Ring Resonator Research Papers - Academia.edu (original) (raw)

AbstractIn this paper, inkjet-printed UHF and microwave cir-cuits fabricated on paper substrates are investigated for the first time as an approach that aims for a system-level solution for fast and ultra-low-cost mass production. First,... more

A simple method for accurately measuring the birefringence of a ring resonator waveguide using its resonant characteristics is presented. A measurement accuracy of 1 10 6 is observed. This approach is then used to measure the effect of... more

- by James Carriere
- •
- Optical Waveguides, Long-baseline optical interferometry, Annealing, Resonance

The objective of this study is to demonstrate ultra-low-cost paper substrates for the realization of inexpensive RFID tags that can be integrated with batteries and sensors for wireless sensing, tracking and monitoring applications. The first step toward achieving this goal is to demonstrate "conductors on paper substrates" from processing standpoint and to characterize the electrical performance of paper substrates up to 2 GHz form design standpoint. The conductors are achieved by (i) direct-write ink jet printing technology with tailored conductive ink and by (ii) conventional copper etching upon lamination of metal foils on to the paper substrates. There are several issues in optimizing the processes in either of the two approaches. For example, ink jet printing would require smooth surface finish, good adhesion, less smearing of the ink, fast curing profile, and ultimately copper-like conductivity of the printed ink and rapid prototyping for high volume manufacturing. On the other hand, metallization using copper will require bonding of copper onto paper surface, adhesion, compatibility with copper etch solutions and lithography, and moisture sealing. Both approaches have been successfully demonstrated for printing conductors on paper substrates which can be easily scaled to large-quantity manufacturing. For the electrical characterization of the paper substrates up to 2 GHz, one microstrip ring resonator was designed and fabricated for extracting dielectric constant and dielectric losses. The copper metallization of paper substrates and the dielectric characterization of paper up to 2 GHz are reported for the first time.

- by Amin Rida and +1
- •
- Rapid Prototyping, Copper, Dielectric Loss, Dielectric Constant

A single slotted circular patch resonator is proposed in this letter to design a novel dual-mode dual-band bandpass filter. Four identical arc-oriented slots are first symmetrically etched into the circular patch resonator to move the TM01-like mode to a lower frequency. Together with the TM21-like mode, these two modes make up the second passband of the proposed filter. A pair of radial-oriented slots is then etched into the edge of the circular patch to split a pair of TM11-like degenerate modes, which forms the first dual-mode passband. Two high-impedance transmission lines are connected to the proposed resonator at a 90° angle to properly excite the four resonant modes described above. Finally, a filter with input/output cross coupling is designed, fabricated and tested to demonstrate the dual-mode dual-band filtering performance, which exhibits a sharp out-of-band rejection skirt and good rejection between the dual passbands.

- by Sha Luo
- •
- Optical physics, Degeneration, Electrical And Electronic Engineering, Ring Resonator

The selective introduction of functional groups on the surface of silicon nitride/silicon oxide nanostructures was studied. Chemical strategies based on organosilane, Si-H and N-H reactivities were assayed. Among these strategies, the use of glutaraldehyde to selectively immobilize biomolecules only on the silicon nitride part of the chip surface was the most effective for the covalent attachment of proteins, maintaining also their bioavailability. The biomolecule surface coverage results up to 80% and the modification is selective versus silicon oxide; the biomolecule attaching only to silicon nitride and leaving the silicon oxide area of the device unmodified. The effectiveness of our novel selective surface modification procedure is also supported by comparing experimental and numerical calculations of the optical performance of a label-free optical ring resonator based on Si 3 N 4 /SiO 2 slot-waveguides.

- by Carlos A Barrios and +2
- •
- Analytical Chemistry, Biomedical Engineering, Biosensors, Nanotechnology

New all-optical NOT and NOR logic gates based on a single ultracompact photonic crystal ring resonator (PCRR) have been proposed. The PCRR was formed by removing the line defect along the ΓM direction instead of the conventional ΓX direction in a square-pattern cylindrical silicon-rod photonic crystal structure. The behavior of the proposed logic gates is qualitatively analyzed with the theory of beam interference and then numerically investigated by use of the two-dimensional finite-difference time-domain method. No nonlinear material is required with less than a 2:2 μm effective ring radius. The wavelengths of the input signal and the probe signal are the same. This new device can potentially be used in on-chip photonic logic-integrated circuits.

