Extinction Ration Research Articles

Terahertz wideband modulator devices using phase change material switchable frequency selective surfaces

Phase change materials (PCMs) such as temperature sensitive materials have received considerable attention in the optics and THz regime because of the reversable switching of their electromagnetic properties. In this paper, wideband switchable absorbers based on vanadium dioxide (VO2) have been designed and simulated at the terahertz (THz) regime. The switching functionality is enabled by the phase change of the VO2 layer from a metal state to an insulator through the temperature transition. The phase change temperature is 68 °C. The first designed absorber shows a wideband absorption spectrum (fractional bandwidth of 92.3%) with absorptivity above 90% in the metal state, where conductivity of the VO2 layer is 200000 S m−1, whereas the absorptivity is less than 3% in the insulator state, when the conductivity of the VO2 reaches 200 S m−1. An equivalent circuit model-based analysis is presented for metal state. Based on the results, the extinction ration is less than –11 dB with 0.9 modulation depth for a wide frequency range from 2.2 to 5.87 THz. This makes the proposed structure a suitable candidate for broadband modulation at THz frequencies. An ultra-broadband absorption spectrum is achieved in the second design utilizing the stacked structure of two VO2 layers in metal state, where each layer acts as a resonator. This absorber prototype offers more than 90% absorptivity within 1.2–6.1 THz corresponding to a relative bandwidth of 135%.

Investigation of Different CW Laser Parameters for 640 Gbps DWDM Transceiver System

This paper demonstrate design of 16 channel Dense Wavelength Division Multiplexing (DWDM) transceiver system and analyze the effect of Continuous Wave (CW) laser parameter on the transmission of data. The proposed system designed to support data rate of 640 Gbps and by using the software of Optisystem 18. The parameters included with investigation are the CW laser extinction ration, CW laser power, and channel spacing. The investigation for these parameters would be based on their effect on the parameters of Quality Factor (QF) and Bit Error Rate (BER). In this study, the effect of chromatic dispersion would be involved along with investigation to and handled during transmission by using Dispersion Compensation Fiber (DCF). Analyzing results obtained indicate the best outcome of these studied parameters and the relation between them and both the QF and BER.

Design of an electric-driven nonvolatile low-energy-consumption phase change optical switch

Traditional optical switches relying on the weak, volatile thermo-optic or electro-optic effects of Si or SiN waveguides show a high consumption and large footprint. In this paper, we reported an electric-driven phase change optical switch consisting of a Si waveguide, Ge2Sb2Te5 (GST) thin film and graphene heater suitable for large-scale integration and high-speed switching. The reversible transition between the amorphous and crystalline states was achieved by applying two different voltage pulses of 1.4 V (SET) and 4 V (RESET). The optical performance of the proposed switch showed a high extinction ration of 44–46 dB in a wide spectral range (1525–1575 nm), an effective index variation of Δn eff = 0.49 and a mode loss variation of Δα = 15 dB μm−1 at the wavelength of 1550 nm. In thermal simulations, thanks to the ultra-high thermal conductivity of graphene, the proposed switch showed that the consumption for the SET process was only 3.528 pJ with a 1.4 V pulse of 5 ns, while a 4 V pulse of 1.5 ns was needed for RESET process with a consumption of 1.05 nJ. Our work is helpful to analyze the thermal-conduction phase transition process of on-chip phase change optical switches, and the design of the low-energy-consumption switch is conducive to the integrated application of photonic chips.

Optical Filter Switchable Between Bandstop and Bandpass Responses in SOI Wafer

An optical filter switchable between bandpass and bandstop responses is proposed by analyzing frequency response in the complex plane. The device is fabricated based on silicon-on-insulator wafer. Experimental results show that the bandstop response has an extinction ration of exceeding 62.5 dB and a full width at half maximum (FWHM) bandwidth of 971 MHz, and the bandpass response has a rejection ration of 19.5 dB and a FWHM bandwidth of 840 MHz, respectively. The device also exhibits good tunability for both bandstop and bandpass responses.

Design and Development of Photonic Biosensors for Swine Viral Diseases Detection.

