Showing papers on "Extinction ratio published in 2021"
20 Mar 2021
TL;DR: In this paper, a record combination of low RF half-wave voltage (Vπ) of 1.3 V while maintaining electro-optic response with 1.8 dB roll-off at 50 GHz using micro-structured electrodes was achieved.
Abstract: Electro-optic modulators with low voltages and large bandwidths are crucial for both analog and digital communication. Recently, thin-film lithium niobate modulators have emerged as a strong candidate for next generation electro-optic solutions. These modulators offer significantly improved voltage–bandwidth performances over the existing bulk lithium niobate modulators while preserving key material advantages such as linear response, high extinction ratio, high optical power handling ability, and low optical losses. However, reduced electrode gaps in miniaturized thin-film modulators lead to higher microwave losses, which limit electro-optic performances at high frequencies. Here we overcome this limitation to achieve a record combination of low RF half-wave voltage (Vπ) of 1.3 V while maintaining electro-optic response with 1.8 dB roll-off at 50 GHz using micro-structured electrodes. Our demonstration represents a significant improvement in voltage–bandwidth performance, one that is comparable to the performance gain in switching from legacy bulk to thin-film lithium niobate modulators. Such a micro-structured electrode design could enable sub-volt modulators with >100GHz bandwidth.
123 citations
TL;DR: In this article, a hybrid cladding composed of a Kagome-tubular lattice (HKT) was proposed to reduce the confinement loss and preserve robust single-mode operation.
Abstract: Remarkable recent demonstrations of ultra-low-loss inhibited-coupling (IC) hollow-core photonic-crystal fibres (HCPCFs) established them as serious candidates for next-generation long-haul fibre optics systems. A hindrance to this prospect and also to short-haul applications such as micromachining, where stable and high-quality beam delivery is needed, is the difficulty in designing and fabricating an IC-guiding fibre that combines ultra-low loss, truly robust single-modeness, and polarisation-maintaining operation. The design solutions proposed to date require a trade-off between low loss and truly single-modeness. Here, we propose a novel IC-HCPCF for achieving low-loss and effective single-mode operation. The fibre is endowed with a hybrid cladding composed of a Kagome-tubular lattice (HKT). This new concept of a microstructured cladding allows us to significantly reduce the confinement loss and, at the same time, preserve truly robust single-mode operation. Experimental results show an HKT-IC-HCPCF with a minimum loss of 1.6 dB/km at 1050 nm and a higher-order mode extinction ratio as high as 47.0 dB for a 10 m long fibre. The robustness of the fibre single-modeness is tested by moving the fibre and varying the coupling conditions. The design proposed herein opens a new route for the development of HCPCFs that combine robust ultra-low-loss transmission and single-mode beam delivery and provides new insight into IC guidance.
36 citations
TL;DR: In this paper, the authors demonstrate a reconfigurable optical bandpass filter based on subwavelength grating (SWG) waveguide operating in the Bragg reflection regime and integrated with a cavity of the phase change material Ge2Sb2Te5 (GST).
Abstract: We demonstrate a reconfigurable optical bandpass filter based on subwavelength grating (SWG) waveguide operating in the Bragg reflection regime and integrated with a cavity of the phase-change material Ge2Sb2Te5 (GST). Partial crystallization of GST provides us with an efficient tool to modify the effective optical properties of the GST governed by the effective medium theory. Consequently, the resonance wavelength as well as the transmission peak can be tuned in the designed filters. Numerical simulations indicate that the presented SWG waveguide with a single GST cavity offers up to 8.8 nm redshift while the transmission amplitude can be modulated from 0.544 to 0.007. The presented Fabry–Perot structure can also be used as a nonvolatile optical switch with a high extinction ratio of about 24 dB at the wavelength of 1548.3 nm.
36 citations
TL;DR: This paper demonstrates a high-power, narrow-linewidth, polarization-maintaining fiber amplifier with near-diffraction-limited beam quality and achieves double the self-pulsing threshold from conventional white noise signal phase modulation with the same optical linewidth.
