Abstract: Aspects of the subject disclosure may include, for example, a system for modulating a first electrical signal to generate first modulated electromagnetic waves, and transmitting the first modulated electromagnetic waves on a waveguide located in proximity to a transmission medium. In one embodiment, the first electromagnetic waves can induce second electromagnetic waves that propagate on an outer surface of the transmission medium. The second electromagnetic waves can have a first spectral range that is divided into, contains or otherwise includes a first control channel and a first plurality of bands. Other embodiments are disclosed.

Abstract: Aspects of the subject disclosure may include, for example, a connector that includes a first port configured to receive electromagnetic waves guided by a first dielectric core of a first transmission medium. A waveguide is configured to guide the electromagnetic waves from the first port to a second port. The second port is configured to transmit the electromagnetic waves to a second dielectric core of a second transmission medium. Other embodiments are disclosed.

Abstract: Aspects of the subject disclosure may include, a generator that facilitates generation of an electromagnetic wave, a core, and a waveguide that facilitates guiding the electromagnetic wave towards the core to induce a second electromagnetic wave that propagates along the core. The core and/or the waveguide can be configured to reduce radiation loss of the second electromagnetic wave, propagation loss of the second electromagnetic wave, or a combination thereof. Other embodiments are disclosed.

Abstract: Going beyond the canonical cavity-optomechanical system consisting of a Fabry–Perot cavity with a movable end mirror, here we explore a new paradigm in which phononic crystal waveguides are used to wire together local cavity elements to form interacting microcircuits of photons and phonons. Single cavity-waveguide elements, fabricated in the device layer of a silicon-on-insulator microchip, are used to optically excite and detect C-band (∼6 GHz) microwave phonons propagating in phononic-bandgap-guided acoustic waveguides. Interconnecting a pair of optomechanical cavities via a phonon waveguide is then used to demonstrate a tunable delay and filter for microwave-over-optical signals in the 1,500 nm wavelength band. Finally, we realize a tight-binding form of mechanical coupling between distant optomechanical cavities, leading to direct phonon exchange without dissipation in the waveguide. These initial demonstrations indicate the potential of cavity-optomechanical circuits for performing coherent signal processing as well as for realizing new modalities of optical readout in distributed micromechanical sensors.

Abstract: Aspects of the subject disclosure may include, generating, by a plurality of dielectric antennas of a waveguide system, a plurality of instances of electromagnetic waves that combines to form a combined electromagnetic wave, and directing, by the waveguide system, the combined electromagnetic wave to an interface of a transmission medium for guiding propagation of the combined electromagnetic wave along the transmission medium without requiring an electrical return path. Other embodiments are disclosed.

Abstract: Aspects of the subject disclosure may include, for example, a system having a first plurality of transmitters for launching according to a signal, first electromagnetic waves, and a second plurality of transmitters for launching, according to the signal, second electromagnetic waves. The first electromagnetic waves and the second electromagnetic waves combine at an interface of a transmission medium to induce a propagation of a third electromagnetic wave, the third electromagnetic wave having a non-fundamental wave mode and a non-optical operating frequency, and wherein the second plurality of transmitters are spaced apart from the first plurality of transmitters in a direction of propagation of the third electromagnetic wave. Other embodiments are disclosed.

Abstract: Aspects of the subject disclosure may include, launching, by a plurality of launchers of a waveguide system, a wave mode that propagates along a transmission medium without requiring an electrical return path, detecting, by the waveguide system, that the wave mode has a propagation loss caused by an obstruction, and generating, by the plurality of launchers, an adjusted wave mode having an electric field structure that reduces the propagation loss of the obstruction. Other embodiments are disclosed.

Abstract: We report experimental observations of a large Bragg reflection from arrays of cold atoms trapped near a one-dimensional nanoscale waveguide. By using an optical lattice in the evanescent field surrounding a nanofiber with a period nearly commensurate with the resonant wavelength, we observe a reflectance of up to 75% for the guided mode. Each atom behaves as a partially reflecting mirror and an ordered chain of about 2000 atoms is sufficient to realize an efficient Bragg mirror. Measurements of the reflection spectra as a function of the lattice period and the probe polarization are reported. The latter shows the effect of the chiral character of nanoscale waveguides on this reflection. The ability to control photon transport in 1D waveguides coupled to spin systems would enable novel quantum network capabilities and the study of many-body effects emerging from long-range interactions.

