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A strong coupling regime with dressed states is formed when a propagating surface plasmon (PSP) mode coherently exchanges energy with an ensemble of excitons at a rate faster than the system’s losses. These states are superpositions of superradiance excitons and PSP modes, accompanied by remaining subradiance or ‘dark’ exciton states. Dark-states are ubiquitous, especially in disordered systems, and they rise in number as the number of excitons increases. Here, the ultra-strong coupling regime was experimentally observed with the coupling strength to bare energy as high as g/ E e x c i t o n ∼ 0.23 using a self-antiaggregation organic dye, BOBzBT2 in an Otto-SPR configuration. We show that the hybrid system of excitons in a nonlinear organic dye layer and a PSP mode can be described by employing dark-state in a theory of nonlinear third-order sum-frequency generation (TSFG). Close agreement between the theory and the experiment has been demonstrated. The study opens up a new perspective for establishing a relationship between the optical properties of a third-order nonlinear material and the extent of strong coupling.

The sandwiched material-analyte layer in the surface plasmon resonance (SPR)-Otto configuration emulates an optical cavity and, coupled with large optical nonlinearity material, the rate of light escaping from the system is reduced, allowing the formation of a strong coupling regime. Here, we report an organic pentamer SPR sensor using the Otto configuration to induce a strong coupling regime for creatinine detection. Prior to that, the SPR sensor chip was modified with an organic pentamer, 1,4-bis[2-(5-thiophene-2-yl)-1-benzothiopene]-2,5-dioctyloxybenzene (BOBzBT2). To improve the experimental calibration curve, a normalisation approach based on the strong coupling-induced second dip was also developed. By using this procedure, the performance of the sensor improved to 0.11 mg/dL and 0.36 mg/dL for the detection and quantification limits, respectively.

The Kretschmann-based surface plasmon resonance (K-SPR) sensor was developed using multilayer graphene and molybdenum disulphide (MoS2) structures on a plasmonic gold (Au) layer for ethanol detection. In this configuration, the SPR spectra of minimum reflectance versus SPR angle was used to determine the sensitivity, detection accuracy and quality factor as the main figure of merit (FOM). Both graphene and MoS2 were used as hybrid detection layers to enhance the ethanol sensing performance using Finite Difference Time Domain (FDTD). The multilayer graphene/Au and MoS2/Au sensors gave a maximum sensitivity of 192.03°/RIU and 153.25°/RIU respectively at 785 nm optical wavelength. In terms of material characterization using the K-SPR technique, chemical vapor deposition (CVD)-grown graphene on Au, had a thickness of 1.17 nm with real and imaginary refractive indices of 2.85, 0.74, and 3.1, 1.19, respectively, at optical wavelengths of 670 nm and 785 nm.

Perovskite solar cells (PSC) are currently exhibiting reproducible high efficiency, low-cost manufacturing, and scalable electron transport layers (ETL), which are becoming increasingly important. The application of photonic crystals (PC) on solar cells has been proven to enhance light harvesting and lead solar cells to adjust the propagation and distribution of photons. In this paper, the optimization of a two-dimensional nanodisk PC introduced in ETL with an organic-inorganic lead-iodide perovskite (methylammonium lead-iodide, MAPbI3) as the absorber layer was studied. A finite-difference time-domain (FDTD) simulation was used to evaluate the optical performance of PSC with various lattice constants and a radius of nanodisk photonic crystals. According to the simulation, the optimum lattice constant and PC radius applied to ETL are 500 nm and 225 nm, respectively. This optimum design enhances PSC absorption performance by more than 94% of incident light.

