Electroabsorption Modulator Research Articles

Measuring the Electro-Optical Kerr Effect Against the Background of Electro-Absorption Modulation in Liquids.

A new approach to the dynamic polarimetric method is proposed, which allows for the decoupling of electro-optical Kerr effect measurements from the electro-absorption effect in partially transparent liquids. The method is illustrated by using the results of engine oil measurements as a function of temperature and modulating field frequency. It was shown that the birefringence induced in the sample, the modulation of the ordinary wave transmission, and the modulation of the extraordinary wave transmission in the sample can be shifted in phase with respect to the square of the applied alternating modulating field. Each of these three phase shifts can depend differently on the temperature and frequency. Neglecting the influence of electro-absorption on electro-optical measurements in liquids or considering electro-absorption as an effect correlated in phase with induced birefringence may lead to significant measurement errors. This indicates that the Kerr constant and the electro-absorption coefficients for an alternating electric field should be considered as complex quantities instead of real values, as they have been traditionally. The proposed approach fills an important gap in measurement techniques described in the literature, which may provide erroneous results for measurements of the Kerr constant in partially transparent liquids including many industrially important liquids.

Adaptive generation of optical single-sideband signal with dually modulated EML

The optical single sideband (SSB) transmitter based on dual modulation of an electro-absorption modulation laser (D-EML) has attracted considerable attention for its capability of monolithic integration and high output power. A model-based modulation method has been developed recently for generating high-quality optical SSB signals with this D-EML scheme. However, this method requires accurate characterization of the EML’s chirps and pre-compensation for frequency responses of all-optical/electrical components, as well as the path difference between two driving signals. This imposes notable requirements on the transmitter characterization in practical applications. In this paper, we propose an adaptive method to approach the required responses of the pre-compensation filters for this optical SSB transmitter. This method avoids cumbersome device characterization and shows great resilience to the variation of system parameters. By using the proposed adaptive method, we generate a 56 Gb/s optical SSB orthogonal frequency-division multiplexed signal with the sideband suppression power ratio exceeding 21 dB. It is convenient with this method to switch the devices, i.e., directly modulated laser (DML) or electro-absorption modulator (EAM), to be pre-compensated for the optical SSB signal generation. Moreover, this method exhibits good tolerance to the path delay (±15 ps) between DML and EAM, as well as modulation depth. We also successfully transmit this signal over 80 km long standard single-mode fiber.

Bias-controlled modulation for monolithic III-nitride optoelectronic integration.

III-nitride multi-quantum well (MQW) diodes can modulate the light emitted by another diode with the same MQW structure by varying the bias voltage owing to the spectral overlap between the electroluminescence spectrum and spectral responsivity curve of the MQW diodes. Here, we investigate bias-controlled modulation by monolithically integrating an optical transmitter, waveguide, electro-absorption modulator (EAM), and slot grating coupler on a silicon-based III-nitride platform using compatible fabrication processes. The modulated light is coupled into a fiber, which is direct to a photodiode for characterization. The bandwidths of forward-biased emission modulation and reverse-biased absorption modulation are of the same order of magnitude, with the latter exhibiting significant performance improvements. In addition, real-time video signal transmission was achieved using an EAM, which provides a meaningful reference for modulation applications of silicon-based GaN optoelectronic integrated systems.

56 Gbps externally modulated widely tunable lasers with SOA boosters heterogeneously integrated on silicon

We demonstrate externally modulated widely tunable lasers co-integrated with semiconductor optical amplifiers (SOAs) heterogeneously integrated on silicon. The widely tunable laser enables continuous single-mode operation over a tuning range of approximately 40 nm, with a side-mode suppression ratio (SMSR) of at least 50 dB and an average waveguide-coupled optical power of 5 mW. The integrated electro-absorption modulator (EAM) exhibits an extinction ratio (ER) of 16 dB when reversed biased at -2 V. The bit-error-rate (BER) measurements conducted across the available optical bandwidth (15 nm) showcase error-free transmission at 32 Gbps using non-return-to-zero (NRZ) signals for the majority of wavelengths in a back-to-back (B2B) configuration. Additionally, transmission measurements over distances of up to 10 km through a standard single-mode fiber (SSMF) have been successfully demonstrated. Dynamic extinction ratio (DER) values exceeding 4.5 dB are achieved for all wavelengths. Open-eye diagrams were measured up to 56 Gbps. These results demonstrate that this compact mono-epitaxial externally modulated tunable laser with integrated optical amplification can be a cost-effective transmitter solution for dense wavelength division multiplexing (DWDM) metropolitan and access networks.

