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Showing papers on "Optical modulator published in 2017"


Journal ArticleDOI
TL;DR: Up-to-date 2D material-based optical modulation in three categories is reviewed: free-space, fiber-based, and on-chip configurations and the outlook for future opportunities of these 2D materials for optical modulation is given.
Abstract: Owing to their atomic layer thickness, strong light–material interaction, high nonlinearity, broadband optical response, fast relaxation, controllable optoelectronic properties, and high compatibility with other photonic structures, 2D materials, including graphene, transition metal dichalcogenides and black phosphorus, have been attracting increasing attention for photonic applications. By tuning the carrier density via electrical or optical means that modifies their physical properties (e.g., Fermi level or nonlinear absorption), optical response of the 2D materials can be instantly changed, making them versatile nanostructures for optical modulation. Here, up-to-date 2D material-based optical modulation in three categories is reviewed: free-space, fiber-based, and on-chip configurations. By analysing cons and pros of different modulation approaches from material and mechanism aspects, the challenges faced by using these materials for device applications are presented. In addition, thermal effects (e.g., laser induced damage) in 2D materials, which are critical to practical applications, are also discussed. Finally, the outlook for future opportunities of these 2D materials for optical modulation is given.

361 citations


Journal ArticleDOI
TL;DR: Xiao et al. as mentioned in this paper investigated the physical origin of the strong excitonic effect and unique optical selection rules in 2D semiconductors and examined control of these excitons by optical, electrical, as well as mechanical means.
Abstract: Author(s): Xiao, J; Zhao, M; Wang, Y; Zhang, X | Abstract: The research on emerging layered two-dimensional (2D) semiconductors, such as molybdenum disulfide (MoS2), reveals unique optical properties generating significant interest. Experimentally, these materials were observed to host extremely strong light-matter interactions as a result of the enhanced excitonic effect in two dimensions. Thus, understanding and manipulating the excitons are crucial to unlocking the potential of 2D materials for future photonic and optoelectronic devices. In this review, we unravel the physical origin of the strong excitonic effect and unique optical selection rules in 2D semiconductors. In addition, control of these excitons by optical, electrical, as well as mechanical means is examined. Finally, the resultant devices such as excitonic light emitting diodes, lasers, optical modulators, and coupling in an optical cavity are overviewed, demonstrating how excitons can shape future 2D optoelectronics.

154 citations


BookDOI
22 Jun 2017
TL;DR: This guide outlines the means by which one can get started with digital holography as well as introduce phase-only, amplitude- only, and complex amplitude modulation as tools to create structured light fields in the laboratory.
Abstract: The shaping of light fields, a topic of interest to the optics community for some time, has taken many forms, e.g., from coherent field mapping to diffusing elements for incoherent light shaping. Since the advent of the laser, structuring laser light in amplitude and phase has been achieved outside the laser cavity (with refractive, adaptive, and diffractive elements) and inside the laser cavity (through a variety of amplitude or phase objects that force the laser internally to oscillate on particular transverse modes). We will not discuss in detail the contribution of these tools for controlling light, but the reader is referred to the references provided for further details. Instead, we will consider a modern derivative of the above, namely shaping light with computer-generated holograms (digital holograms) using spatial light modulators (SLMs). Digital holography for structured light has enabled many new advances, ranging from classical to quantum physics, including communication, microscopy, imaging, metrology, and education. The advent of liquid crystal on silicon (LCoS) SLMs has made the aforementioned techniques accessible to the inexperienced researcher. LCoS devices, colloquially referred to as SLMs, have allowed researchers to display computer-generated holograms as images; thus, controlling light digitally can be realized with just a little know-how. Here, we will show how to “get started” with SLMs for the creation and detection of structured light fields. This guide focuses on the shaping of coherent light with these tools. We outline the means by which one can get started with digital holography as well as introduce phase-only, amplitude-only, and complex amplitude modulation as tools to create structured light fields in the laboratory.

