Showing papers on "Optical modulator published in 2023"

Metasurface-enabled polarization-independent LCoS spatial light modulator for 4K resolution and beyond

Abstract: With the distinct advantages of high resolution, small pixel size, and multi-level pure phase modulation, liquid crystal on silicon (LCoS) devices afford precise and reconfigurable spatial light modulation that enables versatile applications ranging from micro-displays to optical communications. However, LCoS devices suffer from a long-standing problem of polarization-dependent response in that they only perform phase modulation on one linear polarization of light, and polarization-independent phase modulation-essential for most applications-have had to use complicated polarization-diversity optics. We propose and demonstrate, for the first time, an LCoS device that directly achieves high-performance polarization-independent phase modulation at telecommunication wavelengths with 4K resolution and beyond by embedding a polarization-rotating metasurface between the LCoS backplane and the liquid crystal phase-modulating layer. We verify the device with a number of typical polarization-independent application functions including beam steering, holographical display, and in a key optical switching element - wavelength selective switch (WSS), demonstrating the significant benefits in terms of both configuration simplification and performance improvement.

Microtopography‐Guided Double‐Layer Cross Structure for a Terahertz Multiband Amplitude Modulator

Abstract: Terahertz (THz) modulator can be used to modulate the amplitude and frequency of THz wave. A THz multiband amplitude modulator based on temperature control is proposed in this study. The metamaterial structure of proposed modulator is a double‐layer cross structure which attached on a silicon substrate, and the cross‐distribution of different materials in top and middle layer is Cu @ SiO2 and SiO2 @ VO2, respectively. To prepare the modulator, a microtopographic substrate‐guided method with low‐cost and high accuracy capacities is proposed. Finally, the proposed modulator exhibits above 70% transmittance in 1.31–1.36 THz, 1.55–1.60 THz, and 1.76–1.79 THz, respectively, at 35 °C After temperature rises to 70 °C, transmittance decreases below 0.1 in 1–2 THz. The similarity of the experimental and simulated transmission is up to 85.67%, and the mean modulation depth (MD) is 0.73. The performance can fulfill the applications in THz amplitude modulator, and due to the large modulation depth of transmission, the proposed modulator can be used as a filter switch. It also indicates the proposed method can be effectively applied in other multilayer composite materials preparation.

Electrically switchable and tunable infrared light modulator based on functional graphene metasurface

Abstract: Abstract Graphene is emerging as an ideal material for new-generation optoelectronic devices. In this paper, a novel graphene metasurface-based electrically switchable and tunable infrared light modulator has been proposed and theoretically studied. The functional modulator comprises a monolayer graphene sheet sandwiched in a Fabry–Perot (FP) like nanostructure consisting of a metal reflector, a dielectric spacer, and an ellipse patterned anisotropy antenna layer. As a result of the photon localization effect of the guided-mode resonance (GMR) in the FP structure, the graphene electroabsorption can be significantly enhanced to enable a high-performance light modulator. By fine-tuning the Fermi energy (Ef) of graphene via controlling its bias-gate voltage, the proposed modulator can switch between a perfect absorber and a reflective polarization converter of high conversion efficiency (i.e., >90%) at 1550 nm. The conversion mechanism and the geometric dependences of the infrared light modulator have been investigated. We further demonstrated the tunability of the highly-efficient polarization converter over a broad spectrum by adjusting the real dispersion of Ef. Our design concept provides an effective strategy for customizing novel optoelectronic devices by combining an electrically-tunable 2D material with a functional metasurface.