- by Zexuan Qiang
- •
- Mechanical Engineering, Photonic Crystals, Photonic Crystal, Applied Optics

A double ring resonator coupled laser (DR-RCL) is proposed and analyzed in this letter. Benefiting from the uniform peak transmission, narrow bandwidth and other superior characteristics of traveling wave supported high-resonators, DR-RCLs offers many promising advantages over the conventional tunable lasers, including ultra wide wavelength tuning range, high side mode suppression ratio, uniform threshold and efficiency, narrow linewidth, low frequency chirp, and simple fabrication. A DR-RCL with a moderate optical loss 10 dB/cm in the ring resonators can achieve a wavelength tuning enhancement of 50. With such a large tuning leverage, DR-RCLs could utilize the electrooptic effects to achieve ultrafast tuning speed with a wide tuning range covering the material gain bandwidth.

- by John Bowers
- •
- Low Frequency, Semiconductor Lasers, Frequency, Optical physics

An effective and exact synthesis technique for the design of parallel-coupled ring-resonator filters with a maximally f lat stop-band characteristic of any order is presented. Simple closed-form formulas determine the Q factor of each resonator and the coupling coefficients. The performances of these filters are discussed for their applications as interleavers and channel-dropping filters in wavelength-division multiplexing systems.

- by Andrea Melloni
- •
- Quantum Physics, Optical physics, Insertion Loss, Frequency Response
- by Manos Tentzeris
- •
- Antennas, Microstrip Antenna, High Frequency, Radio Frequency Identification

Microring and microdisk resonators are used in photonic circuits to perform filter functions, serve as bandlimited mirrors in lasers, compensate for dispersion and group delay distortion, are used in multiplexers in telecommunication systems, and a number of other applications such as medical instrumentation, biosensing, interferometry, to name a few. This paper outlines some challenges and solutions in this relatively new and prolific discipline.

- by Otto Schwelb
- •
- Seismic analysis and design, Delays, Optical Filters, Ring Resonator

A platform for performing rapid, real-time binding assays on sensor arrays based on silicon ring resonators is presented in this paper. An array of 32 sensors is interrogated simultaneously. Using eight sensors as controls, 24 simultaneous binding curves are produced. The bulk refractive index sensitivity of the system was demonstrated down to 7.6 × 10 −7 and sensor-to-sensor variability is 3.9%. Using an 8-min incubation, real-time binding was observed over 8-logs of concentration down to 60 fM using immobilized biotin to capture streptavidin diluted in bovine serum albumin solution. Multiplexing in complex media is demonstrated with two DNA oligonucleotide probes. Time to result and repeatability are demonstrated to be adequate for clinical applications.

- by Ryan Bailey
- •
- Quantum Physics, Microfluidics, Biosensors, BioMEMS

Micro-ring wavelength filters and resonant modulators using polymer materials at 1300 nm and 1550 nm are analyzed, designed, and demonstrated. The rings are integrated with vertically coupled input and output waveguides. The devices are fabricated using optical lithography. Filters with a finesse of 141 and free spectral range of 5 nm at 1300 nm and finesse of 117 with a free spectral range (FSR) of 8 nm at 1550 nm are demonstrated. Ring resonators with a as high as 1.3 10 5 at 1300 nm are demonstrated. The filters can be temperature tuned at the rate of 14 GHz/ C. Resonant ring modulators, which use an electrooptic polymer, are demonstrated. The resonance wavelength voltage tunes at the rate of 0.82 GHz/V. The modulators have a bandwidth larger than 2 GHz. Using the resonant modulator, and open eye diagram at 1 Gb/s is demonstrated.

- by Chéng Zhang
- •
- Optics, Medical Imaging, Fiber Optics, Telecommunications
- by Mohd Khairul Mohd Salleh
- •
- Resonators, Integration, Circuit simulation, Tunable Filter
- by Alfred Driessen
- •
- Integrated Optics, Higher Order Thinking, Dispersion Compensation, Fabry Perot

Compact optical channel dropping filters incorporating side-coupled ring resonators as small as 3 m in radius are realized in silicon technology. Quality factors up to 250, and a free-spectral range (FSR) as large as 24 nm are measured. Such structures can be used as fundamental building blocks in more sophisticated optical signal processing devices.