146 citations


Journal ArticleDOI
TL;DR: In this article, an InGaAsP/Si hybrid metal-oxide-semiconductor (MOS) optical modulator is proposed for Si photonics, which exhibits a phase-modulation efficiency of 0.047 Vcm and low optical attenuation of 0.,23 dB at π phase shift at 1.55 µm wavelength, which is approximately 5 times higher and 10 times lower than Si MOS optical modulators.
Abstract: Hybrid InGaAsP/Si optical modulator gives silicon photonics an efficient scheme for phase modulation. An optical modulator integrated on silicon is a key enabler for high-performance optical interconnects1,2,3,4,5,6. However, Si-based optical modulators suffer from low phase-modulation efficiency owing to the weak plasma dispersion effect in Si, which also results in large optical loss. Therefore, it is essential to find a novel modulation scheme for Si photonics. Here, we demonstrate an InGaAsP/Si hybrid metal-oxide–semiconductor (MOS) optical modulator formed by direct wafer bonding7,8. Electron accumulation at the InGaAsP MOS interface enables the utilization of the electron-induced refractive index change in InGaAsP, which is significantly greater than that in Si (refs 9,10). The presented modulator exhibits a phase-modulation efficiency of 0.047 Vcm and low optical attenuation of 0.23 dB at π phase shift at 1.55 μm wavelength, which are approximately 5 times higher and 10 times lower than Si MOS optical modulators11,12,13,14,15,16,17, respectively. This approach provides a new, high-performance phase-modulation scheme for Si photonics.

139 citations


Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate an MZ modulator with a 250µm-long InGaAsP/Si metal-oxide-semiconductor (MOS) capacitor phase-shifter and obtain a VπL of 0.09
Abstract: Hybrid silicon optical modulator brings efficiency benefits. Demand for more transmission capacity in data centres is increasing due to the continuous growth of Internet traffic. The introduction of external modulators into datacom networks is essential with advanced modulation formats. However, the large footprint of silicon photonics Mach–Zehnder (MZ) modulators will limit further increases in transmission capacity1,2,3,4. To overcome this, we introduce III–V compound semiconductors because the large electron-induced refractive-index change, high electron mobility and low carrier-plasma absorption are beneficial for overcoming the trade-offs among the voltage–length product (VπL), operation speed and insertion loss of Si MZ modulators. Here, we demonstrate an MZ modulator with a 250-µm-long InGaAsP/Si metal-oxide–semiconductor (MOS) capacitor phase-shifter and obtain a VπL of 0.09 Vcm in accumulation mode, an insertion loss of ∼1.0 dB, a cutoff frequency of ∼2.2 GHz in depletion mode and a 32-Gbit s–1 modulation with signal pre-emphasis. These results are promising for fabricating high-capacity large-scale photonic integrated circuits with low power consumption.

135 citations


Journal ArticleDOI
TL;DR: In this paper, a prototype device for all-optical thresholding and optical modulation using few-layer phosphorene-decorated microfibers is presented, which can enhance the signal-to-noise ratio and reshape the deteriorated signal pulse.
Abstract: Phosphorene, mono/few-layered black phosphorous with advantages of tunable energy bandgaps and strong light–matter interaction, is fabricated by electrochemical intercalation with large area (≈3 µm) and controllable thickness (mainly four layers). Thanks to the direct gap and resonant absorption of four-layer phosphorene at the telecommunication band, all-optical thresholding and optical modulation are demonstrated for optical communications by using few-layer phosphorene-decorated microfibers. This device is experimentally verified as an efficient noise suppressor that can enhance the signal-to-noise ratio and reshape the deteriorated signal pulse, and also as an optical modulator that can switch the signal on/off by pumping light. The findings, as the first prototypic device of all-optical thresholding and optical modulation, might facilitate the development of phosphorene-based optical communication technologies.

