Reduction of effective material loss (EML) using decagonal photonic crystal fiber (D-PCF) for communication applications in the terahertz wave pulse

We present an excellent design of five layers of decagonal shape in the cladding area and two elliptical shapes of core area based photonic crystal fiber (PCF) for many types of communiqué arenas in the THz wave pulse in this study. The Finite Element Method with perfectly matched layers used the optical parameters of our proposed D-PCF structure numerically to design and analyze. Therefore, D-PCF shows a low effective material loss of 0.0079 cm−1, an increase in effective area of 3.49 × 10–8 m2, a core power fraction of 85%, a low confinement and scattering loss, of 3.35 × 10–16 and 1.27 × 10–10 dB/km respectively at 1 THz of frequency. After analyses all the graphical results, our proposed D-PCF will be highly suitable for communiqué parts in the THz regions.


Introduction
Terahertz radiation which ranges from 0.1 to 10 THz, has recently sparked considerable interest due to its many applied submissions. The gray area exists within the situation of ultraviolet radioactivity and the microwave range. The huge THz occurrence has applications in a variety of fields such as detection (Islam et al. 2017a, b), biomedical tomography (Hossain et al. 2021a), transport network (Pinto and Obayya 2007), bioengineering (Nagel et al. 2002), time-domain spectrometry , brininess (Amiri et al. 2018), infection sensor (Selim Hossain and Kamruzzaman , 2021), security screening (Islam et al. 2016a) applications. It also makes significant advances in the roots and documentation systems of the THz wave. The whole THz scheme is made up of three distinct parts: THz sources, wave guidance, and sensors. THz detector are commercially accessible. THz foundations and sensors are being quickly promoted with the help of advanced up-to-date expertise. The most important THz sources are Gunn diodes, freeelectron lasers, quantum lasers, biological gas far-infrared lasers, and so on. Furthermore, the most useful T-ray detectors are bolometers, Golay cells, pyroelectric detectors, and Schottky barrier diodes. Most THz waveguides, however, rely heavily on free-space wave proliferation due to frequency propagation. However, here are some issues with free space wave proliferation, such as path loss, material loss, and high absorption loss. Researchers had previously proposed numerous waveguides to mitigate these issues. Bragg fibers (Jeon et al. 2005), metallic waveguides (Wang and Mittleman 2004), silver coated hollow glass (Bowden et al. 2007;Skorobogatiy and Dupuis 2007), subwavelength waveguides (Hassani et al. 2008), parallel-plate waveguides (Chen et al. 2006), and so on are examples. Metallic waveguides used in THz transmission can encounter issues such as high winding loss and frequency-dependent losses. Bragg fibers are more efficient in diffusion and riddling submissions. Nonetheless, using Bragg fibers to achieve desirable output in applied wavelength division multiplexing submissions is difficult. The main limitation of a parallel-plate waveguide is confinement loss.
Microstructure core PCF has newly demonstrated progressive physical elasticity and extremely high optical possessions. One important gain is that determined optical power permits through the core region, which aids to decrease material loss. Two basic optical managerial possessions are usually originated in microstructure core PCF: modified total internal reflection (MTIR) and photonic bandgap (PBG). When the RI of the cladding is better than the core RI, the photonic bandgap function operates in PCF. When the core RI exceeds the cladding, the MTIR impact is activated. Microstructure PCF is proposed as a THz supervisory standard to attain lower confinement loss, high numerical aperture, lower dispersion, high birefringence, and better waveguiding properties. PCF suffers from material losses due to the use of solid materials in the core region. A porous air core is favored athwart a solid body (Tang et al. 2013a). Such properties make it possible to use porous polymer PCFs in a variety of filtering and sensing submissions. Other kinds of circumstantial resources, such as ZEONEX, TOPAS, Teflon, Polymethyl methacrylate, and ZBLAN (Yuan et al. 2011;Bulbul et al. 2020;Hossain et al. 2021b;Jiang et al. 2015;Dash and Jha 2014), are secondhand to improve optical guiding properties and reduce EML. ZEONEX has been used as the contextual material since it has excellent optical possessions such as low material loss, high temperature insensitivity, and low dispersion (Hossain et al. 2021c).
In past years, low loss THz waveguides are discussed briefly by many researchers. Porous core-based PCF was described by Hasanuzzaman et al. (Hasanuzzaman et al. 2015) and presented the higher effective EML of 0.035 cm − 1. Hasan et al. (Hasan et al. 2016) discussed a square lattice photonic crystal fiber and reported an EML of 0.076 cm − 1. Islam et al. (Islam et al. 2016b) showed their structure such as porous core-based PCF and found an EML of 0.050 cm − 1. Sen et al. (Md. Selim Hossain, Nazmul Hussain, Zakir Hossain, Md. Sakib Zaman, Md. Navid Hasan Rangon, Md. Abdullah-Al-Shafi, Shuvo Sen, Mir Mohammad Azad, Performance analysis of alcohols sensing with optical sensor procedure using circular photonic crystal fiber (C-PCF) in the terahertz regime, Sensing and Bio-Sensing Research, Volume 35 2022) showed the polymer-based photonic crystal fiber and their results of an EML of 0.040 cm −1 . After checking the previous structure (Hasanuzzaman et al. 2015;Hasan et al. 2016;Islam et al. 2016b;Md. Selim Hossain, Nazmul Hussain, Zakir Hossain, Md. Sakib Zaman, Md. Navid Hasan Rangon, Md. Abdullah-Al-Shafi, Shuvo Sen, Mir Mohammad Azad, Performance analysis of alcohols sensing with optical sensor procedure using circular photonic crystal fiber (C-PCF) in the terahertz regime, Sensing and Bio-Sensing Research, Volume 35 2022; ; ; ;;;), we get a good chance to develop a new structure by removing very low losses for communication applications.
Our D-PCF is an arrangement of five layers of decagonal form within the covering area and two elliptical forms of photonically crystal (D-PCF) core area of various types of communication in the terahertz belt. This D-PCF displays a low EML of 0.0079 cm −1 following an examination of numerical findings; a large effective area of 3.49 × 10 -8 m 2 ; a core power fraction (CPF) of 85%, a low CL and SL of as 3.35 × 10 -16 dB/m and 1.27 × 10 -10 dB/km at 1 THz respectively. Figure 1 depicts structural cross sections such as (a) Decagonal cladding regions, (b) Elliptical core regions, and (c) Mode field distribution. In this case, the diameter and pitch at the cladding areas are signified by the constraints d 1 and A 1 . The constraints d 1 /A 1 is called the air filling proportion which is to watch in contradiction of collapse between two air holes in the cladding area. The parameters of A c , d a , and d b are indicated at the core area by the pitch and distances of the two elliptical AHs. The ZEONEX material was used to remove the EML, confinement loss (CL), and Scattering loss (SL) in this case. Here, the optimum cladding

