گروه آموزشی برق
Lab-on-a-chip integrated optical biosensors have shown useful in non-invasive detection of biomaterials. Furthermore they are immune to electromagnetic interference rather than their electronic counterparts. In this paper, an all-optical photonic crystal (PhC)-based biosensor is presented. The biosensor is made up of two PhC-based W1 waveguides which are critically coupled to a PhC-based ring-resonator (RR). The hub of the ring is designed in an all-circular quasi-crystal fashion to enhance output efficiency as well as easy injection of analyte. This PhCRR can distinguish 85 15% of amplitude change via resonant wavelength shift of 0.75 0.15 nm, or equally a 0.005 change in the refractive index unit (RIU). By introducing any change in the optical characteristics of desired biomaterials (i.e. refractive index of glycated hemoglobin), the resonance frequency of resonator changes and due to its high quality factor and sensitivity, a large amplitude difference appears in the output. The proposed glycated hemoglobin biosensor works in the wavelength interval of 1.545–1., and its quality factor, figure of merit (FOM) and sensitivity are calculated to be RIU−1 and 690 50 nm/RIU, respectively. The simulations are performed in two-dimensional and finite difference time domain (FDTD) algorithm is used to numerically solve time-dependent Maxwell-equations within propagation domain.
A four-channel wavelength demultiplexer based on photonic crystal ring resonators (PCRR), which can be used for photonic integrated circuits, is designed. Dropping efficiency and Q factor of single improved ring are 100% and 842, respectively. In order to achieve the structure of demultiplexer, three improved rings have been used, that every ring has an individual inner rod radius; it means that each ring has a varying resonant wavelength. The results of simulation using finite-difference time-domain (FDTD) method in our proposed structure reveals an average transmitted power higher than 90% for each output port, Channel spacing is about 8 nm and bandwidth for each individual channel is about 2.8 nm. The mean value of the crosstalk between output channels and the area of the proposed structure are about −29 dB and 317 μm2, respectively. By changing the radius of inner rods, various wavelengths can be chosen, therefore this device is tunable.
In this study, the design of refractive index sensor with high sensitivity would be provided. This consists of a metal substrate with two metal-insulator-metal waveguide and an array of hexagonal nanoholes. Using the refractive index model obtained for different blood groups A, B and O, we show that the structure can be used as a sensor to determine a human blood group. We used the array of nanoholes, due to the unique optical properties leads to nanoscale confinement, high sensitivity to surface and low propagation losses. Based on the results, resonance wavelength has a linear relationship with the refractive index of a material that is placed inside the nanohole, that this feature makes it easy to identify the material. Considering a tradeoff between the transmitted power, structure size and sensitivity, FDTD simulations show that the sensitivity can be as large as 3172nm per refractive index unit (RIU). In general, our plasmonic sensor can promote the sensitivity through the phenomenon of plasmon exciting on the surface of the nanoholes and would have useful applications in the medical field such as determining blood group, hemoglobin and DNA (deoxyribonucleic acid) quantification.
In this article, a plasmonic nano-sensor by using the nanorods array in square resonator coupled with two slot cavities with properties for the detection of glucose concentration in water is proposed and analyzed. We have investigated the sensing feature by changing the concentration of the glucose from 0~60%. Obtained results show that by placing different water samples in square resonator and two cavities, resonance wavelengths can be changed. These resonances demonstrate different dependence on the glucose concentration of water samples. Also, varying the physical parameters of the configuration can also change the resonance wavelength and can be simply tuned. These features recommend flexibility to propose the structure. Simulation results show that the values of sensitivity and FOM (figure of merit) can be obtained as 892 nm/RIU and 3.5×106 RIU-1, respectively, which can discover greatly applications in the plasmonic sensor domain.
In this paper, we have designed a High sensitivity plasmonic sensor based on three-dimensional plasmonic Metal–Insulator–Metal (MIM) waveguides and racetrack resonator. From the detection of the resonance wavelength, the refractive index changes inside the resonator can be sensed, based on it linear relationship. The structure is numerically simulated by the Finite-difference time-domain method (FDTD) and the results show that the refractive index and temperature sensitivity values can be obtained as high as 4650nm per refractive index unit (RIU) and 0.69nm/°C, respectively. We show that such improved sensitivity can be obtained by using long lateral interaction length along the entire flat resonator sidewalls. The effects of radius and refractive index of racetrack resonator are studied on the sensing spectra to evaluate the sensitivity performance, as well. The proposed structure with such high sensitivity will be useful in bio-sensing that can provide a new possibility for detection of biological parameters such as hemoglobin concentration. Also, the applicability of our structure for sensing of hemoglobin concentration of three different blood groups is presented.