1,4-bis[2-(5-thiophen-2-yl)-1-benzothiophene]-2,5-dioctyloxybenzene (BOBzBT 2 ) is a functionalized organic pentamer that was used to modify the carbon working electrode surface to be used as a biosensor for creatinine detection. BOBzBT 2 has good solubility characteristics in common organic solvents. Although it is insoluble in water, BOBzBT 2 is able to be stored in a relatively stable condition. In addition, the hydrophobic property of BOBzBT 2 enables it to be reusable. This is especially useful for the non-destructive sensing application besides ensuring stability even in environments with high humidity. The BOBzBT 2 modified sensor was compared to the unmodified sensor to see the improvements in charge transfer. A repeatability test was performed on the modified sensor to determine whether the modified sensor can be used repetitively or only for single use. A reproducibility test was also performed on the modified sensor to determine whether the modified sensor can be used to reproduce consistent data. The BOBzBT 2 modified sensor was compared to the unmodified sensor to see the improvements in charge transfer.

The fabrication of silicon nanohole (SiNH) using a combination of electron beam lithography (EBL) and reactive ion etching (RIE) processes is reported. The optimum exposure dose of EBL process was found to be in the range of 210-240 µC/cm2 due to small enlargement of hole diameter after pattern development process. The anisotropic etching and isotropic etching was achieved at low and high reaction pressures, respectively. As expected, the etching rate increase with time and RF power. A relatively smooth and well-defined NH has been obtained at RF power of 100 W and reaction pressure of 0.08 Torr, which is suitable to be applied for optical waveguide.

Kretschmann-based Surface Plasmon Resonance (SPR) optical sensor was applied to detect the presence of kidney wastes such as urea in solutions. To enhance the sensitivity of the SPR sensor, nanolaminated gold film (thickness of 50 nm) was used. In this work, the SPR response to urea in various concentrations were measured and investigated using optical wavelengths of 670 nm and 785 nm. The signals were compared between pure urea solution versus mixed solution in the presence of the 0.227 μmol urease enzyme. The proposed mixed solution is to eliminate doping and gel entrapment process for enzyme immobilization in conventional method. Angular interrogation technique was used to measure the sensor performance in urea detection using pure and mixed solutions with urea concentration of 0 - 800 mM. Upon exposure to mixed solution using 785 nm optical wavelength, the nanolaminated gold film exhibited higher SPR sensitivity as much as 7.8 M-1 than a pure urea solution (1.4 M-1). The coupling activity between urea and urease molecules in the mixed solution near the nanolaminated gold film surface lead to sensitivity enhancement. Angle shifting of mixed solution on 50 nm-thick nanolaminated gold film using 670 nm optical wavelength was greater by ~50% compared to 785 nm. Sensorgram data shows a steady and linear increment in SPR incident angle shifting when urea concentration increased. To the best of our knowledge, this is the first time that Kretschmann-based SPR has been used for urea sensing at 670 nm and 785 nm optical wavelengths.

This research focuses on the design, fabrication and characterization of the graphene based capacitive microphone. Finite element analysis (FEA) is first simulated in order to design and study the proposed graphene based capacitive microphone. While the fabrication introduced MEMS technique in order to reduce the physical size, volume and cost without neglecting the performance. This study discusses on physical characteristics of graphene diaphragm for capacitive microphone. The fabrication of 200 nm air gap and the free-standing suspended graphene with the contribution of the van der Waals force between the graphene layer as a diaphragm and the substrate are presented in this study. The first stage involved in this study was the photolithography process of patterning electrodes with 4 different dimensions of diaphragm. The characterization was performed by using surface profilometer, optical microscopy, Raman spectroscopy and FESEM to evaluate the physical characteristics of the diaphragm. In the last stage, LCR meter was used to measure the capacitive change with different diameter of graphene diaphragm within frequency range of 20 Hz to 20 kHz. FEA analysis showed the good sensitivity against the frequency response for the largest proposed diameter of diaphragm.

