High-speed Electroabsorption Modulator Research Articles

Silicon integrated photonic-electronic neuron for noise-resilient deep learning

This paper presents an experimental demonstration of the photonic segment of a photonic-electronic multiply accumulate neuron (PEMAN) architecture, employing a silicon photonic chip with high-speed electro-absorption modulators for matrix-vector multiplications. The photonic integrated circuit has been evaluated through a noise-sensitive three-layer neural network (NN) with 1350 trainable parameters targeting heartbeat sound classification for health monitoring purposes. Its experimental validation revealed F1-scores of 85.9% and 81% at compute rates of 10 and 20 Gbaud, respectively, exploiting quantization- and noise-aware deep learning techniques and introducing a novel activation function slope stretching strategy for mitigating noise impairments. The enhanced noise-resilient properties of this novel training model are confirmed via simulations for varying noise levels, being in excellent agreement with the respective experimental data obtained at 10, 20, and 30 Gbaud symbol rates.

Dual-wavelength DBR laser integrated with high-speed EAM for THz communications.

We report a novel single-cavity dual-wavelength laser that has two distributed Bragg reflector (DBR) gratings at each side of a gain section for THz communication applications. By varying the inject current of one of the DBR gratings, the optical beat frequency of the laser can be widely tuned. In the device, a high-speed electro-absorption modulator (EAM) is also integrated and can be used for up to 25 Gb/s data modulation.

Multi-Micron Silicon Photonics Platform for Highly Manufacturable and Versatile Photonic Integrated Circuits

We describe and characterize a multi-micron silicon photonics platform that was designed to combine performance, power efficiency, manufacturability, and versatility for integrated photonic applications ranging from data communications to sensors. We outline the attributes needed for broad applicability, high-volume manufacturing, and large-scale deployment of silicon photonics, and describe how the platform is favorable with respect to these attributes. We present demonstrations of key technologies needed for the communications and sensing applications, including low-loss fiber attach, compact low-loss filters, efficient hybrid wavelength division multiplexed lasers, and high-speed electro-absorption modulators and integrated photodetectors.

Increasing the Speed of an InP-Based Integration Platform by Introducing High Speed Electroabsorption Modulators

We report high speed electroabsorption modulators (EAMs), designed, fabricated and characterized within an open access generic foundry process. The EAM as a new building block is optimized in the existing platform, in which other BBs are established. By optimizing the EAM design layout, we show a static extinction ratio (static ER) of 18 dB, a low dc bias voltage below 1 V at an increased temperature, as well as operation in a semicooled environment, tested in the range of 20 °C -60 °C. Furthermore, we improve the intrinsic S-parameter response with a codesign circuit. The intrinsic 3-dB bandwidth of a 100-μm-long EAM is 17 GHz. When measured with the EAM submount design, it is increased to 24 GHz. Simultaneously, the return loss bandwidth is improved by a factor of 2.5 staying below -10 dB up to 20 GHz. Through the realization of the EAM submount design we achieve a three-time speed increase of the existing platform, from previously offered 9 GHz (using an EAM) to 24 GHz shown in this paper.

High-Optical-Power Operation of the Electroabsorption-Modulated Laser and Subsequent Changes in Eye Diagram and 3-dB Bandwidth

We present the 10-Gbps eye diagrams of the multiple-quantum-well electroabsorption-modulated laser at high optical powers and analyze the changes in the eye diagrams. Changes in the differential photocurrent resistance and the capacitance of the electroabsorption modulator (EAM) are considered in the analysis. We show that contrary to the previous report of the bandwidth increase with the optical power, the bandwidth of the EAM remains constant with the 50-Ω parallel matching resistor. Since the 3-dB bandwidth is one of the most important design parameters for the high-speed EAM, understanding its behavior under high optical power should be very useful.

New Nonlinear Electrical Modeling of High-Speed Electroabsorption Modulators for 40 Gb/s Optical Networks

A specific modeling method is investigated in order to predict the large-signal modulation behavior of integrated electroabsorption modulators (EAMs) for high-speed applications in optical networks. The equivalent dynamic model includes the main nonlinearity of the EAM and takes into account the electrical and optical characteristics of the optoelectronic device. The developed specific design process is a suitable and powerful tool for simulating over wide dc bias and frequency ranges, scattering parameters, small-signal modulation response, and large-signal eye-diagram performance. Moreover, 3-D electromagnetic simulations are associated with circuit simulations to carry out for the RF input line of the EAM. This simulation model can be easily integrated in a global optical communication system simulator to estimate the temporal behavior of the modulated output optical power and then digital performances.