In this paper, we have designed a four channel wavelength demultiplexer based on heterostructure photonic crystal (PhC) ring resonator at 1550 nm window. In order to achieve the structure of demultiplexer, three improved rings with different dielectric constants of 11.6, 12, and 12.4 have been used. Every ring has an individual dielectric constant; it means that each ring has a variable resonant wavelength. Quality factor (Q) and dropping efficiency of single ring are 842 and 100%, respectively. The results of simulation using finite difference time domain (FDTD) method shows this structure have a good performances and reveals an average transmitted power is higher than 95%, channel spacing is about 6.1 nm and bandwidth for each individual channel is about 2.75 nm. The mean value of the crosstalk between outputs channels and footprint of the proposed structure are about −24.44dB and 294.25 μm2 (10.7 μm×27.5 μm) respectively.
We have designed a tunable two dimensional (2D) channel drop filter (CDF) based on photonic crystal ring resonators (PCRR). Dropping efficiency and Q factor of single improved ring are 100% and 842, respectively. In this filter the quality factor is significantly improved with respect to other published reports. We investigate parameters which have an effect on resonant wavelength in this CDF, such as dielectric constant of inner, coupling, adjacent and whole rods of the structure and radius of inner rods. The transmission spectrum for our proposed configuration has been investigated using the 2D finite difference time domain (FDTD) method. The area of the proposed structure is about 117 μm2.
In this paper, we investigated a plasmonic demultiplexer structure based on Metal–Insulator–Metal (MIM) waveguides and circular ring resonators. In order to achieve the structure of demultiplexer, two improved ring resonators have been used, which input and outputs MIM waveguides coupled by the ring resonators. To improve the transmission efficiency, a reflector was introduced at the right end of the input and output waveguides. By substituting the ring core with dielectric, the possibility of tuning the resonance wavelength of the proposed structure is illustrated, and the effect of various parameters such as radius and refractive index in transmission efficiency is studied in detail. This is useful for the design of integrated circuits in which it is not possible to extend the dimension of the ring resonator to attain a longer resonance wavelength. Transmission efficiency and quality factor of the single ring are 84% and 110, respectively. The simulation results using finite difference time domain method shows that in the proposed demultiplexer, which is composed of two rings with different core refractive indexes, the average power efficiency, bandwidth for each output channel, and the mean value of crosstalk are estimated 80%, 17 nm, and −26.95 dB, respectively. It is revealed that the significant features of the device are high transmission efficiency, low crosstalk, high-quality factor, and tunability for desired wavelengths. Therefore, the proposed structure has the potential to be applied in plasmonic integrated circuits.
An enhanced structure for compact and high sensitivity plasmonic refractive index sensor by using the coupling of two metal-insulator-metal (MIM) waveguides with a silver nanorods array embedded into a square resonator is proposed and analyzed in this paper. We placed silver nanorods inside the resonator due to their unique optical properties in nanoscale confinement and low propagation losses. Based on obtained results, the resonance wavelengths of the sensor having an approximate linear relationship with the refractive index of the materials under detecting that are placed into the square resonator. With an optimum design and considering a tradeoff among detected power, structure size and sensitivity, the finite difference time domain simulations show that the refractive index and temperature sensitivity values can be obtained as high as 2320 nm per refractive index unit (RIU) and 0.84 nm/°C. The achieved sensor can be used in nanophotonic and plasmonic integrated circuits and in this research; we show its applicability for the detection of different human blood groups as well.