Mathematical analysis of optical properties
It has been known to us that a large EA-based PCF fiber shows a low EML. Here, the EA is calculated the following equation (Ren et al. 2012): where, A ea is the effective area and intensity of electric field is the I(e) =|E e | 2 .
PF is indicated that the most amount of power flowing in the core area of the D-PCF structure. Here, Power fraction is determined by the following equation (Luo et al. 2017): where S zt is area of interest such as cladding, core, or air hole is indicated by nominator integration and the entire cross-section area is denoted by denominator integration.
V-parameter displays the single mood communication and the V-parameter is shown the following equation (Islam et al. 2016c): where, the core and cladding area based effective mood index is defined by the n coe and n cle and c is the radius of the core.
The CL is a vital aspect of D-PCF structure and this CL ( L ce ) is shown by Islam et al. 2017c: where, the free wave number is K 0 = f c , c is the speed of photon, frequency is f and the imaginary part of ERI is Im n ea .
The SL is well-defined with the total amount of loss of the D-PCF structure. At this time, the scattering loss is calculated by Ahmed et al. 2017a: where, the scattering coefficient is C S .
The background material of Zeonex creates a very low EML and this EML is calculated by Rana et al. (2014): (4) L ce = 8.686 × K 0 Im n ea (dB∕m) where, the relative permittivity and the permeability of free space are denoted by ε 0 and μ 0 , the RI of the material is n mat and bulk material absorption loss is α mat.