InGaAs self-assembly quantum dot for high-speed 1300 nm electroabsorption modulator

In this paper, a new type of high-speed electroabsorption modulator (EAM) based on quantum dot (QD) p–i–n heterostructure is demonstrated. The QD layers sandwiched by p-AlGaAs and n-AlGaAs are grown by multilayer InGaAs self-assembled QD with luminance wavelength of 1300nm, serving as the active region of EAM. The photocurrent spectrum measurement exhibits a red shift of 15nm in QD transition energy levels on biasing from 0 to 6V. A quadratic relation of energy shift against the reversed bias is extracted, confirming the quantum-confined Stark effect (QCSE) in QD. On fabricating a 300μm long EAM, as high as DC 5dB extinction ratio by 6V voltage swing at 1310nm is observed. As compared with well-developed quantum well (QW) EAM (well thickness ∼10nm) of the same length, the lower density of states still shows the same order of magnitude in extinction ratio, suggesting strong QCSE in such 3-dimensional confined QD. An electrical-to-optical conversion with −3dB bandwidth of 3.3GHz is also attained in such QD EAM, where the speed is mainly limited by the parasitic capacitance on substrate. It implies that through optimization of QD and device structures, the advantages of QD properties are quite promising to be used in high-speed optoelectronic fields.

Novel monolithic integration scheme for high-speed electroabsorption modulators and semiconductor optical amplifiers using cascaded structure

A new monolithic integration scheme, namely cascaded-integration (CI), for improving high-speed optical modulation is proposed and demonstrated. High-speed electroabsorption modulators (EAMs) and semiconductor optical amplifiers (SOAs) are taken as the integrated elements of CI. This structure is based on an optical waveguide defined by cascading segmented EAMs with segmented SOAs, while high-impedance transmission lines (HITLs) are used for periodically interconnecting EAMs, forming a distributive optical re-amplification and re-modulation. Therefore, not only the optical modulation can be beneficial from SOA gain, but also high electrical reflection due to EAM low characteristic impedance can be greatly reduced. Two integration schemes, CI and conventional single-section (SS), with same total EAM- and SOA- lengths are fabricated and compared to examine the concept. Same modulation-depth against with EAM bias (up to 5V) as well as SOA injection current (up to 60mA) is found in both structures. In comparison with SS, a < 1dB extra optical-propagation loss in CI is measured due to multi-sections of electrical-isolation regions between EAMs and SOAs, suggesting no significant deterioration in CI on DC optical modulation efficiency. Lower than -12dB of electrical reflection from D.C. to 30GHz is observed in CI, better than -5dB reflection in SS for frequency of above 5GHz. Superior high-speed electrical properties in CI structure can thus lead to higher speed of electrical-to-optical (EO) response, where -3dB bandwidths are >30GHz and 13GHz for CI and SS respectively. Simulation results on electrical and EO response are quite consistent with measurement, confirming that CI can lower the driving power at high-speed regime, while the optical loss is still kept the same level. Taking such distributive advantage (CI) with optical gain, not only higher-speed modulation with high output optical power can be attained, but also the trade-off issue due to impedance mismatch can be released to reduce the driving power of modulator. Such kind of monolithic integration scheme also has potential for the applications of other high-speed optoelectronics devices.

High-Speed EA-DFB Laser for 40-G and 100-Gbps

We have developed a high-speed electroabsorption modulator integrated distributed feedback (EA/DFB) lasers. Transmission performance over 10km was investigated under 25Gbps and 43Gbps modulation. In addition, the feasibility of wide temperature range operation was also investigated. An uncooled EA/DFB laser can contribute to the realization of low-power-consumption, small-footprint and cost-effective transceiver module. In this study, we used the temperature-tolerant InGaAlAs materials in an EA modulator. A wide temperature ranged 12km transmission with over 9.6dB dynamic extinction ratio was demonstrated under 25Gbps modulation. A 43Gbps 10km transmission was also demonstrated. The laser achieved a clear, opened eye diagram with a dynamic extinction ratio over 7dB from 25°C to 85°C. The modulated output power was more than +2.9dBm even at 85°C. These devices are suitable for next-generation, high-speed network systems, such as 40Gbps and 100Gbps Ethernet.

