Showing papers on "Optical modulator published in 2019"
TL;DR: In this paper, the authors demonstrate a Mach-Zehnder modulator with high linearity, high bandwidth, and low manufacturing cost on a silicon and lithium niobate hybrid integration platform.
Abstract: Optical modulators are at the heart of optical communication links. Ideally, they should feature low loss, low drive voltage, large bandwidth, high linearity, compact footprint and low manufacturing cost. Unfortunately, these criteria have been achieved only on separate occasions. Based on a silicon and lithium niobate hybrid integration platform, we demonstrate Mach–Zehnder modulators that simultaneously fulfil these criteria. The presented device exhibits an insertion loss of 2.5 dB, voltage–length product of 2.2 V cm in single-drive push–pull operation, high linearity, electro-optic bandwidth of at least 70 GHz and modulation rates up to 112 Gbit s−1. The high-performance modulator is realized by seamless integration of a high-contrast waveguide based on lithium niobate—a popular modulator material—with compact, low-loss silicon circuitry. The hybrid platform demonstrated here allows for the combination of ‘best-in-breed’ active and passive components, opening up new avenues for future high-speed, energy-efficient and cost-effective optical communication networks. Low-loss, high-speed and efficient optical modulators on a silicon platform are demonstrated.
558 citations
318 citations
TL;DR: In this article, the authors demonstrate a 12.5 cm2, 90nm-thick graphene metamaterial with approximately 85% absorptivity of unpolarized, visible and near-infrared light covering almost the entire solar spectrum.
Abstract: Broadband strong light absorption of unpolarized light over a wide range of angles in a large-area ultrathin film is critical for applications such as photovoltaics, photodetectors, thermal emitters and optical modulators. Despite long-standing efforts in design and fabrication, it has been challenging to achieve all these desired properties simultaneously. We experimentally demonstrate a 12.5 cm2, 90-nm-thick graphene metamaterial with approximately 85% absorptivity of unpolarized, visible and near-infrared light covering almost the entire solar spectrum (300–2,500 nm). The metamaterial consists of alternating graphene and dielectric layers; a grating couples the light into waveguide modes to achieve broadband absorption over incident angles up to 60°. The very broad spectral and angular responses of the absorber are ideal for solar thermal applications, as we illustrate by showing heating to 160 °C in natural sunlight. These devices open a novel approach to applications of strongly absorbing large-area photonic devices based on two-dimensional materials. Eighty-five per cent absorptivity of unpolarized light over the wavelength range 300–2,500 nm is realized in a 90-nm-thick, 12.5 cm2 metamaterial.
292 citations
TL;DR: It is proved that the Pockels effect remains strong even in nanoscale devices, and shown as a practical example data modulation up to 50 Gbit s−1.
Abstract: The electro-optical Pockels effect is an essential nonlinear effect used in many applications. The ultrafast modulation of the refractive index is, for example, crucial to optical modulators in photonic circuits. Silicon has emerged as a platform for integrating such compact circuits, but a strong Pockels effect is not available on silicon platforms. Here, we demonstrate a large electro-optical response in silicon photonic devices using barium titanate. We verify the Pockels effect to be the physical origin of the response, with r42 = 923 pm V−1, by confirming key signatures of the Pockels effect in ferroelectrics: the electro-optic response exhibits a crystalline anisotropy, remains strong at high frequencies, and shows hysteresis on changing the electric field. We prove that the Pockels effect remains strong even in nanoscale devices, and show as a practical example data modulation up to 50 Gbit s−1. We foresee that our work will enable novel device concepts with an application area largely extending beyond communication technologies. Electro-optic modulators based on epitaxial barium titanate (BTO) integrated on silicon exhibit speeds up to 50 Gbit s–1 while the Pockels coefficient of the BTO film is found to be approaching the bulk value.
283 citations
TL;DR: In this article, a two-elemental and 2D structural BP-analog monochalcogenide, tin sulfide (SnS), has been demonstrated to show enhanced stability under ambient conditions.
