Novel electroabsorption modulator monolithically integrated with spot-size converter

A novel 1.55-μm spot-size converter integrated electroabsorption modulator was designed with conventional photolithography and chemical wet etching process. A ridge double-core structure was employed for the modulator, and a buried ridge double-core structure was incorporated for the spot-size converter. The passive waveguide was optically combined with a laterally tapered active waveguide to control the mode size. The figure of merit is 4.1667 dB/V(/100 μm) and the beam divergence angles in the horizontal and vertical directions were as small as 11.2°and 13.0°, respectively.     

DFB lasers with integrated electroabsorption modulator

We present high-performance 1550 nm DFB lasers with butt-coupled, bulk type integrated electroabsorption modulators of good manufacturability and reliability. Key issues in device design are reviewed and the strong influence of the exact detuning between lasing wavelength and modulator bandgap is demonstrated. Fibre-coupled output powers as large as 6 dBm and attenuation efficiencies as high as 12 dB V^–1 are obtained. Butterfly-packaged devices show only 1 dB penalty for 10 Gbit s^–1 NRZ transmission over 50-km standard single-mode fibre (SMF) without the use of an optical amplifier. With an optical booster amplifier, self-phase-modulation in the fibre is exploited and repeaterless 10 Gbit s^–1 transmission is possible over 150-km standard SMF.     

Mode beating in spot-size converter lasers

An anomalous modulation in the wavelength spectrum has been observed in lasers with spot-size converters. This intensity modulation is shown to be caused by beating between the fundamental lasing mode and radiation modes in the taper. This results in a periodic modulation in the net gain spectrum, which causes wavelength jumps between adjacent net gain maxima, and a drive current dependent spectral width that is expected to affect system performance. The amplitude of this spectral modulation is reduced significantly by either using an angled rear-facet which reflects the beating radiation modes away from the laser axis, or by using a nonlinear, adiabatic taper.     

超低压选择区域生长法制备产生10GHz重复率超短光脉冲的级联电吸收调制器与分布反馈激光器单片集成光源

采用超低压(22×１０^２Pa)选择区域生长(selective area growth, SAG)金属有机化学气相沉积(metal-organic chemical vapor deposition, MOCVD)技术成功制备了InGaAsP/InGaAsP 级联电吸收调制器(electroabsorption modulator, EAM)与分布反馈激光器(distributed feedback laser, DFB)单片集成光源的新型光电器件.实验结果表明，采用该技术制备的器件 关键词： 超低压 选择区域生长 集成光电子器件 超短光脉冲     

Novel integrated optic intensity modulator based on mode coupling

The analysis, design, realization, and measurements of a novel intensity modulator are reported. The operating principle is based on mode coupling between a passive low-loss SiON waveguide and an electro-optic high-loss polymer waveguiding structure. Matching the waveguides is critical and results in severe demands for the technology. Extended simulations by the Coupled Mode Theory, the Leaky Wave Model, and Finite Difference Beam Propagation Method resulted in the design of several modulator structures. After realization, modulation could be demonstrated at 632 nm and at 1523 nm using lossy waveguiding modes and surface plasmon modes.     

Novel integrated optic intensity modulator based on mode coupling

Abstract

The analysis, design, realization, and measurements of a novel intensity modulator are reported. The operating principle is based on mode coupling between a passive low-loss SiON waveguide and an electro-optic high-loss polymer waveguiding structure. Matching the waveguides is critical and results in severe demands for the technology. Extended simulations by the Coupled Mode Theory, the Leaky Wave Model, and Finite Difference Beam Propagation Method resulted in the design of several modulator structures. After realization, modulation could be demonstrated at 632 nm and at 1523 nm using lossy waveguiding modes and surface plasmon modes.     

Flexible quadrature amplitude modulation with semiconductor optical amplifier and electroabsorption modulator

Optical quadrature amplitude modulation (QAM) is experimentally demonstrated with a low-complexity modulator based on a semiconductor optical amplifier and electroabsorption modulator. Flexible amplitude/phase format transmission is achieved. The applicability of octary QAM for coherent optical access networks with sustainable 3 Gb/s per-user bandwidth is investigated for a long reach of 100 km, and its compatibility with a potentially high split is verified.     