Violet to deep-ultraviolet InGaN∕GaN and GaN∕AlGaN quantum structures for UV electroabsorption modulators

In this paper, we present four GaN based polar quantum structures grown on c-plane embedded in p-i-n diode architecture as a part of high-speed electroabsorption modulators for use in optical communication (free-space non-line-of-sight optical links) in the ultraviolet (UV): the first modulator incorporates ∼4–6nm thick GaN∕AlGaN quantum structures for operation in the deep-UV spectral region and the other three incorporate ∼2–3nm thick InGaN∕GaN quantum structures tuned for operation in violet to near-UV spectral region. Here, we report on the design, epitaxial growth, fabrication, and characterization of these quantum electroabsorption modulators. In reverse bias, these devices exhibit a strong electroabsorption (optical absorption coefficient change in the range of 5500–13000cm−1 with electric field swings of 40–75V∕μm) at their specific operating wavelengths. In this work, we show that these quantum electroabsorption structures hold great promise for future applications in ultraviolet optoelectronics technology such as external modulation and data coding in secure non-line-of-sight communication systems.

A Four-Channel Laser Array with Four 10 Gbps Monolithic EAMs Each Integrated with a DBR Laser

A distributed Bragg reflector (DBR) laser and a high speed electroabsorption modulator (EAM) are integrated on the basis of the selective area growth technique. The typical threshold current is 4 to 6 mA, and the side mode suppression ratio is over 40 dB with single mode operation at 1550 nm. The DBR laser exhibits 2.5 to 3.3 mW fiber output power at a laser gain current of 100 mA, and a modulator bias voltage of 0 V. The 3 dB bandwidth is 13 GHz. A 10 Gbps non-return to zero operation with 12 dB extinction ratio is obtained. A four-channel laser array with 100 GHz wavelength spacing was fabricated and its operation at the designed wavelength was confirmed.

Demonstration of a dual-depletion-region electroabsorption modulator at 1.55-/spl mu/m wavelength for high-speed and low-driving-voltage performance

We demonstrate a novel structure of electroabsorption modulator (EAM) at a 1.55-μm wavelength: the dual-depletion-region EAM. After an n/sup +/ delta-doped layer was inserted into the thick intrinsic region (550 nm) of a tradition p-i-n modulator, the tradeoff between driving-voltage and electrical bandwidth performance can be released effectively. This new structure can also release the burden imposed on downscaling the width or length of high-speed EAM with low driving-voltage performance. The microwave and electrical-to-optical measurement of this novel device with traveling-wave electrodes show very convincing results.

High-Speed Coplanar Waveguide Based Submount for 40 Gbit/s Electroabsorption Modulator

A high-speed submount has been designed and fabricated for 40 Gb/s electroabsorption (EA) modulators. The submount contains a coplanar waveguide (CPW) for microwave signal feeding and a Ta2N thin-film resistor for impedance matching. The CPW transmission line is designed to ensure low microwave loss and reflection, and Ti/Cu/Ni/Au metal is adopted for electrode fabrication to guarantee good contact with the Ta2N thin-film. The typical reflection coefficient of fabricated submount is estimated to be lower than−21 dB up to 40 GHz. As a demonstration, a high-speed EA modulator was chip-level packaged using the high-speed submount, and the measured small-signal modulation bandwidth was over 40 GHz.

10 Gbit s−1 electroabsorption-modulated laser light-source module using selective area MOVPE

A distributed-feedback (DFB) laser and a high-speed electroabsorption (EA) modulator are integrated, on the basis of the selective area MOVPE growth (SAG) technique and the ridge waveguide structure, for a 10 Gbit s−1 optical transmission system. The integrated DFB laser/EA modulator device is packaged in a compact module with a 20% optical coupling efficiency to the single-mode fibre. The typical threshold current is 15 mA, and the side-mode suppression ratio is over 40 dB with the single-mode operation at 1550 nm. The module exhibits 1.2 mW fibre output power at a laser gain current of 70 mA and a modulator bias voltage of 0 V. The 3 dB bandwidth is 12 GHz. A dynamic extinction ratio of over 10 dB has been successfully achieved under 10 Gbit s−1 non-return to zero (NRZ) operation, and a clearly open eye diagram is obtained.