A high sensitive plasmonic refractive index sensor based on metal-insulator-metal (MIM) waveguides with embedding metallic nano-rods in racetrack resonator has been proposed. The refractive index changes of the dielectric material inside the resonator together with temperature changes can be acquired from the detection of the resonance wavelength, based on their linear relationship. With optimum design and considering a tradeoff among detected power, structure size, and sensitivity, the finite difference time domain simulations show that the refractive index and temperature sensitivity values can be obtained as high as 2610 nm per refractive index unit (RIU) and 1.03 nm/°C, respectively. In addition, resonance wavelengths of resonator are obtained experimentally by using the resonant conditions. The effects of nano-rods radius and refractive index of racetrack resonator are studied on the sensing spectra, as well. The proposed structure with such high sensitivity will be useful in optical communications that can provide a new possibility for designing compact and high-performance plasmonic devices.
We have designed a 4-channel wavelength division demultiplexer based on photonic crystal (PhC) ring resonator at 1.55 μm window. The PhC consists of pillars in air background in square lattice. The radius of the pillars is determined to be 126.5 nm having lattice constant of 590 nm. The proposed structure mechanism is performed based on coupling between a waveguide and a ring resonator. This structure is designed and its performance verified by finite difference time domain method. Dropping efficiency and quality factor (Q) of single ring are 100% and 193, respectively. Our proposed demultiplexer is composed of three regions with various dielectric constants of 11.56, 12.96, and 14.44. The proposed demultiplexer has efficiency about 90% and −25 dB crosstalk. The footprint of the proposed structure is about 315 μm2 (11.19 μm × 25.5 μm), therefore this structure suitable for integration.
We have designed a four-channel wavelength demultiplexer based on photonic crystal ring resonators (PCRR), which can be used for photonic integrated circuits. Dropping efficiency and Q factor of single improved ring are 100% and 650, respectively. In order to achieve the structure of demultiplexer, three improved rings have been used, that every ring has an individual inner rod radius; it means that each ring has a varying resonant wavelength. By changing the radius of inner rods, various wavelengths can be chosen, therefore this device is tunable. The results of simulation using finite-difference time-domain (FDTD) method in our proposed structure reveals an average transmitted power higher than 90% for each output port. Channel spacing is about 7.5 nm and bandwidth for each individual channel is about 2.8 nm. The mean value of the crosstalk between output channels is about −27.11 dB. The area of the proposed structure is about 315 μm2.
A compact plasmonic structure is proposed employing symmetrical metal–insulator-metal (MIM) waveguides coupled to the square resonator for nano-sensing applications, especially for water glucose sensing. Finite difference time domain method is chosen to derivate the output characteristics and magnetic-field distributions. Outcomes illustrate the Fano resonance in the output characteristics can be simply managed by varying the inner and outer lengths and the refractive index of the square cavity. Also, between Fano resonance wavelength and resonator length, a linear behavior exists. These features suggest that physical parameters provide flexibility to propose the structure. Our plasmonic device produces a sensitivity and figure of merit of about 6400 nm/RIU and 1 × 104, respectively. By utilizing the mathematical model for water refractive index, we aim to develop a sensor structure to detect the glucose concentration in water. This designed sensor may discover significant applications in future nanosensing domain.
A refractive index sensor using two concentric triple racetrack resonators with plasmonic metal-insulator-metal (MIM) waveguide is suggested to provide more freedom for sensing applications. Due to the momentum matching, the intensive coupling happens between the equivalent modes of each section of the resonators. The sensing properties are numerically discussed by the finite difference time domain (FDTD) method. According to the outcomes, with increasing the refractive index of the material in the outer sections of the racetrack resonators, the dip wavelengths show a notable red-shift. The sensing performance can be enhanced by using two multiple concentric resonators that effectively increase the strength of the light-analyte interaction, which is useful for sensing applications. Our proposed nanosensor, offers a high sensitivity value, sensing resolution and FOM of 1618nm/RIU, 6.18×10‒4RIU, and 89RIU-1, respectively. Also, the racetrack resonators coupled to MIM waveguides can be simply integrated into chip circuits with other optical devices to perform monitoring and filtering tasks.