Silicon-based photonic integrated circuit (PIC) is a research focus in producing high-density photonics. One of the potential applications of silicon PIC is the sensing and measurement system. In this work, we use the one-dimensional photonic crystal (1D-PhC) cavity design which and utilize it at the PIC level design. The 1D PhC design used as the compact model has the same characteristics as experimentally demonstrated in previous works. The compact model is made from the S-parameter extraction of the 1D-PhC device which is done by using Lumerical FDTD software. The PIC design integrates the 1D-PhC device as a sensing component with a PN-phase shifter (PN-PS) to function as a refractive index (RI) sensor calibration or tuning circuit. A custom design of PN-PS device is used by simulating and extracting the bias voltage-effective index (bias-Neff) data by using Lumerical DEVICE and MODE into the circuit simulator. The circuit-level simulation is done by using Lumerical Interconnect software. Finally, we show the GDSII layout design of the 1D-PhC based photonic sensor calibration circuit with an analysis of generic silicon PIC design rules. The designed PIC is applicable for the bio-sensing applications and photonic SOC component. This work also shows the promise of PIC design approach for further PIC development.

In this study, the low-group velocity slow-light mach-zehnder interferometer (MZI) modulator, low loss and high efficiency for two modulator substrate lithium niobate (LN) and silicon were presented and optimized at 1.55µm operating wavelength. The high power consumption of conventional modulator was the major drawback in the operation of modulators. Therefore, it was a good time for low-power modulator design and development and to compare the LN and Silicon modulator on the phase shifted using the slow-light technique by designing the full MZI modulator consisting of splitter and combiner on both substrates. The phase shift of LN is 2% compared with the silicon 0.09% and higher phase shift give better performance with low power consumption due to the change of modulating voltage of the MZI modulator for LN while the silicon depends on modulating voltage manipulating concentration of charge carrier in doped silicon.

We designed and demonstrated a double-peak one-dimensional photonic crystal (1D PhC) cavity device by integrating two 1D PhCs cavities in a parallel configuration. The device design is proposed so that it can be used for bio-sensing purposes and has a self-compensation ability to reduce the measurement error caused by the change of the surrounding temperature. By combining two light resonances, two resonance peaks are obtained. The peak’s separation, which gives the initial value for a sensing system, can be controlled by varying the cavity length difference (Δc) between the first and second 1D PhCs in parallel. Then, by making one arm of the device as the reference arm and the other arm as the sensing arm, the temperature self-compensation device can be realized. The design and simulation of this device are done by using Lumerical software, which are Lumerical MODE, Lumerical finite-difference time-domain, and Lumerical Interconnect. Electron-beam-lithography and deep reactive-ion-etching processes were used for device fabrication. The experimental results show the controllable peaks’ separation, which solves the double-peak requirement for a temperature self-compensated bio-sensor design.

Increasing the quality factor (Q) of an optical resonator device has been a research focus to be utilized in various applications. Higher Q-factor means light is confined in a longer time which will produce a shaper peak and higher transmission. In this paper, we introduce a novel technique to increase further the Q-factor of a one-dimensional photonic crystal (1D PhC) cavity device by using an end loop-mirror (ELM). The technique utilizes and recycles the light transmission from the conventional 1D PhC cavity design. The design has been proved to work by using the 2.5D FDTD simulation with Lumerical FDTD and MODE softwares. By using the ELM technique, the Q- factor of a 1D PhC design has been shown to have increased up to 79.53 % from the initial Q value without the ELM. This novel design technique can be combined with any high Q-factor and very high Q-factor designs to increase more the Q-factor value of a photonic crystal cavity devices or any other suitable optical resonator devices. The experimental result shows that the device is measurable by adding a Y-branch component to the one-port structure and able to get the high-Q result.

Supplemental Material, sj-pdf-1-nax-10.1177_1847980420987774 for On the performance of polymer-inorganic perovskite oxide composite light-emitting diodes: The effect of perovskite SrTiO3 additives by Ummi Kalsom Noor Din, Muhamad Mat Salleh, Tengku Hasnan Tengku Aziz, Ahmad Rifqi Md Zain, Mohd. Ambri Mohamed and Akrajas Ali Umar in Nanomaterials and Nanotechnology