Versatile Tunning of Compact Microring Waveguide Resonator Based on Lithium Niobate Thin Films

Abstract: With the advancement of modulation technology and the requirement for device miniaturization and integration, lithium niobate on insulator (LNOI) can be a versatile platform for this pursuit, as it can confine the transmitted light at the nanoscale, leading to a strong light–matter interaction, which can sensitively capture external variations, such as electric fields and temperature. This paper presents a compact microring modulator with versatile tuning based on X-cut LNOI. The LNOI modulator equipped with electrodes with a coverage angle of 120∘ achieved a maximum electro-optic (EO) tuning efficiency of 13 pm/V and a maximum extinction ratio of 11 dB. The asymmetry in the static or quasi-static electro-optic tuning of the microring modulator was also analyzed. Furthermore, we measured the thermal-optic effect of the device with a sensitivity of 26.33 pm/∘C, which can potentially monitor the environment temperature or compensate for devices’ functional behavior. The demonstrated efficient and versatile compact microring modulator will be an important platform for on-chip active or passive photonic components, microring-based sensor arrays and integrated optics.

Reconfigurable Geometrical Phase Spatial Light Modulator Using Short-Pitch Ferroelectric Liquid Crystals

Abstract: Abstract This article shows a fast continuous 2π geometrical phase modulator based on the dynamic optical axis rotation of the short-pitch Ferroelectric Liquid Crystal (FLC). A continuous multi-level (8-bit) phase modulation, fast switching time (< 250 μs at 2 kHz), low operating voltage (< 7 V), and high diffraction efficiency (> 77%) is achieved using defect-free Deformed Helix Ferroelectric Liquid Crystal (DHFLC) for the first time. We showed a minimum feature size of 1 µm without fringe field effect (FFE). We also developed a new FLC with a cone angle of ~85˚ and a way to provide compensated half-wave condition (HW) during the entire electro-optical operational range. As a result, we achieve both spatial and time modulation with high frequency (1/3 μm -1 and 4 kHz, respectively), which can be used in applications such as a real-time hologram and dynamic beam steering in Light Ranging and Detector (LiDAR).

Low half-wave voltage polymeric electro-optic modulator using CLD-1/PMMA for electrocardiogram (ECG) signal acquisition.

Abstract: Electro-optic (EO) modulators are typically made of inorganic materials such as lithium niobate; the replacement of these modulators with organic EO materials is a promising alternative due to their lower half-wave voltage (Vπ), ease of handling, and relatively low cost. We propose the design and fabrication of a push-pull polymer electro-optic modulator with voltage-length parameters (VπL) of 1.28 V·cm. The device uses a Mach-Zehnder structure and is made of a second-order nonlinear optical host-guest polymer composed of a CLD-1 chromophore and PMMA polymer. The experimental results show that the loss is 1.7 dB, Vπ drops to 1.6 V, and the modulation depth is 0.637 dB at 1550 nm. The results of a preliminary study show that the device is capable of efficiently detecting electrocardiogram (ECG) signals with performance on par with that of commercial ECG devices.

Study of Electrical and Optical Peaking of Si Ring Modulators for Tailoring Modulation Band

Abstract: An operation scheme using electrical peaking and optical peaking to engineer the modulation band of a Si microring modulator is presented. By incorporating an inductor design at the metal traces of a Si microring modulator, the driving signal can be magnified near the peaking frequency. Although adjusting the wavelength detuning of a ring modulator also introduces optical peaking to extend the 3-dB roll-off frequency, using inductive peaking has no detrimental effect on the low-frequency response. By exploiting both effects, the modulation band can be tailored with more degrees of freedom. We accomplish a Si microring modulator design with a wide and flat transmission band over 95 GHz, which is potentially applied for a non-return-to-zero (NRZ) data transmission over 120 Gbit/s without extra signal post-compensation.

