved 1443 RIU−1 for the refractive index of 1.39. Furthermore, a detailed study is also performed to investigate the effects of varying sensor's geometrical parameters such as the thickness of gold and analyte layer, pitch distance, diameters of cladding air holes, geometrical shapes of air hole at core. According to these results along with simple structural design, the proposed model can be practical enough for biochemical and bio-molecular substance detection.

Design and numerical analysis of Zeonex-based photonic crystal fiber for application in different types of communication networks

A photonic crystal fiber (O-PCF) with a novel structure consisting of five octagonal-shaped layers of circular air holes in the cladding region and two elliptical air holes in the core region is presented for application in different communication fields for terahertz (THz) wave propagation. The O-PCF fiber is investigated using perfectly matched layers by applying the finite element method. Based on the results of the simulations, the proposed O-PCF fiber shows a low effective material loss of 0.0162 cm−1, a higher effective area of 5.88 × 10–8 m2, a core power fraction of 80%, a scattering loss of 1.22 × 10–10 dB/km, and a confinement loss of 3.33 × 10–14 dB/m in the target region of 1 terahertz (THz). Due to its excellent characteristics, the proposed O-PCF fiber offers excellent transmission characteristic across a broad band of the terahertz region. Moreover, the suggested O-PCF fiber will be ideal for use in the terahertz (THz) region for different kinds of optical communication and biomedical applications.

Photonic Crystal Fiber SPR Liquid Sensor Based on Elliptical Detective Channel.

This paper proposes a Photonic Crystal Fiber (PCF) refractive index sensor model based on the surface plasmon resonance effect. The proposed PCF model also uses the full vector finite element method to transfer the structure under the anisotropic Perfect Matching Layer (PML) boundary condition. Numerical calculations were carried out on the sensor characteristics. The calculation results show that the elliptical air hole on the left side of the PCF core is coated with a gold-nano film which serves as a Surface Plasmon Resonance (SPR) sensing channel to detect the refractive index of liquid materials. Compared with other structures, the resonant peak generated by the excited SPR effect from the elliptical sensing channel has a high sensitivity to the change of the refractive index of the liquid to be measured. With the help of this attribute, it is relatively easy to adjust the sensitivity. The refractive index range of this structure is within 1.43–1.49 and the sensitivity is up to 12,719.97 nm·RIU−1. The linearity is good; R2 = 0.99927, which is very suitable for liquid sensing.

Design of a photonic crystal fiber with low confinement loss and high birefringence

A photonic crystal fiber (PCF) for long distance communication was proposed in this paper. The circular and elliptical air holes distribute in the cladding, and there are two small elliptical air holes around the core in cross section of the PCF. The characteristics of the PCF were analyzed by using the finite element method (FEM) sys-tematically. The results show that the PCF offers an ultrahigh birefringence of 3.51×10-2 and the confinement loss as low as 1.5×10-9 dB/m with the optimal structure at the wavelength of 1550 nm. Compared with the existing photonic crystal fibers with elliptical air holes, the birefringence has a large increase, and the confinement loss reduces by 5 orders of magnitude. Additionally, we also analyzed the relationship between the dispersion of the PCF and the wavelength, and obtained the Brillouin gain spectrum characteristics. In general, the PCF can be used in long distance communication system.

Design and analysis of porous core photonic crystal fiber based ethylene glycol sensor operated at infrared wavelengths

A novel porous core photonic crystal fiber (PCF) sensor is reported for label-free detection of different concentrations of ethylene glycol present in aqueous solution, over a wavelength range from 1 to 2 μm. Both core and cladding are designed with elliptical air holes, which are arranged in a hexagonal structure with TOPAS as the background material. Various geometrical parameters are judiciously optimized to achieve an efficient sensor. Finite element analysis is employed for numerical simulation of the proposed structure, investigating various sensing parameters including effective refractive index, effective material loss, confinement loss, nonlinearity coefficient, shifts in peak reflected wavelengths, sensitivity, f-parameter, spot size and beam divergence angle. Simulation outcomes reveal a significant shift in the sensing parameters in response to changes in concentration of ethylene glycol, confirming the effectiveness of the sensor. Optimum wavelength sensitivity of 13,144.86 nm/RIU and resolution of $$7.46 \times 10^{ - 7}$$ RIU are attained, which provide a significant theoretical foundation for the design of novel photonic sensors. Benchmarking of the proposed PCF sensor is done against related research results to prove its superiority in terms of resolution and sensitivity.

Design of polarization beam splitter based on dual-core photonic crystal fiber with three layers of elliptical air holes

A polarization beam splitter (PBS) based on dual-core photonic crystal fiber (DC-PCF) with three layers of elliptical air holes is proposed. The full-vector finite element method is used to investigate the coupling and propagation characteristics of the PBS, and the three-dimensional beam propagation method is used to demonstrate the evolutions of the x-pol and y-pol light fields in cores A and B of the DC-PCF. In this design, the elliptical air holes are introduced to enhance the birefringence of the DC-PCF. The simulation results show that, with the proposed PBS, the complete beam splitting can be achieved at wavelength 1.55 μm when the fiber length is 254 μm. Moreover, when the extinction ratio is less than −20 dB, the bandwidth of the PBS can be up to 48 nm, covering the whole C-band. It is believed that the proposed PBS will be a promising candidate in laser and sensor systems.