With the aim of selecting particular frequencies of interest and rejecting others, the waveguiding and filtering properties of a two-dimensional phononic crystal slab are investigated in the context of a filtering application. To this end, we designed and manufactured a metallic device that consists of a square lattice of cylindrical pillars mounted on the top of a plate by using 3D printing technology. We respectively explored the theoretical and experimental characteristics of the device by using finite element method, a Micro System Analyzer (MSA) and a scanning laser Doppler vibrometer. The proposed device shows a complete band gap for Lamb wave around 0.3 MHz with a relative band-width of 30 % . Tailorable waveguides are realized inside this phononic crystal by inserting several space gaps to achieve a demultiplexing effect through the splitting of an acoustic signal towards three different bandpass frequency channels. The demultiplexing performance has been experimentally demonstrated by achieving rejection levels up to 60 dB. The proposed phononic platform can have a significant impact in signal processing as well as droplet manipulation for biological applications.

A novel hydrogen (H2) sensor was developed using optical fiber coated with manganese dioxide (MnO2) nanostructures. Optical multimode fiber (MMF) of 125 μm in diameter as the transducing platform was tapered to 20 μm to enhance the evanescent field of the light propagates in the fiber core. The tapered fiber was coated with MnO2 nanograins synthesised via chemical bath deposition (CBD) process. Catalytic Palladium (Pd) was sputtered onto the MnO2 layer to improve the H2 detection. The sensing layer was characterized through Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray (EDX), X-ray Diffraction (XRD) and Raman Spectroscopy to verify the properties of MnO2. Two sets of sensors consist of as-prepared MnO2 and 200 °C annealed MnO2 were tested towards H2 gas. The tapered optical fiber coated with Pd/MnO2 nanograins was found to be sensitive towards H2 with different concentrations in synthetic air at 240 °C operating temperature. The annealed sensor showed higher response and sensitivity as compared to the as-prepared sensors when measured in the visible to near infra-red optical wavelength range. The absorbance response of the annealed Pd/MnO2 on fiber has increased to 65% as compared to 20% for the as-prepared Pd/MnO2 upon exposure to 1% H2 in synthetic air.

This study reports the performances of a single structured light-emitting diode (LED) devices based on polymer material poly(9,9-di- n-hexylfluorenyl-2,7-diyl) (PHF) mixed with various concentrations of perovskite oxide strontium titanate (SrTiO3) particles deposited as a composite PHF: SrTiO3 emitting layer. The performances of the single structured organic LED indium tin oxide (ITO)/PHF/aluminum (Al) device and the composite LED ITO/PHF: SrTiO3/Al devices were compared in terms of turn-on voltage and luminance intensity. By incorporating perovskite SrTiO3 particles into PHF emitting layer, the turn-on voltage of the device is significantly reduced from 11.25 V to 1.80 V and the luminance intensity increased from 57.7 cd/m2 to 609 cd/m2. The improvement of turn-on voltage and the electroluminescence spectrum of the composite devices were found to be dependent on the weight ratios of SrTiO3 content in the PHF emitting layer.

In this work, we report a graphene-alkaline lignin-poly(3,4-ethylenedioxythiophene) polystyrene sulfonate composite as a transparent conductive electrode for indium tin oxide-free optoelectronic devices. The composite was prepared by dispersing exfoliated graphene-alkaline lignin into aqueous poly(3,4-ethylenedioxythiophene) polystyrene sulfonate. The effect of graphene concentration on the electrical and optical properties of graphene-alkaline lignin-poly(3,4- ethylenedioxythiophene) polystyrene sulfonate was studied. The graphene-alkaline lignin-poly(3,4- ethylenedioxythiophene) polystyrene sulfonate thin films exhibit excellent electrical conductivity and high transparency properties. The electrical conductivity is further increased by 1.9 ± 0.01 × 103 times when graphene content was augmented in the composites; however, the optical transparency was reduced due to the high optical absorbance of graphene. In this condition, the conductivity and optical transparency are as high as (4.19 ± 0.01) × 103 S/cm and 94.2%, respectively. This achievement is attributed to the organization of higher ordered network between conductive exfoliated graphene and poly(3,4-ethylenedioxythiophene) chains that induced a better conducting channel for charge transportation. The poly(3,4-ethylenedioxythiophene) chains act as a bridge connecting the graphene flakes, which, in turn, facilitate the movement of hole charges between them.

