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Optical fiber communication and sensitivity
Published in Muhammad Arif, Guojun Wang, Mazin Abed Mohammed, Md Tabrez Nafis, Vehicular Ad Hoc Networks, 2023
Salma Masuda Binta, Mohammed Hossam-E Haider, Mohammad Farhan Ferdous
Mainly, the working process of SPR-based photonic crystal sensor depends on the evanescent field [21]. To maximize the sensitivity and lessen the fabrication challenge are the purposes of this design. Here, a dual core is placed at the two opposite sides of the elliptical air hole. The advantage of a dual-core sensor over a single-core sensor is that the evanescent field can easily reach the metal surface and excite the electron effectively. So, to reduce the distance between the metal surface and evanescent field dual core is introduced. It is also noted that the small diameter of the air hole in the horizontal direction confirms the generation of SPW. The background material of the sensor is fused silica that is characterized by the Sllmeier equation [22]. The fabrication of the designed PCF sensor is done by the stack and draw technique [23]. Then, gold (plasmonic material) is deposited outside of the PCF by the chemical vapor deposition technique [24]. The plasmonic material gold is characterized by the Drude–Lorentz model [25]. ε(ω)=ε1+iε2=ε∞ωp2ω(ω+iωc)
Materials for Nanosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
For sensor applications, it is this change in the refractive index of the dielectric exit medium at the metal surface that is of interest. Therefore, if the refractive index of the prism is constant, then a change in the resonance condition may be linked to changes in the refractive index of the exit medium. In this way, it is possible to monitor the accumulation of films on the metal surface in order to measure the binding of molecules to a surface that has been coated with an affinity ligand (an ion, a molecule, or a molecular group that binds to another chemical entity to form a larger complex); affinity meaning “natural liking or fondness” is the force attracting atoms to each other and binding them together in a molecule). From these considerations, the SPR configuration may be regarded as a surface-sensitive refractometer (an instrument for measuring the refractive index of a substance), in which the sensitivity depth is defined by the penetration depth of the evanescent field (~200 nm).
Optical Disk Pickup
Published in Kenichi Iga, Yasuo Kokubun, Encyclopedic Handbook of Integrated Optics, 2018
The interface between the gold film and the non-doped GaP crystal may support the charge density oscillations with proportion to the discontinuity of the electric field component of the evanescent wave normal to the interface. An incident electromagnetic wave excites an SPP, if the wave vector component parallel to the non-doped semiconductor and metal interface matches with the propagation vector of the SPP. Since the SPP wave vector is usually larger than the wave vector incident in a non-doped semiconductor or dielectric media adjacent to the metal film, the exciting field is usually an evanescent field produced by the grating. In the experimental conventional array head [4–6,8–11] the refractive index of the GaP is as high as 3.3 of light (780 nm wavelength) beam waist size inside the semiconductor probe is almost 500 nm in diameter. Evanescent light from the 100 nm aperture on the top tip of the GaP probe is reduced to 10 μW, even though the throughput efficiency is as high as 1% in those experimental cases. The required light power for writing bits on the surface of the optical disk is 100 μW for a 100 nm aperture, and 12 μW for a 30 nm aperture. This means that at least ten times evanescent light power increment for a 30 nm aperture with the aid of the SPP is required.
Surface roughness and the sensitivity of D-shaped optical fibre sensors
Published in Journal of Modern Optics, 2019
Hummad Habib Qazi, Sanober Farheen Memon, Muhammad Mahmood Ali, Muhammad Sultan Irshad, Siddique Akhtar Ehsan, Mohd Rashidi bin Salim, Abu Bakar bin Mohammad, Mohd Zamani Zulkifli, Muhammad Idrees
Operationally at the interface of the sensing region of optical fibre sensor and external environment, a decayed electric field is produced, known as evanescent field. This field is dependent upon the order of modes propagating through the optical fibre. Higher order modes cause to have strong evanescent field at the core-external environment boundary. The number of modes in a fibre can be determined by the V-number (29), as given by, where is the radius of the core, the wavelength of light source, and are the RI of the core and cladding, respectively. Snyder et al. (30) theoretically calculated that the V-number should be <2.405 for the most sensitive single-mode optical fibre sensing device.
Theoretical assessment of a highly sensitive photonic crystal fibre based on surface plasmon resonance sensor operating in the near-infrared wavelength
Published in Journal of Modern Optics, 2019
Chao Liu, Weiquan Su, Famei Wang, Xianli Li, Lin Yang, Tao Sun, Haiwei Mu, Paul K. Chu
Surface plasmon resonance (SPR) has great application potentials in various fields such as biomedicine, proteomics, immunogenicity, drug screening, food safety, and environmental monitoring (1, 2) due to advantages such as rapid response, high sensitivity, and free-label monitoring (3, 4). The SPR phenomenon refers to excitation of electron oscillations (known as surface plasmon wave, SPW) at the metal–dielectric interface caused by p-polarized light or TM (transverse magnetic) wave (3, 5, 6). SPR can be excited by illumination at one terminal with an evanescent field produced by total internal reflection and according to this mechanism, optical fibres offer an attractive platform for SPR sensing by depositing gold or silver on the fibre core. However, technical challenges such as removal of cladding by physical or chemical methods for conventional fibre to obtain close proximity between the analyte and fibre core have not been overcome and therefore, application of optical fibres to SPR sensing has been hampered (7). Recently, photonic crystal fibre (PCF) based SPR sensors have drawn a great deal attention due to advantages such as the design flexibility, high confinement, controllable birefringence, single mode propagation and convenient guiding of light in a vacuum (no dopants are needed) (8–12). The fundamental principle of PCF-SPR sensing is phase matching between the core-guided mode and surface plasmon polariton (SPP) mode (12).
Lanthanum hexaboride coated D-shaped fibre for Q-switched pulse generation
Published in Journal of Modern Optics, 2022
S. Omar, B. Musa, N. Ahmed, Z. Jusoh, H. A. Rahman, A. H. A. Rosol, R. Apsari, S.W. Harun
The interaction of photon and material can be used for pulse generation. It can be implemented by depositing the material on a D-shape optical fibre, which has a strong evanescent field. Furthermore, the light propagates along the deposited material in a D-shaped fibre, which increases the efficiency of interaction. The D-shaped fibre can be prepared by various side-polished techniques. For instance, Ahmad et al. [19] employed an arc-polishing technique to construct D-shaped fibre with different diameters and insertion loss. Here, a mechanical wheel technique is used to polish optical fibre so that it becomes D-shape. Figure 1 shows the fabrication setup, which includes a rotating wheel. A sandpaper is pasted around the rotating wheel, in which the speed is controllable by an analogue knob. In this work, a single mode fibre (SMF, corning SMF-28) with a core/cladding diameter of 9/125 µm was used to prepare a D-shape fibre. About few millimetre of the SMF’s buffer at the region of interest was removed and cleansed with alcohol to prevent any impurities or dust from affecting the polishing process. Next, the SMF with a removed buffer was placed at the centre of the rotating wheel. Then, the speed of the polishing wheel is gently increased to a pre-set level to ensure consistency. The SMF was clamped using two fibre holders, which were fixed at both sides around polishing wheel to ensure no possible horizontal or vertical movement of the fibre. During the polishing process, the polished fibre is connected to an amplified stimulated emission light source at one end and an optical power meter (OPM) (Thorlabs: PM100D) on the other end to monitor the transmission loss in real time.