131 citations


Journal ArticleDOI
TL;DR: It is found that the ReS2-covered D-shaped fiber (RDF) displays the remarkable polarization-induced absorption, which indicates the different responses for transverse electric (TE) and transverse magnetic (TM) polarizations relative to ReS1 plane.
Abstract: Monolayer of transition metal dichalcogenides (TMDs), with lamellar structure as that of graphene, has attracted significant attentions in optoelectronics and photonics. Here, we focus on the optical absorption response of a new member TMDs, rhenium disulphide (ReS2) whose monolayer and bulk forms have the nearly identical band structures. The nonlinear saturable and polarization-induced absorption of ReS2 are investigated at near-infrared communication band beyond its bandgap. It is found that the ReS2-covered D-shaped fiber (RDF) displays the remarkable polarization-induced absorption, which indicates the different responses for transverse electric (TE) and transverse magnetic (TM) polarizations relative to ReS2 plane. Nonlinear saturable absorption of RDF exhibits the similar saturable fluence of several tens of μJ/cm2 and modulation depth of about 1% for ultrafast pulses with two orthogonal polarizations. RDF is utilized as a saturable absorber to achieve self-started mode-locking operation in an Er-doped fiber laser. The results broaden the operation wavelength of ReS2 from visible light to around 1550 nm, and numerous applications may benefit from the anisotropic and nonlinear absorption characteristics of ReS2, such as in-line optical polarizers, high-power pulsed lasers, and optical communication system.

111 citations


Journal ArticleDOI
TL;DR: It is shown that EO coefficients as large as 190 pm/V can be obtained in 150 nm wide plasmonic slot waveguides but that the coefficients decrease for narrower slots, and record-low voltage-length products are shown for slot widths in the order of 50 nm for the materials JRD1 and DLD164.
Abstract: The performance of highly nonlinear organic electro-optic (EO) materials incorporated into nanoscale slots is examined. It is shown that EO coefficients as large as 190 pm/V can be obtained in 150 nm wide plasmonic slot waveguides but that the coefficients decrease for narrower slots. Possible mechanism that lead to such a decrease are discussed. Monte-Carlo computer simulations are performed, confirming that chromophore-surface interactions are one important factor influencing the EO coefficient in narrow plasmonic slots. These highly nonlinear materials are of particular interest for applications in optical modulators. However, in modulators the key parameters are the voltage-length product UπL and the insertion loss rather than the linear EO coefficients. We show record-low voltage-length products of 70 Vµm and 50 Vµm for slot widths in the order of 50 nm for the materials JRD1 and DLD164, respectively. This is because the nonlinear interaction is enhanced in narrow slot and thereby compensates for the reduced EO coefficient. Likewise, it is found that lowest insertion losses are observed for slot widths in the range 60 to 100 nm.

111 citations


Journal ArticleDOI
TL;DR: In this paper, a high-bandwidth InP-based Mach-Zehnder modulator and in-phase/quadrature (IQ) modulators were proposed by combining an n-i-p-n heterostructure and a capacitively loaded traveling wave electrode.
Abstract: We report novel high-bandwidth InP-based Mach–Zehnder modulator and in-phase/quadrature (IQ) modulators that we realized by combining an n-i-p-n heterostructure and a capacitively loaded traveling wave electrode. The extremely low electrical and optical loss structure enhances the 3-dB electro-optic bandwidth of over 67 GHz without degrading other properties such as driving voltage and optical loss. The modulator also exhibits a static extinction ratio of over 24 dB with a V π of less than 1.5 V for the entire C-band. Furthermore, we demonstrate the first 120-Gbaud rate IQ modulation without optical pre equalization, and 100-Gb/s non-return-to-zero on-off keying modulation with a dynamic extinction ratio of over 10 dB.

107 citations


Journal ArticleDOI
TL;DR: Measurements of the infrared optical response of thin black phosphorus under field-effect modulation suggest the potential for use of black phosphorus as an active material in mid-infrared optoelectronic modulator applications.
Abstract: We report measurements of the infrared optical response of thin black phosphorus under field-effect modulation. We interpret the observed spectral changes as a combination of an ambipolar Burstein–Moss (BM) shift of the absorption edge due to band-filling under gate control, and a quantum confined Franz-Keldysh (QCFK) effect, phenomena that have been proposed theoretically to occur for black phosphorus under an applied electric field. Distinct optical responses are observed depending on the flake thickness and starting carrier concentration. Transmission extinction modulation amplitudes of more than two percent are observed, suggesting the potential for use of black phosphorus as an active material in mid-infrared optoelectronic modulator applications.