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.

(Invited) Advanced III-V-on-Si Heterogeneously Integrated Platforms for Next Generation Silicon Photonics Integrated Circuits

The field of Silicon Photonics has experienced a solid and continuous progress over the last few years, gaining in technological maturity, design tools, and new methods [1]. The deployment of low-cost, compact, and power-efficient photonic circuits with a high wafer yield and robustness stands as one of the fundamental pillars that sustain such progress [2]. Presently, photonic circuit technology has diversified its number of available platforms. Despite the fact that indium phosphide (InP) [3] and silicon-on-insulator (SOI) platforms are still considered as the workhorses of integrated photonics in terms of maturity and deployment of active (InP) and passive (SOI) components, other alternatives such as germanium-on-silicon [4], silicon nitride-on-insulator [2] or hybrid solutions combining different functional materials with Si are gaining momentum [5]. A representative example is the heterogeneous III-V/Si platform [6], which has been used to develop compact photonic circuits with on-chip gain. Contrarily to the hybrid integration, the III-V-on-Si heterogeneous integration avoids the constraints of chip-to-chip alignment while enabling the simultaneous integration of hundreds of III-V gain chips in a scalable fashion. Still, the integration methods of such III-V materials on silicon need to be improved to attain the maturity level of the monolithic III-V platform, which benefits from a complete palette of technological solutions not yet available in the III-V-on-Si heterogeneous integration. More recently, an advanced heterogeneous scheme based on wafer-seed-bonding and epitaxial regrowth has emerged [7]–[9]. The ambition is to create a generic integration scheme combining the best offered by the III-V and the Si-photonics platforms. The regrowth capability gives access to the large epitaxial toolkit available in the conventional InP monolithic platform, where several epitaxial steps are often implemented [10][11]. To cite some of them, the epitaxial regrowth of III-V materials to bury III-V lasers bonded onto silicon are object of intense research nowadays to overcome the thermally inefficient buried oxide [12].In this paper, we will review the advances on III-V-on-Si heterogeneous integration through the implementation of several key demonstrators and building blocks for silicon photonics, including on-chip semiconductor optical amplifiers, lasers and electro-absorption modulators. We will discuss the progress and benefits of the direct seed bonding and regrowth as well as new device designs to improve the performance.

Plasmonic-based electro-absorption modulator integrated with different dielectric materials at 1.55 µm wavelength

In this paper an electro-absorption modulator (EAM) based on plasmonic material along with different dielectric materials were investigated. The study focuses on the performance matrices of the device based on four different dielectric materials such as hafnium dioxide (HfO2), silicon nitride (Si3N4), boron nitride (hBN), and silicon dioxide (SiO2). A finite element method (FEM) is used to carry out the investigated results like insertion loss (IL), extinction ratio (ER), and figure of merit (FOM). The device yielded a very high ER of 35.42 dB/µm and an IL of 0.02 dB/µm at 1.55 µm wavelength. A modulation frequency (f3dB) of 0.46 THz, 1.50 THz, 2.39 THz, and 4.24 THz was achieved for the EAMs with HfO2, Si3N4, hBN, and SiO2as the dielectric material, respectively. Also, the investigated EAM with different dielectric materials has the potential to be integrated in Photonic Integrated Circuits (PICs).

Partial coherence enhances parallelized photonic computing

Advancements in optical coherence control1–5 have unlocked many cutting-edge applications, including long-haul communication, light detection and ranging (LiDAR) and optical coherence tomography6–8. Prevailing wisdom suggests that using more coherent light sources leads to enhanced system performance and device functionalities9–11. Our study introduces a photonic convolutional processing system that takes advantage of partially coherent light to boost computing parallelism without substantially sacrificing accuracy, potentially enabling larger-size photonic tensor cores. The reduction of the degree of coherence optimizes bandwidth use in the photonic convolutional processing system. This breakthrough challenges the traditional belief that coherence is essential or even advantageous in integrated photonic accelerators, thereby enabling the use of light sources with less rigorous feedback control and thermal-management requirements for high-throughput photonic computing. Here we demonstrate such a system in two photonic platforms for computing applications: a photonic tensor core using phase-change-material photonic memories that delivers parallel convolution operations to classify the gaits of ten patients with Parkinson’s disease with 92.2% accuracy (92.7% theoretically) and a silicon photonic tensor core with embedded electro-absorption modulators (EAMs) to facilitate 0.108 tera operations per second (TOPS) convolutional processing for classifying the Modified National Institute of Standards and Technology (MNIST) handwritten digits dataset with 92.4% accuracy (95.0% theoretically).