Novel low-cost wideband Si-based submount for 40 Gb/s optoelectronic devices

A novel low-cost wideband Si-based submount is proposed and fabricated for 40-Gb/s optoelectronic devices. The submount contains a coplanar waveguide (CPW) for microwave-signal feeding and a TaN thin-film resistor for impedance matching. The CPW transmission line is directly formed on high-resistivity Si substrate and exhibits a transmission loss as low as 0.165 dB/mm up to 40 GHz. Such a configuration has the advantage of a simplified fabrication procedure and efficient heat dissipation. As a demonstration, a high-speed electroabsorption (EA) modulator is chip-level packaged using the Si-based submount. The small-signal modulation bandwidth is measured to be more than 33 GHz, which is the first report of 40-Gb/s optoelectronic devices on Si-based submount. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 90–93, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20733

High-Speed Electroabsorption Modulators Buried With Ruthenium-Doped SI-InP

InGaAlAs-InAlAs electroabsorption modulators are successfully fabricated using ruthenium (Ru)-doped semi-insulating (SI)-InP burying technology. A comparison of measured and calculated microwave characteristics reveals that there is no additional microwave loss because zinc diffusion is inhibited by the use of Ru-doped SI-InP layers. A small-signal electrooptical response with a -3-dB electrical bandwidth of over 50 GHz is demonstrated.

Editorial: Semiconductor optoelectronics

The papers in this special section, drawn from across these areas, cover a range of topics of significant current research interest in optoelectronics, including: resonant cavity light-emitting diodes (RCLEDs); terahertz pulse generation and detection; high-speed electro-absorption modulators; semiconductor photonic crystals for dispersion control; semiconductor optical amplifiers; planar Bragg gratings; bow-tie laser diodes; and co-doped fibres.

Low insertion loss and low dispersion penalty InGaAsP quantum-well high-speed electroabsorption modulator for 40-Gb/s very-short-reach, long-reach, and long-haul applications

We present a metal-organic-chemical-vapor-deposition-grown low-optical-insertion-loss InGaAsP/InP multiple-quantum-well electroabsorption modulator (EAM), suitable for both nonreturn-to-zero (NRZ) and return-to-zero (RZ) applications. The EAM exhibits a dynamic (RF) extinction ratio of 11.5 dB at 1550 nm for 3 Vp-p drive under 40-Gb/s modulation. The optical insertion loss of the modulator in the on-state is -5.2 dB at 1550 nm. In addition, the EAM also exhibits a 3-dB small-signal response (S21) of greater than 38 GHz, allowing it to be used in both 40-Gb/s NRZ and 10-Gb/s RZ applications. The dispersion penalty at 40 Gb/s is measured to be 1.2 dB over /spl plusmn/40 ps/nm of chromatic dispersion. Finally, we demonstrate 40-Gb/s transmission performance over 85 km and 700 km.

Fiber-length extension in an optical 60-GHz transmission system using an EA-modulator with negative chirp

By optimizing the driving conditions of a highspeed electroabsorption modulator, we achieved a significant fiber-length extension and dispersion penalty reduction in a 60-GHz millimeter-wave indoor fiber-optic transmission system. In particular, we demonstrate simultaneous transmission of two 156-Mb/s data channels in the 60-GHz band over 1409-m standard single-mode fiber without employing an additional dispersion compensation technique.

40 Gbit/s GaAs P-HEMT driver module for optical communications

A 40 Gbit/s driver module incorporating a set of two original double-distributed amplifiers, based on 0.15 µm GaAs P-HEMT (high electron mobility transistor) technology, has been designed and realised. This module provides a state-of-the-art output driving voltage of near 3 Vpp, into a 50 Ω load, and an 18 dB gain over a DC to 41.5 GHz bandwidth; it is able to drive a high speed electroabsorption modulator.