Abstract: Black phosphorus (BP), a typical mono-elemental and two-dimensional (2D) material, has gathered significant attention owing to its distinct optoelectronic properties and promising applications, despite its main obstacle of long-term stability. Consequently, BP-analog materials with long-term chemical stability show additional potential. In this contribution, tin sulfide (SnS), a novel two-elemental and 2D structural BP-analog monochalcogenide, has been demonstrated to show enhanced stability under ambient conditions. The broadband nonlinear optical properties and carrier dynamics have been systematically investigated via Z-scan and transient absorption approaches. The excellent nonlinear absorption coefficient of 50.5×10−3 cm/GW, 1 order of magnitude larger than that of BP, endows the promising application of SnS in ultrafast laser generation. Two different decay times of τ1∼873 fs and τ2∼96.9 ps allow the alteration between pure Q switching and continuous-wave (CW) mode locking in an identical laser resonator. Both mode-locked and Q-switched operations have been experimentally demonstrated using an SnS saturable absorber at the telecommunication window. Femtosecond laser pulses with tunable wavelength and high stability are easily obtained, suggesting the promising potential of SnS as an efficient optical modulator for ultrafast photonics. This primary investigation may be considered an important step towards stable and high-performance BP-analog material-based photonic devices.
157 citations
TL;DR: In this paper, the progress in GST-based PCMs and methods for improving the performance within the context of new applications that have come to light in recent years have been reviewed and discussed.
Abstract: Chalcogenide phase change materials based on germanium-antimony-tellurides (GST-PCMs) have shown outstanding properties in non-volatile memory (NVM) technologies due to their high write and read speeds, reversible phase transition, high degree of scalability, low power consumption, good data retention, and multi-level storage capability. However, GST-based PCMs have shown recent promise in other domains, such as in spatial light modulation, beam steering, and neuromorphic computing. This paper reviews the progress in GST-based PCMs and methods for improving the performance within the context of new applications that have come to light in recent years.
129 citations
128 citations
TL;DR: In this paper, the basic interaction between different optical sources and optical detectors for high-speed optical communication networks has been investigated, and it is observed that the interaction between continuous wave (CW) laser/MZM or CW laser/EAM has presented better performance than other combinations.
Abstract:
The study shows the basic interaction between different optical sources and optical detectors for high-speed optical communication networks. Optical sources that are namely continuous wave (CW) laser, laser rate equations as well as the vertical cavity surface emitting laser (VCSEL). The utilized optical modulators are indicated as Mach Zehnder modulator (MZM) as well as the Electro-absorption modulator (EAM). The data rate available 40 Gb/s for propagation length ranges from 10 km to 50 km. It is observed that the interaction between CW laser/MZM or CW laser/EAM has presented better performance than other combinations. In order to measure the system performances, many interesting parameters have been investigated. These can be including the electrical received power, highest signal quality factor, Optical signal per noise ratio as well as the lowest data error rates.
65 citations
TL;DR: 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.
Abstract: 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.
60 citations
TL;DR: In this paper, a first-principles high-throughput study on more than 4000 semiconductors (with a special focus on oxides) was conducted to investigate the general inverse trend between refractive index and band gap but interesting outliers are also identified.
Abstract: Materials combining both a high refractive index and a wide band gap are of great interest for optoelectronic and sensor applications. However, these two properties are typically described by an inverse correlation with high refractive index appearing in small gap materials and vice versa. Here, we conduct a first-principles high-throughput study on more than 4000 semiconductors (with a special focus on oxides). Our data confirm the general inverse trend between refractive index and band gap but interesting outliers are also identified. The data are then analyzed through a simple model involving two main descriptors: the average optical gap and the effective frequency. The former can be determined directly from the electronic structure of the compounds, but the latter cannot. This calls for further analysis in order to obtain a predictive model. Nonetheless, it turns out that the negative effect of a large band gap on the refractive index can be counterbalanced in two ways: (i) by limiting the difference between the direct band gap and the average optical gap which can be realized by a narrow distribution in energy of the optical transitions and (ii) by increasing the effective frequency which can be achieved through either a high number of transitions from the top of the valence band to the bottom of the conduction band or a high average probability for these transitions. Focusing on oxides, we use our data to investigate how the chemistry influences this inverse relationship and rationalize why certain classes of materials would perform better. Our findings can be used to search for new compounds in many optical applications both in the linear and nonlinear regime (waveguides, optical modulators, laser, frequency converter, etc.).