All-optical sampling with a monolithically integrated Mach-Zehnder interferometer gate

An all-optical sampler consisting of a polarization-independent monolithic Mach-Zehnder interferometer with integrated semiconductor optical amplifiers and a temporal resolution of 1 ps is presented. As an example, a simple 320-Gbit/s pattern has been successfully sampled, demonstrating the functionality of this scheme for high-bit-rate waveform characterizations in light-wave systems.     

Improved design for SOI based evanescently coupled multilayer spot-size converter

We report an improved version of a spot-size converter (SSC) consisting of a silicon nanowire evanescently coupled to a phase-matched Poly-Si multilayer structure. With wider transversal dimensions the multilayer structure expands the mode significantly thus increasing the coupling efficiency with the conventional single-mode fiber. Detailed optimization process of a 17-layer based SSC is discussed and its coupling efficiency with a high-NA fiber of radius 2 μm is obtained as 98% providing only 0.087 dB loss. Vertical alignment tolerance between the optimized SSC and a high-NA fiber of radius 2 μm is also shown. This novel design does not consist of a taper and can be fabricated by using CMOS compatible process. It has a short device length and more relaxed alignment tolerances with the fiber. Full-vectorial and computationally efficient finite element method and the least squares boundary residual method have been used for the analysis and optimization of the proposed structure.     

Performance limits of pico-cell systems using radio-over-fiber techniques with an electroabsorption modulator

We investigate the performance limits of a pico-cell system using the radio- over-fiber technique with an electroabsorption modulator (EAM) in a 2.4 GHz wireless local area network (WLAN) environment. To understand the performance limits of the system using an EAM as the optical transceiver, we vary the optical modulation index (OMI) of the transmitter for different bias voltages to the EAM. Power margins in the links are found to estimate a possible service range, and packet loss rates (PLRs) in the pico-cell system are measured to evaluate the transmission performance. The total service range can be extended up to 3 m by adjusting the OMI of the transmitter for different applied bias voltages to the EAM.     

Technology challenges for monolithically integrated waveguide demultiplexers

A short overview of integrated waveguide demultiplexers for different applications in future highly integrated optical communication systems is presented. Some fabricated devices based on amorphous silicon nanowire technology are described.     

Nonlinearity of traveling-wave electroabsorption modulator according to microwave characteristics

In this paper, we introduce a model to analyze the linearity of multiple-quantum-well (MQW) traveling-wave electroabsorption modulator (TW-EAM). The device length, microwave loss (ML), velocity mismatch (VM) between lightwaves and the microwaves, and internal reflection (IR) due to impedance mismatch have effect on the linearity of a TW-EAM. ML has little effect on the intermodulation distortions (IMDs). VM also has little influence on IMD3 (third-order IMD), but severely affect IMD2 (second-order IMD), which become as high as 30 dB for the input frequency of 100 GHz, the device length of 0.8 mm, and VM of 20%. IR has different nonlinear characteristics according to the wavelength of the input frequency and the device length. As a result, it is known that IMDs improve when the device length equal to a quarter of the wavelength of the input signal and that the device length of 0.4 mm is appropriate for the analog fiber-optic communication with the frequency range of 50 GHz.     

Experimental study of NRZ format wavelength conversion using electroabsorption modulator

In this paper, NRZ format wavelength conversion using cross absorption modulation (XAM) in InGaAsP MQW electroabsorption modulator (EAM) is investigated experimentally in detail for the first time, to the best of our knowledge. The influence of two key operating parameters, input signal power and bias voltage of EAM, on wavelength conversion performance is studied. Experimental results indicate that there exists optimal bias voltage for fixed input signal power and that there exists also optimal input signal power for fixed bias voltage and the lowest power penalty of 0.9 dB is obtained by optimizing these two parameters. The physical explanations are given for these results based on operating characteristic of EAM device. Finally, the probe light wavelength dependence of wavelength conversion is studied for span of 1530–1560 nm.     