- by Sai Chu
- •
- Optical Waveguides, Quality Factor, Q factor, Optical Signal Processing

A rectangular waveguide filled with anisotropic uniaxial metamaterial with transversal negative effective permeability is investigated both theoretically and experimentally. It is shown that such a waveguide supports propagation of the backward wave below the cutoff frequency, thus, it can be considered as a dual of the ordinary waveguide. The transversal dimension of this waveguide can be arbitrarily smaller than half of a wavelength in the filling material, provided that the transversal permeability is negative. This peculiar behavior may be used for fabrication of miniaturized rectangular waveguides. Several experimental miniaturized waveguides loaded with double ring resonators in 7 GHz frequency band have been designed, fabricated and tested. The measured results revealed backward-wave passband located below the cutoff frequency. Furthermore, it was experimentally shown that the increase of the physical length of the waveguide caused the decrease of the electrical length. This is a direct proof of the backward-wave propagation since the phase of the backward wave increases along the waveguide.

A tri-band dual-mode chip filter, which is fabricated in a commercial pHEMT GaAs technology and suitable for millimeter-wave applications, is presented in this paper. This filter is constructed by using stacked ring resonators with individual perturbations and feeding capacitors; thus, fractional bandwidths and center frequencies of three pass bands can be flexibly controlled. A model of the tri-band filter that considers coupling effects between stacked ring resonators is first proposed, and then a synthesis method that can determine values of all elements of a typical dual-mode ring filter based on specifications of required characteristics is also described. According to the proposed design method, filter designers can quickly determine the layout pattern of the tri-band dual-mode filter which employs proper metal-insulator-metal (MIM) capacitors to obtain the desired filter performance. To verify the proposed design concept, an experimental prototype, locating three pass bands at 60 GHz, 77 GHz and 100 GHz, respectively, was fabricated on GaAs substrate. The size of the filter is about 0.46×0.91 mm2 and the measured insertion losses in the three passbands are less than 2.4 dB, 2.7 dB and 3.5 dB. The associated return losses are greater 18 dB, 17 dB and 8 dB over the frequency bands of interest.

- by Yi-Chyun Chiang
- •
- Millimeter Wave Antennas, Design method, Mott metal-insulator transition, Mmic

Four identical varactor-based tuning circuits are proposed to tune the centre frequency of a microwave quarterwavelength side-coupled ring resonator (QWSCR). Each of the tuning circuit is placed at every corner of the ring to give a shunt capacitor effect. The overall electrical length of the resonator can be varied according to the desired resonant frequency through the biased voltage applied to the varactordiode that controls the value of the resultant shunt capacitor. The complete tunable resonator circuit is simulated using the integration of microstrip technology and lumped elements on FR4 substrate. The proposed concept of the tunable QWSCR filters allows a tuning up to 15% of the nominal frequency of the filter.

- by Zaiki Awang
- •
- Band Pass Filter, Ring Resonator, Resonant Frequency
- by Manos Tentzeris
- •
- Antennas, Microstrip Antenna, High Frequency, Radio Frequency Identification

We give an overview of recent progress in passive spectral filters and demultiplexers based on silicon-on-insulator photonic wire waveguides: ring resonators, interferometers, arrayed waveguide gratings, and echelle diffraction gratings, all benefit from the high-index contrast possible with silicon photonics. We show how the current generation of devices has improved crosstalk levels, insertion loss, and uniformity due to an improved fabrication process based on 193 nm lithography.

- by shankar kumar
- •
- Quantum Physics, Silicon Photonics, Silicon on Insulator, Optical physics

We present a simple and fast technique for the design of ring resonator-based optical filters. The technique is based on tapering the ring scattering parameters to achieve the optimal filter response. A perturbation method is developed for the linearization of the resulting design problem. The design problem is then formulated as an optimization problem. The optimal filter design is achieved by solving a constrained linear least square problem. This optimization problem can be solved efficiently to get the global optimal design. Our technique has been verified using different proposed targeted filter responses.