96 citations


Journal ArticleDOI
TL;DR: It is shown that, despite their binary amplitude-only modulation, DMDs are capable of higher beam-shaping fidelity compared to LC-SLMs in all considered regimes.
Abstract: Digital micro-mirror devices (DMDs) have recently emerged as practical spatial light modulators (SLMs) for applications in photonics, primarily due to their modulation rates, which exceed by several orders of magnitude those of the already well-established nematic liquid crystal (LC)-based SLMs. This, however, comes at the expense of limited modulation depth and diffraction efficiency. Here we compare the beam-shaping fidelity of both technologies when applied to light control in complex environments, including an aberrated optical system, a highly scattering layer and a multimode optical fibre. We show that, despite their binary amplitude-only modulation, DMDs are capable of higher beam-shaping fidelity compared to LC-SLMs in all considered regimes.

Patent
18 May 2017
TL;DR: In this article, a light source system consisting of a light emitting device, a light splitting system, a first spatial light modulator, a second spatial modulator and a second spatio-temporal modulator is described.
Abstract: The embodiment of the invention discloses a light source system which comprises a light emitting device, a light splitting system, a first spatial light modulator and a second spatial light modulator. The light emitting device is used for emitting first light and second light in sequence. The light splitting system is used for splitting the first light from the light emitting device into first range wavelength light and second range wavelength light which are emitted along a first light channel and a second light channel respectively and further used for emitting at least some second light from the light emitting device along the first light channel. The first spatial light modulator is used for modulating the light emitted by the light splitting system along the first light channel. The second spatial light modulator is used for modulating at least some light emitted by the light splitting system along the second light channel. The light source system is high in light emitting efficiency and low in cost.

Journal ArticleDOI
TL;DR: This represents the shortest pulses in Q-switched MIR lasers based on a 2D material as the saturable absorber, which demonstrated the superiority of ReS2 acting as an optical modulator for generating short-pulsed lasers.
Abstract: A novel two-dimensional (2D) material member in the transition metal dichalcogenides family, few-layered rhenium disulfide (ReS2) was prepared by liquid phase method successfully. By using the open-aperture Z-scan method, the saturable absorption properties at 2.8 μm were characterized with a saturable fluence of 22.6 μJ/cm2 and a modulation depth of 9.7%. A passively Q-switched solid-state laser at 2.8 μm was demonstrated by using the as-prepared ReS2 saturable absorber successfully. Under an absorbed pump power of 920 mW, a maximum output power of 104 mW was obtained with a pulse width of 324 ns and a repetition rate of 126 kHz. To the best of our knowledge, this is the first demonstration of applying ReS2 in an all-solid-state laser. Moreover, this represents the shortest pulses in Q-switched MIR lasers based on a 2D material as the saturable absorber, which demonstrated the superiority of ReS2 acting as an optical modulator for generating short-pulsed lasers. The results well prove that 2D ReS2 is a reliable optical modulator for MIR solid-state lasers.

Journal ArticleDOI
TL;DR: In this article, a holistic analysis for high-performance and ultra-compact electro-optic modulators on-chip is presented, based on physical tradeoffs such as index modulation, loss, optical confinement factors and slow-light effects.
Abstract: Electro-optic modulation is a key function in optical data communication and possible future optical computing engines. The performance of modulators intricately depends on the interaction between the actively modulated material and the propagating waveguide mode. While high-performing modulators were demonstrated before, the approaches were taken as ad-hoc. Here we show the first systematic investigation to incorporate a holistic analysis for high-performance and ultra-compact electro-optic modulators on-chip. We show that intricate interplay between active modulation material and optical mode plays a key role in the device operation. Based on physical tradeoffs such as index modulation, loss, optical confinement factors and slow-light effects, we find that bias-material-mode regions exist where high phase modulation and high loss (absorption) modulation is found. This work paves the way for a holistic design rule of electro-optic modulators for on-chip integration.

