High-speed Optical Switching Research Articles

ВЛИЯНИЕ НАДМОЛЕКУЛЯРНЫХ СТРУКТУР ПОЛИМЕРОВ НА ИХ ЭЛЕКТРООПТИЧЕСКИЕ СВОЙСТВА

The influence of supramolecular structures on the optical characteristics of polymers is considered. Studies of fluorine-containing acrylic polymers with fluorine-containing electro-optical chromophores in the side chain have shown that they should have a fibrillar supramolecular structure. The preservation of the fibrillar structure determines the technical condi-tions (temperature range) for the operation of high-speed integrated optical modulators and switches. The polymers con-sidered in the work were divided into three types according to the degree of polarization kp: polymers for which kp1 = 1.39; polymers with kp2 = <1.17>; polymers with kp3 = 1.003. To calculate nonlinear optical characteristics, the Jepsen equation was used. The possibility of calculating the polarizability of a polymer x from experimental values of the dielec-tric constant εexp is shown. The approach being developed can be used in medicine and biology to analyze the functioning of neurons (tubulin protein) and identify the causes of age-related changes in human memory. The latter is due to plastici-zation of tubulin and disruption of its fibrillar structure over time at brain temperature.

Ultra compact, high contrast ratio all optical NOR gate using two dimensional photonic crystals

An all-optical NOR gate is implemented using a two-dimensional photonic crystal waveguide. The paper provides a structure of an all-optical NOR gate constructed by introducing a line and point defect. The proposed NOR gate uses a hexagonal lattice structure with E shaped waveguide. The contrast ratio, response time and bit rate of three input NOR gate are 29.59 dB, 0.8 ps and 1.19 Tbps, respectively. The proposed gate is constructed with the operating wavelength of 1550 nm. The structure has been simulated and analyzed using Finite Difference Time Domain (FDTD) and Plane Wave Expansion (PWE) methods. It offers high contrast ratio, better response time with ultra-compact size. Hence it is suitable for high speed optical integrated circuits and switching devices.

High-speed 4 × 4 silicon photonic plasma dispersive switch, operating at the 2 µm waveband.

The escalating need for expansive data bandwidth, and the resulting capacity constraints of the single mode fiber (SMF) have positioned the 2-μm waveband as a prospective window for emerging applications in optical communication. This has initiated an ecosystem of silicon photonic components in the region driven by CMOS compatibility, low cost, high efficiency and potential for large-scale integration. In this study, we demonstrate a plasma dispersive 4 × 4 photonic switch operating at the 2-μm waveband with the highest switching speed. The demonstrated switch operates across a 45-nm bandwidth, with 10-90% rise and 90-10% fall time of 1.78 ns and 3.02 ns respectively. In a 4 × 4 implementation, crosstalk below -15 dB and power consumption lower than 19.15 mW across all 16 optical paths are indicated. This result brings high-speed optical switching to the portfolio of devices at the promising waveband.

Application of optical switching technology inalunar laser ranging system based on a superconducting detector.

The TianQin laser ranging station has successfully obtained the effective echo signals of the all five corner-cube reflectors on the lunar surface by using a 1064nm Nd:YAG laser with 100Hz repetition frequency and a 2×2 array of superconducting nanowire single-photon detectors (SNSPDs). The application of the SNSPD in the lunar laser ranging system (LLRS) has demonstrated its detection ability, but it loses its superconducting state and cannot work under strong stray light conditions. In this paper, a high-speed optical switch experimental device based on 100Hz is developed to solve the application problem of the SNSPD in the LLRS, and its main technical parameters are tested. The results show that the maximum running distance of the switch is 200µm; the switching time is better than 2ms; and the extinction ratio is better than 57dB. Moreover, the application of the high-speed optical switch experimental device in the lunar laser ranging system is designed, and the effective detection time between two laser pulses (10ms) is determined to be 6.1ms.

High-Speed Optical Mode Switch in Lithium Niobate on Insulator

Mode-division-multiplexing technology is highly attractive to increase the capacity of optical interconnects. Various multimode operations have been investigated, among which optical mode switches provide one of the most important functions in mode-division-multiplexing systems. However, current optical mode switches have a non-negligible switching time, which can lead to an undesired cumulative delay in the optical network. In this contribution, we propose and experimentally demonstrate an optical mode switch using a three-waveguide-coupling structure in the lithium niobate on insulator platform. The demonstrated optical mode switch has an insertion loss of 4.3 dB, an extinction ratio of 17.1 dB, and a switching time of below 28 ps. This work paves the way for future chip-scale high-speed mode-division-multiplexing systems.