Abstract: In this paper, we demonstrate a high-power, narrow-linewidth, polarization-maintaining fiber amplifier with near-diffraction-limited beam quality. By optimizing the phase modulation signal, a nearly top-hat-shaped spectrum was generated for self-pulsing suppressing. That results in doubling the self-pulsing threshold we got from conventional white noise signal phase modulation with the same optical linewidth. Based on an optimized signal and a high power, polarization-maintaining, counter-pumped fiber amplifier, we obtain a 3.25 kW narrow-linewidth linearly polarized laser output with a linewidth of ∼20GHz, the polarization extinction ratio is about 15 dB, and the M2 is less than 1.22 at the maximum output power. To the best of our knowledge, this is the first demonstration of a narrow-linewidth, linear polarization, all-fiber amplifier with 3.25 kW laser output.
28 citations
TL;DR: In this paper, two ultra-short polarization beam splitters based on surface plasma resonance (SPR) were designed for wavelengths of 1.31 and 1.55 μm respectively.
28 citations
TL;DR: In this paper, an optical filter based on a silicon subwavelength grating (SWG) waveguide evanescently coupled to phase-change material loading segments arranged periodically around the SWG core is presented.
Abstract: Subwavelength engineering and utilizing phase-change materials with large contrast in their optical properties have become powerful design tools for integrated silicon photonics. Reversible phase-transition of phase-change materials such as Ge2Sb2Te5 (GST) provide a new degree of freedom and open up the possibility of adding new functionalities to the designed devices. We present an optical filter based on a silicon subwavelength grating (SWG) waveguide evanescently coupled to phase-change material loading segments arranged periodically around the SWG core. The effect of the GST loading segments’ geometry and their distance from the SWG core on the filter’s central wavelength and bandwidth are studied with three-dimensional finite-difference time-domain simulations. The employment of GST in the structure adds a switching functionality with an extinction ratio of 28.8 dB. We also examine the possibility of using the proposed structure as a reconfigurable filter by controlling the partial crystallization of the GST offering a blueshift of more than 4 nm.
27 citations
TL;DR: An on-chip optoectromechanical phase shifter with low insertion loss and low half-wave voltage using a silicon nitride platform is presented and can be operated in the MHz range and allow for the generation of sub-µs pulses.
Abstract: We present an on-chip optoectromechanical phase shifter with low insertion loss and low half-wave voltage using a silicon nitride platform. The device is based on a slot waveguide in which the electrostatic displacement of mechanical structures results in a change of the effective refractive index. We achieve insertion loss below 0.5 dB at a wavelength of 1550 nm in a Mach-Zehnder Interferometer with an extinction ratio of 31 dB. With a phase tuning length of 210 µm, we demonstrate a half-wave voltage of Vπ = 2.0 V and a 2π phase shift at V2π = 2.7 V. We measure phase shifts up to 13.3 π at 17 V. Our devices can be operated in the MHz range and allow for the generation of sub-µs pulses.
27 citations
Posted Content•
TL;DR: In this article, a portfolio of thin-film lithium niobate devices for essential polarization management functionalities, including arbitrary polarization generation, fast polarization measurement, polarization scrambling, and automatic polarization control, is presented.
Abstract: High-speed polarization management is highly desirable for many applications, such as remote sensing, telecommunication, and medical diagnosis. However, most of the approaches for polarization management rely on bulky optical components that are slow to respond, cumbersome to use, and sometimes with high drive voltages. Here, we overcome these limitations by harnessing photonic integrated circuits based on thin-film lithium niobate platform. We successfully realize a portfolio of thin-film lithium niobate devices for essential polarization management functionalities, including arbitrary polarization generation, fast polarization measurement, polarization scrambling, and automatic polarization control. The present devices feature ultra-fast control speed, low drive voltages, low optical losses and compact footprints. Using these devices, we achieve high fidelity polarization generation with a polarization extinction ratio up to 41.9 dB, fast polarization scrambling with a scrambling rate up to 65 Mrad/s, and endless polarization control with a tracking speed up to 10 Krad/s, all of which are best results in integrated optics. The demonstrated devices unlock a drastically new level of performance and scales in polarization management devices, leading to a paradigm shift in polarization management.