Abstract: This paper introduces the concept, theory, and design of 3-D frequency selective rasorbers (FSRs), which have a transmission window transparent to the incident electromagnetic wave with two absorption bands located at both sides of the window. The proposed rasorber consists of a 2-D periodic array of parallel waveguides. The transmission characteristics with high selectivity are produced by lossless resonators implemented using a parallel waveguide with a metallic post in the center. On the other hand, the absorption bands are obtained by lossy resonators constructed by loading of lumped resistors at the entry port of short-circuited waveguides. Physical mechanism of the proposed FSRs is explained with the aid of an equivalent circuit model, and relevant design equations are formulated. Two prototypes of the designed FSRs are fabricated and measured as a proof of concept. The experimental results show that a bandwidth of 50% for the insertion loss less than 3 dB and two absorption bands with a high absorptance of around 90% can be achieved. Moreover, the simulated results also show that the proposed structure exhibits stable performance against the variation of the incident angle of an incoming plane wave.

Abstract: Spin-wave-based devices promise to usher in an era of low-power computing where information is carried by the precession of the electrons' spin instead of dissipative translation of their charge. This potential is, however, undermined by the need for a bias magnetic field, which must remain powered on to maintain an anisotropic device characteristic. Here, we propose a reconfigurable waveguide design that can transmit and locally manipulate spin waves without the need for any external bias field once initialized. We experimentally demonstrate the transmission of spin waves in straight as well as curved waveguides without a bias field, which has been elusive so far. Furthermore, we experimentally show a binary gating of the spin-wave signal by controlled switching of the magnetization, locally, in the waveguide. The results have potential implications in high-density integration and energy-efficient operation of nanomagnetic devices at room temperature.

Abstract: Integrated optical components on lithium niobate play a major role in standard high-speed communication systems. Over the last two decades, after the birth and positioning of quantum information science, lithium niobate waveguide architectures have emerged as one of the key platforms for enabling photonics quantum technologies. Due to mature technological processes for waveguide structure integration, as well as inherent and efficient properties for nonlinear optical effects, lithium niobate devices are nowadays at the heart of many photon-pair or triplet sources, single-photon detectors, coherent wavelength-conversion interfaces, and quantum memories. Consequently, they find applications in advanced and complex quantum communication systems, where compactness, stability, efficiency, and interconnectability with other guided-wave technologies are required. In this review paper, we first introduce the material aspects of lithium niobate, and subsequently discuss all of the above mentioned quantum components, ranging from standard photon-pair sources to more complex and advanced circuits.

Abstract: We demonstrate an on-chip sensor for room-temperature detection of methane gas using a broadband spiral chalcogenide glass waveguide coupled with off-chip laser and detector. The waveguide is fabricated using UV lithography patterning and lift-off after thermal evaporation. We measure the intensity change due to the presence and concentration of methane gas in the mid-infrared (MIR) range. This work provides an approach for broadband planar MIR gas sensing.

Abstract: A 3-D printed fourth-order cavity bandpass filter (BPF) centered at 10 GHz and with a 3% fractional bandwidth is presented in this letter. The BPF was designed using two high- $Q$ spherical dual-mode cavity resonators, and was fabricated using a stereolithography-based 3-D printing technique. Compared to dual-mode filters constructed by square or cylindrical resonators, the use of spherical resonator gives a wider spurious-free region. In order to fully exhibit the light weight advantage of additive manufacturing, the redundant material outside of the filter was removed. In addition, rectangular apertures were added through the cavities and waveguide walls without interrupting the surface current distributions, which further yields reduced filter weight as well as easier electroplating. Measured results of the BPF exhibit an excellent agreement with simulations.