57 citations
20 Sep 2019
TL;DR: In this paper, the authors investigate the electric field effect on optical properties of a MoS2 monolayer and extract the dependence of MoS 2 optical constants on gating voltage.
Abstract: Two-dimensional materials hold a great promise for developing extremely fast, compact and inexpensive optoelectronic devices. A molybdenum disulphide (MoS2) monolayer is an important example which shows strong, stable and gate tunable optical response even at room temperature near excitonic transitions. However, optical properties of a MoS2monolayer are not documented well. Here, we investigate the electric field effect on optical properties of a MoS2 monolayer and extract the dependence of MoS2 optical constants on gating voltage. The field effect is utilised to achieve ~10% visible light modulation for a hybrid electro-optical waveguide modulator based on MoS2. A suggested hybrid nanostructure consists of a CMOS compatible Si3N4 dielectric waveguide sandwiched between a thin gold film and a MoS2 monolayer which enables a selective enhancement of polarised electro-absorption in a narrow window of angles of incidence and a narrow wavelength range near MoS2 exciton binding energies. The possibility to modulate visible light with 2D materials and the robust nature of light modulation by MoS2 could be useful for creation of reliable ultra-compact electro-optical hybrid visible-light modulators.
TL;DR: In this paper, a few-layer MXene Ti3C2Tx was fabricated and utilized as a saturable absorber (SA) to realize passive Q-switched visible bulk laser covering the spectral range of orange (607nm), red (639nm), and deep red (721 nm).
Abstract: The novel two-dimensional MXenes have been investigated in the photonics field in areas such as broadband nonlinearity, pulse laser generation and passive photonic diode, and so on. In this contribution, the nonlinear optical response at the visible band and the demand pulse laser generation based on MXenes was initially realized. The few-layer MXene Ti3C2Tx was fabricated and utilized as a saturable absorber (SA) to realize passive Q-switched visible bulk laser covering the spectral range of orange (607 nm), red (639 nm), and deep red (721 nm). At the three wavelength, the maximum average output powers and the shortest pulse widths were (111 mW, 426 ns) for 607 nm, (150 mW, 264 ns) for 639 nm, (115 mW, 328 ns) for 721 nm, respectively. Our experimental results indicate the MXene Ti3C2Tx SA could be an efficient and promising optical modulator in the visible domain.
TL;DR: In this paper, a liquid-crystal-filled photonic crystal fiber (PCF) was proposed for electro-optical modulation and the E7 liquid crystal was precisely filled in one of the innermost air holes of the PCF and formed an in-fiber optical coupler, and the resonance wavelength can be tuned with a sensitivity of 5.594nm/V rms when an external voltage is applied.
Abstract: A liquid-crystal-filled photonic crystal fiber (PCF) is proposed for electro-optical modulation. The E7 liquid crystal is precisely filled in one of the innermost air holes of the PCF and forms an in-fiber optical coupler, and the resonance wavelength can be tuned with a sensitivity of 5.594 nm/ V rms when an external voltage is applied. The device can operate as an electro-optical switch/modulator and exhibits response and recovery times of approximately 47 and 24 ms, respectively from 1414 nm to more than 1700 nm. The proposed structure is expected to have potential applications in electric field sensing and wavelength-tunable electro-optical devices.
TL;DR: A novel absorber with bulk Dirac semimetal (BDS)-AlCuFe quasicrystals is proposed to realize bidirectional and dynamically tunable terahertz (THz) perfect absorption.