- by Mohamed Swillam
- •
- Convex Optimization, Optimization Problem, Matched Filter, Optical physics

We present results from novel compact InGaAsP/InP based flattened micro-ring resonators and lasers. Resonators with circumferences 30-300μm by using etched beam-splitters (EBS) are demonstrated. EBS coupler insertion loss is measured as... more

- by Yung-Jr Hung
- •
- Reflection, Optical Waveguides, Semiconductor Lasers, Optical Waveguide

In this paper, polarization rotation due to optical waveguide bending is analytically and numerically investigated. It is shown that the process of polarization conversion in the bend strictly depends on the characteristics of the straight waveguide. The strength of polarization coupling linearly increases with the waveguide refractive index contrast, whereas birefringence is responsible for the phase mismatch that limits the conversion efficiency. Waveguides with refractive index profile symmetrical in the direction orthogonal to the plane of the bend do not exhibit polarization rotation. Inside optical ring resonators, polarization rotation induced by waveguide bending is found to be highly enhanced by the cavity effect, which gives rise to strongly frequency dependent polarization rotation and dramatically alters the ring's spectral response. In the case of single-ring phase shifters, polarization rotation is effectively described by means of an approach based on the theory of poles-zeros loci, which straightforwardly provides conditions for complete polarization conversion, also in the presence of birefringence and losses. The detrimental effects caused by undesired polarization coupling on the spectral response of widespread optical devices based on ring resonators are also discussed. From this point of view, birefringence is demonstrated to be beneficial to make optical components less sensitive to the effects of polarization rotation.

- by mario martinelli
- •
- Optics, Medical Imaging, Fiber Optics, Telecommunications

A novel double-ring resonator of the double square loop configuration is introduced to achieve the performance of the wideband bandpass filter. To obtain lower insertion loss (0.97 dB), deeper transmission zero level (35.4/34.6 dB), and wider bandwidth (43.22%), using the double square loop and aluminum nitride substrate are proposed. The transmission zeros and resonances are determined and studied in this article. Simulation and measurement results including surface current distributions and frequency responses are presented and discussed. It can be applied to 1.8 to 2.7 GHz high thermal conductivity systems. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2878–2882, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24787

In this paper a detailed investigation of slot waveguides for optical sensing in near-IR wavelength region is carried out, assuming Silicon-on-Insulator technology. Optimized guided-wave structures are found in terms of high sensitivity (Sh) and low propagation losses (αprop) and design guidelines are clearly selected. A number of possible application fields for environmental monitoring are covered, including gas sensing (gas identification or measure of their physical parameters as pressure) and liquid sensing (as pollutants in water). Influence of fabrication tolerances and wavelength dependence are also studied.

- by Giovanni Giannoccaro
- •
- Genetics, Food Safety, Photonics, Environmental Monitoring

We review the use of the oxide cladding stress induced photoelastic effect to eliminate the modal birefringence in silicon-on-insulator (SOI) ridge waveguide components, and highlight characteristics particular to high index contrast (HIC) systems. The birefringence in planar waveguides has its origin in the electromagnetic boundary conditions at the waveguide boundaries, and can be further modified by the presence of stress in the materials. It is shown that geometrical constraints imposed by different design and fabrication considerations become increasingly difficult to satisfy with decreasing core sizes. On the other hand, with typical stress levels of -100 MPa to -400 MPa (compressive) in SiO 2 used as the upper cladding, the effective indices are altered up to the order of 10 -3 for ridges with heights ranging from 1 m to 5 m. We demonstrate that the stress can be effectively used to balance the geometrical birefringence. Birefringence-free operation is achieved for waveguides with otherwise large birefringence by using properly chosen thickness and stress of the upper cladding layer. This allows the waveguide cross-section profiles to be optimized for design criteria other than zero-birefringence. Since the index changes induced by the stress are orders of magnitude smaller than the waveguide core/cladding index contrast, changes in the mode profiles are insignificant and the associated mode mismatch loss is negligible. We study the stress-induced effects in two parallel waveguides of varying spacing, to emulate the condition in directional couplers and ring-resonators. In the arrayed waveguide grating (AWG) demultiplexers fabricated in the SOI platform, we demonstrated the reduction of the birefringence from 1.3 10 -3 (without the upper cladding) to below 1 10 -4 across the spectral band by using a 0.6 µm oxide upper cladding with a stress of -320 MPa (compressive). Design options for relaxed dimensional tolerance and improved coupler performance made available by using stress engineering are discussed.

- by Pavel Cheben and +1
- •
- Silicon on Insulator, Cross Section, Design Criteria, Boolean Satisfiability

In this paper we report on the effects of two optical beams counterpropagating in a passive ring resonator that is the building block of several devices in a lot of sensing applications. By using the transfer matrix method in combination with the coupled mode theory, the analytical expressions of the power transfer functions for drop and through port configurations are derived in both cases of single beam and double beams inside the ring. The implemented model has shown some improvements in the resonator performance, such as the increase of the transmission power and the reduction of the linewidth, when the interaction between the two beams is considered, with respect to the single beam ring resonator configuration.

