Ultra-Broadband Add-Drop Filter/Switch Circuit Using Subwavelength Grating Waveguides

Subwavelength Grating Waveguide Devices for Telecommunications Applications

Abstract: Subwavelength grating (SWG) waveguides in silicon-on-insulator are emerging as an enabling technology for implementing compact, high-performance photonic integrated devices and circuits for signal processing and sensing applications. We provide an overview of recent work on developing wavelength selective SWG waveguide filters based on Bragg gratings, ring resonators, and contra-directional couplers, as well as optical delay lines for applications in optical communications and microwave photonics. These components increase the SWG waveguide component toolbox and can be used to realize more complex photonic integrated circuits with enhanced or new functionality.

Silicon Quantum Photonics

Abstract: Photonics is a promising approach to realising quantum information technologies, where entangled states of light are generated and manipulated to realise fundamentally new modes of computation [1], simulation [2] and communication [3], as well as enhanced measurements and sensing. Historically bulk optical elements on large optical tables have been the means by which to realise proof-of-principle demonstrators in quantum physics. More recently, integrated quantum photonics has enabled a step change in this technology by utilising low-index-contrast waveguide material systems, such as silica-on-silicon [4] and silicon-oxy-nitride [5]. Such technologies offer benefits in terms of low propagation losses, but their associated large bend radii and low component density ultimately limit the scalability and usefulness of this technology.

A Novel Hedgehog Waveguide and its Application in Designing a Phase Shifter Compatible With Hollow Waveguide Technology

Abstract: A new Hedgehog waveguide, consisting of a bed of nails embedded in a host rectangular hollow waveguide, is proposed and investigated as a promising state-of-the-art low-loss waveguide for millimeter-wave frequency bands. The proposed Hedgehog waveguide gets its name from its electromagnetic behavior. As hedgehogs root through hedges and other undergrowth in search of their favorite food, the proposed waveguide root through its embedded bed of nails. When we choose a host waveguide technology, it is worthwhile spending some time weighing up the pros and cons of the various types of waveguides on offer. The proposed Hedgehog waveguide is extremely low loss and is compatible with the hollow waveguide technology, which gives the ability to develop different components such as low-loss flat phase response phase shifters. In this paper, the proposed Hedgehog waveguide is analytically investigated, and a transition to the hollow waveguide is designed. Moreover, the low-loss nature of the designed Hedgehog waveguide is compared with the ridge gap waveguide, substrate-integrated waveguide (SIW), hollow waveguide, and microstrip line. Finally, the proposed waveguide is designed, simulated, and fabricated. The simulated and measured results show a good agreement, which validates the proposed concept.

Silicon photonic devices realized on refractive index engineered subwavelength grating waveguides-A review

Abstract: It is a remarkable and straightforward approach to customize the dispersion and nonlinear properties of the photonic devices without varying the composition of the material by employing periodic segmented waveguide structures at the subwavelength level of the operational wavelength. This method addresses the diffraction limit and it is likely to engineer the waveguides as a uniform optical medium with an effective refractive index that relies on the waveguide geometry. In recent years, advances in lithographic technology in the semiconductor-on-insulator platform providing sub-100-nm patterning resolution have been renowned with many useful devices based on subwavelength structures. At the beginning of the paper, the modal characteristics of the subwavelength grating (SWG) waveguides are presented. And in afterwards, we provide an insight into noteworthy progress in the subwavelength grating (SWG) waveguides based devices for signal processing and sensing applications such as ring resonators for surface and bulk sensing, couplers, suspended membrane waveguides for mid-infrared applications, filters, and fiber-to-chip couplers.

Performance analysis of metal-microheater integrated silicon waveguide phase-shifters

Abstract: A detailed theoretical and experimental study of metal-microheater integrated silicon waveguide phase-shifters has been carried out. It has been shown that the effective thermal conductance gw and the effective heat capacitance hw evaluated per unit length of the waveguide are two useful parameters contributing to the overall performance of a thermo-optic phase-shifter. Calculated values of temperature sensitivity, SH = 1/gw and thermal response time, τth = hw/gw of the phase-shifter are found to be consistent with the experimental results. Thus, a new parameter ℱH = SH/τth = 1/hw has been introduced to capture the overall figure of merit of a thermo-optic phase-shifter. A folded waveguide phase-shifter design integrated in one of the arms of a balanced MZI switch is shown to be superior to that of a straight waveguide phase-shifter of the same waveguide cross-sectional geometry. The MZI switches were designed to operate in TE-polarization over a broad wavelength range (λ ∼ 1550 nm).