Abstract: Traditional absorbers are usually sandwich structures in which a metallic ground plane is employed to prevent the transmission. Such absorbers suffer from a major drawback that incident light can only irradiate from the front of the absorbers. In this paper, a novel absorber with bulk Dirac semimetal (BDS)-AlCuFe quasicrystals is proposed to realize bidirectional and dynamically tunable terahertz (THz) perfect absorption. The proposed structure consists of two layers of AlCuFe plates with rectangular apertures and a dielectric spacer. By adjusting transverse distance between the top and bottom rectangular apertures, perfect absorption could be realized under TM polarization. Simulation results show that perfect absorption can be obtained whether light irradiates from the front or back of the system, indicating a performance of bidirectional absorption. In addition, benefiting from the variable Fermi level of AlCuFe, the resonance frequency can be dynamically tuned in the THz range. Our work will stimulate more investigations on BDS-based bidirectional absorbers and optical modulators.
TL;DR: In this article, a general strategy for tailoring the bandwidth of an optical absorber (to broaden or narrow it) is presented based on the coupled-mode theory, and it is shown that by increasing the layer number of graphene and adjusting structure parameters, the broadband absorber at critical coupling could be realized.
Abstract: For an optical absorber, its efficiency and bandwidth determine ultimately its light-collection performance. A general way to realize the high-efficiency absorption and manipulate the absorption bandwidth is certainly important and highly desired. In this paper, based on the coupled-mode theory, a general strategy for tailoring the bandwidth of an absorber (to broaden or narrow it) is presented. A graphene-based absorber integrated with a lossless resonator is designed, and it is shown that by increasing the layer number of graphene and adjusting structure parameters, the broadband absorber at critical coupling could be realized. Meanwhile, by adjusting the location of graphene in the structure, an ultra-narrow-band absorber could also be realized. Present work of controlling both efficiency and bandwidth of an absorber would be particularly favorable for applications in light harvesting, light emitting devices, and optical modulators.
TL;DR: In this article, an integrated WDM-compatible multimode optical switching system-on-chip (SoC) for large-capacity optical switching among processors is presented, where the interfaces for the input and output of the processor signals are electrical, and the on-chip data transmission and switching process are optical.
Abstract: The development of optical interconnect techniques greatly expands the communication bandwidth and decreases the power consumption at the same time. It provides a prospective solution for both intra-chip and inter-chip links. Herein reported is an integrated wavelength-division multiplexing (WDM)-compatible multimode optical switching system-on-chip (SoC) for large-capacity optical switching among processors. The interfaces for the input and output of the processor signals are electrical, and the on-chip data transmission and switching process are optical. It includes silicon-based microring optical modulator arrays, mode multiplexers/ de-multiplexers, optical switches, microring wavelength de-multiplexers and germanium-silicon high-speed photodetectors. By introducing external multi-wavelength laser sources, the SoC achieved the function of on-chip WDM and mode-division multiplexing (MDM) hybrid-signal data transmission and switching on a standard silicon photonics platform. As a proof of concept, signals with a 25 Gbps data rate are implemented on each microring modulator of the fabricated SoC. We illustrated 25 x 3 x 2 Gbps on-chip data throughput with two-by-two multimode switching functionality through implementing three wavelength-channels and two mode-channel hybrid-multiplexed signals for each multimode transmission waveguide. The architecture of the SoC is flexible to scale, both for the number of supported processors and the data throughput. The demonstration paves the way to a large-capacity multimode optical switching SoC.
TL;DR: In this article, the authors performed power-dependent third-harmonic generation measurements on gated single-layer graphene and detected a significant deviation from the cubic power law expected for a thirdharmonic generating process.
Abstract: Hot electrons dominate the ultrafast (∼fs–ps) optical and electronic properties of metals and semiconductors, and they are exploited in a variety of applications including photovoltaics and photodetection. We perform power-dependent third-harmonic generation measurements on gated single-layer graphene and detect a significant deviation from the cubic power law expected for a third-harmonic generation process. We assign this to the presence of hot electrons. Our results indicate that the performance of nonlinear photonics devices based on graphene, such as optical modulators and frequency converters, can be affected by changes in the electronic temperature, which might occur due to an increase in absorbed optical power or Joule heating.