26 citations
TL;DR: In this article, a high-performance graphene-on-silicon nitride (Si3N4) all-optical switch based on a Mach-Zehnder interferometer (MZI) was proposed and experimentally demonstrated.
Abstract: We propose and experimentally demonstrate a high-performance graphene-on-silicon nitride (Si3N4) all-optical switch based on a Mach–Zehnder interferometer (MZI). In our device, the graphene overlaying on a Si3N4 waveguide absorbs part of the pump light power and generates heat. Then, the Si3N4 waveguide underneath can be heated and its refractive index can be changed due to the thermo-optic effect. In this way, the phase of the probe light in the Si3N4 arm with graphene on top is tuned and all optical switching can then be implemented. In the experimental demonstration, an all-optical switch with a chip size of ∼0.36 mm2 is realized with an extinction ratio of 11 dB. The tuning efficiency is measured to be 0.00917 π/mW, which is insensitive to the wavelength of the pump light. All-optical switching is also demonstrated, while the rise and fall time constants are measured to be 571 ns and 1.29 μs, respectively. These results show that our proposed configuration provides a functional integrated component for the development of efficient all-optical control devices with a fast switching speed on the insulator platform. Moreover, by using integrated MZI structure, our design could potentially achieve a broad bandwidth.
25 citations
TL;DR: In this article, an octave-spanning coherent supercontinuum (SC) fiber laser with excellent noise and polarization properties was achieved by pumping a highly birefringent all-normal dispersion photonic crystal fiber with a compact high-power ytterbium femtosecond laser at 1049 nm.
Abstract: We report an octave-spanning coherent supercontinuum (SC) fiber laser with excellent noise and polarization properties. This was achieved by pumping a highly birefringent all-normal dispersion photonic crystal fiber with a compact high-power ytterbium femtosecond laser at 1049 nm. This system generates an ultra-flat SC spectrum from 670 to 1390 nm with a power spectral density higher than 0.4 mW/nm and a polarization extinction ratio of 17 dB across the entire bandwidth. An average pulse-to-pulse relative intensity noise down to 0.54% from 700 to 1100 nm was measured and found to be in good agreement with numerical simulations. This highly stable broadband source could find strong potential applications in biomedical imaging and spectroscopy where an improved signal-to-noise ratio is essential.
25 citations
TL;DR: The proposed device can realize polarization beam splitting in single beat length, and the footprint of the proposed PBS can be reduced to 8 µm × 160 µm (with S-bend), which proves strong robustness of the fabrication tolerance.
Abstract: In this paper, theoretical modeling and numerical simulations of a high-performance polarization beam splitter (PBS) based on hetero-anisotropic metamaterials are proposed on the lithium-niobate-on-insulator (LNOI) platform. The hetero-anisotropic metamaterials constructed by sub-wavelength gratings (SWGs) can be regarded as effective anisotropy medium, which exhibits strong birefringence without breaking the geometrical symmetry, contributing to the formation of PBS. Rather than the principle of PBS based on beat-length difference of transverse electric (TE) polarization and transverse magnetic (TM) polarization, the device can realize polarization beam splitting in single beat length, and the footprint of the proposed PBS can be reduced to 8 µm × 160 µm (with S-bend). The simulation results show that the bandwidth is 185 nm (1450∼1634 nm) for TE polarization while the bandwidth is 85 nm (1490∼1575 nm) for TM polarization when the polarization extinction ratio is >20 dB. Furthermore, the insertion loss is less than 1 dB in the range of 1450 to 1650 nm, for both TE and TM polarization. Additionally, the proposed device proves strong robustness of the fabrication tolerance.