High-Speed and On-Chip Optical Switch Based on a Graphene Microheater.

Graphene is a promising material for producing optical devices because of its optical, electronic, thermal, and mechanical properties. Here, we demonstrated on-chip optical switches equipped with a graphene heater, which exhibited high modulation speed and efficiency. We designed the optimal structure of the optical switch with an add/drop-type racetrack resonator and two output waveguides (the through and drop ports) by the electromagnetic field calculation. We fabricated the optical switch in which the graphene microheater was directly placed on the resonator and directly observed its operation utilizing a near-infrared camera. As observed from the transmission spectra, this device exhibited high wavelength tuning efficiency of 0.24 nm/mW and high heating efficiency of 7.66 K·μm3/mW. Further, we measured the real-time high-speed operation at 100 kHz and verified that the graphene-based optical switch achieved high-speed modulation with 10%-90% rise and fall response times, 1.2 and 3.6 μs, respectively, thus confirming that they are significantly faster than typical optical switches that are based on racetrack resonators and metal heaters with response times of ∼100 μs. These graphene-based optical switches on silicon chips with high efficiency and speed are expected to enable high-performance silicon photonics and integrated optoelectronic applications.

Design and simulation of optical logic gates at ultra high speed of 200 Gb/s employing single SOA

For Future high speed optical networking and switching applications there is a need of realization of high-speed all-optical devices and functionalities which are capable of performing processing at high bit rate. So, this study has come along by means of implementation of all-optical logic gates at ultra-high speed of 200 Gb/s. Optical AND and OR functionality is attained with the help of two data signals along with two pump signals using single SOA. While NOT gate is achieved with single data source along with the two pump signals in single SOA structure. Thus, the attainment of all-optical logics at ultra-high speed of 200 Gb/s with single SOA will bring high speed operation in the field of all-optical data handling and processing.

Investigating the effect of number of metal electrodes on performance parameters of AlGaN MSM photodetectors

Abstract In most past studies, MSM (Metal–Semiconductor–Metal) detectors with the varying area have been investigated for varying number of fingers (metal electrodes) of equal width (W) and spacing (S). Therefore, there is a need to investigate fixed area MSM detectors with varying number of fingers as there are few reports on electrical analysis of larger electrode spacing dimensions. In the current work effect of variation in the number of fingers is studied for two types of Al0.5Ga0.5N/AlN/Sapphire based fixed area MSM detectors. Comparative performance analysis between (S = W) and (S = 2W) based detectors is carried out for photocurrent, dark current density and transient response. I–V characteristics, structure diagram plots are generated using the TCAD Silvaco simulator. It has been observed that S = W detectors exhibit higher photocurrent and lower dark current density is shown by S = 2W designs. Therefore, simulation outcomes can be beneficial for selecting suitable MSM detector for reliable, high-speed optical communication and switching applications.

Fast Wavelength Switching at Tunable DFB Laser Array by Current/Temperature Cooperative Control

We proposed a new control method of the tunable distributed feedback (DFB) laser array (TLA) to realize high-speed optical switching by changing the injection current without sacrificing reliability. Previous studies of high-speed wavelength switching at DFB lasers achieved a sub-second switching time by injecting a large current to the active layer. However, a large injection current caused laser degradation that seriously reduced laser lifetime and reliability. In this paper, based on fast wavelength switching by injection current control, a new switching method was proposed that reduces an averaged injection current by increasing temperature. We successfully demonstrated 400-GHz-wide wavelength switching, which is the maximum tuning range of a single DFB laser in the TLA, with a switching time of 130 ms and reduced the injection current from 402 to 52 mA. Thus, we were able to greatly improve the reliability and increase the lifetime of the TLA by 60 times.

Single-step etched grating couplers for silicon nitride loaded lithium niobate on insulator platform

Dielectrically loaded thin-film lithium niobate (LiNbO3) on insulator (LNOI) platforms have enabled a range of photonic integrated circuit components, such as high-speed optical modulators, switches, and nonlinear devices, while avoiding the direct etching of the LiNbO3 thin film. Silicon nitride (Si3N4) is one of the most attractive dielectric loading materials as it has a similar refractive index and transparency window to LiNbO3 and can be deposited and patterned by mature fabrication processes. The patterning of Si3N4 opens the opportunity to fabricate grating couplers in the same fabrication step, providing efficient optical interfaces for wafer-scale testing. In this paper, we investigate and demonstrate single-step etched grating couplers on a Si3N4-LNOI (X-cut) platform. The grating couplers (straight and curved) are designed and fabricated for TE-polarized modes along the Y and Z crystallographic directions, considering the LiNbO3 crystal’s birefringence. The experimentally demonstrated coupling losses are as low as 4.02 and 4.24 dB along the crystallographic Y and Z directions, respectively. The corresponding peak wavelengths are 1609 and 1615 nm, respectively. The measured 3-dB bandwidths are wider than 70 nm for both crystallographic directions. We also numerically investigated the influence of fabrication variations and the fiber angle on the transmission. To the best of our knowledge, this work is the first demonstration of grating couplers with different light propagation directions on the Si3N4 loaded LNOI platform.