TL;DR: In this paper, a few-layer graphene oxide (GO) dispersions is successfully synthesized using liquid-phase exfoliation and the nonlinear optical response of GO is investigated by the spatial self-phase modulation (SSPM) experiments.
TL;DR: It is found that the compact optical modulators fabricated showed an additional loss in the OFF state, which is attributable to a structural effect, and an 8-µm-long device showed a large extinction ratio of more than 33 dB.
Abstract: We have fabricated compact optical modulators consisting of a Si waveguide with a VO2 cladding layer. These devices showed a sharp decrease in transmittance at around 60 °C, which is attributable to the metal-insulator transition of the VO2 cladding layer. By systematically varying the length of the device, we evaluated the transmission losses per unit length of the device to be 1.27 dB/µm, when the VO2 cladding layer was in the insulating (ON) state and 4.55 dB/µm when it was in the metallic (OFF) state. Furthermore, we found that the device showed an additional loss in the OFF state, which is attributable to a structural effect. As a result, an 8-µm-long device showed a large extinction ratio of more than 33 dB.
TL;DR: In this paper, an all-optical modulator with high modulation efficiency based on a graphene-plasmonic slot waveguide structure is proposed, where the modulation efficiency is enhanced by the strong interaction between the light and the graphene structure.
Abstract: An all-optical modulator with high modulation efficiency based on a graphene-plasmonic slot waveguide structure is proposed. The modulation efficiency is enhanced by the strong interaction between the light and the graphene–plasmonic structure. A modulation efficiency of 0.21 dB μm−1 is obtained with the signal light at a wavelength of 1550 nm. A graphene–plasmonic slot waveguide device of length of 10 μm is fabricated in the experiment. Benefiting from the strong modulation, it is a promising candidate as an on-chip optical modulator with high modulation efficiency and micrometer-scale footprint.
TL;DR: In this paper, a high-speed electro-optic modulator based on CMOS compatible silicon waveguide is proposed, which is formed by creating a slot in a rib structure that results in a strong optical confinement with an acceptably low propagation loss.
TL;DR: In this article, a high efficiency intensity/phase modulator by exploiting ultra-thin silicon strip waveguide (UTSSW) structure is presented, where the propagating transverse electric (TE) mode is less confined to the core of silicon and penetrate deeper into the cladding SiO2 layer, making the double-layer graphene closer to the maximum of electric field.
Abstract: Based on the electro-absorption/electro-refraction effect of graphene, we present a high efficiency intensity/phase modulator by exploiting ultra-thin silicon strip waveguide (UTSSW) structure. Due to the special structure of UTSSW, the propagating transverse electric (TE) mode is less confined to the core of silicon and penetrate deeper into the cladding SiO2 layer, which makes the double-layer graphene closer to the maximum of electric field. The combination of UTSSW structure and double-layer graphene facilitate low insertion loss (IL) together with high modulation efficiency modulator. The graphene intensity/phase modulator performances are comprehensively studied in terms of attenuation, IL, modulation depth (MD), optical operation bandwidth, phase shift, energy per bit (Ebit) consumption, and 3-dB electro-optic bandwidth. With graphene chemical potential μ = 0 eV, the MD is about 0.297 dB/μm, 0.304 dB/μm, 0.306 dB/μm for typical incident light wavelength λ = 1310 nm, 1550 nm, 2000 nm, respectively. When the electro-refraction working region is set between 0.6 eV and 1.0 eV, the $\Delta {\rm{Re}}({{\rm{n}}_{{\rm{eff}}}})$ keeps >6.8 × 10−3 with the wavelength increasing from 1250 nm to 2000 nm, which can be used for phase modulation. The maximum value of $\Delta {\rm{Re}}({{\rm{n}}_{{\rm{eff}}}})$ is 8.055 × 10−3 at incident light wavelength of 1616 nm. The 3-dB electro-optic bandwidth of graphene intensity/phase optical modulator are estimated by using an RC circuit model. Moreover, performances metrics dependence on the distance between the capacitor plates d and the doping level (EF) of transferred graphene are quantitatively analyzed and described. Finally, the quantum capacitance of designed graphene-based intensity modulator with different charged impurity concentration are also discussed when graphene μ = 0 eV and μ = 0.6 eV, respectively.