- by Mario N. Armenise
- •
- Sensors, Quality Factor, Ring Resonator, The European

An experimental prototype is presented that illustrates the implementation aspects and feasibility of the novel ring resonator-based optical beamformer concept that has been developed and analyzed in Part I of this paper . This concept can be used for seamless control of the reception angle in broadband wireless receivers employing a large phased array antenna (PAA). The design, fabrication, and characterization of a dedicated chip are described, in which an 81 optical beamforming network, an optical sideband filter for single-sideband suppressed carrier modulation, and a carrier re-insertion coupler for balanced optical detection are integrated. The chip was designed for satellite television reception using a broadband PAA, and was realized in a low-loss, CMOS-compatible optical waveguide technology. Tuning is performed thermo-optically, with a switching time of 1 ms. Group delay response and power response measurements show the correct operation of the OBFN and OSBF, respectively. Measurements on a complete beamformer prototype (including the electro-optical and opto-electrical conversions) demonstrate an optical sideband suppression of 25 dB, RF-to-RF delay generation up to 0.63 ns with a phase accuracy better than /10 radians, and coherent combining of four RF input signals, all in a frequency range of 1–2 GHz.

- by Maurizio Burla
- •
- Performance Analysis, Optical Waveguide, Phased Array, Optical physics

We demonstrate a novel, highly sensitive integrated hydrogen sensor based on a silicon ring resonator on the silicon-oninsulator platform. The hydrogen sensitive element in the sensor structure is a platinum-doped tungsten oxide catalytic coating. The catalytic combustion of hydrogen in air leads to a local temperature rise in the ring resonator. The resulting thermo-optic effect shifts the ring resonator resonance. Resonance wavelength shifts higher than a nanometer are measured for hydrogen concentrations below the 4% lower explosion limit. A potentially tunable sensitivity of around 480 pm shift per %H 2 is achieved at an operating temperature of about 40 C.

- by driss lahem
- •
- Catalysis, Integrated Optics, Silicon on Insulator, Optical physics

Multilevel thin film processing, global planarization and advanced photolithography enables the ability to integrate complimentary materials and process sequences required for high index contrast photonic components all within a single CMOS process flow. Developing high performance photonic components that can be integrated with electronic circuits at a high level of functionality in silicon CMOS is one of the basic objectives of the EPIC program sponsored by the Microsystems Technology Office (MTO) of DARPA. Our research team consisting of members from: BAE Systems, Alcatel-Lucent, Massachusetts Institute of Technology, Cornell University and Applied Wave Research reports on the latest developments of the technology to fabricate an application specific, electronic-photonic integrated circuit (AS_EPIC). Now in its second phase of the EPIC program, the team has designed, developed and integrated fourth order optical tunable filters, both silicon ring resonator and germanium electro-absorption modulators and germanium pin diode photodetectors using silicon waveguides within a full 150nm CMOS process flow for a broadband RF channelizer application. This presentation will review the latest advances of the passive and active photonic devices developed and the processes used for monolithic integration with CMOS processing. Examples include multilevel waveguides for optical interconnect and germanium epitaxy for active photonic devices such as p-i-n photodiodes and modulators.

- by Jurgen Michel
- •
- Thin Film, High performance, Tunable Filter, Integrated Circuit

A novel optical beamformer concept is introduced that can be used for seamless control of the reception angle in broadband wireless receivers employing a large phased array antenna (PAA). The core of this beamformer is an optical beamforming network (OBFN), using ring resonator-based broadband delays, and coherent optical combining. The electro-optical conversion is performed by means of single-sideband suppressed carrier modulation, employing a common laser, Mach-Zehnder modulators, and a common optical sideband filter after the OBFN. The unmodulated laser signal is then re-injected in order to perform balanced coherent optical detection, for the opto-electrical conversion. This scheme minimizes the requirements on the complexity of the OBFN, and has potential for compact realization by means of full integration on chip. The impact of the optical beamformer concept on the performance of the full receiver system is analyzed, by modeling the combination of the PAA and the beamformer as an equivalent two-port RF system. The results are illustrated by a numerical example of a PAA receiver for satellite TV reception, showing that—when properly designed—the beamformer hardly affects the sensitivity of the receiver.