In this paper we introduce a field diagnostic device based on the combination of advanced bio-sensing and photonics technologies, to tackle emerging and endemic viruses causing swine epidemics, and consequently significant economic damage in farms. The device is based on the use of microring resonators fabricated in silicon nitride with CMOS compatible techniques. In the paper, the designed and fabricated photonic integrated circuit (PIC) sensors are presented and characterized, showing an optimized performance in terms of optical losses (30 dB per ring) and extinction ration for ring resonances (15 dB). Furthermore, the results of an experiment for porcine circovirus 2 (PCV2) detection by using the developed biosensors are presented. Positive detection for different virus concentrations has been obtained. The device is currently under development in the framework of the EU Commission co-funded project SWINOSTICS.

Directly modulated 1.3 μm quantum dot lasers epitaxially grown on silicon.

We report the first demonstration of direct modulation of InAs/GaAs quantum dot (QD) lasers grown on on-axis (001) Si substrate. A low threading dislocation density GaAs buffer layer enables us to grow a high quality 5-layered QD active region on on-axis Si substrate. The active layer has p-modulation doped GaAs barrier layers with a hole concentration of 5 × 1017 cm-3to suppress gain saturation. Small-signal measurement on a 3 × 580 μm2 Fabry-Perot laser showed a 3dB bandwidth of 6.5 GHz at a bias current of 116 mA. A 12.5 Gbit/s non-return-to-zero signal modulation was achieved by directly probing the chip. Open eyes with an extinction ration of 3.3dB was observed at room temperature. The bit-error-rate (BER) curve showed no error-floor up to BER of 1 × 10-13. 12 km single-mode fiber transmission experiments using the QD laser on Si showed a low power penalty of 1 dB at 5Gbit/s. These results demonstrate the potential for QD lasers epitaxially grown on Si to be used as a low-cost light source for optical communication systems.

Design Techniques for Signal Reflection Suppression in High-Speed 25-Gb/s Laser Drivers in CMOS

In this letter, we propose design techniques to suppress high-speed signal reflections observed in direct-modulated laser drivers. The first technique utilizes active back-termination (ABT) to absorb the reflected energy from the laser impedance mismatch. In the second design, capacitively coupled pre-emphasis (CCPE) is proposed to cancel the transient over-shooting observed from the bond-wire reflections. In order to evaluate these techniques, the two 25-Gb/s CMOS laser drivers are designed and fabricated in a standard 65-nm process. Experimental results show that both drivers exhibit clear 25.78-Gb/s optical eye-diagrams with >4 dB extinction ration, and also exhibit significant improvement in jitter performance when the ABT or CCPE is enabled.

Double-stage guided-mode converter for pure TM-mode guiding in pillar photonic-crystal waveguide devices.

We propose a double-stage guided-mode converter for pillar photonic-crystal (PhC) waveguide devices. The converter consists of a pillar-to-wire waveguide coupler and a transverse-magnetic-mode-selective spot-size converter. The former secures high-efficiency wide-band optical coupling of a pillar-PhC waveguide to a wire waveguide. The latter improves the coupling efficiency of the wire waveguide and an outside waveguide such as an optical fiber and also the signal-to-noise ratio of light guided in the pillar-PhC waveguide. The transmission band of a fabricated pillar-PhC waveguide having the converters on both ends was 88 nm in wavelength. The cutoff at the band edge was steep and deep with an extinction ration of 40 dB in a 4-nm wavelength range.

KW-level, narrow-linewidth linearly polarized fiber laser with excellent beam quality through compact one-stage amplification scheme

In this manuscript, we demonstrate high-power, narrow-linewidth linearly polarized fiber laser with excellent beam quality through compact one-stage amplification scheme. By employing a single-mode–multimode–single-mode structure seed laser, a linearly polarized Yb-doped fiber laser with narrow linewidth and high output power is achieved. This laser, when used as a master oscillator, can be capable of suppressing the ASE in the process of power amplification. Thus, only one-stage amplification structure is used to scale up the laser power, and linearly polarized output with a polarization extinction ration of 14 dB, a narrow linewidth of 0.3 nm and an output power of 1018 W are achieved. Moreover, due to the good beam quality of seed laser and the well-designed amplifier stage, the beam quality of the output laser is near-diffraction-limited with $M_{x}^{2}\sim 1.18$ and $M_{y}^{2}\sim 1.24$ at the maximum power, and without mode instability occurring.

Atomic Scale Plasmonic Switch.

