It's challenging to measure non-repetitive events in real time in the field of instrumentation and measurement. Dispersive Fourier transformation is an emerging method that permits capture of rare events, such as optical rogue waves and rare cancer cells in blood. This Review article covers the principle of dispersive Fourier transformation and its implementation in diverse applications.

Dispersive Fourier transformation for fast continuous single-shot measurements

Part I. Silicon Photonics - Introduction: 1. Fabless Silicon Photonics: 1.1 Introduction 1.2 Silicon photonics - the next fabless semiconductor industry 1.3 Applications 1.4 Technical challenges and the state of the art 1.5 Opportunities 2. Modelling and Design Approaches: 2.1 Optical Waveguide Mode Solver 2.2 Wave Propagation 2.3 Optoelectronic models 2.4 Microwave Modelling 2.5 Thermal Modelling 2.6 Photonic Circuit Modelling 2.7 Physical Layout 2.8 Software Tools Integration Part II. Silicon Photonics - Passive Components: 3. Optical Materials and Waveguides: 3.1 Silicon-on-Insulator 3.2 Waveguides 3.3 Bent waveguides 3.4 Code Listings 3.5 Problems 4. Fundamental Building Blocks: 4.1 Directional couplers 4.2 Y-Branch 4.3 Mach-Zehnder Interferometer 4.4 Ring resonators 4.5 Waveguide Bragg Grating Filters 4.6 Code Listings 4.7 Problems 5. Optical I/O: 5.1 The challenge of optical coupling to silicon photonic chips 5.2 Grating Coupler 5.3 Edge Coupler 5.4 Polarization 5.5 Code Listings 5.6 Problems Part III. Silicon Photonics - Active Components: 6. Modulators: 6.1 Plasma Dispersion E 6.2 PN Junction Phase Shifter 6.3 Micro-ring Modulators 6.4 Forward-biased PIN Junction 6.5 Active Tuning 6.6 Thermo-Optic Switch 6.7 Code Listings 6.8 Problems 7. Detectors: 7.1 Performance Parameters 7.2 Fabrication 7.3 Types of detectors 7.4 Design Considerations 7.5 Detector modelling 7.5.2 Electronic Simulations 7.6 Code Listings 7.7 Problems 8. Lasers: 8.1 External Lasers 8.2 Laser Modelling 8.3 Co-Packaging 8.4 Hybrid Silicon Lasers 8.5 Monolithic Lasers 8.6 Alternative Light Sources 8.7 Problems Part IV. Silicon Photonics - System Design: 9. Photonic Circuit Modelling: 9.1 Need for photonic circuit modelling 9.2 Components for System Design 9.3 Compact Models 9.4 Directional Coupler - Compact Model 9.5 Ring Modulator - Circuit Model 9.6 Grating Coupler - S Parameters 9.7 Code Listings 10. Tools and Techniques: 10.1 Process Design Kit (PDK) 10.2 Mask Layout 11. Fabrication: 11.1 Fabrication Non-Uniformity 11.2 Problems 12. Testing and Packaging: 12.1 Electrical and Optical Interfacing 12.2 Automated Optical Probe Stations 12.3 Design for Test 13. Silicon Photonic System Example: 13.1 Wavelength Division Multiplexed Transmitter.

Silicon Photonics Design: From Devices to Systems

Photonics has long been used to study non-solid materials such as liquids, gases and plasmas, but these fluidic media have traditionally not comprised a functional part of the photonic device or system. The emerging field of optofluidics seeks to create new ways of uniting solid and non-solid materials in a single photonic system whose optical properties are typically defined by the fluidic component. This Review summarizes the current state of optofluidics from a photonics perspective. First, we describe a new class of photonic elements based on the combination of fluidic media and integrated optical structures. We then discuss the applications of optofluidic principles to particle sensing and manipulation in fluids, and finally assess current challenges and potential directions for future developments.

The photonic integration of non-solid media using optofluidics

Since its emergence as a field, optofluidics has developed unique tools and techniques for enabling the simultaneous delivery of light and fluids with microscopic precision. In this Review, we describe the possibilities for applying these same capabilities to the field of energy. We focus in particular on optofluidic opportunities in sunlight-based fuel production in photobioreactors and photocatalytic systems, as well as optofluidically enabled solar energy collection and control. We then provide a series of physical and scaling arguments that demonstrate the potential benefits of incorporating optofluidic elements into energy systems. Throughout the Review we draw attention to the ways in which optofluidics must evolve to enable the up-scaling required to impact the energy field.

