Square-tooth split ring resonator – a novel metamaterial for bandwidth and radiation improvement in microstrip-based radiating structure design

A square multiband truncated microstrip patch antenna was investigated using a square-tooth split ring resonator for multiband applications in both S- and C-bands. The square-tooth split ring resonator is formed from metallic inclusions in a substrate to create a metamaterial. We introduce a new square-tooth split ring resonator which increases the radiation of the antenna as well as the bandwidth. This new design creates a slow wave structure. The square-tooth addition to the split ring resonator works like a slow wave structure. The square-tooth split ring resonator design is compared with the simple split ring resonator design. The square-tooth design has four bands with center frequencies of 3.88, 4.81, 5.4, and 5.62 GHz, whereas design with the simple split ring resonator has just three bands with center frequencies of 3.88, 4.74, and 5.50 GHz. The bandwidth is increased by 20% to 30% using the square-tooth split ring resonator compared to the simple split ring resonator.     

Hybrid plasmonic waveguide-assisted Metal–Insulator–Metal ring resonator for refractive index sensing

A highly sensitive refractive index sensor based on an integrated hybrid plasmonic waveguide (HPWG) and a Metal–Insulator–Metal (M–I–M) micro-ring resonator is presented. In our design, there are two slot-waveguide-based micro-rings that encircle a gold disc. The outer slot WG is formed by the combination of Silicon–Air–Gold ring and the inner slot-waveguide is formed by Gold ring–Air–Gold disc. The slot-waveguide rings provide an interaction length sufficient to accumulate a detectable wavelength shift. The transmission spectrum and electric field distribution of this sensor structure are simulated using Finite Element Method (FEM). The sensitivity of this micro-ring resonator is achieved at 800 nm/RIU which is about six times higher than that of the conventional Si ring with the same geometry. Our proposed sensor design has a potential to find further applications in biomedical science and nano-photonic circuits.     

Switchable triple-wavelength thulium-doped fibre laser based on a Mach–Zehnder interferometer and fibre ring filter

A switchable triple-wavelength thulium-doped fibre laser based on an all-fibre Mach–Zehnder interferometer and fibre ring filter with a polarization-maintaining fibre is proposed and experimentally demonstrated. In the proposed fibre laser, a Mach–Zehnder interferometer comprising two 1 × 2 optical couplers is inserted into the optical cavity to produce the comb filter effect. The fibre ring filter comprises two optical couplers with a 3:7 splitting ratio and a 2-m-long polarization-maintaining fibre to improve lasing stability. Single-wavelength lasing can be tuned continuously from 1864.4 to 1884.5 nm, and five different modes of dual-wavelength and switchable triple-wavelength lasers can be realized by changing the polarization state. The signal-to-noise ratios of all lasers are more than 33 dB. The maximum power fluctuations and wavelength variations are less than 1.5 dB and 0.3 nm at room temperature, respectively, and the 3 dB bandwidth is less than 0.2 nm. The results demonstrate that stable and switchable single- or dual-wavelength lasers can be generated using the designed fibre laser.     

Surface plasmon polariton based band-pass and stop-band filters in symmetric double ring resonators

We carried out the numerical simulations on plasmonic filters composed by a Metal–Insulator–Metal (MIM) waveguide and a resonator of double rings. Both the band-pass filter and stop-band filters are discussed. The results show that the characteristic wavelengths of the band-pass or stop-band filter have red shift when the size of the resonator increases. The filters of double-ring resonator show better sensitivity on the wavelength than the one for the single ring. The simulations are based on the two-dimensional (2D) finite-difference time-domain (FDTD) method. The introduced filters have potential applications on optical integrated circuits.     

MIM plasmonic waveguide splitter with tooth-shaped structures

A plasmonic splitter based on subwavelength metal–insulator–metal (MIM) waveguides with tooth-shaped structures is proposed and numerically researched by using the finite-difference time-domain (FDTD) method in visible and near infrared frequencies. The splitter is regarded as two zigzag-shaped MIM waveguides, which naturally stretch out two tooth structures in bending corners. Each tooth forms a resonant cavity. The transmission of the zigzag-shaped waveguide is close to zero at some resonant wavelength of the tooth cavity. The same-order resonant wavelength has an approximately linear relationship with the depth of the tooth. When the geometric parameters of the two zigzag-shaped waveguides of teeth are suitably initialized, both frequency splitter and power splitter can be simply achieved.     