TL;DR: In this paper, the current state of knowledge and progress of developing optical modulators, photodetectors, and emitters based on Ge/SiGe quantum wells are discussed.
Abstract: Germanium/Silicon-Germanium (Ge/SiGe) multiple quantum wells receive great attention for the realization of Si-based optical modulators, photodetectors, and light emitters for short distance optical interconnects on Si chips. Ge quantum wells incorporated between SiGe barriers, allowing a strong electro-absorption mechanism of the quantum-confined Stark effect (QCSE) within telecommunication wavelengths. In this review, we respectively discuss the current state of knowledge and progress of developing optical modulators, photodetectors, and emitters based on Ge/SiGe quantum wells. Key performance parameters, including extinction ratio, optical loss, swing bias voltages, and electric fields, and modulation bandwidth for optical modulators, dark currents, and optical responsivities for photodetectors, and emission characteristics of the structures will be presented.
TL;DR: In this paper, the authors performed power-dependent third harmonic generation measurements on gated single-layer graphene and detected a significant deviation from the cubic power-law expected for a third harmonic generator.
Abstract: Hot electrons dominate the ultrafast ($\sim$fs-ps) optical and electronic properties of metals and semiconductors and they are exploited in a variety of applications including photovoltaics and photodetection. We perform power-dependent third harmonic generation measurements on gated single-layer graphene and detect a significant deviation from the cubic power-law expected for a third harmonic generation process. We assign this to the presence of hot electrons. Our results indicate that the performance of nonlinear photonics devices based on graphene, such as optical modulators and frequency converters, can be affected by changes in the electronic temperature, which might occur due to increase of absorbed optical power or Joule heating.
TL;DR: In this article, the authors demonstrate intensity-modulated direct-detection optical transmission at a record-high data rate with single wavelength and single polarization using a digital-preprocessed analog-multiplexed digital-to-analog converter with a >100 GHz analog multiplexer (AMUX) to drive an 80 GHz Mach-Zehnder optical modulator (MZM).
Abstract: We demonstrate intensity-modulated direct-detection optical transmission at a record-high data rate with single wavelength and single polarization. The high data rate is achieved with simple optics by using electronic and electrooptic devices with large operation bandwidths. We use a digital-preprocessed analog-multiplexed digital-to-analog converter with a >100-GHz analog multiplexer (AMUX) to drive an 80-GHz Mach–Zehnder optical modulator (MZM). The AMUX is based on 0.25-μm-emitter-width InP heterojunction bipolar transistor technology, and the MZM has InP n-i-p-n heterostructure optical waveguides with capacitance-loaded travelling-wave electrodes. We employ discrete multi-tone modulation controlled by a margin-adaptive bit-loading algorithm. In the experiment, the signal was transmitted over a 20-km dispersion-compensated single-mode fiber link and received by a single photodiode followed by a digital signal processor including a nonlinear equalizer. At a gross bit rate of 400 Gb/s, the bit error rate of the received signal was below the threshold of 20% overhead soft-decision forward error correction code. This result corresponds to a net data rate of 333 Gb/s.
TL;DR: Meander line electrodes broke the phase mismatch limit and enhanced the cutoff frequency by up to 31 and 38 GHz using 50 Ω and 20 Ω termination resistors, respectively, and greatly improved the quality of the modulation characteristics at 25 and 32 Gbps.