Traveling-Wave Mach–Zehnder Modulator Integrated with Electro-Optic Frequency-Domain Equalizer for Broadband Modulation

Abstract: Broadband modulator is a key component of future high-capacity and high-baud-rate optical fiber communication. An electro-optic (EO) frequency-domain equalizer is proposed and investigated to increase the 3-dB bandwidth of optical modulators. The equalizer can be integrated with conventional traveling-wave modulators using a crossing waveguide, U-turn waveguide, or ferroelectric-domain-inversion. The 3-dB bandwidth of the modulator can be doubled by integrating the equalizer. As a theoretical consideration, we modeled several types of EO equalizers and investigated the function and parameter dependency of the equalizers in detail. For the experimental demonstration, a titanium-diffused lithium niobate optical waveguide modulator integrated with the EO equalizer was fabricated. The optical loss including fiber-coupling was as low as 5.4 dB, and the half-wave voltage was 3.7 V. The measured electro-optic response at 110 GHz is –0.4 dB, and that of the 3-dB bandwidth is larger than 110 GHz, which is the upper frequency limit of our measurement equipment. The 3-dB bandwidth of the modulator estimated using the fitting curve obtained from the measured electrical propagation loss of the modulator electrode was approximately 200 GHz.

Simulation and design of cascade modulator based on lithium niobate thin film

Abstract: Integrated electro-optical modulators play an important role in fields such as broadband wireless communication and phase code radar. Electro-optical modulator based on Lithium Niobate (LN) ridge waveguide is easy to be integrated and has good electro-optical response. In this paper, a cascade modulator based on the lithium niobate thin-film structure is designed to achieve both the phase and intensity modulation. The structure parameters of the modulator are determined through collaborative simulation, then the phase modulator and the intensity modulator are simulated. Then, the phase-intensity cascade modulator is simulated to test the output light field in three working states, respectively. The experimental results show that it not only can perform phase modulation or intensity modulation of the input light wave separately, but also can adjust the phase and intensity of the light waves simultaneously.

Compact thin-film lithium niobate modulators using slotted coplanar waveguide electrode suitable for high-volume fabrication

Abstract: Lithium niobate (LN) is a good candidate for fabricating modulators due to its superior material characteristics. However, the application of traditional LN modulators is limited due to their large footprint and low modulation efficiency resulting from weak optical confinement. In recent years, with the development of the thin-film lithium niobate (TFLN) platform and LN etching technology, the size of the optical mode of the TFLN modulator is 20 times smaller than that of the traditional LN modulator. Furthermore, TFLN modulators have demonstrated a wide bandwidth, low half-wave voltage and small footprint in recent reports. The length of the TFLN modulators can be further reduced by employing a folded design and therefore applicable to compact transceiver package, such as being packaged in the quad small form factor pluggable double density transceiver. In this paper, we report on a folded TFLN modulator fabricated from a 4 inch LN wafer, which is suitable for large-volume fabrication. A fiber-to-fiber insertion loss of 2.5 dB and a voltage–length product of 1.85 V cm have been achieved. The measured electro-optic response curve has a 2.3 dB roll-off at 40 GHz, and the simulated 3 dB bandwidth reaches 65 GHz. Compared to traditional coplanar waveguide traveling wave electrodes, the slotted coplanar waveguide traveling wave electrode (slotted CPW-TWE) design adopted in this work allows adjusting the high-speed characteristics and modulation efficiency with more flexibility. This is the first time a slotted CPW-TWE design has been applied in a folded TFLN modulator.

Nonlocal electro-optic metasurfaces for free-space light modulation

Abstract: Abstract Dynamic optical metasurfaces with ultrafast temporal response, i.e., spatiotemporal optical metasurfaces, provide attractive solutions and open fascinating perspectives for modern highly integrated optics and photonics. In this work, electro-optically controlled optical metasurfaces operating in reflection and utilizing resonant waveguide mode excitation are demonstrated from the viewpoint of free-space propagating light modulation. The modulation of reflected light power with superior characteristics in comparison with prior research is achieved by identifying a suitable low-loss waveguide mode and exploiting its resonant excitation. The electro-optic Pockels effect in a 300 nm-thick lithium niobate (LN) film sandwiched between a continuous thick gold film and an array of gold nanostripes, serving also as control electrodes, is exploited to realize fast and efficient light modulation. The fabricated compact (active area <1000 µm2) modulators operate in the wavelength range of 850–950 nm, featuring a maximum intensity modulation depth of 42 % at the driving voltage of ±10 V within the bandwidth of 13.5 MHz (with the potential bandwidth of 6.5 GHz). The introduced nonlocal electro-optic metasurface configuration opens new avenues towards the realization of ultrafast, efficient, and robust free-space light modulators based on an LN flat optics approach.

