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We present a new configuration based on multimode interference with a microring resonator feedback waveguide. The proposed configuration can create a deep Fano shape and provide a high sensitive sensor structure. In this paper, we is applied to seawater salinity sensor with a high sensitivity. We also propose an approach for these optical sensors integated with wireless sensor networks for online and real-time applications. The sensor structure can provide a sensitivity of 581nm/RIU based on wavelength shift based mechanism. We use silicon waveguides for the whole sensor designs and working at operating wavelength of 1550nm.

We propose a new structure for generating a Fano shape. This structure can be applied to design an optical sensor with a high sensitivity based on intensity mechanism using a 2×4 multimode interference (MMI) coupler. The sensor structure can provide a very sensitivity (higher than 10 times) compared with the traditional structure based on Mach Zehnder interferometer (MZI) and microring resonators (MRR). For CMOS compatibility, we use silicon on insluator (SOI) waveguide for the whole sensor designs. The sensing structure can work at operating wavelength of 1550nm, that is suitable for fiber-optic communication and real-time measurement applications.

This research presents a new method for generation of multilevel pulse amplitude modulation (PAM-4) signals for optical interconnects and data center networks. The new approach uses multimode interference (MMI) structure with two phase shifters in push-pull configuration instead of microring resonators and two couplers as shown in the literature. Based on this structure, an extreme high bandwidth and compact footprint can be achieved. The whole device is designed and analyzed using the existing VLSI silicon photonics.

A cascaded microring resonator based on silicon waveguides with an MMI (Multimode Interference) based Sagnac reflector is proposed in this study. By controlling the coupling coefficients with the used of the MMI based Sagnac reflector, the double of both pulse delay and advancement for the slow and fast light can be achieved. The new structure can produce the fast and slow light phenomenon on one chip with a double of the time delay and pulse advancement. By using the Sagnac reflector, the device is very compact. Transfer matrix method and FDTD (Finite Difference Time Domain) simulation are used to obtain the characteristics of the device. The transmission, phase, group delay and pulse propagation are analyzed in detail. Our FDTD simulations show a good agreement with the analytical theory.

In this paper, a new all-optical switch based on 1×3 and 3×3 General Interference (GI) multimode interference (MMI) structures is proposed. By using nonlinear directional couplers in two arms of the structure as phase shifters, all-optical switching mechanism can be achieved. In this study, we use chalcogenide glass on silica for designing the device structure. The switching states of the device can be controlled by adjusting the optical control signals at the phase shifters. The transfer matrix method and beam propagation method (BPM) are used for designing and optimizing the device structure.

A new microring resonators (MRR) based on 4×4 multimode interference (MMI) couplers for multichannel and highly sensitive chemical and biological sensors is proposed in this paper. The proposed sensor structure has advantages of compactness, high sensitivity compared with the reported sensing structures. By using the transfer matrix method (TMM) and numerical simulations, the designs of the sensor based on silicon nanowires are optimized and demonstrated in detail. The glucose and ethanol sensing by using our structure is investigated.

We propose a novel microring resonator coupled 4×4 generalized Mach Zehnder interferometer (GMZI) structure to produce Fano resonance line shapes. The structure can produce two independent Fano resonance line shapes. Two phase shifters are introduced in two arms of the 4×4 GMZI to control the variation of the Fano line shapes. The other aim of this study is to use silicon waveguides, that are compatible with the existing CMOS (Complementary Metal-Oxide-Semiconductor) fabrication technology, for designing the proposed devices. The transfer matrix method (TMM) and beam propagation method (BPM) are used for analytical analysis and first order design of the device. Finally, we discuss potential applications of the new device for sensing, all-optical switching applications and generation of electromagnetically induced transparency (EIT) effect.

We show that it is possible to obtain 2 × 2 couplers based on multimode interference (MMI) structures with nineteen new power-splitting ratios by cascading three or four MMI couplers. The other aim of this study is to use silicon waveguides, that are compatible with the existing CMOS (Complementary Metal-Oxide-Semiconductor) fabrication technology, for designing the proposed devices. The proposed MMI couplers with new power splitting ratios have simple geometries and low losses. These MMI couplers can offer valuable new possibilities for designing MMI waveguide-based photonic integrated circuits such as all-optical interconnects, microring resonators, clock distribution, Mach Zehnder Interferometer based on MMI couplers and other all-optical processing applications. The transfer matrix method (TMM) and modified effective index method (MEIM) along with the support of the 3D Beam Propagation Method (3D BPM) are used to optimize the proposed devices.

We propose a method for realization of multiple Fano resonances and double electromagnetically induced transparency. The proposed device is based on only three cascaded identical 3 × 3 multimode interference microresonators on a single silicon on insulator chip. We derive the analytical expressions for the normalized transmission characteristics. The structure offers a high-modulation depth of nearly 100%, an extremely large fabrication tolerance of ±100 nm, and a compact size of 700 × 1000 μm2.