Simulated results and discussions
We chose the optimum porosity of 86, 76, and 66% because it is clear from Figs. 2,3,4,5,6,7,8,9 that the total light transmits inside the CA. This D-PCF fiber exhibits improved graphic outputs for optical possessions such as low EML, low SL, larger EA, high core power fraction, better V-parameter, and low CL with frequency ranges; ranging from 0.08 to 3 THz. In Fig. 2, the EA is decreasing with the frequency varieties from 0.80 to 3 THz for three porosities for such as 66, 76, and 86%. At 1 THz frequency of optimum parameters for 86, 76, and 66% porosities, the EA is determined of 3.49 × 10 -8 , 3.60 × 10 -8 , and 4.55 × 10 -8 m 2 respectively.
In these graphical results, the EML is slightly increased with the core diameters from D core = 280 μm to D core = 440 μm for three porosities for such as 66, 76, and 86%. At 1 THz frequency of optimum parameters for 86, 76, and 66% porosities and optimum core diameter D core = 420 μm, EML is calculated 0.0079 cm −1 .   Figure 6 displays that the PF of the core, cladding, and materials has good relationships with frequency ranges; ranging from 0.80 to 3 THz. The majority of the light passes through the core area, while some power is lost in the cladding and materials areas. Optimum values are D core = 420 μm, 85, 0.25, and 21% of core, cladding, and materials of the power fraction respectively which has been found at 1 THz.
In Fig. 7, the SL is slightly growing with the frequency ranges from 0.80 to 3 THz. For 86% porosity and 1 THz frequency, the SL is at 1.27 × 10 -10 dB/km.  Fig. 8, the confinement loss (CL) is decreasing with the frequency ranges from 0.80 to 3 THz. For 86% porosity and 1 THz frequency, confinement loss (CL) is the order of 3.35 × 10 -16 dB/m.
In this graphical Fig. 9, the V-parameter is increasing from 0.80 to 3 THz and this V-parameter shows single mood communication system (V − parameter ≤ 2.045). Here, the optimum cladding diameter is 282 μm, cladding pitch of 345 μm, diameter of core d a = 70 μm,d b = 160 μm and core pitch Λ c = 100 μm.
Here, fabrication is an important way to fabricate the photonic crystal fiber. Many advanced fabrication techniques such as stack and draw, tube stacking drilling, sol-gel Rana et al. 2014;Paul et al. 2019b;Islam et al. 2017d;Tang et al. 2013b) can be considered, however the sol-gel (Hamzaoui et al. 2012;Hasan et al. 2017;Bao et al. 2012;Nielsen et al. 2009;Ponseca et al. 2008) process will be appropriate to manufacture the proposed D-PCF.

Conclusion
In this study, a decagonal (D-PCF) photonic crystal fiber was examined using PML and the FEM based COMSOL Multiphysics software tool for communication network performance analysis. In addition, we used ZEONEX as a background material to remove EML, CL, and SL. After reviewing all of the graphical results, we discovered that our D-PCF has an EML, a large effective area, a core power fraction, and a low CL and SL of 0.0079 cm −1 , 3.49 × 10 -8 m 2 , 85%, 3.35 × 10 -16 dB/m and 1.27 × 10 -10 dB/km correspondingly at 1 THz frequency range. So, our D-PCF is proper for communication parts in the THz regions.