Abstract: We demonstrate 64 Gbps operation in a compact Si photonic crystal optical modulator that employs meander line electrodes and compensate for the phase mismatch between slow light and RF signals. Although low dispersion slow light increases the modulation efficiency, maintaining a sufficiently wide working spectrum, the phase mismatch becomes a limiting factor on the operation speed even when the phase shifter length is as short as 200 μm. Meander line electrodes broke this limit and enhanced the cutoff frequency by up to 31 and 38 GHz using 50 Ω and 20 Ω termination resistors, respectively. This allowed to use a group index of slow light higher than 20, and greatly improved the quality of the modulation characteristics at 25 and 32 Gbps. Clear open eye was observed even at 40–64 Gbps.
TL;DR: In this paper, the authors theoretically investigated the structural stability, electronic and optical properties of the sandwich graphene-MoSe2-graphene heterostructure via the density functional theory (DFT).
10 Oct 2019
TL;DR: In this paper, the performance of InP modulators based on the Franz-Keldysh effect (bulk) and the quantum confined Stark effect (quantum-well) is investigated for wavelengths ranging within 1460 nm-1580 nm.
Abstract: Heterogeneous integration of InP modulators on a silicon photonic platform, fabricated by bonding III–V wafer on patterned silicon waveguides, are proved to work between 77 K and 295 K. The performance of modulators based on the Franz-Keldysh effect (bulk) and the quantum confined Stark effect (quantum-well) is investigated for wavelengths ranging within 1460 nm–1580 nm. The bulk modulator is preferred when operating over a wide range of temperatures. The demonstration of such integrated optical components at low temperatures is especially attractive for applications that demand massive data communication between cryogenic and room temperatures requiring photonic interconnect, as well as applications with extreme environmental conditions, such as outer space exploration.
TL;DR: The experimental results prove that the Cr2Ge2Te6 has outstanding nonlinear optical properties and advantages in performing as an ultra-fast optical modulator and provide valuable references and open new avenues for developing two-dimensional, material-based, ultra- fast optical modulators and advanced photonic devices based on Cr2 Ge 2Te6.
Abstract: In this manuscript, the nonlinear absorption properties of Cr2Ge2Te6 and its application in ultra-fast optical modulation are investigated. Typical parameters, namely, nonlinear absorption coefficient (β), saturation intensity, and modulation depth are measured to be ~1.66 × 10−9 m/W, 15.3 MW/cm2, and 5.8%, respectively. To investigate the feasibility of using the Cr2Ge2Te6 as an ultra-fast optical modulator, a ring-cavity passively mode-locked Er-doped fiber laser has been constructed. The output power/pulse, duration/pulse, and repetition rate/signal-to-noise ratios for the stable mode-locked operation are 2.88 mW/881 fs/19.33 MHz/48 dB, respectively, which proves that the Cr2Ge2Te6 has outstanding nonlinear optical properties and advantages in performing as an ultra-fast optical modulator. Further, the experimental results provide valuable references and open new avenues for developing two-dimensional, material-based, ultra-fast optical modulators and advanced photonic devices based on Cr2Ge2Te6.
TL;DR: The results fully present the capacity of CGT in designing bright-dark soliton operations and provide a meaningful reference for promoting the ultra-fast modulation applications of ferromagnetic insulators.
Abstract: Novel two-dimensional (2D)-materials-based ultra-fast modulators exhibit significance in extending the fundamental investigations and practical applications of mode-locked fiber lasers. In our work, employing the liquid-phase exfoliation method, a ${{\rm Cr}_2}{{\rm Ge}_2}{{\rm Te}_6}$Cr2Ge2Te6 (CGT) optical modulator with a modulation depth and a saturable intensity of 1.64% and ${6.31}\,\,{{\rm MW/cm}^2}$6.31MW/cm2 was fabricated. Due to its suitable modulation properties and high nonlinear coefficient, a stable bright-dark soliton pair was successfully achieved within an Er-doped fiber laser. Under the pump power of 560 mW, the maximum average output power was 5.36 mW with a pulse repetition rate of 1.835 MHz. Our results fully present the capacity of CGT in designing bright-dark soliton operations and provide a meaningful reference for promoting the ultra-fast modulation applications of ferromagnetic insulators.