Design of two miniaturized and broadband polarization filters based on two types of square-lattice gold-filled photonic crystal fibers

Two ultra-broadband polarization filters based on Structure 1 and Structure 2 are reported and characterized in terms of attenuation, crosstalk, bandwidth, and polarization filtering properties by the finite element method. Structure 1 is formed by introducing partial elliptical air holes in the first layer of the square-lattice gold-filled photonic crystal fiber. Based on the design solution of Structure 1, Structure 2 is arranged by using circular air holes with the changed transverse pitch to replace elliptical ones. Numerical results show that high resonance intensities of 2265.07 and 1831.83 dB/cm for y polarization, together with the corresponding x polarization losses of 0.50 and 0.18 dB/cm at respective communication wavelengths of 1.55 and 1.31 μm can be achieved by varying the gold film thickness for Structure 1.Moreover, the design of Structure 2 with all circle holes can also realize a high resonance loss of 1942.54 dB/cm for y polarization with a low loss of 0.43 dB/cm for x polarization at 1.55 μm. Structure 1 and Structure 2 with the fixed fiber length of 300 μm can obtain the crosstalk values of −590.09 and −506.07 dB at 1.55 μm, together with the bandwidths of 1500 and 900 nm, respectively. Additionally, two types of designs represent good produce tolerances. These results show a high potential of the suggested fiber for application in polarization-dependent filtering and other polarizing devices.

Adjustable unidirectional beam splitters in two dimensional photonic crystals

The splitting properties are investigated in two dimensional silicon photonic crystals by adjusting the interface of the structure. Introducing elliptical air holes with optimized parameters on the heterointerface, the forward transmittance is significantly improved in a wide frequency range. Correspondingly, the unidirectional two-beam splitter is realized and the relative light intensities of each beam can be continuously adjusted by modulating the area ratio (AR) of elliptical air holes. Furthermore, the output beams can be changed into three and five beams by alternately introducing elliptical air holes on the monolayer output interface. Not only the forward light intensities of each beam can be continuously adjusted, but also the reverse can be tuned simultaneously by modulating the shape of elliptical air holes. Particularly, the light transmission behaviors along two opposite directions are significantly different. Moreover, the elliptical-shaped air holes have more structural freedoms and increase the design flexibility of the devices. The performance of the splitter is found to be very encouraging in the complex photonic integrated circuits.

Broadening bandgap of thermocrystal by tailoring air hole

Thermocrystal is a new type of artificial periodic crystal structure, which reduces the thermal conductivity of materials. The main factor affecting the thermal conductivity of thermocrystals is the coverage area between the bandgap frequency range and the thermal spectrum. In this letter, we found that, compared with the circular air hole, the elliptical air hole can significantly improve the thermal bandgap of thermocrystal, which will effectively reduce the thermal conductivity. Among them, the cross-shaped ellipse air hole can widen the thermal bandgap of thermocrystal to more than twice. This improves the efficiency of heat transfer by 62%.

Modeling of low non-linearity and low confinement loss photonic crystal fiber by introducing asymmetric defect structures

In this article, confinement loss in hexagonal lattice photonic crystal fiber has been investigated, by using COMSOL Multiphysics based on finite element method. The proposed structure consists of four circular air holes rings, where three circular air holes near the center are replaced by elliptical air holes, which have a major and minor diameter. The Confinement loss was studied in term of minor diameter and wavelength in the range of about 1200–1800 (nm). We realized that the rise of minor diameter lead to decreases of imaginary part of effective index and therefore the confinement loss reduces.

A dual-core fiber for tunable polarization splitters in the terahertz regime

We present a new scheme of dual-core THz fiber for tunable polarization splitter based on the mode coupling theory. Each elliptical polymer core is modified with two elliptical air holes, which is helpful for high modal birefringence and low transmission loss. Due to different coupling lengths for x and y polarizations, the two orthogonal polarizations can be easily separated in an appropriate transmission length. Characteristics of the proposed fiber are discussed numerically in detail, including modal birefringence, effective material absorption loss, coupling and splitting length, transmission loss, extinction ratio, tunability. For the THz polarization splitters, 0.865 cm splitting length is numerically demonstrated at the operation frequency of 1 THz. An efficient tuning method is provided that the operation frequency can be tuned by the applied pressure. This tuning method extends the operation frequency bandwidth from 0.9 to 1 THz in the fixed splitting length. This proposed pressure-tuning THz fiber polarization splitter has potential applications in the field of on-chip integrated THz polarization devices and in-fiber integrated optical devices.

Highly negative dispersion dual-core liquid crystal photonic crystal fiber

Abstract A novel design for dispersion compensation based on dual core liquid crystal photonic crystal fiber (DC-LCPCF) is reported and analyzed. The new structure is based on the optical coupling between the dual cores of the suggested PCF. The full vectorial finite element method (FVFEM) is used to study the dispersion characteristics of the DC-LCPCF. A very large negative chromatic dispersion of 27101.8 ps/(nm-km) is achieved at λ = 1.542 μm with circular air holes only. In addition, the proposed PCF has good tunability with the temperature. Further, the coupling can be switched between transverse electric (TE) and transverse magnetic (TM) modes through external electric field due to the infiltration of the liquid crystal (LC) material. Furthermore, the DC-LCPCF with elliptical air holes has an ultra-high negative dispersion of 289,118 ps/(nm-km) at λ = 1.543 μm.