Dynamics of bright optical solitons through a coherent atomic medium

A coherent atomic medium is proposed for manipulating the absorption, dispersion, transmission and reflection of an optical soliton via two strong coherent control field’s Rabi oscillations, detunings and incident angles. Significant anomalous dispersion regions and a negative group index are investigated. A group index of n g = −1500 and a negative group velocity of v g = −2.0 × 105ms−1 is calculated. This leads to superluminal propagation (v g > c) in the anomalous dispersion region. A significant cancellation of linear and nonlinear effects results a bright optical soliton in the coherent atomic medium. Similarly the shape-preserving phenomenon of the bright optical solitons is investigated by launching the input pulse at different incident angles. As a result, the intensity distribution of the optical solitons has no fluctuation in time t/τ 0 with any values of y/ω 0 and shows a significant bright form of solitary waves. These solitons show remarkable applications in optics, particularly in soliton radar technology for medical purposes, controlling the intensity of bright solitons for the modification of optical information processing, high-speed optical switching and quantum communication.

Optically Switched Dual-Wavelength Cavity Ring-Down Spectrometer for High-Precision Isotope Ratio Measurements of Methane δD in the Near Infrared.

We report a spectrometer employing optically switched dual-wavelength cavity ring-down spectroscopy (OSDW-CRDS) for high-precision measurements of methane isotope ratios. A waveguide optical switch rapidly alternated between two wavelengths to detect absorption by two isotopologues using near-infrared CRDS. This approach alleviated common-mode noise that originated primarily from temperature and frequency fluctuations. We demonstrated the measurement of δD in natural abundance methane to a precision of 2.3 ‰, despite the lack of active temperature or frequency stabilization of the cavity. The ability of alternating OSDW-CRDS to improve the isotope precision in the absence of cavity stabilization were measured by comparing the Allan deviation with that obtained when frequency-stabilizing the cavity length. The system can be extended to a wide variety of applications such as isotope analysis of other species, kinetic isotope effects, ortho-para ratio measurements, and isomer abundance measurements. Furthermore, our technique can be extended to multiple isotope analysis or two species involved in kinetics studies through the use of multiport or high-speed optical switches, respectively.

Optical switch based on Graphene clad two surface plasmonic polariton mode coupler

Graphene exhibits both surface plasmonics and non linear optical property. Considering these properties, an optical controlled compact graphene clad surface plasmonic polariton two modes interference (GCSPPTMI) structure with silicon waveguide core has been presented for all optical switching. The cross and bar state power of the device are obtained by introducing an additional phase between the excited SPP modes in silicon coupling region through nonlinear refractive index modulation of graphene clad with incidence of very low optical pulse energy of 0.82 pJ and width of 4 ps. The coupling length of the proposed device is ∼21.6 times less than that of existing all optical switch based on SPP modes. The degradation of power imbalances of the Graphene clad SPPTMI with fabrication tolerances (±) of both width and thickness is less than that of multimode interference based nonlinear directional coupler due to having less of device parameters. Our results promise to achieve high speed and compact optical switch.

Ultra Compact, High Contrast Ratio Based all Optical OR Gate Using Two Dimensional Photonic Crystals

In this paper, Two Dimensional Photonic Crystals (2DPC) based all-optical two/three input OR gate is proposed and designed. A logic gate is an elementary building block of a digital circuit. The proposed all-optical OR gate is designed by creating Y shaped defect with ring resonator in a hexagonal lattice structure. The performance of the proposed all-optical OR gate is investigated using the Plane Wave Expansion (PWE) and Finite Difference Time Domain (FDTD) method. The functional parameters namely normalized efficiency, contrast ratio, response time and bit rate, are calculated. The proposed all-optical OR gate operates at a wavelength of 1550 nm. The size of the proposed structure is compact in nature. It offers high contrast ratio and minimum delay time. Hence it is suitable for optical processors, high speed optical integrated circuits and switching devices.

