Development of Membrane Optical Modulators for IOWN

We numerically analyzed the modulation characteristics of an InP organic hybrid (IOH) optical modulator consisting of an InP slot waveguide and an electro-optic (EO) polymer. Since InP has a higher electron mobility and a lower electron-induced free-carrier absorption than Si, the series resistance of an InP slot waveguide can be significantly reduced with relatively smaller optical loss than an Si slot waveguide. As a result, the trade-off between optical loss and modulation bandwidth can be remarkably improved compared with a Si organic hybrid (SOH) optical modulator. When the modulation bandwidth was designed to be 100 GHz, the optical loss of the IOH modulator was 13-fold smaller than that of the SOH one. The simulation of the eye diagram revealed that the improved optical modulation amplitude enabled the clear eye opening with a 100 Gbps non return-to-zero signal using the IOH modulator. The IOH integration is promising for a high-speed modulator with low energy consumption beyond 100 Gbps.

In this study, the potential of employing SiNx (silicon nitride) waveguide platforms to enable the use of liquid-crystal-based phase shifters for on-chip optical modulators was thoroughly investigated using 3D-FDTD (3D finite-difference time-domain) simulations. The entire structure of liquid-crystal-based Mach–Zehnder interferometer (MZI) optical modulators, consisting of multi-mode interferometer splitters, different tapering sections, and liquid-crystal-based phase shifters, was systematically and holistically investigated with a view to developing a compact, wideband, and CMOS-compatible (complementary metal-oxide semiconductor) bias voltage optical modulator with competitive modulation efficiency, good fabrication tolerance, and single-mode operation using the same SiNx waveguide layer for the entire device. The trade-off between several important parameters is critically discussed in order to reach a conclusion on the possible optimized parameter sets. Contrary to previous demonstrations, this investigation focused on the potential of achieving such an optical device using the same SiNx waveguide layer for the entire device, including both the passive and active regions. Significantly, we show that it is necessary to carefully select the phase shifter length of the LC-based (liquid crystal) MZI optical modulator, as the phase shifter length required to obtain a π phase shift could be as low as a few tens of microns; therefore, a phase shifter length that is too long can contradictorily worsen the optical modulation.

Since the growth of fiber optic communications, extremely low cost optical modules have been expected to be realized. Particularly for the subscriber applications and local area networks (LANs), less than half of past module cost is required. In accordance with the spread of fiber optic transmission, higher volume manufacture is also needed. To attain both of low cost and high productivity, we developed passive alignment technique and optical coupling structure that is suitable for automatic assembly. We also developed automatic assemble equipment for producing several types of optical modules. To reduce optical module cost, it is important to cut down the assembly cost and expensive parts such as optical lens. The passive alignment technique brings us to realize easy assembly of modules and minimize the constructed components of optical coupling. Our mass production techniques include not only for optical coupling but also packaging of the module. We have several types of optical modules according to different fiber communication systems; there are laser modules, detector modules, optical interface modules that are integrated optical coupling and electrical circuit, and PLC (Planar Lightwave Circuit) modules that are integrated passive component. Basically all modules have same optical coupling structure and keep the design rules for automatic assembly. Accordingly, we can use the same equipment for the same assembly process. In this paper, we will introduce basic assembly process and our mass production line for optical coupling and packaging by using passive alignment technique.

A novel phased array receive antenna steering system is introduced. The core of this system is an optical ring resonator-hased broadband, continuously tunable optical beam forming network (OBFN). In the proposed system architecture, filter-based optical single-sideband suppressed-carrier modulation and balanced coherent optical detection are used. Such architecture has significant advantages over a straightforward architecture using optical double-sideband modulation and direct optical detection, namely relaxed bandwidth requirements on the optical modulators and detectors, reduced complexity of the OBFN chip, and enhanced dynamic range. Initial measurements on an actual 1 times 8 OBFN chip and an optical sideband filter chip arc presented. Both are realized in CMOS-compatible planar optical waveguide technology.

The D-Egg, an acronym for “Dual optical sensors in an Ellipsoid Glass for Gen2,” is one of the optical modules designed for future extensions of the IceCube experiment at the South Pole. The D-Egg has an elongated-sphere shape to maximize the photon-sensitive effective area while maintaining a narrow diameter to reduce the cost and the time needed for drilling of the deployment holes in the glacial ice for the optical modules at depths up to 2700 m.The D-Egg design is utilized for the IceCube Upgrade, the next stage of the IceCube project also known as IceCube-Gen2 Phase 1, where nearly half of the optical sensors to be deployed are D-Eggs. With two 8-inch high-quantum efficiency photomultiplier tubes (PMTs) per module, D-Eggs offer an increased effective area while retaining the successful design of the IceCube digital optical module (DOM). The convolution of the wavelength-dependent effective area and the Cherenkov emission spectrum provides an effective photodetection sensitivity that is 2.8 times larger than that of IceCube DOMs. The signal of each of the two PMTs is digitized using ultra-low-power 14-bit analog-to-digital converters with a sampling frequency of 240 MSPS, enabling a flexible event triggering, as well as seamless and lossless event recording of single-photon signals to multi-photons exceeding 200 photoelectrons within 10 ns. Mass production of D-Eggs has been completed, with 277 out of the 310 D-Eggs produced to be used in the IceCube Upgrade. In this paper, we report the design of the D-Eggs, as well as the sensitivity and the single to multi-photon detection performance of mass-produced D-Eggs measured in a laboratory using the built-in data acquisition system in each D-Egg optical sensor module.