Micro-transfer printed high-speed InP-based electro-absorption modulator on silicon-on-insulator

A high-speed InP-based electro-absorption modulator (EAM) on 220 nm silicon-on-insulator (SOI) is designed, fabricated, and measured. The III–V device is heterogeneously integrated to the SOI using transfer printing, with direct bonding. The printing accuracy of the device was within ±0.5 μm. This design evanescently couples light between the III–V waveguide and the SOI via a taper region in the InP ridge for high transmission. This method is a flexible and robust method of transferring an InP EAM to SOI, where multiple device variations have been transferred. At 1550 nm, the printed EAM has a measured electrical bandwidth of up to 40 GHz, an extinction ratio (ER) of 30 dB from 0 to −6 V, and an insertion loss of 6.5 dB, which reduces with longer wavelengths. An ER of 25 dB is obtained over a spectral bandwidth of 30 nm with biasing to −8 V. Open-eye diagrams were measured up to 50 Gbps in a back-to-back measurement. This device is suitable for applications in high-speed communications and sensing, leveraging the added advantage of III–V absorption modulation on a silicon photonics platform.

Performance improvement of 1.3 μm InAlGaAs MQW modulators grown by MOVPE using C-doped InAl(Ga)As cladding layers

We propose a novel epitaxial layer structure to prevent Zn from diffusing into a multiple quantum well (MQW) layer of an electro-absorption modulator (EAM). Zn is practically employed as a p-type dopant in an InP material system, but there is a technical issue of unintentional Zn diffusion. In this work, we introduce a novel C-doped p-type layer between a Zn-doped p-cladding layer of InP and MQW to both reduce Zn diffusion and accurately define a p-i-n junction interface. The Zn concentrations in the MQW for each device are compared by measuring secondary ion mass spectrometry (SIMS). To clarify how the reduction of diffused Zn affects the EAM characteristics, we fabricate the EAMs with each epitaxial structure and compare their extinction ratio characteristics. The evaluation of extinction ratio per EAM capacitance successfully demonstrates that employing the C-doped layer effectively improves the EAM characteristics.

Investigation of Dual-Layer Si-ITO-Dielectric Based Hybrid Plasmonic Electro-Absorption Modulator at 1.55 µm Wavelength

ABSTRACT In this paper, a dual-layer plasmonic material-based electro-absorption modulator (EAM) is designed and investigated. Indium-tin-oxide (ITO), along with dielectric materials such as boron nitride (hBN) and hafnium dioxide (HfO2), is integrated into the Si waveguide for tuning the light propagating inside the device. The device showed enhanced performance in terms of extinction ratio (ER) = 34.48 dB/µm, the figure of merit (FOM) = 493, and insertion loss (IL) = 0.06 dB/µm for On-state at 1.55 µm wavelength. Also, the dual-state behavior of the EAM was observed and investigated. An IL of 22.22 dB/µm and 25.39 dB/µm was observed for the Off-On and On-Off configurations, respectively. A modulation frequency ( f 3 dB ) of 1.72 THz and 340 GHz was achieved for the EAM with hBN and HfO2 as the dielectric material. The investigated EAM with different dielectric materials has the potential to be integrated into future-generation photonic integrated circuits (PICs).

Electro-absorption modulated 53 Gbps widely tunable laser based on half-wave V-coupled cavities.

In this paper, a 53 Gbps widely tunable transmitter is experimentally demonstrated for the first time, to our knowledge. An InGaAlAs/InP multiple-quantum-well (MQW) wafer is used with an identical layer structure for both the V-coupled cavity laser (VCL) and the electro-absorption modulator (EAM). The VCL uses a shallow-etched waveguide to reduce loss, while the EAM uses a deep-etched waveguide to increase the 3-dB modulation bandwidth. With the temperature varying from 19.5 to 30°C, the transmitter achieves wavelength tuning of 42 channels with a spacing of 100 GHz, corresponding to a tuning range of 32.6 nm from 1538.94 to 1571.54 nm. The static extinction ratio (ER) for all channels is higher than 14 dB. The measured 3-dB electro-optic (E0) bandwidth of the transmitter is over 40 GHz, which fits well with the calculated 3-dB bandwidth. At a fixed peak-to-peak driving voltage of 2.4 V, all channels exhibit clearly an open eye diagram with a 53 Gbps non-return-to-zero (NRZ) signal, while the dynamic ER is higher than 4.5 dB.