Optical mid-infrared modulator based on D-shaped photonic crystal fiber and GST phase changing material

Abstract: Abstract Photonic crystal fibers (PCFs) have recently attracted compelling attention because of their numerous applications, particularly in the mid-infrared (mid-IR) wavelength region. In this paper, we have presented and analyzed mid-IR optical modulator based on phase-changing material (PCM) known as germanium-antimony-tellurium (GST) and D-shaped PCF. The modulation process can be performed as the GST material’s phase undergoes a transition between amorphous (on) and crystalline (off) states. To analyze the proposed design numerically, full vectorial finite element method (FVFEM) is employed. Further, we studied the light propagation through the suggested structure using 3D finite difference time domain (FDTD) method. The optical losses of the fundamental transverse electric (TE) mode supported by the reported structure in the two GST states are studied. The obtained extinction ratio (ER) of the proposed modulator approaches 302.61 dB, whereas the insertion loss (IL) is less than 0.00014 dB throughout the wavelength range from 3 to 5.8 μm at a device length (L D ) of 0.2 mm. Therefore, the suggested modulator can be utilized in photonic integrated circuits that require high ER, very low IL, and large optical bandwidth.

Reconfigurable design of a thermo-optically addressed liquid-crystal phase modulator by a neural network.

Abstract: We present a machine learning approach to program the light phase modulation function of an innovative thermo-optically addressed, liquid-crystal based, spatial light modulator (TOA-SLM). The designed neural network is trained with a little amount of experimental data and is enabled to efficiently generate prescribed low-order spatial phase distortions. These results demonstrate the potential of neural network-driven TOA-SLM technology for ultrabroadband and large aperture phase modulation, from adaptive optics to ultrafast pulse shaping.

Efficient and Fast All-Optical Modulator with In Situ Grown MoTe2 Nanosheets on Silicon

Abstract: All-optical modulators play a key role in building all-optical networks for efficient optical signal processing and have attracted intensive attention. In this paper, all-optical modulators with in situ grown molybdenum telluride (MoTe2) nanosheets on silicon are proposed and demonstrated for the first time with a self-developed complementary-metal-oxide-semiconductor (CMOS)-compatible fabrication processes. For the silicon-based all-optical modulators with a MoTe2-integrated microring resonator and microdisk resonator, the modulation is as efficient as 17.76 and 158.48 pm/mW while the rise/fall time is 3.7/3.6 and 1.5/3.3 μs, respectively. This is the highest tuning efficiency and the fastest response speed among all-optical silicon modulators based on the photothermal effect of two-dimensional materials under the out-of-plane pumping configuration. Furthermore, the manufacturing processes of the present devices are developed from in situ grown MoTe2 nanosheets on a silicon-on-insulator platform, which is CMOS-compatible, stable, and suitable for large-scale photonic integration.

Development of thin film quarter-waveplate for polarization-independent liquid crystal on silicon phase modulators

Abstract: Liquid crystal on silicon (LCoS) phase modulators spatially modulate the phase of light across the panel. The orientation order and elongated molecules of nematic liquid crystals (LCs) means that traditional LCoS phase modulators are inherently polarization-dependent, resulting in either complicated polarization manipulation systems or high optical power loss for unpolarized incident light. We propose a polarization-independent LCoS (PI-LCoS) device that combines existing technologies, which allows for cost-effective fabrication. Our PI-LCoS phase modulator is suitable for a wide variety of applications in telecommunication, adaptive optics, and display technologies. We have demonstrated the feasibility of the proposed PI-LCoS device by fabricating polarization-independent LC cells using a thin-film quarter-wave plate composed of a photoalignment layer and a layer of LC polymer. We show experimentally that the proposed design can efficiently modulate the phase of light with arbitrary input polarization.