Photonic highway switches based on ring resonators used as frequency-selective components

A new concept for a highway switch, which can be used to connect different optical wavelength division multiplexing data highways for data exchange, is proposed and the system relevant properties are outlined. For the required add-drop filter elements we used ring resonators. Typical characteristics of channel bandwidth, channel spacing, free spectral range, amplification, and cross-talk behavior of a highway switch with double-cavity ring resonators are basically examined and to some extent compared with solutions that were obtained with standard single-ring resonators. A signal flow chart transformation for evaluating filter transfer functions is presented.     

Plasmonic refractive index sensor based on metal–insulator-metal waveguides with high sensitivity

A plasmonic square ring resonator sensor design based on metal–insulator-metal waveguide is proposed. The transmission spectra and electric field distribution of the resonator are simulated using the finite element method (FEM). The numerical simulation results achieved from the transmission spectra are used to investigate the sensing characteristics of the structure. The effect of structural parameters on the spectral characteristics and sensing performance are investigated in detail. The sensitivity is obtained to a value as high as 1367?nm/RIU with a figure of merit of ～25. The suggested design can possibly be applied in optical network-on-chip and on-chip nanosensors.     

Design and Performance of SuperSpec: An On-Chip,KID-Based,mm-Wavelength Spectrometer

SuperSpec is an ultra-compact spectrometer-on-a-chip for mm and submm wavelength astronomy. Its very small size, wide spectral bandwidth, and highly multiplexed detector readout will enable construction of powerful multi-object spectrometers for observations of galaxies at high redshift. SuperSpec is a filter bank with planar, lithographed, superconducting transmission line resonator filters and lumped-element kinetic inductance detectors made from Titanium Nitride. We have built an 81 detector prototype that operates in the 195–310 GHz band. The prototype has a wide-band metal feed horn with a transition to microstrip that feeds the filter bank. The prototype has demonstrated optical filter bank channels with a range of resolving powers from 300 to 700, measured fractional frequency noise of \(10^{-17} \mathrm{Hz}^{-1}\) at \(1\,\) Hz.     

Flash-lamp-excited self-injection-seeded Q-switched Ti:Al(2)O(3) laser oscillator

A self-injection-seeded, flash-lamp-excited, Q-switched laser oscillator is presented. The laser comprises two resonators that are operated sequentially. The first resonator, which includes all the high insertion loss, damage prone, wavelength tuning, and line-narrowing components, is used to generate the seed signal. The second resonator is a low-loss, Q-switched resonator whose output wavelength and line width are controlled by the seed signal. Output pulses of energy as high as 325 mJ have been obtained that are tunable over a range of the order of 90 nm and with a bandwidth of the order of 0.05 nm.     

All-Dielectric Electrooptic Sensor Based on a Polymer Microresonator Coupled Side-Polished Optical Fiber

A novel electrooptic (EO) electric field (E-field) sensor based on side-polished fiber coupled with an EO polymer microring resonator is proposed and demonstrated. An EO polymer waveguide with a ring shape is fabricated on the polished flat of an optical fiber. Light in the fiber evanescently couples into the resonator and forms resonant modes for certain wavelengths and produces notches in the output intensity of the fiber. External electric fields change the index of refraction of the ring waveguide and therefore dither its resonant wavelengths. For light of wavelength on the slope of a resonance notch, a change in the output intensity can be detected. The sensor is all dielectric without metal layers to distort the measured E-field. The resonant structure allows the sensor to potentially have much higher sensitivity than other electrooptic sensors based on Mach-Zehnder or polarization modulation. Since electrooptic polymers have higher electrooptic coefficients, lower dielectric constants and faster electrooptic responses than inorganic crystals, higher sensitivity, lower invasiveness, and higher bandwidth of E-field sensing can be expected. This sensor eliminates unreliable fiber-to-waveguide butt coupling as well as the high propagation loss encountered in the long straight EO polymer waveguides of sensors based on Mach-Zehnder structures. By using the fiber itself as the supporting substrate of the ring waveguide, the sensor can have small size and low disturbance to the measured electric field. The concept is demonstrated using AJLS103 EO polymer. A sensitivity of 100 mV/m has been achieved at frequencies up to 550 MHz (limited by the measurement system)     