Silicon platform enables the monolithic realization of large-scale photonic integrated systems. Many emerging applications facilitated by silicon photonics such as optical biosensing, optical neurostimulation, optical phased arrays, holographic displays, 3D cameras, optical machine learning, and optical quantum information processing systems require the integration of a large number of optical phase modulators with modest modulation speed. Classical optical modulators are not suitable for such large-scale integration because of their inability to provide low optical loss, compact size, high efficiency, and wide optical bandwidth, all at the same time. We report a thermo-optic silicon modulator realized in a 0.0023-mm2 silicon footprint of a commercial foundry silicon photonics process. The optical modulator consumes 2.56 mW for 180° phase modulation over 100-nm optical bandwidth while achieving 1.23-dB optical loss without air-gap trench or silicon undercut post-processing. Geometrical design optimization, at the core of this demonstration, is applicable to the realization of compact thermo-optic devices for large-scale programmable photonic integrated systems, with a potential to reduce power consumption roughly by an order of magnitude without sacrificing scalability and optical modulation bandwidth.

Electrolytes-relevant cyclic durability of nickel oxide thin films as an ion-storage layer in an all-solid-state complementary electrochromic device

A simple GaAs etalon has been used to observe optical bistability, pulse shaping, and modulation of one light beam by another. Such devices may lead to all-optical, high-speed computation and communication; all-optical signal processing may be appropriate with the advent of low-loss, high bit-rate optical transmission systems. The etalon consists of a sandwich of 4 µm of GaAs between 0.2 µm layers of Al0.42Ga0.58As grown by molecular beam epitaxy. Nonlinear laser spectroscopy was used to identify appropriate non-linearities essential to the operation of this device.

Recently, Si-photonics received a growing interest and started to move from laboratories to industrial product development, mainly for the applications inside data-centers. One of the weaknesses of Si is its relatively low plasma dispersion efficiency, making the size of phase modulator large. This efficiency can be improved by using the heterogeneous integration of material such as InP, InGaAsP, or SiGe to fabricate hybrid semiconductor–insulator–semiconductor (SIS) optical phase modulators. At the same time, the standard figure of merit for modulator benchmarking $V_{\pi }L_{\pi }$ does not consider the dynamic behavior of the SIS devices, nor is making the link with the system level specifications such as optical modulation amplitude (OMA), widely used in 100G to 400G parallel single mode or coarse wavelength division multiplexing applications. In this paper, we propose to simply link the modulator performance to the OMA, to derive a compact model for SIS devices and to compare hybrid device performances for various materials.

We present a 100-GHz-bandwidth coherent transmitter (Tx) front-end consisting of a cost-effective PCB with a flip-chip-bonded InP-HBT-based driver IC and InP-MZM-based optical IQ modulator, which enables net 2.11- and 2.03-Tb/s/λ 80-km optical transmission. Achieving this 100-GHz bandwidth requires the use of wideband driver ICs and optical modulators as well as the implementation of a low-loss substrate and broadening the bandwidth of the interconnections between the chips and the substrate. We demonstrated the importance of such assembly technology by using a low-loss substrate with a dielectric constant of 3.06 and a dielectric loss tangent of 0.002 as the platform and flip-chip bonding, which reduces parasitic inductance, to achieve the desired wideband performance. To the best of our knowledge, this is the first demonstration of 100-GHz bandwidth and over 2-Tb/s/λ transmission using a coherent Tx front-end.

We describe ultra wideband frequency control of millimetre-wave and lightwave signals using optical single-sideband modulation. Precise and rapid frequency control can be achieved by digital arbitrary waveform generation and high-speed electro-optic modulation. Frequency multiplication in optical modulators also plays important roles. Ultra-wideband frequency chirp signals from 9.6 GHz to 16 GHz, which were generated by using a computer controlled arbitrary waveform generator and a wideband frequency multiplier, were fed to an optical single-sideband modulator consisting of two sub Mach-Zehnder interferometers.

This paper concerns the application of lightwave technology to microwave systems, specifically the design of a novel optical modulator. This new modulator uses a Fabry-Perot interferometer with internal Bragg reflector mirrors. The device is expected to be small, less the 500?m in length, have a bandwidth in excess of 10GHz, and a driving voltage below 5 Volts.

The comparison of collective optic designs is described for the Thomson scattering system of the Korea superconducting tokamak advanced research (KSTAR) device. The optical systems collecting the light emission induced through the interaction between the plasma electrons and a laser beam are the key components for the Thomson scattering system. In the first conceptual design of the collection optics for the KSTAR Thomson scattering system, a duo-lens system covering individually the core and the edge regions of the KSTAR plasma with two optical lens modules was proposed. In optical designs, the number of optical modules is a great concern in the case of limited system space. Here, the duo-lens system is evaluated through a comparison with a uni-lens system covering the whole region of the plasma with a single optical module. The duo-lens system turned out to have 2.0 times and 4.73 times higher light collections of the plasma core and edge compared with the uni-lens system.

One approach to improving the performance of large processing or telecommunications switching systems is to interconnect integrated circuits using optics. Smart pixels, with integrated optical detectors, modulators, and electronic logic, could potentially be used in these systems. The FET-SEED, consisting of the monolithic integration of multiple quantum well (MQW) optical modulators and detectors with GaAs field effect transistors, is one design platform for these smart pixels [1,2]. Another potential design platform uses the hybrid integration of MQW modulators and detectors with commercial electronic circuits [3-7]. This latter approach allows one to design circuits with greater complexity and circuit yield, because it uses available established VLSI processes.

An acoustic domain in CdS crystals modulates a radiated optical beam near the intrinsic absorption edge. This paper reports that the equivalent band-gap alteration caused by the scattering effect and intrinsic absorption are superimposed and cause optical modulation. The equivalent band-gap alteration is dependent on sample thickness but the intrinsic absorption is caused by the Franz-Keldysh effect and is not affected by sample thickness.