Investigation on the Effect of Fluorescence Material based on D-Shaped Hollow Core Photonic Crystal Fiber

In this paper, we report the outcomes when fluorescence material coated the hollow core (inner part) of D-shaped photonic crystal fiber (PCF) that has internal diameter (ID), 10 μm. Fluorescence involves the emission of light by a substance that has absorbed light or other electromagnetic radiation. The coated material namely, allene has contributed significantly to the output of transmission spectra at the visible region. The changes in transmission wavelength are remarked when certain parameters vary along the study. The air hole deposited with allene exhibits strong electromagnetic interaction which is good for optical absorption and hence could promote high-sensitivity performance. The optimum condition on how allene covered the hollow PCF which this includes the number of days dipping leads to the bigger wavelength shifting comparing to its emission at 530 nm. Therefore, this study report that allene material could promote an important role in sensing applications at the visible as it displays a good response.


Introduction
The 1990s witnessed the emergence of photonic crystal fiber (PCF) which later on the application has been developed into sensor purposes (P. S. J. Russell, 2006).The specialty of PCF is the structures (size and geometry of air holes) are easily modified in order for phasematching conditions.It is proven that the utilization of PCF as a device can improve the sensing performance such as broad detection range (Wang, Lu, Duan, & Yao, 2020) (Otupiri, Akowuah, & Haxha, 2015) even it has been implemented on gas detection (Bakker & Telting-Diaz, 2002;Moseley, 1997;Shimizu & Egashira, 1999;Smith & Španěl, 2007).Anyhow, the response time of the sensor depends on the capillary action (Kuhlmey, Eggleton, & Wu, 2009) and analyte diffusion mechanisms.Studies report that the D-shaped PCF is more viable as it permits the analyte to penetrate the airholes effortlessly due to its flat surface.Single-mode fiber (SMF) is desirable in this work as a way to eliminate multiple peak losses if other modes are applied (Falah, Wong, & Adikan, 2022).Hollow-core photonic crystal fiber (HC-PCF) comes in two different varieties (Benabid, 2006;Knight, 2003;P. Russell, 2003; P. S. J. Russell, 2006).Here, we proposed a hollow core D-shaped PCF with a single air hole made up of borosilicate.As light travels faster in air compared to the other mediums like glass, hollow-core fiber provides higher speed and lower latency.
Fluorescent molecules absorb photons of specific wavelengths and emit a longer wavelength photon within nanoseconds (Benito-Pena, Valdés, Glahn-Martinez, & Moreno-Bondi, 2016).Recently, fluorescent materials have been widely used in the life and material sciences.Heterocyclic compounds that carry out fluorescent characterisation are useful in bioanalytical applications, including light-emitting diodes (Ullah et al., 2022).Modern heterocyclic molecules are at the core of this development of fluorescence (Schramm & Weiss, 2019).The aromaticity of a heterocyclic compound is what defines a heteroaromatic chemical.
Currently, the newly synthesized heteroaromatic compound contains a function group of allenes.Allenes are organic compounds that contain one carbon-centered connected to two adjacent carbons through double bonds.The parent compound of this class is propadiene, which is itself also called allene, also known as the simplest form of allenes.

H2C = C = CH2
where H is a hydrogen and C is a carbon.According to Taylor (1967), the most stable bonding arrangement involves two mutually perpendicular pie bonds, with the central carbon atom (sphybridized) joined in a straight line to the two terminal carbon atoms (sp2-hybridized).Today, many patents address the use of allenes as colours, medicines, antioxidants, fibres, and beator corrosion-resistant materials, indicating that their industrial potential is being explored.

Methodology
The first part of the project is to prepare the allene material through process of chemistry.As the material is ready, the concentration of allene solution is varied to obtain the emission at 530 nm.Specific concentration at 33 g/L of allene solution is proven to be the best indication has proceeded towards fiber testing.Dipping process take place to allow the diffusion based on the capillary action of the airhole.
A 3.0 cm length hollow core PCF is placed between the light source and optical spectrum analyzer (OSA) as shown in Figure 1 (a).The tested sample with inner coated of allene material by dipping technique has been measured at a specified time.After a proper alignment is done (Figure 1b), the transmission signal is observed at the OSA device while the input to the PCF fiber is a supercontinuum source at wavelength range 400 nm -2400 nm with ~100mW power.Figure 1 (c) indicate the feature of allene solution in yellow colour.

Results and discussion
At first, the study is about the emission spectra of the material itself which it is called allene.In order to understand the interaction of the material with the light, the optimum  The outcomes were based on the transmission spectra that showing notable values when the day of dipping fiber in the allene solution are varied.Figure 3 (a) depicts the transmittance result regarding bare fiber, 1-day dip, and 4 days dip.There is a significant shift in wavelength when the days of dipping are increased at 10 nm difference comparing of 1-day dip, 538 nm with 4 days dip, 548 nm. Figure 3 (b) shows the prominent transmittance spectra of 642 nm and 658 nm respectively when second round dipping take place using the previous samples (in Figure 3 (a)).The day of dipping fiber also has been manipulated which show fiber with a minimum day dipping (1-day) has better results in contrast of second time dipping for three days (Figure 3 (c)) that showing no significant spectra probably due to the losses of propagated light throughout the core.Second dipping for about one day exhibits larger shifting, ~ 10 nm from the result in Figure 3 (a).The amount of solution formed inside the hollow core in this period is barely enough for the light to interact well with the surrounding.The other thing that plays a role is the length of fiber testing.The presence of air bubbles (Figure 3 (d)) and the distribution of the solution in the inner fiber approximately at 10.54 µm hollow core (Figure 3 (e)) could affect the transmission.

Conclusion
Experimental work has been carried out using fluorescence material namely allene coated internally of hollow-core photonic crystal fiber (PCF).The optimized condition of the coating area has increased the shifting of transmission spectra.Thus, this study should be well pursued as it is manifest a strong response that could help in sensor applications.

Figure 1 .
Figure 1.(a) Experimental setup (b) Fiber alignment (c) Allene solution concentration of allene has to figure out.Several attempts (Figure 2 (a) and Figure 2 (b)) had been carried out to find the best single peak emission of allene such in Figure 2 (c).Lower concentration producing double peak probably due to not strong or enough emission where the peak arises at wavelength around 450 nm.

Figure 3 :
Figure 3: Transmission spectra with number of day dipping (a) first dipping (b) second dipping, 1 day (c) second dipping, 3 days (d) allene distribution inside core (e) ID of hollow core