High-efficiency electro-optic modulator on thin-film lithium niobate with high-permittivity cladding

Abstract: Thin-film lithium niobate is a promising platform owing to its large electro-optic coefficients and low propagation loss. However, the large footprints of devices limit their application in large-scale integrated optical systems. A crucial challenge is how to maintain the performance advantage given the design space restrictions in this situation. This article proposes and demonstrates a high-efficiency lithium niobate electro-optic (EO) modulator with high-permittivity cladding to improve the electric field strength in waveguides and its overlap with optical fields while maintaining low optical loss and broad bandwidth. The proposed modulator exhibits considerable improvement, featuring a low half-wave voltage-length product of 1.41 Vcm, a low excess loss of 0.5 dB, and a broad 3 dB EO bandwidth of more than 40 GHz. This modulation efficiency is the highest reported for a broadband lithium niobate modulator so far. The design scheme of using high-permittivity cladding may provide a promising solution for improving the integration of photonic devices on the thin-film lithium niobate platform and these devices may serve as fundamental components in large-scale photonic integrated circuits in the future.

Near ultraviolet light modulator based on InGaN/AlGaN MQW diode

Abstract: Compared with the direct modulation technology used in traditional visible light communication, the indirect modulation method can share a single light source in multiple channels, which features reduced system size and power consumption. In this paper, a near ultraviolet light modulator with InGaN/AlGaN multiple quantum well (MQW) structure is proposed based on GaN-on-silicon light-emitting diode (LED) wafer. Because the MQW diode structure is consistent with the light source and the photodetector (PD), the modulator can be monolithically integrated with the light source, PD, waveguide and other devices through compatible manufacturing processes. The MQW of the wafer is sandwiched by the waveguide layers and the light emitted by the light source is confined in the waveguide for transmission. The extinction ratio can be adjusted by changing the modulation voltage and the incident signal is loaded onto the optical carrier through the modulator. The optical signal is received by the MQW PD near the end of the waveguide and converted into electrical signal. The results show that the modulator has a significant modulation effect with the extinction ratio greater than 24.4 % and has important application prospects in light processing and transmission.

Ultrafast charge and field driven optical modulators and switches

Abstract: Electro-optic modulators are critical building blocks for many signal processing systems which adhere to requirements given by both electrical and optical constraints. We discuss the fundamental speed limitations of recently developed charge and field driven nanophotonic electro-optic devices enabling the next generation of electro-optic modulators featuring a significantly improved device performance regarding modulation efficiency (VπL ⪅1 Vcm), device footprint (⪅ 1 mm2) and bandwidth (⪆ 100 GHz). We show that the practical limits of the operation speed is for both, ferroelectric Pockels modulators and the proposed transparent conducting oxides (ITO) modulators, determined by the frequency response of the corresponding electronic circuit driving the modulator.

Ultra-compact plexcitonic electro-absorption modulator

Abstract: Compact electro-optic (EO) modulators with large extinction ratios, low-switching energies, and high operation speeds are desirable for integrated photonic and linear optical computing. Traditional 3D semiconductors and dielectrics are unsuitable for achieving such modulators due to the small magnitude of EO effects in them. Excitonic 2D semiconductors present a unique opportunity in this regard given their large and tunable optical constants near the excitonic resonances. However, strategies for confining and electrically tuning the excitons into compact EO modulators have not been realized thus far. Here, we design and simulate an ultra-compact, plexcitonic (strongly-coupled exciton-plasmon) electro-absorption modulator (EAM) with a sub-micron linear footprint operating close to the excitonic peak of the WS2 monolayer (641 nm) hybridized with the plasmon mode of a silver slot waveguide. Electrostatically injected free carriers in WS2 modulate the light-matter interaction via Coulomb screening of the excitons as well as promoting the formation of charged excitons (trions). For our optimized designs, the EAM is expected to achieve a 9.1 dB extinction ratio, concurrently with a 7.6 dB insertion loss in a 400 nm lateral footprint operating with a predicted < 3 fJ/bit switching energy at 15 GHz for 3-dB bandwidth modulation. Our work shows the potential of plexcitonic quasi-particles for integrated optical modulators.