We propose a method for generating the electromagnetically induced transparency (EIT) like-transmission by using microring resonator based on cascaded 3 &times, 3 multimode interference (MMI) structures. Based on the Fano resonance unit created from a 3 &times, 3 MMI coupler with a feedback waveguide, two schemes of two coupled Fano resonator unit (FRU) are investigated to generate the EIT like transmission. The theoretical and numerical analysis based on the coupled mode theory and transfer matrix is used for the designs. Our proposed structure has advantages of compactness and ease of fabrication. We use silicon waveguide for the design of the whole device so it is compatible with the existing Complementary Metal-Oxide-Semiconductor (CMOS) circuitry foundry. The fabrication tolerance and design parameters are also investigated in this study.

A polarization beam splitter is used for dividing transverse electric (TE) and transverse magnetic (TM) modes, in which a silicon on insulator platform based multimode interference coupler is etched depth by a butterfly form is proposed and designed by using the semi-vectorial three-dimensional beam-propagation method. The device is operated on quasi state mechanism that only four modes are excited in the multimode region. High birefringence property of the device incorporated with butterfly form allows to shortening the size. The polarization extinction ratio is smaller than 20 dB, and the excess loss is not excess 0.6 dB for both polarization modes. The splitter also has a relaxed fabrication tolerance. These attributes make it as a good candidate for polarization diversity circuits and compact photonic integrated circuits.

A novel sensing structure based on microring resonators with feedback using silicon waveguides is proposed in this paper. The proposed structure can produce a sharp asymmetric Fano resonance line shape, in which the slope between the zero and the unity transmission is greatly enhanced, comparing with that of the conventional microring resonators. As a result, biological sensors using this structure can provide a high sensitivity. In addition, multimode interference (MMI) couplers are employed as coupling elements instead of using directional couplers in the microring resonators. MMI couplers have shown to have relaxed fabrication requirements, simplicity, compactness and are less sensitive to the wavelength. The analytical description of output spectrum response of the proposed sensor is analyzed and derived. The transfer matrix method (TMM) and beam propagation method (BPM) are used to optimally design the sensor structure.

A new mirroring resonators (MRR) based on 6x6 multimode interference (MMI) couplers for multichannel and highly sensitive chemical and biological sensors is proposed in this paper. The proposed sensor structure has advantages of compactness, high sensitivity compared with the reported sensing structures. By using the transfer matrix method (TMM) and numerical simulations, the designs of the sensor based on silicon nanowires are optimized and demonstrated in detail. Current approaches to the real time analysis of chemical and biological sensing applications utilize systematic approaches such as mass spectrometry for detection. Such systems are expensive, heavy and cannot monolithically integrated in one single chip (1). Electronic sensors use metallic probes which produces electro magnetic noise, which can disturb the electro magnetic field being measured. This can be avoided in the case of using optical sensors. Optical sensors are very attractive due to their advantages of high sensitivity and ultra-wide bandwidth. A large class of optical sensors based on optical fibre and waveguides uses evanescent wave to monitor the presence of the analyte in the environment. Detection can be made by the optical absorption of the analytes, optic spectroscopy or the refractive index change (1). The two former methods can be directly obtained by measuring optical intensity. The third method is to monitor various chemical and biological systems via sensing of the change in refractive index (2). Optical waveguide devices can perform as refractive index sensors particularly when the analyte becomes a physical part of the device, such as waveguide cladding. In this case, the evanescent portion of the guided mode within the cladding will overlap and interact with the analyte. The measurement of the refractive index change of the guided mode of the optical waveguides requires a special structure to convert the refractive index change into detectable signals. A number of refractive index sensors based on optical waveguide structures have been reported, including Bragg grating sensors, directional coupler sensors, Mach- Zehnder interferometer (MZI) sensors, microring resonator sensors and surface plasmon resonance sensors (1-5).

Optical couplers having arbitrary splitting ratios are useful in a range of communications and sensing applications. In this paper, it is shown that SOI-MMI couplers having a shallow slot can provide such splitting ratios.

In this paper, new microresonator structures based on 3×3 multimode interference (MMI) coupler on the silicon on insulator (SOI) platform are presented. The transfer matrix method and the three-dimensional beam propagation method (3D-BPM) are used to design the device.

A method for obtaining variable power splitting ratios using multimode interference couplers is presented. The method relies on etching the surface on either the top of the MMI coupler or on the linking waveguides. Devices have been designed for the silicon on insulator (SOI) platform. The 3D beam propagation method (3D-BPM) and the full-vectorial finite difference method (FV-FDM) are used to verify the working principle of the devices and to evaluate performance.

Some novel configurations for microring resonators, based on MMI couplers, that are suitable for photonic signal processing applications. A number of relevant design issues are discussed. As an example, a microring resonator based on 3x3 MMI couplers has been designed; simulation results show that such a device has the potential advantages of high performance and size reduction.