Abstract: We present a graphene-on-silicon (GoS) suspended vertical slot waveguide. By changing the Fermi level of graphene, the variation in the effective refractive index (RI) of the waveguide is a factor of two larger than that in the traditional GoS rib waveguide. The improvement is due to the light-intensity enhancement and the poor confinement of the optical mode in the slot nanostructure. We design Mach–Zehnder interferometer (MZI) and microring modulators based on the GoS suspended vertical slot waveguide. Our calculations show that the modulators can be energy-efficient and footprint-compact due to the large phase shift of the propagating mode in the waveguide after applying a gate voltage on the graphene. Fabrication of our design is easy and CMOS-compatible. It paves the way for chip-integrated electronic-RI modulators.

Abstract: A low-loss hollow core terahertz waveguide based on Kagome photonic crystal structure has been designed and fabricated by 3D printing. The 3D printed waveguide has been characterized by using THz time-domain spectroscopy. The results demonstrate that the obtained waveguide features average power propagation loss of 0.02 cm-1 for 0.2-1.0 THz (the minimum is about 0.002 cm-1 at 0.75 THz). More interesting, it could be simply mechanically spliced without any additional alignment, while maintaining the excellent performance. The 3D printing technique will be a promising solution to fabricate Kagome THz waveguide with well controllable characteristics and low cost.

Abstract: Nano-computer numerical control (CNC) machining technology is employed for the fabrication of sub-THz (100–1000 GHz) vacuum electron devices. Submicron feature tolerances and placement accuracy have been achieved and surface roughness of a few tens of nanometers has been demonstrated providing high-quality radio frequency (RF) transmission and reflection parameters on the tested circuit structures. Details of the manufacturing approach are reported for the following devices: W-band sheet beam (SB) klystron, two designs of a 220-GHz SB double-staggered grating traveling wave tube (TWT), 263-GHz SB TWT amplifier for an electron paramagnetic resonance spectrometer, 346-GHz SB backward wave oscillator for fusion plasma diagnostics, 346-GHz pencil beam backward wave oscillator, and 270-GHz pencil beam folded waveguide TWT self-driving amplifier. Application of the nano-CNC machining to nanocomposite scandate tungsten cathodes as well as to passive RF components is also discussed.

Abstract: We experimentally demonstrate a nanoscale mode converter that performs coupling between the first two transverse electric-like modes of a silicon-on-insulator waveguide. The device operates by introducing a nanoscale periodic perturbation in its effective refractive index along the propagation direction and a graded effective index profile along its transverse direction. The periodic perturbation provides phase matching between the modes, while the graded index profile, which is realized by the implementation of nanoscale dielectric metasurface consisting of silicon features that are etched into the waveguide taking advantage of the effective medium concept, provides the overlap between the modes. Following the device design and numerical analysis using three-dimensional finite difference time domain simulations, we have fabricated the device and characterized it by directly measuring the modal content using optical imaging microscopy. From these measurements, the mode purity is estimated to be 95% and th...

Abstract: A dual-mode 3 dB power coupler based on silicon-on-insulator platform for mode division multiplexing system is proposed and demonstrated. The device, which consists of a tapered directional coupler and two output bend waveguides, has a 50:50 coupling ratio around the wavelength of 1550 nm for both fundamental and first order transverse magnetic (TM0 and TM1) modes. Based on asymmetrical tapered structure, a short common coupling length of ~15.2 μm for both modes is realized by optimizing the width of the tapered waveguide. The measured insertion loss for both modes is less than 0.7 dB. The crosstalks are about −14.3 dB for TM0 mode and −18.1 dB for TM1 mode.

Abstract: We present Ge rib waveguide devices fabricated on a Ge-on-insulator (GeOI) wafer as a proof-of-concept Ge mid-infrared photonics platform. Numerical analysis revealed that the driving current for a given optical attenuation in a carrier-injection Ge waveguide device at a 1.95 μm wavelength can be approximately five times smaller than that in a Si device, enabling in-line carrier-injection Ge optical modulators based on free-carrier absorption. We prepared a GeOI wafer with a 2-μm-thick buried oxide layer (BOX) by wafer bonding. By using the GeOI wafer, we fabricated Ge rib waveguides. The Ge rib waveguides were transparent to 2 μm wavelengths and the propagation loss was found to be 1.4 dB/mm, which may have been caused by sidewall scattering. We achieved a negligible bend loss in the Ge rib waveguide, even with a 5 μm bend radius, owing to the strong optical confinement in the GeOI structure. We also formed a lateral p-i-n junction along the Ge rib waveguide to explore the capability of absorption modulation by carrier injection. By injecting current through the lateral p-i-n junction, we achieved optical intensity modulation in the 2 μm band based on the free-carrier absorption in Ge.