Integrated optics based on electro optic modulators for long distance links and high bit rate communication

Abstract: Abstract This paper has clarified the gallium aluminum arsenide and plastic modulators and its element circuit modeling design considerations for high signal processing distance links communications. Modulator circuit model design considerations and equations analysis are taken into account. Modulator source resistance, modulator inductance, and modulator capacitance based electro-optic modulator (EOM) is studied and analyzed against temperature variations. In addition to the switching voltage for EOM is analyzed at both 1300 nm and 1550 nm wavelength versus temperature variations. The operation efficiency and maximum modulation resonance frequency are studied for previous and proposed EOM versus modulator length variations. The lower modulator resistance, modulator capacitance, and modulator inductance can be achieved with the proposed EOM. As well as the proposed EOM has outlined the optimum operational efficiency and maximum resonance modulation frequency compared to the previous EOM.

Polarization independent silicon on calcium fluoride-based MIR optical modulator

Abstract: Abstract Efficient mid-infrared (MIR) optical modulator is reported and numerically analyzed for both the transverse electric (TE) and transverse magnetic (TM) polarized modes. The proposed design is based on the silicon-on-calcium-fluoride platform with vanadium dioxide (VO 2 ) as a phase changing material. Due to the attractive property of its phase transition between dielectric (ON) and metallic (OFF) states under the effect of an applied electric field, VO 2 is utilized to enable the modulation process. At an operating wavelength of 3.5 μm, the reported modulator realizes an extinction ratio (ER) of 10.9 dB/μm with an insertion loss (IL) of 0.24 dB/μm for the TE polarized mode. However, for the TM polarized mode, an ER, and IL of 9.5 dB/μm, and 0.19 dB/μm, respectively are achieved. Additionally, the suggested design has a good fabrication tolerance of ± 10% where the ER is better than 10.4 dB/μm and 8.6 dB/μm for the TE and TM polarized modes with IL less than 0.26 dB/ μm. Therefore, the suggested modulator can play a pivotal role in different MIR applications including imaging, sensing, security, and communications.

A Route to Ultra‐Fast Amplitude‐Only Spatial Light Modulation using Phase‐Change Materials

Abstract: A phase-change material based, thin-film, amplitude-only spatial light modulator is presented. The modulator operates in reflection and modulates the amplitude of light incident on its surface with no effect on optical phase when the phase-change material is switched between its amorphous and crystalline states. This is achieved using a thin-film device with an embedded, switchable, GeTe phase-change layer. Test modulation patterns are written to the device using laser scans, and the amplitude and phase response measured, using optical spectroscopy and off-axis digital holography. Experimental results reveal reflected intensity to be modulated by up to 38%, with an averaged phase difference of less than ≈π/50. Since phase-change materials such as GeTe can be switched on sub-microsecond timescales, this approach maps out a route for ultra-fast amplitude spatial light modulators with widespread applications in fields such as wavefront shaping, communications, sensing, and imaging.