TL;DR: In this article, the authors demonstrate highly directional light emission from a full-area organic LED with a small divergence angle less than 3° and a TE to transverse magnetic (TM) polarization extinction ratio of 13.6 times compared to the reference planar device.
Abstract: Light-emitting diodes (LEDs) with directional and polarized light emission have many photonic applications, and beam shaping of these devices is fundamentally challenging because they are Lambertian light sources. In this work, using organic and perovskite LEDs (PeLEDs) for demonstrations, by selectively diffracting the transverse electric (TE) waveguide mode while suppressing other optical modes in a nanostructured LED, the authors first demonstrate highly directional light emission from a full-area organic LED with a small divergence angle less than 3° and a TE to transverse magnetic (TM) polarization extinction ratio of 13. The highly selective diffraction of only the TE waveguide mode is possible due to the planarization of the device stack by thermal evaporation and solution processing. Using this strategy, directional and polarized emission from a perovskite LED having a current efficiency 2.6 times compared to the reference planar device is further demonstrated. This large enhancement in efficiency in the PeLED is attributed to a larger contribution from the TE waveguide mode resulting from the high refractive index in perovskite materials.
TL;DR: In this paper, the authors presented the design concept and experimental demonstration for highly efficient subwavelength-thick plasmonic chiral metamaterials with strong chirality.
Abstract: Plasmonic chiral metamaterials have attracted broad research interest because of their potential applications in optical communication, biomedical diagnosis, polarization imaging, and circular dichroism spectroscopy. However, optical losses in plasmonic structures severely limit practical applications. Here, we present the design concept and experimental demonstration for highly efficient subwavelength-thick plasmonic chiral metamaterials with strong chirality. The proposed designs utilize plasmonic metasurfaces to control the phase and polarization of light and exploit anisotropic thin-film interference effects to enhance optical chirality while minimizing optical loss. Based on such design concepts, we demonstrated experimentally optical devices such as circular polarization filters with transmission efficiency up to 90% and extinction ratio >180, polarization converters with conversion efficiency up to 90%, as well as on-chip integrated microfilter arrays for full Stokes polarization detection with high accuracy over a broad wavelength range (3.5-5 μm). The proposed design concepts are applicable from near-infrared to Terahertz regions via structural engineering.
TL;DR: A low-loss, highly extinctive resonant EO modulator based on a suspended graphene plasmonic waveguide that can be effectively tuned to operate at the desired wavelength by applying a suitable gate voltage is proposed.
Abstract: The exceptional tunable waveguiding characteristics of graphene surface plasmons have remained unrivaled since it has inspired many electro-optical (EO) devices in terahertz (THz) and mid-infrared (MIR) photonic circuits. We propose and numerically investigate a low-loss, highly extinctive resonant EO modulator based on a suspended graphene plasmonic waveguide. Unlike other resonance-based modulators, the input power has negligible interaction with lossy resonance cavity in on-state, remarkably reducing the losses. Achieving the insertion loss (IL) of 1.3 dB and the extinction ratio (ER) of 22 dB within a footprint less than 3 µm2 substantiates the superiority of the proposed structure. The charge transport simulations are first conducted to calculate the steady-state charge distribution. The three-dimensional finite-difference time-domain (3D-FDTD) method is utilized to monitor the guided wave propagation and modulation properties. We show that the transmission spectrum is highly dependent upon geometric parameters of the structure, and the modulator can be effectively tuned to operate at the desired wavelength by applying a suitable gate voltage. Simulation results show the modulation bandwidth of 71 GHz corresponding to the total capacitance of 4.8 fF within the active area. The novel EO modulator structure has shown great potentiality and flexibility to find other applications in MIR and THz integrated circuits like controllable notch filters and switches.
TL;DR: In this article, an ultra-compact plasmonic nanostructure was proposed to realize multiple Fano resonance (FR) modes, comprising two separated metal-insulator-metal (MIM) bus waveguides side-coupled with a circular ring, including an air path.