Optofluidics for energy applications

We demonstrate the design, fabrication and measurement of integrated Bragg gratings in a compact single-mode silicon-on-insulator ridge waveguide. The gratings are realized by corrugating the sidewalls of the waveguide, either on the ridge or on the slab. The coupling coefficient is varied by changing the corrugation width which allows precise control of the bandwidth and has a high fabrication tolerance. The grating devices are fabricated using a CMOS-compatible process with 193 nm deep ultraviolet lithography. Spectral measurements show bandwidths as narrow as 0.4 nm, which are promising for on-chip applications that require narrow bandwidths such as WDM channel filters. We also present the die-to-die nonuniformity for the grating devices on the wafer, and our analysis shows that the Bragg wavelength deviation is mainly caused by the wafer thickness variation.

Narrow-band waveguide Bragg gratings on SOI wafers with CMOS-compatible fabrication process.

We demonstrate an add/drop filter based on coupled vertical gratings on silicon. Tailoring of the channel bandwidth and wavelength is experimentally demonstrated. The concept is extended to implement a 1 by 4 wavelength division multiplexer with 6 nm channel separation, 3 nm bandwidth, a flat top response with < 0.8 dB ripple within the 3 dB passband, 1 dB insertion loss and 16 dB crosstalk suppression. The device is ultracompact, having a footprint < 2 X 10(-9)/2.

Wide bandwidth, low loss 1 by 4 wavelength division multiplexer on silicon for optical interconnects

An optofluidic 1×4 switch is designed, fabricated, and tested. The switch is based on a blazed diffraction grating imprinted onto silicone elastomer at the bottom of a microfluidic channel that is filled with liquids with different refractive indices. When the condition of a diffraction maximum is met, the laser beam incident on the grating is deflected by an angle proportional to the refractive index mismatch between the elastomer and the liquid in the channel. The switch was tested using four different aqueous salt solutions generating 0th to 3rd orders of diffraction. The insertion loss was 9.8dB, and the response time was 55 ms. The same basic design can be used to build optofluidic switches with more than 4 outputs.

Optofluidic 1x4 switch.

We propose a method for miniaturization of filters based on curved waveguide Bragg gratings, so that long structures can be packed into a small area on a chip. This eliminates the stitching errors introduced in the fabrication process, which compromise the performance of long Bragg gratings. Our approach relies on cascading curved waveguide Bragg gratings with the same radius of curvature. An analytical model for the analysis of these devices was developed, and a filter based on this model was designed and fabricated in a silicon on insulator platform. The filter had a total length of 920μm, occupied an area of 190μm×114μm, and exhibited a stop band of 1.7nm at 1.55μm and an extinction ratio larger than 23dB.

Compact chip-scale filter based on curved waveguide Bragg gratings

In remote sensing, atmospheric turbulence and aerosols usually limit the image quality. For many practical cases, turbulence is shown to be dominant, especially for horizontal close-to-earth imaging in hot environments. In a horizontal long-range imaging, it is usually impractical to calculate path-averaged refractive index structure constant C2n (which characterizes the turbulence strength) with conventional equipment. We propose a method for estimating C2n from the available atmospherically degraded video sequence by calculating temporal intensity fluctuations in spatially high variance areas. Experimental comparison with C2n measurements using a scintillometer shows reliable estimation results.

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Turbulence strength estimation from an arbitrary set of atmospherically degraded images.

We demonstrate optical bistability in a silicon waveguide Fabry-Perot resonator formed by a pair of distributed Bragg reflectors. In the bistable regime, the output power of the resonator ceases to be uniquely determined by the input power because multiple powers within the cavity satisfy the resonance condition. Pulsating behavior is observed within the resonator output, and is attributed to noise within the experimental setup driving the resonator between the multiple allowed output powers.

Steve Zamek

Papers

Wide bandwidth, low loss 1 by 4 wavelength division multiplexer on silicon for optical interconnects

Optofluidic 1x4 switch.

Compact chip-scale filter based on curved waveguide Bragg gratings

Turbulence strength estimation from an arbitrary set of atmospherically degraded images.

Optical Bistability in a Silicon Waveguide Distributed Bragg Reflector Fabry–Pérot Resonator