High-speed polarization-independent plasmonic modulator on a silicon waveguide

Abstract: The electrical bandwidth of an electro-optic modulator plays a vital role in determining the throughput of an optical communications link. We propose a broadband plasmonic electro-optic modulator operating at telecommunications wavelengths (λ 0 ∼ 1550 nm), based on free carrier dispersion in indium tin oxide (ITO). The ITO is driven through its epsilon-near-zero point within the accumulation layers of metal-oxide-semiconductor (MOS) structures. The MOS structures are integrated into a pair of coupled metal-insulator-metal (MIM) waveguides aligned on a planarized silicon waveguide. The coupled MIM waveguides support symmetric and asymmetric plasmonic supermodes, excited adiabatically using mode transformation tapers, by the fundamental TM 0 and TE 0 modes of the underlying silicon waveguide, respectively, such that the modulator can operate in either mode as selected by the input polarisation to the silicon waveguide. The modulator has an active section 1.5 to 2 µm long, enabling the modulator to operate as a lumped element to bandwidths exceeding 200 GHz (3 dB electrical, RC-limited). The modulators produce an extinction ratio in the range of 3.5 to 6 dB, and an insertion loss in the range of 4 to 7.5 dB including input/output mode conversion losses. The AC drive voltage is ±1.75 V. The devices comprise only inorganic materials and are realisable using standard deposition, etching and nanolithography techniques.

High-efficiency thin-film lithium niobate modulator with highly confined optical modes.

Abstract: We demonstrate a low-loss, high-efficiency lithium niobate electro-optic (EO) modulator with optical isolation trenches to achieve stronger field confinement and reduced light absorption loss. The proposed modulator realized considerable improvements, including a low half-wave voltage-length product of 1.2 V·cm, an excess loss of ∼2.4 dB, and a broad 3-dB EO bandwidth of over 40 GHz. We developed a lithium niobate modulator with, to the best of our knowledge, the highest reported modulation efficiency of any Mach-Zehnder interferometer (MZI) modulator.

Design and simulation of high modulation efficiency, low group velocity dispersion lithium niobate slow-wave electro-optic modulator based on a fishbone-like grating

Abstract: • In this paper, we propose an on-chip slow-wave electro-optic modulator with improved modulation efficiency on lithium-niobate-on-insulator platform. • The slow-light effect is realized with flat optical operating bandwidth, near zero group velocity dispersion, and low loss. • A matched micro-structure electrode is designed to realize the low group velocity of the microwave modulation signal. Thin-film lithium niobate (LN) has emerged as an excellent platform for electro-optic modulators (EOMs) owing to its strong electro-optic (Pockels) effect. However, it remains an open challenge to achieve high modulation efficiency in chip-scale EOMs, primarily due to the limitation of light-matter interaction. Here, we propose an on-chip slow-wave LN EOM with a length of 3.4 mm with high modulation efficiency by using a fishbone-like grating. By assembling the fishbone-like grating, the Pockels effect is significantly enhanced as a result of the compression of the local density of states. Benefiting from this effect, the modulation efficiency of the modulator can be improved to 4.6 times of the original. In addition, a 3 mm matched micro-structure electrode is designed to realize the low group velocity of the microwave modulation signal. The simulation results show that the modulation efficiency of this slow-wave EOM is 1.42 V·cm. The slow-light effect is realized theoretically with a flat optical operating bandwidth of about 21 nm, group velocity dispersion < 2 ps 2 /mm, and low loss < 0.33 dB. Additionally, a 3 dB modulation bandwidth of 80 GHz is verified by simulation by virtue of the proposed micro-structure electrode.

Differential and phase-diverse electrooptic modulators

Abstract: Abstract Bandwidth and noise are fundamental considerations in all communication and signal processing systems. The group-velocity dispersion of optical fibers creates nulls in their frequency response, limiting the bandwidth and hence the temporal response of communication and signal processing systems. Intensity noise is often the dominant optical noise source for semiconductor lasers in data communication. In this paper, we propose and demonstrate a new class of electrooptic modulators that is capable of mitigating both of these problems. Fabricated in thin-film lithium niobate, the modulator simultaneously achieves phase diversity and differential operations. The former compensates for the dispersion penalty of the fiber, and the latter overcomes the intensity noise and other common mode fluctuations. Applications of the so-called four-phase electrooptic modulator in time-stretch data acquisition and in optical communication are demonstrated.