Journal ArticleDOI
Gui-Dong Liu1, Xiang Zhai1, Sheng-Xuan Xia1, Qi Lin1, Chujun Zhao1, Ling-Ling Wang1 
TL;DR: Numerical simulation results show that the transmission amplitude of the toroidal dipolar resonance can be efficiently modulated by varying the Fermi energy EF when the graphene layer is integrated with the dielectric metasurface, and a max transmission coefficient difference up to 78% is achieved indicating that the proposed hybrid graphene/dielectric meetasurfaces shows good performance as an optical modulator.
Abstract: In this paper, we demonstrate the combination of a dielectric metasurface with a graphene layer to realize a high performance toroidal resonance based optical modulator. The dielectric metasurface consists of two mirrored asymmetric silicon split-ring resonators (ASSRRs) that can support strong toroidal dipolar resonance with narrow line width (~0.77 nm) and high quality (Q)-factor (~1702) and contrast ratio (~100%). Numerical simulation results show that the transmission amplitude of the toroidal dipolar resonance can be efficiently modulated by varying the Fermi energy EF when the graphene layer is integrated with the dielectric metasurface, and a max transmission coefficient difference up to 78% is achieved indicating that the proposed hybrid graphene/dielectric metasurface shows good performance as an optical modulator. The effects of the asymmetry degree of the ASSRRs on the toroidal dipolar resonance are studied and the efficiency of the transmission amplitude modulation of graphene is also investigated. Our results may also provide potential applications in optical filter and bio-chemical sensing.

Journal ArticleDOI
TL;DR: In this paper, a high-speed optical phase modulator based on graphene-silicon waveguide (GSW) is presented, where two graphene flakes, sandwiched by insulating dielectric spacers, are embedded in a silicon waveguide to enhance the interaction between the graphene and light.
Abstract: A high-speed optical phase modulator based on graphene-silicon waveguide (GSW) is presented. Two graphene flakes, sandwiched by insulating dielectric spacers, are embedded in a silicon waveguide to enhance the interaction between the graphene and light. By applying a bias on the graphene flakes, the refractive index variation of TE mode in the waveguide shows a large quasi-linear dynamic range, which is ideal for achieving optical phase modulation. Based on this structure, a π phase shift can be achieved by a 75.6 μm-long GSW. Calculations show that the 3 dB modulation bandwidth of the optical phase modulator can be as high as 119.5 GHz with a low consumption of 0.452 pJ/bit.

Journal ArticleDOI
TL;DR: In this paper, the authors show that the overall losses, power consumption and the footprint of plasmonic electro-optic modulators can be reduced when a device is operated in the vicinity of absorption resonances of an electrooptical material.
Abstract: The electro-optic coefficient (Pockels coefficient) is largest around the absorption resonance of a material Here, we show that the overall losses, the power consumption and the footprint of plasmonic electro-optic modulators can be reduced when a device is operated in the vicinity of absorption resonances of an electro-optical material This near-resonant operation in plasmonics is contrary to what is known from photonics where off-resonant operation is required to minimize the overall losses The findings are supported by experiments demonstrating a reduction in voltage-length product by a factor of 3 and a reduction in loss by a factor 2 when operating a plasmonic modulator near resonance compared to off-resonant

Journal ArticleDOI
TL;DR: Broadband atomic-layer MoS2 optical modulators for the visible ultrafast pulse generation are developed and selected based on the proposed design criteria for novel two-dimensional (2D) optical modulator.
Abstract: Visible lasers are a fascinating regime, and their significance is illustrated by the 2014 Noble prizes in physics and chemistry. With the development of blue laser diodes (LDs), the LD-pumped solid-state visible lasers become a burgeoning direction today. Constrained by the scarce visible optical modulators, the solid-state ultrafast visible lasers are rarely realized. Based on the bandgap structure and optoelectronic properties of atomic-layer MoS2, it can be proposed that MoS2 has the potential as a visible optical modulator. Here, by originally revealing layer-dependent nonlinear absorption of the atomic-layer MoS2 in the visible range, broadband atomic-layer MoS2 optical modulators for the visible ultrafast pulse generation are developed and selected based on the proposed design criteria for novel two-dimensional (2D) optical modulators. By applying the selected MoS2 optical modulators in the solid-state praseodymium lasers, broadband mode-locked ultrafast lasers from 522 to 639 nm are originally realized. We believe that this Letter should promote the development of visible ultrafast photonics and further applications of 2D optoelectronic materials.