High melting point refractory tantalum (Ta) metal is frequently grown into thin film layer for many applications in biomedical implants, microelectronic devices and micro-level mechanical systems. Tantalum growth mechanism is still in debate and the inconsistent crystal phase outcome has puzzled many, though it is certain that the properties of the grown film are highly dependent on the formed crystal phase configuration. The microstructure, surface morphology, crystal orientation and residual stress of the sputter-deposited Ta thin films using direct current (DC) magnetron sputtering technique are studied at 0.4 Pa – 2 Pa of sputtering pressure, 100 W – 250 W of DC sputtering power on bare silicon and silicon dioxide substrate and 10 min – 50 min of sputtering duration. α-phase Ta is preferably grown at high sputtering time (high thickness) and high DC sputtering power (high growth rate). The sputtering pressure affects the thin film's microstructural porosity while the sputtering power controls the crystallisation's quality. Both sputtering pressure and power affect the generated argon plasma in the DC magnetron sputterer where α-phase Ta is preferably formed at high plasma. The presence of 3 μm silicon dioxide underlayer makes no difference compared to bare silicon substrate. Our study reveals that β-phase Ta is grown first irrespective of sputtering conditions and then transformed into α-phase Ta after reaching a certain thickness. The grown major α-phase content promotes small thin film sheet resistivity (58.9 μΩcm – 86.1 μΩcm) and is suspected to be the dominant factor that increases the compressive stress within the thin film layer and reduces the adhesion of Ta layer onto the substrate surface. The study has given a new insight in controlling the conductivity and adhesion level of Ta thin film based on the grown phase layer.

We present the simulation and experimental demonstration of a coupled-cavity 1D photonic-crystal/photonic-wire (PhC/PhW) structure that produces multiple resonance wavelengths. The combination of several cavities results in the assembly of a spectral response that exhibits multiple resonance wavelengths and potentially leads to the wavelength control required for wavelength division multiplexing (WDM) applications. By using a structure with three distinct in-line cavities, we have obtained three distinct resonance wavelengths—in conformity with the rule that the number of distinct resonance wavelengths is proportional to the number of cavities. The experimental photonic wire waveguide structure had cross-sectional dimensions of 600 nm (width) × 260 nm (height)—with an embedded photonic crystal (PhC) micro-cavity—all based on a silicon-on-insulator (SOI) platform. The embedded PhC structure was tailored to give resonance wavelengths in the C-band and L-band fiber telecommunication range. With the introduction of tapering in the multiple micro-cavity structure, it was possible to obtain three resonance wavelengths that correspond to WDM wavelengths of 1534.87, 1554.63 and 1594.86 nm—whereas, without tapering, the resonance wavelengths were 1645.60, 1670.76 and 1698.68 nm, respectively. We have observed an asymmetric free spectral range (FSR) situation with un-equal resonance wavelength spacing. The taper regions are also responsible for high optical transmission and lower Q-factor values at resonance. Transmission values of 0.17, 0.47 and 0.43 were obtained, together with Q-factor values of 1179.32, 930.05 and 970.35, respectively, without using tapered sections—while transmission values of 0.45, 0.74 and 0.43 were obtained, together with Q-factor values of 1083.24, 850.10 and 885.22, respectively, using tapered sections. (The normalisation values for the experiments were obtained with respect to an unstructured photonic wire). We have demonstrated that the taper structures used must be designed accurately, in order to maximize the transmission values at the desired resonance wavelengths. The demonstration of fabricated device structures that have measured properties that are in close agreement with predictions obtained using finite-difference time-domain (FDTD) computational software is an indication of the precision of the fabrication process. With the introduction of multiple cavities into the structures realised, the number of resonance wavelengths can be tailored for application as WDM components or other wavelength selective filters, such as arrayed-waveguide grating structures (AWGs) and Bragg gratings.