- by Maurizio Burla
- •
- Performance Analysis, Optical Waveguide, Phased Array, Optical physics

We present an experimental study of an integrated slotwaveguide refractive index sensor array fabricated in silicon nitride on silica. We study the temperature dependence of the slot-waveguide ring resonator sensors and find that they show a low temperature dependence of −16.6 pm/K, while at the same time a large refractive index sensitivity of 240 nm per refractive index unit. Furthermore, by using on-chip temperature referencing, a differential temperature sensitivity of only 0.3 pm/K is obtained, without individual sensor calibration. This low value indicates good sensor-to-sensor repeatability, thus enabling use in highly parallel chemical assays. We demonstrate refractive index measurements during temperature drift and show a detection limit of 8.8 × 10 −6 refractive index units in a 7 K temperature operating window, without external temperature control. Finally, we suggest the possibility of athermal slot-waveguide sensor design.

- by Carlos A Barrios
- •
- Optics, Systems Integration, Transducers, Temperature Compensation

A quasi-monolithic second-harmonic-generation ring resonator assembled with miniaturized components is presented. The ring contains a 10-mm-long bulk periodically poled lithium niobate crystal for second-harmonic generation, four plane mirrors and two gradient-index lenses. All parts are mounted on a glass substrate with an overall size of 19.5 mm × 8.5 mm × 4 mm. As pump source a broad-area laser diode operated in an external resonator with Littrow arrangement is utilized. This external cavity diode laser provides near diffraction limited, narrow-bandwidth emission with an optical output power of 450 mW at a wavelength of 976 nm. Locking of the diode laser emission to the resonance frequency of the ring cavity was achieved by an optical self-injection locking technique. With this setup more than 126 mW of diffraction-limited blue light at 488 nm could be generated. The opto-optical conversion efficiency was 28% and a wall plug efficiency better than 5.5% could be achieved.

- by Joachim Sacher
- •
- Mechanical Engineering, Blue Light, Second Harmonic Generation, Optical physics

Superconducting microstrip ring resonators operating at 35 GHz have been fabricated from laser ablated YBa,Cu,O,-, (YBCO) films on lanthanum aluminate substrates. The circuits consist of superconducting strips over normal metal ground planes. The circuits are measured from 20 K to 90 K and with microwave input powers ranging from 0.25 mW to 10 mW. The superconducting resonators show significant improvement in Q (six to seven times higher) over identical gold resonators at 20 K, but only marginal improvement at 77 K. No variation in the superconductor performance is ,observed with varying input power. Using a microstrip loss model, the microwave surface resistance of the superconductors is extracted; the lowest value obtained at 77 K is 9 m a . The change in the resonant frequency with temperature is analyzed and a value for the penetration depth computed. "Double resonances" observed in some superconducting ring resonators are described and an explanation for their presence advanced. Factors limiting millimeter-wave high-temperature superconductor circuits are explored and potential performance levels calculated based on current reported values for high-temperature superconductor surface resistances.

- by Joseph Warner and +1
- •
- Millimeter Wave Antennas, Superconductors, Laser Ablation, Penetration Depth

A thermally tuneable, wide FSR switch, based on integrated-optic micro-ring resonators is described. This wavelength-selective switch allows high ON/OFF ratios combined with small dimensions. Furthermore allows the structure for a wide Free Spectral Range, since multiple resonators are used. This switch can be used in WDM filter arrays for a transceiver in an access network. Measurements of the thermal behaviour of a single resonator confirm the switching capability of the switch.

In this work, a novel single-longitudinal-mode (SLM) four-wavelength laser configuration for sensing applications in the L-band is proposed and experimentally demonstrated. The sensor system presented here is based on ring resonators, and employs fiber Bragg gratings to select the operation wavelengths. The stable SLM operation is guaranteed when all the lasing channels present similar output powers. It is also experimentally demonstrated that when a SLM behavior is achieved, lower output power fluctuations are obtained. Characterization of the lasing structure for temperature sensing is also shown.