در این مقاله یک رمزگذار تمام نوری متشکل از سه موج¬بر درگاه ورودی، دو تزویج گر شش ضلعی و دو موج بر خروجی Y شکل در شبکه مربعی از میله های دی الکتریک در هوا ارایه شده است. جنس میله ها از نوع سیلیکون با ضریب شکست 46/3 با شعاع a2/0r1= و ثابت شبکه nm554a= می¬باشد. موج برها با حذف میله های دی الکتریک در ساختار ایجاد شده اند و برای دستیابی به تزویج¬گرها با عملکرد مناسب از دو نمونه دی الکتریک جهت تزویج و انسداد نور به ترتیب با شعاع a2/0r1= و a2/0r2= استفاده شده است. ساختار ارایه شده می¬تواند یک کد دودویی دو بیتی با توجه به ترتیب ورودی¬های فعال در خروجی تولید کند که بدون استفاده از اثرات خطی عمل می¬کند. برای تحقق این ساختار یک دروازه OR طراحی کردیم، سپس برای تحکیم رمزگذار مورد نظر دو دروازه OR با یکدیگر ترکیب شده است. حداکثر زمان تاخیر بدست آمده و ابعاد ساختار ارایه شده به ترتیب حدود fs166 و μm2390 است و نرخ سوییچینگ THz6 می باشد.
به دلیل کاهش قیمت سلول خورشیدی ضخامت لایه فعال آن را کم میکنند. ولی این امر منجر به کاهش جذب نور مخصوصاً در طول موجهای بلند خواهد شد. یکی از روشهای افزایش جذب و بازدهی سلول خورشیدی، استفاده از نانوذرات فلزی و بهره بردن از اثر تشدید پلاسمون سطحی جایگزیده میباشد. در این مقاله سعی شده است با قرار دادن آرایه نانوذرات نقره روی اکسید زینک (ZnO) در سلول خورشیدی لایهنازک با لایه فعال سیلیکون بیشکل (a-Si)، جذب و درنتیجه بازدهی سلول خورشیدی را افزایش داد. همچنین ضمن مقایسه با سایر آرایههای مستطیلی، مثلثی و نیم استوانه، نشان داده خواهد شد نانوذرات نقره باعث افزایش بازدهی بیشتری خواهند شد. در آخر پارامترهای اساسی سلول خورشیدی طراحی شده مورد بررسی قرار خواهد گرفت.
سلول خورشیدی مبتنی بر سیلیکون بلوری به دلیل بازده زیاد و سادگی طراحی و ساخت، بهعنوان پر کاربردترین سلول خورشیدی شناخته میشوند. امروزه بیشتر مطالعات در زمینه این سلولها در جهت بهبود عملکرد و بازده آنها انجام میگیرد. یکی از روشهای افزایش بازده سلول خورشیدی، افزایش میزان جذب نور خورشید است. استفاده از نانوساختارهای پلاسمونی برای بهبود جذب نور در سلولهای خورشیدی بسیار پرکاربرد هستند. تعامل قوی میان نور با نانوساختارهای فلزی امکان کنترل بر انتشار نور در مقیاس نانومتر و در نتیجه طراحی سلولهای خورشیدی لایه نازک که در آن نور در لایه فعال به دام میافتد و بهطور موثر جذب میشود، را فراهم میکند. در این مقاله شبیه¬سازی سلول خورشیدی لایه نازک سیلیکونی که شامل نانوساختارهای فلزی نقره میباشد با روش تفاضل محدود در حوزه زمان مورد مطالعه قرار میگیرد. نتایج نشان میدهند که جذب نور در لایه فعال سیلیکون به دلیل تشدید پلاسمون سطحی موضعی بهبود یافته است.
در این مقاله یک فیلتر جدید مبتنی بر موجبرهای پلاسمونی فلز-عایق-فلز با استفاده از تشدیدگر چند ضلعی پیشنهاد و مورد بررسی قرار گرفته است. با مدل¬سازی و شبیه سازی فیلتر پلاسمونی مبتنی بر نانو کاواک شش ضلعی، دریافتیم که طول موج تشدید را می¬توان به راحتی با تغییر شعاع و ضریب¬شکست نانوحفره، که با نتایج بدست آمده از شبیه سازی های تفاضل محدود در حوزه زمان (FDTD) نیز همخوانی دارد، تحت کنترل درآوریم. علاوه بر این، پهنای باند طیف¬های تشدید با تغییر فاصله اتصال بین نانو کاواک و موجبر قابل تنظیم می¬باشد. فیلتر بررسی شده در این مقاله دارای کاربردهای قابل توجه در مدارهای مجتمع پلاسمونی با تراکم بالا می¬باشد.