Abstract: We propose an ultra-compact plasmonic nanostructure to realize multiple Fano resonance (FR) modes, comprising two separated metal–insulator-metal (MIM) bus waveguides side-coupled with a circular ring, including an air path, and this design is less considered before in the plasmonic MIM-cavity system. The sensing performance can significantly improve by introducing an air path to induce a new coupled plasmonic structure, generating multiple FR modes and unique optical properties. Using the finite element method, we numerically simulate the influences of transmittance spectra on structural parameters of the proposed plasmonic sensor. Results reveal that these multiple resonance modes stem from the interference among two bus waveguides, a circular ring, and an air path. Optimizing the structure parameters, we can obtain ten FR modes in the proposed structure. The calculated maximum refractive index and temperature sensitivities are 2900 nm/RIU and 1.13 nm/°C, respectively. Besides, its maximum on/off extinction ratio achieves about 44.03 dB. We find that the proposed all-system structure can offer a high sensitivity application of refractive index and temperature sensing. The research results have more functional and diverse applications for designing high sensitivity to the next-generation plasmonic sensor.
TL;DR: In this paper, dual-channel phase-shifted Bragg grating filters in the telecom band on thin-film lithium niobate are demonstrated, with an extinction ratio of 27 dB and two channels with close linewidths of about 19 pm.
Abstract: We demonstrate dual-channel phase-shifted Bragg grating filters in the telecom band on thin-film lithium niobate. These integrated tunable ultra-narrow linewidth filters are crucial components for optical communication and sensing systems, as well as future quantum-photonic applications. Thin-film lithium niobate is an emerging platform suitable for these applications and has been exploited in this Letter. The demonstrated device has an extinction ratio of 27 dB and two channels with close linewidths of about 19 pm (quality factor of ${8} \times {{10}^4}$), separated by 19 GHz. The central wavelength could be efficiently tuned using the high electro-optic effect in lithium niobate with a tuning factor of 3.83 pm/V. This demonstration can be extended to tunable filters with multiple channels, along with desired frequency separations and optimized tunability, which would be useful for a variety of complex photonic integrated circuits.
TL;DR: In this paper, the authors showed that the performance on BER and modulation loss is strongly affected by the equalization bandwidth due to peak-to-average-power-ratio (PAPR).
Abstract: We reviewed recent breakthroughs on silicon photonic for 100Gbaud operation. Recent progress on high-speed Ge photodetector and carrier depletion modulator promises 100Gbaud optical transceivers with all-silicon material platform for commercial applications. We achieved high performance high-speed all-silicon photonics carrier-depletion Mach–Zehnder modulation by co-optimization of doping and device design assisted with an accurate electro-optical (EO) model. We reported all-silicon Mach–Zehnder modulator with a measured 6 dB EO bandwidth of >60 GHz by using a medium doping and 2 mm long phase shifter. We experimentally demonstrated 120Gbaud QPSK and 100Gbaud 32QAM operations using a high performance all-silicon in-phase/quadrature (IQ) modulator with extinction ratio of >25 dB, moderate ${{\boldsymbol{V}}_{\boldsymbol{\pi }}}$ of 6.3 V, and 6 dB electro-optic bandwidth of 50 GHz employing practical Nyquist filter and linear compensation in commercial arbitrary wave generator (AWG) and optical modulation analyzer (OMA). We studied both performance optimization and limitation. Our results show that BER performance can be optimized by pre-equalization (Pre-EQ) method for bandwidth-limited silicon photonic modulators. However, the performance on BER and modulation loss is strongly affected by the equalization bandwidth due to peak-to-average-power-ratio (PAPR). The frequency at fast roll-off of transmitter response is more critical than 3 dB electro-optic bandwidth when Pre-EQ is used for bandwidth compensation.
TL;DR: In this article, a Mach-Zehnder interferometer-based modulator was designed and experimentally demonstrated on a silicon nitride loaded LNOI platform, which not only takes full advantage of the excellent EO effect of LiNbO3, but also avoids the direct etching of LiNiobate on insulator thin film.