Campus Universitario s / n 36200 Vigo Spain KEY TERMS Fiber r~~. s o n a~~r s . ~ionlineu~ oprics, optical oscillators. optical signal prow~sing ABSTRACT I n r1ii.s Lerter u'e srirdy /tie rransienr hehai,ior. of a notilinear iwo-coupler fiber-ring resorio~or operaring as im optical oscillaior. The shape of die pi1w.s genrratetl atid the speed in [lie e.sruhlishtneni of osci1lririori.s are itrr~esri~~~ted.

- by Antonio Montero Seoane
- •
- Nonlinear Optics, Transient analysis, Oscillations, Optical physics

A dual-mode dual-band bandpass filter is designed using a single stub-loaded slot ring resonator. This resonator is coupled to the two external feed lines at two positions spaced at 135 • along the slot ring through a pair of microstrip-slotline T-junctions. With a proper choice of the degree of external coupling, the first-order degenerate modes are split to make up the first passband with two transmission poles. The second passband is realized by the second-order degenerate modes, which are stimulated by symmetrically attaching four identical stubs along the slotring. The center frequency ratio of the two operating passbands is controlled by the nature and strength of the external coupling, which is determined by the characteristics of the microstrip open-circuited stubs. Finally, a dualband filter with center frequencies at 2.4 and 5.2 GHz is designed and fabricated. Measured results verify the design principle and predicted dual-passband performance. Benefiting from an additional transmission zero brought by the transitions,the upper stopband is expanded up to 12.75 GHz with at least 13 dB of rejection.

- by Sha Luo
- •
- Optical physics, Degeneration, Electrical And Electronic Engineering, Ring Resonator

We have investigated an optical signal processor using electro-optic polymer waveguides operating at a wavelength of 1.55 m. Due to recent developments, many useful optical devices have become available such as optical filters, modulators, switches, and multiplexers. It will be useful to have a single optical device, which is reconfigurable to implement all of these functions. We call such a device an "optical signal processor," which will play a similar role to digital signal processors in electrical circuits. We realize such an optical device in a planar lightwave circuit. Since the planar lightwave circuits are based on the multiple interference of coherent light and can be integrated with significant complexity, they have been implemented for various purposes of optical processing such as optical filters. However, their guiding waveguides are mostly passive, and the only viable mechanism to reconfigure their functions is thermal effects, which is slow and cannot be used for high-speed applications such as optical modulators or optical packet switches. On the other hand, electro-optic polymer has a very high electro-optic coefficient and a good velocity match between electrical and optical signals, thus, permitting the creation of high-speed optical devices with high efficiency. Therefore, we have implemented a planar lightwave circuit using the electro-optic polymer waveguides. As a result, the structure is complex enough to generate arbitrary functions and fast enough to obtain high data rates. Using the optical signal processor, we investigate interesting applications including arbitrary waveform generators.

- by H. Fetterman
- •
- Electrical Circuit Theory, Optical physics, High Speed, Optical Modulator

Using near-field microscopy, the performance of dielectricloaded plasmonic waveguide-ring resonators (WRRs) operating at telecom wavelengths is investigated for various waveguide-ring separations. It is demonstrated that compact (footprint ∼ 150 μm 2 ) and efficient (extinction ratio ∼ 13 dB) WRR-based filters can be realized using UV-lithography. The WRR wavelength responses measured and calculated using the effective-index method are found in good agreement.

- by Sergey Bozhevolnyi
- •
- Optics, Computer Aided Design, Polymers, Transducers
- by P. Ferraro
- •
- Condensed Matter Physics, Domain Engineering, Ferroelectrics, Photonic Crystal

We review the design considerations and experimental results of a novel design of polarization insensitive ring resonators in silicon-on-insulator (SOI) ridge waveguides. The polarization insensitive coupling is achieved using a multi-mode-interference (MMI) coupler. Cladding stress-induced birefringence is used to correct the round trip phase difference between the TE and TM polarizations. Experimental demonstration is presented for such ring resonators fabricated on SOI with 1.5 µm Si waveguide core layer. For resonators with radius R = 200 µm, polarization insensitive operation is achieved in both the resonance wavelength and linewidth over a ~ 4 nm wavelength range using a 7.5 µm × 84 µm MMI coupler and 0.8 µm thick oxide cladding with -250 MPa stress, with the resonance wavelength shifts between TE and TM polarizations less than 3 pm. The quality factor Q of ~ 15,000 and free-spectral range (FSR) of 0.46 nm is measured. For resonators with a smaller radius of 50 µm, similar FRS of 1.3 nm and extinction of 13 dB are observed for TE and TM, although the resonance wavelengths are shifted, in agreement with the theoretical prediction. By choosing the proper combination of the cladding stress and thickness, zero-birefringence condition can be achieved for resonators of different cavity lengths.