Single-chip microprocessor that communicates directly using light

Abstract: An electronic–photonic microprocessor chip manufactured using a conventional microelectronics foundry process is demonstrated; the chip contains 70 million transistors and 850 photonic components and directly uses light to communicate to other chips. The rapid transfer of data between chips in computer systems and data centres has become one of the bottlenecks in modern information processing. One way of increasing speeds is to use optical connections rather than electrical wires and the past decade has seen significant efforts to develop silicon-based nanophotonic approaches to integrate such links within silicon chips, but incompatibility between the manufacturing processes used in electronics and photonics has proved a hindrance. Now Chen Sun et al. describe a 'system on a chip' microprocessor that successfully integrates electronics and photonics yet is produced using standard microelectronic chip fabrication techniques. The resulting microprocessor combines 70 million transistors and 850 photonic components and can communicate optically with the outside world. This result promises a way forward for new fast, low-power computing systems architectures. Data transport across short electrical wires is limited by both bandwidth and power density, which creates a performance bottleneck for semiconductor microchips in modern computer systems—from mobile phones to large-scale data centres. These limitations can be overcome1,2,3 by using optical communications based on chip-scale electronic–photonic systems4,5,6,7 enabled by silicon-based nanophotonic devices8. However, combining electronics and photonics on the same chip has proved challenging, owing to microchip manufacturing conflicts between electronics and photonics. Consequently, current electronic–photonic chips9,10,11 are limited to niche manufacturing processes and include only a few optical devices alongside simple circuits. Here we report an electronic–photonic system on a single chip integrating over 70 million transistors and 850 photonic components that work together to provide logic, memory, and interconnect functions. This system is a realization of a microprocessor that uses on-chip photonic devices to directly communicate with other chips using light. To integrate electronics and photonics at the scale of a microprocessor chip, we adopt a ‘zero-change’ approach to the integration of photonics. Instead of developing a custom process to enable the fabrication of photonics12, which would complicate or eliminate the possibility of integration with state-of-the-art transistors at large scale and at high yield, we design optical devices using a standard microelectronics foundry process that is used for modern microprocessors13,14,15,16. This demonstration could represent the beginning of an era of chip-scale electronic–photonic systems with the potential to transform computing system architectures, enabling more powerful computers, from network infrastructure to data centres and supercomputers.

Integrated optical devices for lab-on-a-chip biosensing applications

Abstract: The application of portable, easy-to-use and highly sensitive lab-on-a-chip biosensing devices for real-time diagnosis could offer significant advantages over current analytical methods. Integrated optics-based biosensors have become the most suitable technology for lab-on-chip integration due to their ability for miniaturization, their extreme sensitivity, robustness, reliability, and their potential for multiplexing and mass production at low cost. This review provides an extended overview of the state-of-the-art in integrated photonic biosensors technology including interferometers, grating couplers, microring resonators, photonic crystals and other novel nanophotonic transducers. Particular emphasis has been placed on describing their real biosensing applications and wherever possible a comparison of the sensing performances between each type of device is included. The way towards achieving operative lab-on-a-chip platform incorporating the photonic biosensors is also reviewed. Concluding remarks regarding the future prospects and potential impact of this technology are also provided.

Waveguide sub-wavelength structures: a review of principles and applications

Abstract: Periodic structures with a sub-wavelength pitch have been known since Hertz conducted his first experiments on the polarization of electromagnetic waves. While the use of these structures in waveguide optics was proposed in the 1990s, it has been with the more recent developments of silicon photonics and high-precision lithography techniques that sub-wavelength structures have found widespread application in the field of pho- tonics. This review first provides an introduction to the physics of sub-wavelength structures. An overview of the applications of sub-wavelength structures is then given including: anti-reflective coatings, polarization rotators, high-efficiency fiber-chip cou- plers, spectrometers, high-reflectivity mirrors, athermal waveg- uides, multimode interference couplers, and dispersion engi- neered, ultra-broadband waveguide couplers among others. Particular attention is paid to providing insight into the design strategies for these devices. The concluding remarks provide an outlook on the future development of sub-wavelength structures and their impact in photonics.

Subwavelength grating periodic structures in silicon-on-insulator: a new type of microphotonic waveguide.

Abstract: We report on the experimental demonstration and analysis of a new waveguide principle using subwavelength gratings. Unlike other periodic waveguides such as line-defects in a 2D photonic crystal lattice, a subwavelength grating waveguide confines the light as a conventional index-guided structure and does not exhibit optically resonant behaviour. Subwavelength grating waveguides in silicon-on-insulator are fabricated with a single etch step and allow for flexible control of the effective refractive index of the waveguide core simply by lithographic patterning. Experimental measurements indicate a propagation loss as low as 2.1 dB/cm for subwavelength grating waveguides with negligible polarization and wavelength dependent loss, which compares favourably to conventional microphotonic silicon waveguides. The measured group index is nearly constant n(g) ~1.5 over a wavelength range exceeding the telecom C-band.

Silicon Quantum Photonics

Abstract: Integrated quantum photonic applications, providing physically guaranteed communications security, subshot-noise measurement, and tremendous computational power, are nearly within technological reach. Silicon as a technology platform has proven formidable in establishing the micro-electronics revolution, and it might do so again in the quantum technology revolution. Silicon has taken photonics by storm, with its promise of scalable manufacture, integration, and compatibility with CMOS microelectronics. These same properties, and a few others, motivate its use for large-scale quantum optics as well. In this paper, we provide context to the development of quantum optics in silicon. We review the development of the various components that constitute integrated quantum photonic systems, and we identify the challenges that must be faced and their potential solutions for silicon quantum photonics to make quantum technology a reality.