Advances in Synthetic Gauge Fields for Light Through Dynamic Modulation

Photons are weak particles that do not directly couple to magnetic fields. However, it is possible to generate a photonic gauge field by breaking reciprocity such that the phase of light depends on its direction of propagation. This non-reciprocal phase indicates the presence of an effective magnetic field for the light itself. By suitable tailoring of this phase it is possible to demonstrate quantum effects typically associated with electrons, and as has been recently shown, non-trivial topological properties of light. This paper reviews dynamic modulation as a process for breaking the time-reversal symmetry of light and generating a synthetic gauge field, and discusses its role in topological photonics, as well as recent developments in exploring topological photonics in higher dimensions.Comment: 20 pages, 3 figure

Fiber-optic temperature sensor based on interference of selective higher-order modes

A fiber-optic temperature sensor based on the interference of selective higher-order modes in circular optical fibers is described. The authors demonstrate that by coupling the LP01 mode in a standard single-mode fiber to the LP0m modes in a multimode fiber, and utilizing the interference of the higher-order modes, a fiber-optic temperature sensor which has an extremely simple structure and is suitable for high-temperature measurements can be constructed. The sensing principle, temperature measurement experiments, and results are presented

Investigation of ultrasmall 1 x N AWG for SOI-Based AWG demodulation integration microsystem

Optoelectronic integration technologies based on silicon-on-insulator (SOI) can bring revolutionary change to on-chip arrayed waveguide grating (AWG) demodulation systems. In this study, we present several ultrasmall 1 x N AWGs for an SOI-based AWG demodulation integration microsystem of different scales. The core sizes of the fabricated AWGs are smaller than 400 x 600 μm2. Experimental results match the simulation results, indicating that AWGs have a good transmission spectrum of low crosstalk below -20 dB and low insertion loss below -6.5 dB. The fabricated AWGs can be perfectly applied to improve the integration level and performance of the SOI-based AWG demodulation integration microsystem

Optical signal processing for fiber Bragg grating based wear sensors

In this study, we propose a simplified signal processing scheme for fiber Bragg grating (FBG) based wear sensing. Instead of using a chirped FBG and detecting the bandwidth, we use uniform gratings as sensors and measure the optical power reflected by the sensing grating to determine the length of the sensor grating, hence detect the wear. We demonstrate by the experiments that the proposed method is feasible and practical. The advantage of the proposed method lies in the fact that structure of the wear sensing system is simplified and therefore the cost can be significantly reduced. The principle of the proposed method, the design of the wear sensor, and the experiments are described

Terahertz-wave parametic oscillator with misalignment-resistant tuning cavity

We demonstrate a terahertz-wave parametric oscillator (TPO) with a corner-cube resonator consisting of a corner-cube prism (CCP) and a flat mirror. By using the cavity configuration proposed in this Letter, the generation of tunable monochromatic terahertz (THz) waves can be achieved just by rotating the flat mirror instead of rotating the TPO cavity relative to the pump beam. The THz-wave output intensity and pulse width can be controlled periodically by rotating the CCP around the cavity axis. The TPO stability against cavity misalignment is significantly improved by at least 1 to 2 orders of magnitude compared with the conventional plane–parallel resonator configuration

Photonic Aharonov–Bohm effect in photon–phonon interactions

The Aharonov–Bohm effect is one of the most intriguing phenomena in both classical and quantum physics, and associates with a number of important and fundamental issues in quantum mechanics. The Aharonov–Bohm effects of charged particles have been experimentally demonstrated and found applications in various fields. Recently, attention has also focused on the Aharonov–Bohm effect for neutral particles, such as photons. Here we propose to utilize the photon–phonon interactions to demonstrate that photonic Aharonov–Bohm effects do exist for photons. By introducing nonreciprocal phases for photons, we observe experimentally a gauge potential for photons in the visible range based on the photon– phonon interactions in acousto-optic crystals, and demonstrate the photonic Aharonov–Bohm effect. The results presented here point to new possibilities to control and manipulate photons by designing an effective gauge potential

Optimisation of triangulation based optical profilometers utilising digital video projection technology

Fast, high precision and automated optical noncontact surface profile and shape measurement has been an extensively studied research area due to its many potential applications including 3D sensing, industrial monitoring, mechanical engineering, medicine, robotics, machine vision,animation, virtual reality, dressmaking, prosthetics, ergonomics. Among others, structured light approaches including fringe profilometry have proven to be one of the most promising techniques. In such profilometry techniques a structured light pattern, generally composed of parallel lines is projected onto a diffuse surface to be measured and viewed from an offset angle. The observed pattern is distorted by the object in such a way that represents information about the height of the object perpendicular to the plane of observation. The distorted structured light pattern is recorded, commonly by a CCD camera and through computer analysis of the recorded image the object can be recreated in 3D space, typically with a high degree of precision

Effect of polarization sensitivity on ultrasmall SOI-based AWG for FBG sensor interrogation

Polarization sensitivity is an important factor that affects the interrogation of ultrasmall arrayed waveguide grating (AWG) for fiber Bragg grating (FBG) sensor. An ultrasmall 1  ×  8 silicon-on-insulator (SoI) AWG with a core size of less than 530  μm  ×  480  μm is proposed in this study. This ultrasmall SoI AWG exhibits good transmission spectra and high polarization sensitivity. The increased channel numbers and tight structure increase the polarization sensitivity of AWG. Temperature interrogation experiments show that the FBG sensor interrogation is drastically affected when the effect of polarization sensitivity on the ultrasmall AWG is sufficiently large

Measuring multiple parameters in a self-mixing optical feedback system

We propose a new approach that yields the values of multiple parameters at the same time for self-mixing optical feedback interferometric systems. These parameters are the linewidth enhancement factor of Semiconductor Lasers, the optical feedback level factor as well as vibration information of a target including the frequency and the amplitude. The method is based on optical feedback interferometry. Its effectiveness has been confirmed by computer simulations and experiments

Experimental demonstration and analysis of compact silicon-nanowire-based couplers

Compact 2 x 2 couplers based on silicon nanowires are fabricated and tested. They include a directional (X) coupler, a cross-gap coupler (CGC), and a multimode interference (MMI) coupler. The length of the X coupler\u27s parallel film waveguide is 1 μm. The theoretical minimum excess loss of the X coupler is 0.73 dB, whereas its experimental value is 1.0817 dB. CGC has a coupling region length of 24 μm. The minimum excess loss of CGC, which is 0.6 dB in theory, is experimentally determined to be 0.6737 dB. Taper waveguides are used as input/output waveguides for the MMI coupler. The footprint of the MMI region is only 6 x 57 μm2. The excess loss of the MMI coupler is theoretically 0.46 dB, but its experimental value is 0.5423 dB. The experimental nonuniformity of the MMI coupler is 0.0063 dB when the center wavelength is 1.55 μm. The maximum excess loss of the MMI coupler is 0.8233 dB in the wavelength range of 1.52 to 1.58 μm. The simulated and experimental results show that a small 2 x 2 MMI coupler that is suitable for optoelectronic integration exhibits lower excess loss, wider bandwidth, and better uniformity