- by Pavel Cheben
- •
- Quality Factor, Silicon on Insulator, Multi-mode Interference, Directional Coupler

- by Pavel Cheben
- •
- Quality Factor, Silicon on Insulator, Optical physics, Multimode Interference (MMI)

All-optical integrated circuits bring the promise to vastly increase the bandwidth, improve the flexibility as well as reduce the cost of future communication networks. All optical integrated components, like switches and wavelength converters, must meet fundamental requirements such as low optical losses, strong nonlinear response and ease of fabrication. To date, however, research on these devices has been based either on semiconductors, such as silicon and GaAs, or highly nonlinear glasses, such as chalcogenides which, although exhibit a Kerr nonlinearity (n2) of 100x-400x silica glass, also present limitations such as remarkable linear and nonlinear losses and, for certain applications, a not developed fabrication techniques. Specifically, the possibility to rely upon a mature technology recently has proved itself to be a powerful solution to fabricate micrometric resonant structures which are able to locally enhance the desired nonlinearities. In this work we present the first example of nonlinear optics in silica glass waveguides using continuous wave (CW) light. We achieve wavelength conversion via four wave mixing (FWM) at ultra-low (≈ 5 mW CW) power levels in C-MOS compatible micro-ring resonator.

- by Sai Chu
- •
- Frequency Conversion, Ring Resonator, Two Photon Absorption, Ultra Low Power

In this paper, we report on the fabrication and the characterization of a ring-resonator-based interleaver/deinterleaver circuit we proposed in a previous work. The experimental and theoretical transmission spectra as well as the... more

We present an ultra-compact comb filter using an add-drop ring resonator with an Archimedean spiral cavity. The cavity consists of two interleaved spiral branches which are connected in the center using arcs of circle of a radius that causes minimum bend loss. We describe the design procedure and examine the physical parameters governing the resonator performance. As an example, we demonstrate experimentally a comb filter with a 25 GHz channel spacing made of silicon photonic wires and only occupies an area of 80 × 90 µm 2 , approximately a 70 fold size reduction compared to a racetrack resonator. The filter transmission is free of spurious reflections, attesting to the smooth transition between different sections of the resonator cavity. Over a 40 channel wavelength span, the filter exhibits a quality factor Q > 35,000, extinction ratios > 10 dB, and an excellent power uniformity with variations < 0.5 dB for both the through and drop ports.

- by Pavel Cheben
- •
- Optics, Optical physics, Electrical And Electronic Engineering, Ring Resonator

Multiple stop-bands are required in order to suppress interference in radio spectrum with multiple wireless systems operating in it. In addition, wireless communication systems usually require small devices to fulfill the miniaturization requirements and simplicity of mobile unit. As a result, this paper is to propose a novel miniaturized matched band-stop filter with high rejection level. This filter results in 50 % size reduction compared with the dual-mode ring resonator that has an electrical length of 360˚. In addition for the short electrical length of this filter the first spurious resonance occurs at 4.7 times the fundamental resonance frequency. The filter design is cascaded to achieve multiband band-stop filter at center frequencies of 0.99 GHz and 1.04GHz. Theoretical analysis together with experimental results is presented to demonstrate the feasibility of the approach.

- by Bakhit Amine Adoum
- •
- Wireless Systems, Theoretical Analysis, Matched Filter, Spectrum

We study the resonant transmission of light in a coupled-resonator optical waveguide interacting with two nearly identical side cavities. We reveal and describe a novel effect of the coupled-resonator-induced reflection (CRIR) characterized by a very high and easily tunable quality factor of the reflection line, for the case of the inter-site coupling between the cavities and the waveguide. This effect differs sharply from the coupled-resonator-induced transparency (CRIT) -- an all-optical analogue of the electromagnetically-induced transparency -- which has recently been studied theoretically and observed experimentally for the structures based on micro-ring resonators and photonic crystal cavities. Both CRIR and CRIT effects have the same physical origin which can be attributed to the Fano-Feshbach resonances in the systems exhibiting more than one resonance. We discuss the applicability of the novel CRIR effect to the control of the slow-light propagation and low-threshold all-optical switching.