High-Speed Wavelength Switching at TDA-DFB Laser Based on a Nonlinear Model

In order to realize a high-speed optical switch for optical packet switching (OPS), we have been focused on a wavelength routing optical switch consisting of tunable lasers and an arrayed waveguide grating (AWG), and have studied high-speed wavelength switching of a tunable distributed amplification (TDA)-distributed feedback (DFB) laser. Previously, we achieved high-speed wavelength switching by feedforward control based on linear control theory. In this article, to realize higher-speed wavelength switching, we proposed a more accurate control model based on the nonlinearity of the TDA-DFB laser. We applied our nonlinear model to 400-GHz-wide and 600-GHz-wide wavelength switching and realized high-speed wavelength switching times of 33 ns and 39 ns, respectively.

High speed optical switching gain based EDFA model with 30 Gb/s NRZ modulation code in optical systems

Abstract This study presents high speed optical switching gain based Erbium doped fiber amplifier model. By using the proposed model the optical fiber loss can be minimized. The system is stabilized with the power budget of 25.875 mW a long 75 km as a length of optical fiber in this study can be verified. The modulation rate of 10 Gb/s can be upgrade up to reach 30 Gb/s. The suitable power for the optical transmitter is −2.440 dBm and NRZ modulation code is verified. The receiver sensitivity can be upgraded with the minimum bit error rate and max Q factor are 1.806 e−009 and 5.899.

Electro-optically tunable laser with ultra-low tuning power dissipation and nanosecond-order wavelength switching for coherent networks

The huge amount of data traffic behind the rapid growth of cloud computing is putting pressure on the operation of mobile fronthauls and data center networks so there is a need to improve their power consumption and latency. We developed an electro-optically tunable laser diode employing a tunable filter that is practically tuned even with small refractive index change of the electro-optic effect. The laser shows a small tuning power dissipation of less than 10 mW for a practical tuning range of over 35 nm with a linewidth of about 350 kHz. We also achieved high-speed optical switching of less than 50 ns for 100 Gb/s coherent signals. In addition to its application in optical communications, the electro-optically tunable laser diode is also beneficial to laser sensing applications because its higher tuning speed increases the time resolution of the sensing system. Furthermore, a narrow linewidth, conventionally difficult to reconcile with high-speed tuning, can also enable a longer sensing distance and/or a higher signal-to-noise ratio when using coherent detection. Our result shows that we can use the electro-optic effect to overcome the limitations of conventional tunable laser diodes and drastically change optical communications and laser sensing systems.

Tungsten-doped Ge2Sb2Te5 phase change material for high-speed optical switching devices

The large impedance mismatch between the highly resistive amorphous state and the highly conductive crystalline state of Ge2Sb2Te5 is an impediment for the realization of high-speed electrically switched optical devices. In this paper, we demonstrate that tungsten doping can reduce this resistivity contrast and also results in a lower amorphous state resistivity. Additionally, it lowers the contact resistance, improves the optical contrast, and extends the face-centered-cubic state up to 350 °C, with a minimal impact on thermal conductivity.

Open loop control theory algorithms for high-speed 3D MEMS optical switches

There is a world-wide push to create the next-generation all-optical transmission and switching technologies for exascale data centers. In this paper we focus on the switching fabrics. Many different types of 2D architectures are being explored including MEMS/waveguides and semiconductor optical amplifiers. However, these tend to suffer from high, path-dependent losses and crosstalk issues. The technologies with the best optical properties demonstrated to date in large fabrics (>100 ports) are 3D MEMS beam steering approaches. These have low average insertion losses and, equally important, a narrow loss distribution. However, 3D MEMS fabrics are generally dismissed from serious consideration for this application because of their slow switching speeds (∼few milliseconds) and high costs ($100/port). In this paper we show how novel feedforward open loop controls can solve both problems by improving MEMS switching speeds by two orders of magnitude and costs by a factor of three. With these improvements in hand, we believe 3D MEMS fabrics can become the technology of choice for data centers.

Fast Polarization-Insensitive Optical Switch Based on Hybrid Silicon and Lithium Niobate Platform

We propose and demonstrate a polarization-insensitive and high speed optical switch unit based on a silicon and lithium niobate hybrid integration platform. The presented device exhibits a sub nano-second switching time, low drive voltages of 4.97 V, and low power dissipation due to electrostatic operation. The measured polarization dependence loss was lower than 0.8 dB. The demonstrated optical switch could provide as a building block for polarization-insensitive and high-speed optical matrix switches.