Abstract: Electro-optic (EO) modulators, which convert signals from the electrical to optical domain plays a key role in modern optical communication systems. Lithium niobate on insulator (LNOI) technology has emerged as a competitive solution to realize high-performance integrated EO modulators. In this Letter, we design and experimentally demonstrate a Mach–Zehnder interferometer-based modulator on a silicon nitride loaded LNOI platform, which not only takes full advantage of the excellent EO effect of LiNbO3, but also avoids the direct etching of LiNbO3 thin film. The measured half-wave voltage length product of the fabricated modulator is 2.24 V·cm, and the extinction ratio is ∼20dB. Moreover, the 3 dB EO bandwidth is ∼30GHz, while the modulated data rate for on–off key signals can reach up to 80 Gbps.
TL;DR: In this article, a broadband and compact TE-pass/TM-stop polarizer is presented based on hybrid plasmonic grating (HPG) on an x-cut Lithium-Niobate-on-isolator (LNOI) platform.
Abstract: A broadband and compact TE-pass/TM-stop polarizer is presented based on hybrid plasmonic grating (HPG) on an x-cut Lithium-Niobate-on-isolator (LNOI) platform. By comprehensively analyzing the effects of metal width on mode effective index, mode similarity, and mode conversion, we demonstrate the structure with a narrow metal layer. The simulation results indicate that the polarizer with a compact length of 9 μm achieves an extinction ratio over 20 dB within the wavelength range from 1470 nm to 1700 nm. The insertion loss is below 2.3 dB in C-band. Furthermore, the polarizer exhibits large fabrication tolerance to current fabrication technology.
TL;DR: In this article, a broadband long-wave infrared (LWIR) absorber with classical metal-dielectric-metal configuration is numerically demonstrated, consisting of single-sized cut-wire arrays that show broadband and high extinction ratio, attributed to polarization-selective simultaneous excitation of propagated and localized surface plasmon resonances.
Abstract: Broadband absorption is critical for the applications of metamaterial absorbers. In this work, a broadband long-wave infrared (LWIR) absorber with classical metal-dielectric-metal configuration is numerically demonstrated. The absorber consists of single-sized cut-wire arrays that show broadband and high extinction ratio, attributed to polarization-selective simultaneous excitation of propagated and localized surface plasmon resonances. The average absorption rate of the TM wave reaches 91.7% and 90% of the incident light is absorbed by the resonator in the wavelength range of 7.5–13.25µm so that the average extinction ratio in the resonator layer reaches 125. The polarization insensitive broadband absorption can be obtained by a cross resonator which can be treated as a pair of cut-wires perpendicular to each other. Our metamaterial absorber with single-sized resonators shows spatially concentrated broadband absorption and may have promising applications for hot-electron devices, infrared imaging, and thermal detection.
TL;DR: In this paper, a power combiner based all-optical AND gate is proposed based on the principle of linear interference, and the insertion loss and extinction ratio are given as 0.165 and 14.11 dB, respectively.
Abstract: All-optical logic gates have proven their significance in the digital world for the implementation of high-speed computations. We propose herein a novel structure for an all-optical AND gate using the concept of a power combiner based on a Y-shaped metal–insulator–metal waveguide with a 4 µm × 7 µm footprint. This design works based on the principle of linear interference. The insertion loss and extinction ratio of the design are given as 0.165 and 14.11 dB, respectively. The design is analyzed by using the finite-difference time-domain (FDTD) method and verified using MATLAB. The minimized structure can be used to design any complex logic circuit to achieve better performance in the future.
TL;DR: In this paper, the authors presented a novel design of polarization beam splitter (PBS) based on the integration of heterostructure 2D- Photonic crystals (PhCs).