Proceedings ArticleDOI
27 Mar 2017
TL;DR: Detailed electrical and optical models of the elements that comprise a WDM silicon photonic link are presented to analyze the energy consumption and scalability of the link by finding the right combination of channels × data rate per channel that fully covers the available optical power budget.
Abstract: We present detailed electrical and optical models of the elements that comprise a WDM silicon photonic link. The electronics is assumed to be based on 65 nm CMOS node and the optical modulators and demultiplexers are based on microring resonators. The goal of this study is to analyze the energy consumption and scalability of the link by finding the right combination of (number of channels × data rate per channel) that fully covers the available optical power budget. Based on the set of empirical and analytical models presented in this work, a maximum capacity of 0.75 Tbps can be envisioned for a point-to-point link with an energy consumption of 1.9 pJ/bit. Sub-pJ/bit energy consumption is also predicted for aggregated bitrates up to 0.35 Tbps.

Journal ArticleDOI
TL;DR: In this article, a hybrid Si-PCM optical modulator was proposed by integrating vanadium dioxide (a PCM) within a Si photonic waveguide, in a non-resonant geometry.
Abstract: Phase-change materials (PCMs) have emerged as promising active elements in silicon (Si) photonic systems. In this work, we design, fabricate, and characterize a hybrid Si-PCM optical modulator. By integrating vanadium dioxide (a PCM) within a Si photonic waveguide, in a non-resonant geometry, we demonstrate ~ 10 dB broadband modulation with a PCM length of 500 nm.

Journal ArticleDOI
TL;DR: Proposed GHMM waveguides could offer great opportunities in the field of integrated photonics that are compatible with CMOS technology, especially since such structures can be utilized as photonic memory cells, tunable optical buffers, delays, optical modulators etc.
Abstract: The tunability of slow light in graphene-based hyperbolic metamaterial waveguide operating in SCLU telecom bands is investigated. For the first time it has been shown that proper design of a GHMM structure forming waveguide layer and the geometry of the waveguide itself allows stopped light to be obtained in an almost freely selected range of wavelengths within SCLU bands. In particular, the possibility of controlling light propagation in GHMM waveguides by external biasing has been presented. The change of external electric field enables the stop light of the selected wavelength as well as the control of a number of modes, which can be stopped, cut off or supported. Proposed GHMM waveguides could offer great opportunities in the field of integrated photonics that are compatible with CMOS technology, especially since such structures can be utilized as photonic memory cells, tunable optical buffers, delays, optical modulators etc.

Journal ArticleDOI
Meiyong Fan1, Huimin Yang1, Pengfei Zheng1, Guohua Hu1, Binfeng Yun1, Yiping Cui1 
TL;DR: A graphene electro-absorption optical modulator based on double-stripe silicon nitride waveguide and the graphene layers co-electrode design is proposed and analyzed, which can remedy the lack of high speed modulator on the passive silicon nitrite waveguide.
Abstract: A graphene electro-absorption optical modulator based on double-stripe silicon nitride waveguide is proposed and analyzed. By embedding four graphene layers in the double-stripe silicon nitride waveguide and the graphene layers co-electrode design, the total metal-graphene contact resistance can be reduced 50% and as high as 30.6GHz modulation bandwidth can be achieved theoretically. The calculated extinction ratio and figure of merit are 0.1658dB/um and 9.7, respectively. And the required switching voltage from its minimum to maximum absorption state is 3.8180V and 780.50fJ/bit power consuming can be achieved. The proposed modulator can remedy the lack of high speed modulator on the passive silicon nitride waveguide.

Journal ArticleDOI
TL;DR: This work achieves optical focusing through scattering media by using polarization modulation based generalized DOPC using an inexpensive twisted nematic liquid crystal based spatial light modulator (SLM) and experimentally demonstrates light focusing through 3-mm thick chicken breast tissue.
Abstract: Optical scattering prevents light from being focused through thick biological tissue at depths greater than ∼1 mm. To break this optical diffusion limit, digital optical phase conjugation (DOPC) based wavefront shaping techniques are being actively developed. Previous DOPC systems employed spatial light modulators that modulated either the phase or the amplitude of the conjugate light field. Here, we achieve optical focusing through scattering media by using polarization modulation based generalized DOPC. First, we describe an algorithm to extract the polarization map from the measured scattered field. Then, we validate the algorithm through numerical simulations and find that the focusing contrast achieved by polarization modulation is similar to that achieved by phase modulation. Finally, we build a system using an inexpensive twisted nematic liquid crystal based spatial light modulator (SLM) and experimentally demonstrate light focusing through 3-mm thick chicken breast tissue. Since the polarization modulation based SLMs are widely used in displays and are having more and more pixel counts with the prevalence of 4 K displays, these SLMs are inexpensive and valuable devices for wavefront shaping.