A monolithically integrated CMOS labchip using sensor devices

A new concept for a monolithic labchip platform to combine standard CMOS-integrated circuit technology and novel solid-state components is presented. The capability to perform laboratory analysis operations on small-scale labchip devices holds exceptional advantages compared to commonly used diagnostic instrumentation. The objective is to improve cost-efficiency, performance and functionality of chemical or biological systems on-a-chip by increasing the level of integration and miniaturization. The integration of hydrogenated amorphous silicon color sensors enables a novel combinatoric labchip-based chemical verification method in a specifically arranged microarray of capillaries and sensors. To test the labchip functionality, results about an electrophoretic separation as well as a pH-sensitive luminescent sensor complex are shown.     

Fluorescence monitoring of microchip capillary electrophoresis separation with monolithically integrated waveguides

Using femtosecond laser writing, optical waveguides were monolithically integrated into a commercial microfluidic lab-on-a-chip device, with the waveguides intersecting a microfluidic channel. Continuous-wave laser excitation through these optical waveguides confines the excitation window to a width of 12 microm, enabling high-resolution monitoring of the passage of different types of fluorescent analytes when migrating and being separated in the microfluidic channel by microchip capillary electrophoresis. Furthermore, we demonstrate on-chip-integrated waveguide excitation and detection of a biologically relevant species, fluorescently labeled DNA molecules, during microchip capillary electrophoresis. Well-controlled plug formation as required for on-chip integrated capillary electrophoresis separation of DNA molecules, and the combination of waveguide excitation and a low limit of detection, will enable monitoring of extremely small quantities with high spatial resolution.     

Submicron-scale spatial compression of light beam through two-stage photonic crystals spot-size converter

Photonic crystals spot-size converter that achieved the controlling of the spot-size through two-stage conversions was proposed. The pre-conversion depended on the efficient coupling between the high quality factor resonator and photonic crystal waveguide. Nearly unity transmission efficiency of the pre-conversion can be achieved through optimizing the radii of the rods located surrounding the resonator. Nanowire waveguide with width of 0.14 μm at a distance 1.05 μm from the resonator was introduced to realize the second stage conversion. Through two-stage conversions, the light beam width was converted to 0.16 μm. The transmission efficiency and conversion ratio reached to 94.6% and 14.875 respectively in theory.     

2R-Regeneration in a monolithically integrated four-section SOA-EA chip

Optical regeneration using a monolithically integrated chip formed by a cascade of semiconductor optical amplifiers and saturable absorbers is investigated. Static transfer functions, signal reshaping, extinction ratio enhancement, noise dynamics and device dependence on operation conditions are measured. Results show that by cascading two-pairs of SOA-EAs a steep static transfer function is achieved. Dynamical measurements show large improvements in extinction ratio as well as a large improvement in the receiver-sensitivity when used as a regenerator for NRZ signals at 10 Gb/s.     

Technology challenges for monolithically integrated waveguide demultiplexers Invited Paper

A short overview of integrated waveguide demultiplexers for different applications in future highly inte- grated optical communication systems is presented. Some fabricated devices based on amorphous silicon nanowire technology are described.     

Nonreciprocity of counterpropagating signals in a monolithically integrated Sagnac interferometer

We demonstrate nonlinearly induced nonreciprocity of counterpropagating waves in a monolithically integrated Sagnac interferometer that employs a semiconductor optical amplifier as the nonlinear element. We show that the dependence of the linewidth enhancement factor on charge injection can influence the third-order nonlinearity in the semiconductor gain medium to a surprisingly large degree. This effect is utilized to control the phases of the counterpropagating signals in the interferometer. A theoretical model is used to explain the experimental observations. We show that these effects have significant practical implications by demonstrating an all-optical controlled-NOT gate.     

High repetition rate optical switch using an electroabsorption modulator in TOAD configuration

A novel optical switch featured with high repetition rate, short switching window width, and high contrast ratio is proposed and demonstrated for the first time by placing an electroabsorption modulator (EAM) in a terahertz optical asymmetric demultiplexer (TOAD) configuration. The feasibility and main characteristics of the switch are investigated by numerical simulations and experiments. With this EAM-based TOAD, an error-free return-to-zero signal wavelength conversion with 0.62 dB power penalty at 20 Gbit/s is demonstrated.