Strain in the lattice has a profound effect on the electrical and optoelectronic properties of the material. Here, we demonstrate the extent effect of micro-strain applied to graphene, induced by silver nanowires (AgNWs), on its lattice and electronic properties. In the typical process, we found that the micro-strain effect has critically expanded the lattice carbon-carbon bond length as confirmed by a dramatic red-shift in the Raman main character of graphene. For example, the G and 2D band vibration mode of graphene shifts as high as 11.31 and 13.47 cm−1, respectively, that is from 1593.67 to 2687.46 cm−1 for unstrained graphene to 1583.36 and 2673.99 cm−1 for graphene under micro-strain induced by AgNWs with density 5 wire/100 μm2. Raman spectra also indicated that the shifting value is dependable on the nanowire's density. XPS analysis results also reveals that the changes in bond length directly cause a strong modification in its electronic state, altering its overall electronic properties. Enhanced electrical and optoelectronic properties is expected from this micro-strained graphene system.

The need for environmental protection and water pollution control has led to the development of different sensors for determining many kinds of pollutants in water. Ammonia nitrogen presence is an important indicator of water quality in environmental monitoring applications. In this paper, a high sensitivity sensor for monitoring ammonia nitrogen concentration in water using a tapered microfiber interferometer (MFI) as a sensor platform and a broad supercontinuum laser as the light source is realized. The MFI is fabricated to the waist diameter of 8 µm producing a strong interference pattern due to the coupling of the fundamental mode with the cladding mode. The MFI sensor is investigated for a low concentration of ammonia nitrogen in water in the wide wavelength range from 1500–1800 nm with a high-power signal provided by the supercontinuum source. The broad source allows optical sensing characteristics of the MFI to be evaluated at four different wavelengths (1505, 1605, 1705, and 1785 nm) upon exposure towards various ammonia nitrogen concentrations. The highest sensitivity of 0.099 nm/ppm that indicates the wavelength shift is observed at 1785 nm operating wavelength. The response is linear in the ammonia nitrogen range of 5–30 ppm with the best measurement resolution calculated to be 0.5 ppm. The low concentration ammonia nitrogen detected by the MFI in the unique infrared region reveals the potential application of this optical fiber-based sensor for rivers and drinking water monitoring.

Diabetes mellitus is a disease of metabolic disorders where human blood contains a high amount of sugar level for a prolonged period. This study aims to simulate how effective sensor based on MRR and SPR for the purpose of diabetes monitoring. The results show that sensor based on MRR and SPR provides the ability to detect low level of glucose concentration as low as 7 mmol/L (0.13%) and the ability to detect resonance shift for very small glucose concentration change. Therefore, the sensor based on MRR and SPR can be used for diabetes monitoring. The sensitivity of the sensor based on MRR and SPR is 85.84 nm/RIU and 116.69 °/RIU respectively. These findings are important for the development of diabetes monitoring based on MRR or SPR.

Diabetes mellitus is a disease of metabolic disorders where human blood contains a high amount of sugar level for a prolonged period. This study aims to simulate the effectiveness of sensors based on microring resonator (MRR) and surface plasmon resonance (SPR) for diabetes monitoring. The results show that a sensor based on MRR and SPR provides the ability to detect low levels of glucose concentration as low as 7 mM (0.13%) and the ability to detect resonance shift for very small glucose concentration change. Therefore, the sensor based on MRR and SPR can be used for diabetes monitoring. The sensitivity of the sensor based on MRR and SPR is 85.84 nm/RIU and 116.69°/RIU, respectively. These findings are important for the development of diabetes monitoring based on MRR or SPR.

In this article, we report modeling, simulation, and analysis of shifting 2D photonic crystal cavity side holes in GaN-AlN-sapphire layered structure. The design was simulated with Lumerical finite-difference time-domain. A lattice constant a, 157 nm, and a hole diameter d, 106 nm, were used in the design. The cavities are based on L3, which we demonstrated by simply shifting two holes away from a line cavity with distances of 132, 142, and 152 nm, respectively. The highest quality factor, Q, value achieved is 2.25 × 104 at 152-nm cavity distance.