Journal ArticleDOI
05 May 2017
TL;DR: In this article, the authors reported the first actively Q-switched laser with a GEOM, which achieved high-repetition-rate, electrically modulated ultrafast pulses with output energies of up to 123 nJ.
Abstract: Graphene electro-optic modulators (GEOMs) are emerging as a viable alternative to conventional material-based modulators mainly due to their broadband and ultrafast performance. These GEOMs with combined advantages of small footprint and low energy consumption can potentially enable various high-performance applications that are not possible using conventional approaches. Here, we report the first actively Q-switched lasers with a GEOM. In contrast to the previously reported lasers that are passively modulated by two-dimensional layered material-based saturable absorbers, our actively modulated laser concept represents significant advantages, such as electrically tunable output parameters (e.g. output repetition rate, pulse duration and pulse energy) and electro-optical synchronization. Using a single GEOM, we generate broadband Q-switched pulses at ~1.55 and 2 μm with output energies of up to 123 nJ. This indicates the broadband pulse generation capability of the graphene-based active devices, superior to widely used bulk material-based active modulation approaches. Our results demonstrate a simple and viable design towards broadband, high-repetition-rate, electrically modulated ultrafast lasers for various applications, such as telecommunications and spectroscopy.

Journal ArticleDOI
Jun Guo1, Leiming Wu1, Xiaoyu Dai1, Yuanjiang Xiang1, Dianyuan Fan1 
TL;DR: In this article, the authors proposed a graphene/planar waveguide hybrid structure, and demonstrated total absorption in the visible wavelength range by means of attenuated total reflectance, and achieved broadband absorption enhancement in near-IR range by cascading multiple graphene-waveguide hybrid structures.
Abstract: We propose a graphene/planar waveguide hybrid structure, and demonstrate total absorption in the visible wavelength range by means of attenuated total reflectance. The excitation of planar waveguide mode, which has strong near field enhancement and increased light interaction length with graphene, plays a vital role in total absorption. We analyze the origin and physical insight of total absorption theoretically by using an approximated reflectance, and show how to design such hybrid structure numerically. Utilizing the tunability of doped graphene, we discuss the possible application in optical modulators. We also achieve broadband absorption enhancement in near-IR range by cascading multiple graphene-waveguide hybrid structures. We believe our results will be useful not only for potential applications in optical devices, but also for studying other two-dimension materials.

Journal ArticleDOI
TL;DR: In this paper, a horizontal slot Si-VO2-Si optical waveguide is proposed and its optical properties are investigated, and it is shown that the effective index and the propagation loss of the proposed waveguide undergo substantial changes upon the VO2 transition from insulating to metallic phase.
Abstract: In this paper, a horizontal slot Si–VO2–Si optical waveguide is proposed and its optical properties are investigated. Numerical simulation results show that the effective index and the propagation loss of the proposed waveguide undergo substantial changes upon the VO2 transition from insulating to metallic phase. The effective index and the propagation loss variations of the proposed waveguide are then maximized by optimizing waveguide dimensions. It is shown that 0.226 change in the effective index (Δ n eff = 0.226) and 30 dB/ μ m change in the propagation loss (Δ l dB = 30 dB/μm) are achievable using the optimum dimensions. These extraordinary variations in waveguide properties recommend the proposed waveguide as an excellent candidate for optical active device realization. To investigate these applications, performance parameters of the proposed waveguide are further studied in terms of the transition speed and the power consumption. In these studies, the VO2 phase transition is assumed to be actuated by applying an electric field. Two examples of optical active devices based on the proposed waveguide are then presented: an electro-absorption modulator and a 1 × 2 directional coupler optical switch. Finite-difference time-domain simulation of the proposed devices shows very high extinction ratio of 21 dB along the ultrasmall propagation length of 1 μ m, for the proposed electro-absorption modulator, and high extinction ratios of ∼18.5 dB and ∼8.6 dB in off - and on -state of the proposed 1 × 2 switch, which has very small length of ∼6 μ m. Further simulations also show interesting properties of the proposed devices in terms of the power consumption, insertion loss, and bandwidth.