Abstract: We demonstrate experimentally the efficient control of light intensity distribution inside a random scattering system. The adaptive wave front shaping technique is applied to a silicon waveguide containing scattering nanostructures, and the on-chip coupling scheme enables access to all input spatial modes. By selectively coupling the incident light to the open or closed channels of the disordered system, we not only vary the total energy stored inside the system by a factor of 7.4, but also change the energy density distribution from an exponential decay to a linear decay and to a profile peaked near the center. This work provides an on-chip platform for controlling light-matter interactions in turbid media.

Abstract: A compact and high extinction ratio polarization beam splitter using subwavelength grating (SWG) couplers is proposed and characterized, where the SWG couplers are located between the two input/output strip waveguides, including SWG-based transitions combined at both ends. The TM mode can be confined well in the strip waveguide and transmits along it with nearly neglected coupling, while the TE mode undergoes a strong coupling and is transferred to the adjacent waveguide with the help of SWG couplers due to dissimilar modal characteristics and cutoff conditions between these two polarizations. To further enhance the performance, an additional tapered waveguide is added in the lateral end of the input SWG-based transition. Results show that a total length of 6.8 μm with an insertion loss of 0.08 (0.36) dB, extinction ratio (ER) of 32.19 (20.93) dB, and reflection loss of -34.76 (-32.59) dB for TE (TM) mode is obtained at 1.55 μm; its bandwidth can be enlarged to ∼81 nm for an ER>18 dB. In addition, fabrication tolerances and mode-field evolution are also presented.

Abstract: Recently, gap waveguides have been shown as a potential alternative to convenational waveguides in the millimeter-wave band. Until now, groove gap waveguide (GGW) has been studied through direct correspondence with rectangular waveguide with the same physical dimensions. However, there have been observed differences in the above cutoff propagation characteristics between these two waveguide types. Furthermore, the behavior of GGW below cutoff remains unknown. This work presents a discussion of both below and above cutoff propagation characteristics of GGW, and introduces a simple model that explains the observed GGW behavior and establishes well its propagation characteristics. Two thru-reflect-line calibration kits have been manufactured, and the measurements have good agreement with the proposed analysis model results.

Abstract: A biosensor is a device that is used to detect the analytes or molecules of a sample by means of a binding mechanism. A two-dimensional photonic crystal waveguide-based biosensor is designed with a diamond-shaped ring resonator and two waveguides: a bus waveguide and a drop waveguide. The sensing mechanism is based on change in refractive index of the analytes, leading to a shift in the peak resonant wavelength. This mechanism can be used in the field of biomedical treatment where different body fluids such as blood, tears, saliva, or urine can be used as the analyte in which different components of the fluid can be detected. It can also be used to differentiate between the cell lines of a normal and an unhealthy human being. Average value of quality factor for this device comes out to be 1082.2063. For different analytes used, the device exhibits enhanced sensitivity and, hence, it is useful for the detection of diseases.

Abstract: Low-propagation-loss silicon wire waveguides are key components of optical integrated circuits. In this paper, we clarified, through assessment of the relationship between waveguide loss and fabrication technology that high-resolution lithography and an adjusted lithography process window are important for low-loss waveguides. The silicon wire waveguides fabricated by high-resolution lithography technology using ArF immersion lithography process showed world-record low propagation losses of au]0._40 dB/cm for the C-band and au]1._28 dB/cm for the O-band. Analysis with Barwicz and Haus’s theory indicated that sidewall scattering is the main cause of propagation loss even in such low-loss waveguides.