The atom sets an ultimate scaling limit to Moore's law in the electronics industry. While electronics research already explores atomic scales devices, photonics research still deals with devices at the micrometer scale. Here we demonstrate that photonic scaling, similar to electronics, is only limited by the atom. More precisely, we introduce an electrically controlled plasmonic switch operating at the atomic scale. The switch allows for fast and reproducible switching by means of the relocation of an individual or, at most, a few atoms in a plasmonic cavity. Depending on the location of the atom either of two distinct plasmonic cavity resonance states are supported. Experimental results show reversible digital optical switching with an extinction ratio of 9.2 dB and operation at room temperature up to MHz with femtojoule (fJ) power consumption for a single switch operation. This demonstration of an integrated quantum device allowing to control photons at the atomic level opens intriguing perspectives for a fully integrated and highly scalable chip platform, a platform where optics, electronics, and memory may be controlled at the single-atom level.

Investigation of thermal effects in a resonance condition of microfibre double‐knot resonators as high‐order filter

Theoretical and experimental investigations are conducted into the thermal effect on resonance conditions of microfibre double-knot resonators. A double-knot microfibre resonator which utilises heat for optical path correction is introduced to increase the finesse. The proposed resonator consists of two knots with radii of 357.66 and 357.73 µm which are placed in series. Each individual knot has a finesse of 5 and an extinction ratio of 6 dB. When placed in series, the extinction ratio of the comb spectrum varies from 3.5 to 15 dB by controlling the resonance wavelength of both knots through optical correction. Optical path correction is implemented by placing a hot metal bar with a temperature of 30°C close to the smallest knot. This path resulted in a flat comb spectrum with a high extinction ration of 15 dB. The produced resonance has an unchanged free spectral range of 715 pm, a quality factor of 20 000, FWHD of 85 pm and a finesse of 9.5.

Gold Nanoparticles as Dual Functional Sensor to Detect E.coliDH5α as a Model for Gram‐negative Bacteria

Abstract4‐aminothiophenol‐modified gold nanoparticles (PATP‐AuNPs) were used as colorimetric and Surface Enhanced Raman Scattering (SERS) probes for the sensitive detection of Escherichia coliDH5α, as a model for Gram‐negative bacteria. The nano‐probes were easy to prepare through Au‐S bonding. Under optimized conditions, the PATP‐AuNPs surface with positive charge can bind with negatively charged E.coliDH5α via electrostatic adhesion, resulting in a quick color change from red to blue, and also a dramatic SERS signal enhancement from thousands of AuNPs aggregated on the surface of bacteria, which was utilized for both colorimetric and SERS detection of E.coliDH5α. For colorimetric analysis, it is the first time that the classical partial least square (PLS) regression was utilized to deal with the relationship between adsorption and E.coliDH5α concentrations. Excellent linear relationship was observed from 1.1 x 107 to 1.3 x 108 cfu mL‐1 with the average relative error (ARE) of 5.430, which was more accurate than the traditional extinction ration method. When coupled with confocal Raman microscope, this PATP‐AuNPs probes could be used to detection SERS signals produced from even one single bacterium. This bioassay is rapid, less expensive and convenient for bacteria detection and analysis. Therefore, PATP‐AuNPs system as a novel, versatile, on‐site and real‐time Gram‐negative bacteria sensor, would have a wide range of practical applications.

Corrections to “Low Loss, High Extinction Ration and Ultra-Compact Plasmonic Polarization Beam Splitter” [Apr 1 2014 660-663

The title of the above paper <xref ref-type="bibr" rid="ref1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</xref> was published with an error. The word “Ration” is not correct. The correct title is as follows:

Low Loss, High Extinction Ration and Ultra-Compact Plasmonic Polarization Beam Splitter

In this letter, an ultra-compact plasmonic polarization beam splitter (PBS) is proposed and investigated by numerical simulations using the finite element method. The PBS is based on a three-core plasmonic directional coupler, which uses a long range surface plasmon polaritons waveguide as the middle waveguide to achieve polarization selective coupling. The calculations show that with proper structural parameters, the PBS with low insertion losses of 0.17 and 0.25 dB for TE and TM polarizations, respectively, and high extinction ratios of 20.17 and 19.83 dB for TE and TM polarizations, respectively, can be realized at a telecommunication wavelength of 1550 nm. Furthermore, an insertion loss and an extinction ratio > 14 dB can be realized across the entire C-band for both TE and TM polarizations.