Abstract: Herein, we presented a novel design of polarization beam splitter (PBS) based on the integration of heterostructure 2D- Photonic crystals (PhCs). Two PhC structures, namely PhC-type 1 and PhC-type 2, with different transmission characteristics are proposed. The first type of PhC is composed of a 2D-periodic array of circular air holes embedded in silicon substrate which facilitates the propagation of self-collimated TE and TM-polarized light. The second type of PhC consists of a 2D-periodic array of square-shaped air holes embedded in silicon substrate which carry a photonic bandgap (PBG) for TE-polarized light whereas TM-polarized light propagates unaffected by diffraction. When PhC-type 2 structure is arranged at 45° on both sides of the PhC-type 1 structure, this combination leads to the formation of PBS with a polarization extinction ratio (PER) as high as 30.7 dB. Furthermore, the same structure can be used to steer the TE-polarized light at 180° in a small footprint. Additionally, the heterostructure PhC can be used for TM-polarization maintain devices.
TL;DR: The basic structure for a half-adder circuit is proposed by inducing nonlinear Kerr-material to the Mach-Zehnder interferometers (MZIs) by using MIM plasmonic waveguide-based MZIs in the footprint of 85 μm.
TL;DR: In this paper, the authors proposed an ultra-high-performance rejection filter based on a silicon dual-loaded single input/output Mach-Zehnder Interferometer (MZI), with one branch coupled to a Ring Resonator (RR) and the other to three serially coupled RRs forming a Coupled Optical Resonator Waveguide (CROW).
Abstract: Integrated photonic circuits have become an attractive platform for the quantum information processing, paving the way for quantum information management with scalable device. In this context, silicon photonics represents the most mature technology to implement the quantum system functionalities, due to its large scalability and compatibility with CMOS technology. Efficient photon-pairs sources based on Spontaneous Four-Wave Mixing (SFWM) and high-performance photodetector have been already demonstrated. The efficient detection of photon-pairs requires a pump filter at the photodetector, preserving the signal-idler pair. Thus, filters with high Extinction Ratio (ER), low Insertion Loss (IL) and narrow rejection Bandwidth (BW) are needed. Here, we propose the design of an ultra-high-performance rejection filter, based on a silicon dual-loaded single input/output Mach-Zehnder Interferometer (MZI), with one branch coupled to a Ring Resonator (RR) and the other to three serially coupled RRs forming a Coupled Optical Resonator Waveguide (CROW). Very high performance (ER = 150.55 dB, IL = 0.104 dB, BW = 0.243 nm), within a footprint of 60 µm × 160 µm, has been calculated, demonstrating its suitability for an efficient suppression of the pump signal. The filter response is also thermo-optically tuneable in a 6 MHz range, with a reconfigurability time of about 8 µs.
TL;DR: In this article, a generic multiport optical switch capable of generating all-logic outputs is demonstrated by altering the mode profiles and propagation characteristics in a multimode waveguide through a combination of microheaters.
Abstract: A generic multiport optical switch capable of generating all-logic outputs is demonstrated by altering the mode profiles and propagation characteristics in a multimode waveguide through a combination of microheaters. The principles and design rules are introduced. As proof of concept, a 3-bit all-logic switch is fabricated on a polymer waveguide platform. The experimental results are in good agreement with the simulations based on a heat solver and the eigenmode expansion method. The device shows polarization insensitive and colorless operation from 1520 to 1600 nm with an extinction ratio between “On” and “Off” states larger than 11.9 dB in all cases. The maximum heat power is 43.9 mW (for (1, 0, 0) state). The simple, compact, and easily scalable device can be used to construct 1×N and M×N switch networks, showing promising applications in on-chip photonic signal processing and computation.
TL;DR: In this article, an ultra-broadband polarization beam splitter (PBS) consisting of cascaded Mach-Zehnder interferometers (MZIs) is proposed on 220 nm-thick silicon-on-insulator (SOI) platform.