Simulation experiments to generate broadband chaos using dual-wavelength optically injected Fabry–Perot laser

Abstract

Broadband chaos can be generated by beating two wavelengths in a hybrid arrangement of Fabry–Perot (FP) Laser and Fiber ring cavity by injecting dual wavelengths. The bandwidth of generated chaos can be controlled by detuning different modes of FP Laser for beating. The bandwidth of generated chaos increased to many folds depending upon the injected strength and wavelength spacing matched to FP laser modes. The bandwidth enhancement in different simulation experiments conducted is optimized by varying different parameters of FP laser and cavity. The waveforms are analyzed and Lyapunov exponents are calculated in order to validate the existence of high bandwidth non-pulsating chaos.     

Tunable ultracompact electro-optical photonic crystal ring resonator

A tunable ultracompact electro-optical photonic crystal ring resonator with high transmission is reported. The photonic crystal ring resonator is obtained by removing a ring shape of cylinders from a square lattice of dielectric cylinders in air. The transmission spectra of this ring resonator have been investigated by using the finite-difference time-domain technique. The general characteristics of the ring elements to achieve resonant tunneling are determined. By modulating the conductibility of the inner cylinders in the ring resonator, the electrical tunability of the resonant modes is observed in the transmission spectrum. The research results should open opportunities for this ring resonator as ultracompact filters, optical add-drop multiplexers, electro-optical N × N switches, and modulators.     

Dual wavelength demultiplexer based on metal–insulator–metal plasmonic circular ring resonators

Abstract

In this paper, we investigated a plasmonic demultiplexer structure based on Metal–Insulator–Metal (MIM) waveguides and circular ring resonators. In order to achieve the structure of demultiplexer, two improved ring resonators have been used, which input and outputs MIM waveguides coupled by the ring resonators. To improve the transmission efficiency, a reflector was introduced at the right end of the input and output waveguides. By substituting the ring core with dielectric, the possibility of tuning the resonance wavelength of the proposed structure is illustrated, and the effect of various parameters such as radius and refractive index in transmission efficiency is studied in detail. This is useful for the design of integrated circuits in which it is not possible to extend the dimension of the ring resonator to attain a longer resonance wavelength. Transmission efficiency and quality factor of the single ring are 84% and 110, respectively. The simulation results using finite difference time domain method shows that in the proposed demultiplexer, which is composed of two rings with different core refractive indexes, the average power efficiency, bandwidth for each output channel, and the mean value of crosstalk are estimated 80%, 17 nm, and ?26.95 dB, respectively. It is revealed that the significant features of the device are high transmission efficiency, low crosstalk, high-quality factor, and tunability for desired wavelengths. Therefore, the proposed structure has the potential to be applied in plasmonic integrated circuits.     

Design of circular polarisation microstrip patch antennas with complementary split ring resonator

A novel design of circular polarisation microstrip patch antennas based on the complementary split ring resonator is numerically evaluated and experimentally verified. The non-resonant property of complementary split ring resonator is used as an asymmetric perturbation to excite the square microstrip patch antenna for circular polarisation radiation. The detailed parameters of the complementary split ring resonator on the circular polarisation radiation are studied.     

Mode-hop-free single-longitudinal-mode erbium-doped fiber laser frequency scanned with a fiber ring resonator

We describe the experimental construction of a single-longitudinal-mode erbium-doped fiber ring laser equipped with a ring resonator filter. The system is designed to avoid mode hopping and can be frequency scanned for spectroscopic sensor applications. We modified a conventional ring resonator filter to have the capability to reduce transmittance of unwanted modes, which is essential for frequency scanning without mode hopping.     