The study of few-layer graphene based Mach−Zehnder modulator

The investigation of few-layer graphene embedded in silicon waveguide (GESW) exhibits it has a superior performance than monolayer GESW where the effective mode index variation (Δneff) at the given chemical potential change and the number of graphene layers N (N<5) shows in a linear relationship. The results from modal analysis show that the Δneff of quadri-layer GESW can be as large as 0.047, based on which a Mach–Zehnder modulator has been proposed with the advantages of only 16.5μm arm length, low energy consumption (8fJ/bit), high extinction ration (31.8dB) and small applied voltage (<1V). Furthermore, the working temperature of the proposed modulator can span in a large range from 300K to 400K and the modulation performance stays almost unchanged when the input wavelength varies from 1520nm to 1580nm.

Theoretical Analysis of a Acoupled Fiber Ring Resonator

A fiber ring is very commonly used to generate stimulated Brillouin scatterings(SBS), especially by using fiber ring resonator. In this paper we theoretically analyzed some parameters of our interest in a coupled fiber ring resonator. We firstly analyzed a directional coupler, determined the optical power distribution among the four ports of the coupler. Then theoretically analyzed the transmission function of a coupled fiber ring resonator, followed by the simulation of the analysis. The simulation results show that the smaller the coupling coefficient is, the better the cavity finesse and extinction ration are, the lower the SBS threshold is, which is of great importance when it comes to the generation of SBS.

Low Power Mach–Zehnder Modulator in Silicon-Organic Hybrid Technology

We report on a silicon-organic hybrid modulator based on a Mach-Zehnder interferometer (MZI) operating at 10 Gbit/s with an energy consumption of 320 fJ/bit. The device consists of a striploaded slot waveguide covered with an electro-optic polymer cladding. The MZI modulator is poled to be driven in push-pull operation by a single coplanar RF line. Our nonlinear coefficient r33 = 15 pm/V in combination with an 80 nm narrow slot enables RF peak-to-peak drive voltages as low as 800 mVpp to suffice for an extinction ration of 4.4 dB for a 1.5 mm long modulator.

Demonstration of all-optical RZ-to-NRZ format conversion based on self phase modulation in a dispersion flattened highly nonlinear photonic crystal fiber

We propose a novel all-optical format conversion scheme from the return-to-zero (RZ) to non-return-to-zero (NRZ) based on a single dispersion-flattened highly nonlinear photonic crystal fiber (DF-HNL-PCF) and an optical band-pass filter (OBPF). The polarity-preserved, 30Gbit/s RZ-to-NRZ format conversion with Q factor and extinction ration (ER) of 6.57 and 16.06dB is demonstrated by exploiting self-phase modulation (SPM) induced spectral broadening together with subsequent spectral tailoring in the DF-HNL-PCF. The experiments are carried out to investigate the wavelength tunability and the dynamic characteristics of the newly designed PCF-based format converter. Our results show that the designed format converter has a wide operating wavelength range of 24nm and higher tolerance to input signal power fluctuation. This is very useful and attractive for engineering applications of optical-fiber-based RZ-to-NRZ format converter in future ultra-high speed photonic networks.

Performance tradeoff between lateral and interdigitated doping patterns for high speed carrier-depletion based silicon modulators

Carrier-depletion based silicon modulators with lateral and interdigitated PN junctions are compared systematically on the same fabrication platform. The interdigitated diode is shown to outperform the lateral diode in achieving a low VπLπ of 0.62 V∙cm with comparable propagation loss at the expense of a higher depletion capacitance. The low VπLπ of the interdigitated PN junction is employed to demonstrate 10 Gbit/s modulation with 7.5 dB extinction ration from a 500 µm long device whose static insertion loss is 2.8 dB. In addition, up to 40 Gbit/s modulation is demonstrated for a 3 mm long device comprising a lateral diode and a co-designed traveling wave electrode.

Direct CATV modulation and phase remodulated radio-over-fiber transport system

A novel transport system, with directly modulating community antenna television (CATV) signal downstream and phase-remodulating radio-over-fiber (ROF) signal upstream, is proposed and experimentally demonstrated. By modulating multi-carriers CATV signal in amplitude domain and ROF signal in phase domain, a single optical wavelength is able to serve these two applications simultaneous. To be the first system of communicating CATV signal downstream and phase remodulating radio signal upstream, the performances of transmitting CATV and radio signals over 20 km single-mode fiber (SMF) were experimentally verified. Good performances of carrier-to-noise ratio (CNR), composite second-order (CSO), and composite triple beat (CTB) were obtained for CATV applications as well as high extinction ration (ER) and low bit error rate (BER) values were measured for ROF transmission.