Aging is a natural consequence of a society developing process. Although many adults retain good hearing as they aging, hearing loss related with age-presbycusis which can vary in severity from mild to substantial is common among elderly persons. There are a number of pathophysiological processes underlying age-related changes in the auditory system as well as in the central nervous systems. Many studies have been dedicated to the illustration of risk factors accumulating presbycusis such as heritability, environment factors, medical conditions, free radical (reactive oxygen species, ROS) and damage of mitochondrial DNA. Left untreated, presbycusis can not only lead sufferers to reduced quality of life, isolation, dependence and frustration, but also affect the healthy people around. These can be partly corrected using hearing aids, but it is not enough, more and more strategies of treatment based on the findings associating with presbycusis should be added rather than using single hearing aids. We review here the pathophysiology; heritability, susceptibility genes and other risk factors including environmental, medical, especially free radical (ROS) and damage of mitochondrial DNA; and some strategies of treatment, as well as promising rehabilitations associating with presbycusis.

Abstract:In the paper, we review our work on heterogeneous III-V-on-silicon photonic components and circuits for applications in optical communication and sensing. We elaborate on the integration strategy and describe a broad range of devices realized on this platform covering a wavelength range from 850 nm to 3.85 μm.

An ultra-small disk resonator consisting of a suspended silicon disk with a submicron bending radius sitting on an SiO(2) pedestal is demonstrated experimentally. An asymmetrical suspended rib waveguide is integrated as the access waveguide for the suspended submicron disk resonator, which is used to realize an ultra-small optical sensor with an improved sensitivity due to the enhanced evanescent field interaction with the analyte. The present optical sensor also has a large measurement range because of the ultra-large free-spectral range of the submicron-disk resonator. As an example, a suspended submicron disk sensor with a bending radius of 0.8 μm is designed, fabricated, and characterized. The concentration of NaCl aqueous solution and organic liquids is measured with the suspended submicron-disk sensor, and the measured sensitivity is about 130 nm/RIU, which agrees well with the simulation value.

The effect of nonlocal optical response is studied for a novel silicon hybrid plasmonic waveguide (HPW). Finite element method is used to implement the hydrodynamic model and the propagation mode is analyzed for a hybrid plasmonic waveguide of arbitrary cross section. The waveguide has an inverted metal nano-rib over a silicon-on-insulator (SOI) structure. An extremely small mode area of~10⁻⁶λ² is achieved together with several microns long propagation distance at the telecom wavelength of 1.55 μm. The figure of merit (FoM) is also improved in the same time, compared to the pervious hybrid plasmonic waveguide. We demonstrate the validity of our method by comparing our simulating results with some analytical results for a metal cylindrical waveguide and a metal slab waveguide in a wide wavelength range. For the HPW, we find that the nonlocal effects can give less loss and better confinement. In particular, we explore the influence of the radius of the rib's tip on the loss and the confinement. We show that the nonlocal effects give some new fundamental limitation on the confinement, leaving the mode area finite even for geometries with infinitely sharp tips.

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Abstract:We present a five-channel wavelength division multiplexed modulator module that heterogeneously integrates a 200GHz channelspacing silicon arrayed-waveguide grating multiplexer and a 20Gbps electro -absorption modulator array, showing the potential for 100 Gbps transmission capacity on a 1.5x0.5 mm 2 footprint. ©2015 Optical Society of America IntroductionWavelength division multiplexing (WDM) modules are of key importance for realizing high aggregate bitrate optical networks and optical interconnects. WDM transmitters and receivers require low cost and high performance devices for maximal bandwidth usage and high energy-efficiency. For the key opto-electronic components in a WDM system, both silicon and III-V based devices are available. Potentially CMOS compatible, low-cost, monolithic silicon WDM modulator chips have been reported [1,2]. However, an optically broadband silicon-based modulator usually has a large footprint and requires a relatively high driving voltage and hence high power consumption for sufficient extinction ratio [3]. Alternatively, purely III-V WDM modulator chips have been demonstrated [4, 5]. Although they are more efficient than silicon modulators, the monolithic integration with passive wavelength division multiplexing devices, e.g. arrayed waveguide gratings (AWG) and etched diffractive gratings (EDG) is not straightforward. In order to overcome these issues, a hybrid silicon platform that combines the advantages of III-V based materials and silicon is being studied. III-V/Si hybrid active devices with excellent performance, such as hybrid silicon narrow linewidth lasers [6], high-speed modulators [7], and high-speed detectors [8] have already been demonstrated. The highest speed modulators on silicon were achieved by transferring a III-V epitaxy stack onto a SOI wafer to realize a 67GHz bandwidth traveling-wave hybrid silicon electro-absorption modulator (EAM) [7]. These hybrid devices can be integrated together to build up more complex on-chip photonic modules [9, 10] on silicon-based substrates, which shows its potential for high density, high performance WDM transmitters and receivers for optical communication networks and multi-CPU optical interconnects in the future.

We present a novel and simple method to obtain an ultrawide free spectral range (FSR) silicon ring resonator together with a tuning range covering the entire spectrum from 1500 to 1600 nm. A ring resonator with a large FSR together with a high Q factor, high tuning efficiency, and low fabrication cost and complexity is desired for many applications. In this paper, we introduce a novel way to make such a ring resonator, which takes advantage of the well-known resonance-splitting phenomenon. It is a single ring resonator with an FSR of more than 150 nm around 1550 nm and which has an easy thermo-optic tunability that can produce a tuning range around 90 nm or even more. Moreover, the device is simple to implement and can be fabricated in standard complementary metal-oxide semiconductor technology without requiring any kind of complicated processing or extra materials. The potential applications include single mode laser cavities, wavelength division multiplexing filters, (de)multiplexers, optical sensors, and integrated reflectors.

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