Dual-broadband multistandard printed slot antenna with a composite back-patch

A square slot antenna fed by a coplanar waveguide for dual-band multistandard applications is presented. Printed on the back of the square slot is a composite patch formed by an annular metal ring inscribed by a circular patch. Appropriate design of the composite back-patch resulted in five resonant bands, the first (last) two of which were combined to form a lower (upper) operating band. The ratio of the two operating band centre frequencies can be tuned larger than 2.5. A pair of notches was embedded in the annular metal ring to further broaden the lower (upper) operating band up to a fractional bandwidth of 37% (20%). The measured results indicate that the proposed antenna can cover the frequency bands of the following wireless communication standards: digital communication system, personal communication services, universal mobile telecommunications system and 2.4/5-GHz wireless local-area networks.     

Low-loss, multimode 5-IDT SAW filter

Longitudinally coupled resonator filters provide unbalanced-balanced operation with wide bandwidth, low loss, and high suppression levels. However, reducing the insertion loss in the 1.8-2.2 GHz range remains a challenging problem because at high frequencies the resistive losses arising from the relatively wide aperture of the filter may degrade the performance. A 5-interdigital transducer (IDT) filter has six gaps at which the periodicity of the grating is broken, resulting in additional loss due to scattering into the bulk. In this paper, we show that replacing the gaps between the transducers with short transducer sections having their pitch different from that of the main transducers reduces the insertion loss of the device. We present devices with balun operation at 1842 MHz with wide bandwidth of 4.5% and -40 dB suppression, with a minimum insertion loss less than 1 dB in the best devices, and a maximum insertion loss of -1.2 dB in the passband. The passband is quite flat, with <1 dB ripple. We also discuss the layout of the contact pads and the connections, and its effect on the device performance and balance characteristics.     

Plasmonic-induced transparency in a metallic stub with two cuts and transmission line model

We investigate a metal–insulator–metal (MIM) structure, which is composed of a bus MIM waveguide and a stub modified by two cuts. A transmission line (TL) model is proposed to depict the propagation characteristics of surface plasmon polaritons (SPPs). The finite element method is conducted to calculate the transmission spectrum of SPPs. Plasmonic-induced transparency spectral response can be achieved when different cuts are introduced. Under different parameters, theoretical results based on the TL model match with the simulation results very well. It is believed that our findings provide a smart way to design MIM-based plasmonic sensors and slow light devices.     

A Novel HTS Shuttle-Shape Resonator for High-Power Application

A novel shuttle-shape microstrip resonator for high-power high-temperature superconductor (HTS) filters is presented. By transmission line theory analysis, it can improve the power handling capability up to 20%, depending on the configuration of the resonator. To confirm this analysis result, two 2-pole HTS filters based on shuttle-shape resonator and rectangle resonator were simulated. Considering the limitation of computer memory, a moderate configuration was chosen for HTS filter design. By computer simulation, a comparison between filters with shuttle-shape and rectangle resonators showed a 10% increase in power handling capability. The HTS shuttle-shape filter was fabricated and tested. It has a center frequency of 2022 MHz with a 2.5% bandwidth. The measured power level was over 34 dBm at 70 K with sufficiently low insertion loss.     

Wavelength selective nanophotonic components utilizing channel plasmon polaritons

We fabricate and investigate wavelength selective components utilizing channel plasmon polaritons (CPPs) and operate at telecom wavelengths: a waveguide-ring resonator-based add-drop multiplexer (WRR-ADM) and a compact (3.75-microm-long) Bragg grating filter (BGF). The CPP waveguides represent 0.5-microm-wide and 1.3-microm-deep V-grooves in gold, which are combined with a 5-microm-radius ring resonator (in the WRR-ADM) or 0.5-microm-long wells milled with the period of 0.75 microm across a groove (in the BGF). The CPP-based components are characterized in the wavelength range of 1425-1600 nm by use of near-field optical microscopy, exhibiting the wavelength selectivity of approximately 40 nm.