Graphene-Based Silicon Photonic Electro-Absorption Modulators and Phase Modulators

Graphene-Based Silicon Photonic Electro-Absorption Modulators and Phase Modulators

Computation of the near-infrared electro-absorption in GeSn/SiGeSn step quantum wells

In this study, we propose a theoretical simulation of the type-I step quantum well obtained from GeSn/SiGeSn to scan a wide range of telecommunication wavelengths and obtain near-infrared optical modulators. At T = 300 K, the band discontinuities and energy gap between stretched Ge1−xSnx and relaxed Si0.1Ge0.9−ySny due to the acquisition of the heterostructure were calculated.Then, optimization of this heterostructure based on (Si) GeSn was performed using the solid theory model to balance out the composition y of Si0.1Ge0.9-ySny relaxed and thickness of Ge0.91Sn0.09 QWs. The eigenenergies and their related wavefunctions are computed by solving the Schrödinger equation using the finite difference method under the framework of the effective mass approximation. Depending on the y concentration, the energy levels of the electron and the heavy hole, the change of transition energies and oscillator strength were examined for different well widths. Additionally, the absorption coefficient with y concentration and structure parameters were examined.From the findings obtained, it was determined that this material group is very important to obtain high efficiency from electro-absorption modulators covering the 1.55 μm wavelength range.

Nanophotonic integrated active-passive InP membrane devices and circuits fabricated using ArF scanner lithography

We present a novel fabrication approach to an integrated nanophotonic platform, based on a III-V membrane bonded to a Si substrate with benzocyclobutene (BCB). The process incorporates a hybrid lithography strategy combining deep-UV and electron-beam lithography on the same wafer. We report for the first time the usage of deep-UV scanner lithography for the fabrication of the active-passive tapers and sub-micron waveguides on the same wafer, which enables better critical dimension control, uniformity, and reproducibility. The platform uses an active-passive butt-joint interface and includes components such as distributed feedback (DFB) and distributed Bragg reflector (DBR) lasers, electro-optical (EO) and electro-absorption (EA) modulators, and sub-micron ultra-confined passive waveguides, all monolithically integrated into a single membrane layer. The active devices have a heat sink achieved by ultra-thin BCB bonding. Lasers demonstrate up to 26 mW of optical power in the waveguide and a direct modulation bandwidth of up to 21 GHz. The modulators show static extinction up to 28.8 dB.

Highly efficient single-layer graphene electro-absorption modulator.

We propose a single-layer graphene electro-absorption modulator (EAM) with an angled waveguide sidewall. By utilizing the hybridization of the TM0 mode and the TE1 mode in the waveguide, the light-graphene interaction is enhanced. A modulation depth of 0.124 dB/µm and a figure of merit up to 25 are obtained at 1550 nm. Moreover, we show that the longitudinal electric field plays a significant role in making the optical absorption efficient, which indicates that modulation depth can be increased by enhancing the longitudinal electric field in modulators. This provides a promising solution for the future design of graphene optical modulators.

225 Gb/s PAM4 2 km and 10 km Transmission of Electro-Absorption Modulator Integrated Laser With Hybrid Waveguide Structure for 800 Gb/s and 1.6 Tb/s Transceivers

225 Gb/s PAM4 2 km and 10 km Transmission of Electro-Absorption Modulator Integrated Laser With Hybrid Waveguide Structure for 800 Gb/s and 1.6 Tb/s Transceivers

Different modulation schemes for direct and external modulators based on various laser sources

Abstract Different types of laser source modulation techniques have been used in various applications depending on the objective. As optical systems extract the laws and the best solutions from experiments and simulations, the present study uses simulation software with different modulation types so the output signals can be compared. The modulators used are Mach-Zehnder, which is an external modulator, and electro-absorption modulator and laser rate equation modulator, which are direct modulators. All these types have an optical link multimode (MM) fiber with a photodiode in the receiver end that can be modeled. The input and output signals are analyzed using different types of modulations.

Graphene-based hybrid plasmonic optical electro-absorption modulator on InP platform

Graphene-based hybrid plasmonic optical electro-absorption modulator on InP platform

Improvement in bandwidth of an electro-absorption modulator by optical pre-emphasis utilizing photon-photon resonance

Improvement in bandwidth of an electro-absorption modulator by optical pre-emphasis utilizing photon-photon resonance