Abstract: An ultra-broadband polarization beam splitter (PBS) consisting of cascaded Mach-Zehnder interferometers (MZIs) is proposed on 220 nm-thick silicon-on-insulator (SOI) platform. The configuration of the cascaded MZIs has a point symmetry in order to broaden the bandwidth of the cross-coupling for the TM polarization. The sub-wavelength grating (SWG) structures act as effectively anisotropic cladding to enhance the separation of the two fundamental polarizations. Two filters with cascaded bends and a Bragg reflection structure at the two outputs, respectively, are used to further improve the extinction ratio (ER). The proposed PBS has a remarkable performance with ER > 20 dB over a record broad bandwidth of 310 nm (IL < 0.5 dB) or 350nm (IL < 1 dB) for both TE and TM polarization inputs.
TL;DR: In this article, a broadband, compact and low-loss Silicon Photonic MEMS switch based on a Single-Pole Double-Throw (SPDT) architecture is presented, where curved electrostatic actuators mechanically displace a movable input waveguide to redirect the optical signal on chip efficiently to either of two output waveguides.
Abstract: Photonic Integrated Circuits (PICs) benefit from the technology advances in the semiconductor industry to incorporate an ever-increasing number of photonic components on a single chip to create large-scale photonic integrated circuits. We here present a broadband, compact and low-loss Silicon Photonic MEMS switch based on a Single-Pole Double-Throw (SPDT) architecture, where curved electrostatic actuators mechanically displace a movable input waveguide to redirect the optical signal on chip efficiently to either of two output waveguides. The photonic switch has been fabricated in an established silicon photonics technology platform with custom MEMS release post-processing. With a compact footprint of $\mathbf {65\times 62}\, \boldsymbol {\mu }\mathbf {m}^{\mathbf {2}}$ , the switch exhibits an extinction ratio exceeding 23 dB over 70 nm optical bandwidth, a low insertion loss and a fast response time below $1~\mu \text{s}$ , meeting the requirements for integration in large-scale reconfigurable Photonic Integrated Circuits. [2020-0391]
TL;DR: In this paper, a probabilistic amplitude shaping (PAS) was used to generate symbols that are protected by forward error correction (FEC) and that have the optimal input distribution.
Abstract: Probabilistic shaping for intensity modulation and direct detection (IM/DD) links is discussed and a peak power constraint determined by the limited modulation extinction ratio (ER) of optical modulators is introduced. The input distribution of 4-ary unipolar pulse amplitude modulation (PAM) symbols is optimized for short-reach transmission links without optical amplification nor in-line dispersion compensation. The resulting distribution is symmetric around its mean allowing to use probabilistic amplitude shaping (PAS) to generate symbols that are protected by forward error correction (FEC) and that have the optimal input distribution. The numerical analysis is confirmed experimentally for both an additive white Gaussian noise (AWGN) channel and a fiber channel, showing gains in transmission reach and transmission rate, as well as rate adaptability.
TL;DR: In this article, the authors proposed a thermoptically tunable polarization beam splitter (PBS) based on a selectively gold-filled dual-core photonic crystal fiber (DC-PCF), which has two internal electrodes for thermo-optical tuning of the operating band of the PBS.
Abstract: A thermo-optically tunable polarization beam splitter (PBS) is proposed and numerically studied. The proposed structure is based on a selectively gold-filled dual-core photonic crystal fiber (DC-PCF), which has two internal electrodes for thermo-optical tuning of the operating band of the PBS. A full-vector finite element method is used to analyze the behavior of the main parameters of the proposed device, such as coupling length, coupling length ratio, propagation distance and extinction ratio. Numerical results show that with a small length of 1.890 mm, the coupling length for the two polarization states is not modified in the analyzed temperature range. In addition, the splitter exhibits a coupling length ratio of approximately 1.5 with slightly changes as the temperature increases. The proposed PBS presents a bandwidth of 9 nm, a high extinction ratio of − 83.2 dB and tuning sensitivities of − 67 and $$66\hbox { pm/}^{\circ }\hbox {C}$$
when the internal electrodes are arranged horizontally and vertically, respectively. The DC-PCF based platform with internal electrodes has remarkable advantage such as ease of implementation and high tuning sensitivity, which ensures its potential applications in compact optical systems, optical switching and sensing applications.