Journal ArticleDOI
TL;DR: This work demonstrates a method of generating broadband vector beams with dynamically tunable intensity, phase and polarisation over a bandwidth of 100 nm, and uses this system to generate radially and azimuthally polarised vector vortex beams carrying orbital angular momentum and beams whose polarisation states span the majority of the Poincaré sphere.
Abstract: Spatial structuring of the intensity, phase and polarisation of light is useful in a wide variety of modern applications, from microscopy to optical communications. This shaping is most commonly achieved using liquid crystal spatial light modulators (LC-SLMs). However, the inherent chromatic dispersion of LC-SLMs when used as diffractive elements presents a challenge to the extension of such techniques from monochromatic to broadband light. In this work we demonstrate a method of generating broadband vector beams with dynamically tunable intensity, phase and polarisation over a bandwidth of 100 nm. We use our system to generate radially and azimuthally polarised vector vortex beams carrying orbital angular momentum, and beams whose polarisation states span the majority of the Poincare sphere. We characterise these broadband vector beams using spatially and spectrally resolved Stokes measurements, and detail the technical and fundamental limitations of our technique, including beam generation fidelity and efficiency. The broadband vector beam shaper that we demonstrate here may find use in applications such as ultrafast beam shaping and white light microscopy.

Journal ArticleDOI
TL;DR: A novel metasurface modulator based on electro-optic polymer that utilizes bimodal resonance inside a metallic subwavelength grating to increase the modulation efficiency and is potentially applicable to high-speed surface-normal modulators.
Abstract: Electrically tunable metasurfaces have gained special interest as they can realize ultrathin surface-normal modulators in planar geometries. In this paper, we demonstrate a novel metasurface modulator based on electro-optic (EO) polymer that utilizes bimodal resonance inside a metallic subwavelength grating to increase the modulation efficiency. When two metal-insulator-metal (MIM) resonant modes are excited simultaneously inside the grating, they couple strongly to generate a sharp dip in the reflected spectrum. As a result, efficient intensity modulation with 15-dB extinction ratio can be obtained at the resonant wavelength under a small refractive index change of 8.5 × 10-3, corresponding to modulation voltage of less than 10 V. Due to the low parasitic capacitance of EO polymer and high conductivity of metallic gratings which is also used as the electrodes, the RC bandwidth of the device should easily exceed 100 GHz, potentially applicable to high-speed surface-normal modulators.

Proceedings ArticleDOI
19 Mar 2017
TL;DR: The progress on high speed silicon photonic modulators based on dispersion plasma effect is reviewed and the demonstrations of silicon-based 90 Gbaud intensity modulator, 100G CWDM4 transmitter, I-Q modulator and optical frequency comb generator are presented.
Abstract: We review the progress on high speed silicon photonic modulators based on dispersion plasma effect. We present the demonstrations of silicon-based 90 Gbaud intensity modulator, 100G CWDM4 transmitter, I-Q modulator and optical frequency comb generator.

Journal ArticleDOI
TL;DR: The large-area MoSe2 possessing superior nonlinear optical properties compared to exfoliated nanoflakes affords possibility for the larger-area two-dimensional materials family as high performance optical devices.
Abstract: Transition metal dichalcogenides (TMDs) have been successfully used as broadband optical modulator materials for pulsed fiber laser systems. However, the nonlinear optical absorptions of exfoliated TMDs are strongly limited by their nanoflakes morphology with uncontrollable lateral size and thickness. In this work, we provide an effective method to fully explore the nonlinear optical properties of MoSe2. Large-area and high quality lattice MoSe2 grown by chemical vapor deposition method was adopted as an optical modulator for the first time. The large-area MoSe2 shows excellent nonlinear optical absorption with a large modulation depth of 21.7% and small saturable intensity of 9.4 MW cm-2. After incorporating the MoSe2 optical modulator into fiber laser cavity as a saturable absorber, a highly stable Q-switching operation with single pulse energy of 224 nJ is achieved. The large-area MoSe2 possessing superior nonlinear optical properties compared to exfoliated nanoflakes affords possibility for the larger-area two-dimensional materials family as high performance optical devices.