Abstract: Ultra-short pulses are an attractive way of expanding today’s terahertz time-domain systems toward frequencies above 2 THz, and moreover mode control enables reliable generation of terahertz frequency combs based on quantum cascade lasers. We report on a waveguide engineering technique that enables the generation of a bandwidth up to ∼1 THz and an ultra-short pulse length of 2.5 ps in injection-seeded terahertz quantum cascade lasers. The reported technique is able to control and fully suppress higher order lateral modes in broadband terahertz quantum cascade lasers by introducing side-absorbers to metal–metal waveguides. The side-absorbers consist of a top metallization setback with respect to the laser ridge and an additional lossy metal layer. In continuous wave operation, the side-absorbers lead to octave-spanning laser emission, ranging from 1.63 to 3.37 THz, exhibiting a 725 GHz wide flat top within a 10 dB intensity range, as well as frequency comb operation with a bandwidth of 442 GHz. Numerical and experimental studies have been performed to optimize the impact of the side-absorbers on the emission properties and to determine the required increase of waveguide losses. Furthermore, these studies have led to a better understanding of the pulse formation dynamics of injection-seeded quantum cascade lasers.

Abstract: We use a 3D printer to fabricate rectangular dielectric single mode waveguides for 120 GHz. The rectangular waveguides consisting of polystyrene showed an attenuation of 6.3 dB/m, which is low enough for short devices. We also characterize 3D printed Y-splitters and a 1x3-splitter based on multimode interference. Further, we construct and measure a variable planar waveguide coupler which can be used as a 3-dB coupler, a cross-coupler and no coupler at all.

Abstract: The ability to control flexural wave propagation is of fundamental interest in many areas of structural engineering and physics. Metamaterials have shown a great potential in subwavelength wave propagation control due to their inherent local resonance mechanism. In this study, we propose a transformation method to derive the material properties of a flexural waveguide and implement the functionality based on a design of active elastic metamaterials. The numerically demonstrated flexural waveguide can not only steer an elastic wave beam as predicted from the transformation method but also exhibit various unique properties including extraordinary wave beam deflection and tunabilities over a broad frequency range and various steering directions. The waveguide is equipped with an array of active elastic metamaterials composed of the electrorheological elastomer subjected to adjustable electric fields. Such metamaterial-based waveguides provide a new design methodology for guided wave signal modulation devices...

Abstract: We experimentally demonstrate a tunable Fano resonance which originates from the optical interference between two different resonant cavities using silicon micro-ring resonator with feedback coupled waveguide fabricated on silicon-on-insulator (SOI) substrate. The resonance spectrum can be periodically tuned via changing the resonant wavelengths of two resonators through the thermo-optic effect. In addition to this, we can also change the transmission loss of the feedback coupled waveguide (FCW) to tune the resonance spectrum by the injection free carriers to FCW. We also build the theoretical model and we analyze the device performance by using the scattering matrix method. The simulation results are in a good agreement with the experimental results. The measurement maximum extinction ratio of the Fano resonance is as high as 30.8dB. Therefore, the proposed device is a most promising candidate for high on/off ratio optical switching/modulating, high-sensitivity biochemical sensing.

Abstract: GeSbS ridge waveguides have recently been demonstrated as a promising mid – infrared platform for integrated waveguide – based chemical sensing and photodetection. To date, their nonlinear optical properties remain relatively unexplored. In this paper, we characterize the nonlinear optical properties of GeSbS glasses, and show negligible nonlinear losses at 1.55 μm. Using self – phase modulation experiments, we characterize a waveguide nonlinear parameter of 7 W−1/m and nonlinear refractive index of 3.71 × 10−18 m2/W. GeSbS waveguides are used to generate supercontinuum from 1280 nm to 2120 nm at the −30 dB level. The spectrum expands along the red shifted side of the spectrum faster than on the blue shifted side, facilitated by cascaded stimulated Raman scattering arising from the large Raman gain of chalcogenides. Fourier transform infrared spectroscopic measurements show that these glasses are optically transparent up to 25 μm, making them useful for short – wave to long – wave infrared applications in both linear and nonlinear optics.