Anodic aluminum oxide (AAO) has been synthesized through anodization method. The effect of electropolishing on the growth of AAO template has been investigated. The surface roughness was measured by AFM. While the surface morphology and cross-sectional image were observed by FESEM. The statistical analysis was done using image J2 software to determine the pore diameter and pore distribution. The polished surface exhibited lower surface roughness of 4.42 nm compared to unpolished surface (16.45 nm). Formation of nanopores on top of polished surface was found to have higher uniformity. Apparently, good pore ordering was obtained for polished surface which resulted in high uniformity and welldistribution of nanopores at the bottom of AAO template. Polished surface also exhibited smaller standard deviation diameter of pores compared to unpolished surface.

In this paper a surface plasmon resonance (SPR)-based biosensor is proposed. This sensor is based on Kretschmann configuration by considering the efficiency of graphene and MoS 2 layers. The biosensor is simulated by the Lumerical’s finite-difference-time-domain (FDTD) method. The performance parameters of the proposed sensor are defined in terms of the reflectance intensity that clarifies the sensor sensitivity and the full-width-at-half-maximum (FWHM) of the spectrum for detection accuracy. The measurement is observed at two wavelengths that are 670 nm and 785 nm for urea detection at the concentration of 50nM with the reflective index of 1.33433. The results show that the sensitivity increases by 3.58% and 5.24% with the addition of graphene and MoS 2 at 670 nm and 785 nm respectively. This designates that the proposed SPR-biosensor is sensitive for urea detection.

We report the design and simulation of the tapered optical fiber with large presence of the evanescent field. The evanescent field of the optical fiber is strongly affected by the surrounding environment which will be exploited into fabricating variety of photonic-based devices such as photodetectors, optical sensors and ultra-high Q resonators. The simulation results show that by adiabatically tapered the waist region, there is a fairly large amount of evanescent field intensity observed at the air-cladding region. The smooth transition region of the tapered fiber has also minimized the multimode interference in the waist and transition region thus reducing the energy loss and contributing to the higher output power.

We report the modelling of a band-pass filter at conventional band (c-band) and the effect of different shapes of photonic crystal (PhC) holes embedded on silicon-on-insulator (SOI) waveguide. The designed embedded waveguides was simulated with LUMERICAL finite different time domain (FDTD) and a filter response with a bandwidth of approximately 30 nm complying with international telecommunication unit (ITU-T) standard was observed. The simulated bandwidth observed was sufficient for guarding against other band interference in telecommunication applications such as wavelength division multiplexing (WDM). The waveguide was designed with a dimension of 600 nm width × 260 nm height and embedded with PhC of 4 mirrors and 3 cavities. 2 mirrors at both end of the whole structure were designed with less number of holes for obtaining the band-pass filter profile. With a value of lattice constant a, hole radius r and cavity distance c of 370, 115 and 315 nm respectively, the simulated device spectrum complimented the erbium doped fiber amplifier (EDFA) spectrum to obtain wavelength profile flatness. The PhC embedded waveguide was tailored to give a 70 percent value of transmission. A flat profile was observed by reducing the photonic crystal hole radii in the middle mirrors. The wavelength band and the bandwidth of the band can be tuned by manipulating the number of mirrors and cavities in waveguide. A different types of PhC hole shapes were also studied and compared. The transmission quality and bandpass quality with different types of hole shapes show that the circular PhC shape are superior in comparison with square hole shapes.

In this work, a study of two-dimensional (2D) photonic crystal (PhC) cavities on a triangular photonic crystal lattice on Gallium Nitride have been demonstrated by using the 2D Finite Different Time Domain (FDTD) method. The resonant wavelength and quality factor (Q-factor) of designed PhC structures were studied. The forbidden region or stopband observed are between 420 to 520 nm. Therefore, the resonant wavelength of GaN-based PhC cavity was observed at $\sim460$ nm for H1 and L3 cavity. Both results show a high Qfactor obtained and calculated with a value of 65 700 and 65 957 respectively.