Abstract: An array of pairs of parallel gold nanorods is shown to have a negative refractive index in the optical range, close to a wavelength of 1 μm.

Abstract: High-repetition rate femtosecond lasers are shown to drive heat accumulation processes that are attractive for rapid writing of low-loss optical waveguides in transparent glasses. A novel femtosecond fiber laser system (IMRA America, FCPA muJewel) providing variable repetition rate between 0.1 and 5 MHz was used to study the relationship between heat accumulation and resulting waveguide properties in fused silica and various borosilicate glasses. Increasing repetition rate was seen to increase the waveguide diameter and decrease the waveguide loss, with waveguides written with 1-MHz repetition rate yielding ~0.2-dB/cm propagation loss in Schott AF45 glass. A finite-difference thermal diffusion model accurately tracks the waveguide diameter as cumulative heating expands the modification zone above 200-kHz repetition rate.

Abstract: This work presents our recent progress in the development of an Si wire waveguiding system for microphotonics devices. The Si wire waveguide promises size reduction and high-density integration of optical circuits due to its strong light confinement. However, large connection and propagation losses had been serious problems. We solved these problems by using a spot-size converter and improving the microfabrication technology. As a result, propagation losses as low as 2.8 dB/cm for a 400/spl times/200 nm waveguide and a coupling loss of 0.5 dB per connection were obtained. As we have the technologies for the fabrication of complex, practical optical devices using Si wire waveguides, we used them to make microphotonics devices, such as a ring resonator and lattice filter. The devices we made exhibit excellent characteristics because of the microfabrication with the precision of a few nanometers. We have also demonstrated that Si wire waveguides have great potential for use in nonlinear optical devices.

Abstract: A virtual image display device with an optical waveguide to guide, by internal total reflection, parallel pencil groups meeting a condition of internal total reflection, a first reflection volume hologram grating to diffract and reflect the parallel pencil groups incident upon the optical waveguide from outside and traveling in different directions as they are so as to meet the condition of internal total reflection inside the optical waveguide and a second reflection volume hologram grating to project the parallel pencil groups guided by internal total reflection inside the optical waveguide as they are from the optical waveguide by diffraction and reflection thereof so as to depart from the condition of internal total reflection inside the optical waveguide.

Abstract: We propose an optical circulator formed of a magneto-optical cavity in a 2D photonic crystal. With spatially engineered magnetic domain structures, the cavity can be designed to support a pair of counterrotating states at different frequencies. By coupling the cavity to three waveguides, and by proper matching of the frequency split of the cavity modes with the coupling strength between the cavity and the waveguide, ideal three-port circulators with complete isolation and transmission can be created. We present a guideline for domain design needed to maximize the modal coupling and the operational bandwidth for any given magneto-optical constant.

Abstract: The nonlinear index of refraction is responsible for self-action effects in optical beam propagation, including self-focusing. We review self-focusing and related phenomena and discuss physical mechanisms that give rise to the refractive index nonlinearity.

Abstract: A nitride semiconductor laser device has an improved stability of the lateral mode under high output power and a longer lifetime, so that the device can be applied to write and read light sources for recording media with high capacity. The nitride semiconductor laser device includes an active layer, a p-side cladding layer, and a p-side contact layer laminated in turn. The device further includes a waveguide region of a stripe structure formed by etching from the p-side contact layer. The stripe width provided by etching is within the stripe range of 1 to 3 μm and the etching depth is below the thickness of the p-side cladding layer of 0.1 μm and above the active layer. Particularly, when a p-side optical waveguide layer includes a projection part of the stripe structure and a p-type nitride semiconductor layer on the projection part and the projection part of the p-side optical waveguide layer has a thickness of not more than 1 μm, an aspect ratio is improved in far field image. Moreover, the thickness of the p-side optical waveguide layer is greater than that of an n-side optical waveguide layer.

Abstract: We present a three-dimensional (3-D) analysis of scattering losses due to sidewall roughness in rectangular dielectric waveguides valid for any refractive-index contrast and field polarization. The analysis is based on the volume current method and uses array factors to introduce significant mathematical simplifications to better understand the influence of individual waveguide parameters on scattering losses. We show that the typical two-dimensional (2-D) analyses can substantially overestimate scattering losses in small waveguides and that scattering losses exhibit considerable polarization dependence. We produce scattering-loss estimates for a wide variety of waveguides and provide guidelines for design of waveguide cross sections that are less sensitive to sidewall roughness.

Abstract: Electric field modulation of visible and ultraviolet nanoscale lasers consisting of single CdS or GaN nanowires has been achieved using integrated, microfabricated electrodes. Modulation of laser emission intensity is achieved with no detectable change in the laser wavelength. The devices can also be operated below the lasing threshold to modulate the intensity of light propagating within the nanowire waveguide. Studies of the electric field dependence in devices of varied geometry indicate that modulation is due to an electroabsorption mechanism. These findings expand opportunities for multicolor, nanowire-based photonic devices and circuits.

Abstract: We describe a low-loss single-mode waveguide in planar light-wave circuit (PLC) glass doped with boron and phosphorus, which is more difficult to write than pure-silica glass. The written waveguide has a rectangular core, a symmetric near-field pattern, and a propagation loss of 0.35?dB?cm. The loss that originates from the mode-field mismatch between the mode-field diameters of the written and the PLC waveguides is less than 0.1?dB?point. In addition, we successfully connected PLC waveguides with a 500-?m-long waveguide written with a laser. The laser-written waveguide can flexibly connect PLC waveguides with a low coupling loss.

Abstract: It is demonstrated that the propagation of electromagnetic waves in an appropriately designed waveguide is (for large wavelengths) analogous to that within a curved space-time---such as around a black hole. As electromagnetic radiation (e.g., microwaves) can be controlled, amplified, and detected (with present-day technology) much easier than sound, for example, we propose a setup for the experimental verification of the Hawking effect. Apart from experimentally testing this striking prediction, this would facilitate the investigation of the trans-Planckian problem.

Abstract: A six-port junction based on the substrate integrated waveguide (SIW) technology is proposed and presented. In this design of such a junction, the SIW is first converted to an equivalent rectangular waveguide, then regular rectangular waveguide design techniques are used. In this structure, an SIW power divider and SIW hybrid 3-dB coupler are designed as fundamental building blocks. A six-port junction circuit operating at 24 GHz is fabricated and measured. Good agreement between simulated and measured results is found for the proposed six-port junction.

Abstract: An optical communication device of the invention includes a reflector for reflecting the light that has reached one end surface of a waveguide chip to turn the optical path of the light The reflector includes a transparent thin film layer formed on one end surface of the waveguide chip by using a material to which a metal that forms an intermetallic compound or the like with Au is added to a substance that is transparent to the light that propagates through the waveguide, as well as an Au thin film layer formed on the front surface of the transparent thin film layer This allows formation of a reflector having an Au thin film layer as a reflecting surface in an optical medium with high adhesion strength Thus, an optical communication device can be provided having a high reliability with little loss

Abstract: An optical waveguide comprises a core, an inner cladding laterally surrounding the core, and an outer cladding laterally surrounding the inner cladding, wherein the core, inner cladding, and outer cladding have a depressed well configuration. The waveguide operates in three or more wavelength bands, wherein a first wavelength band is centered at about 1300 nm, and wherein a second wavelength band is centered at about 1625 nm. The waveguide has bend losses that are less than or equal to 1.0 dB/turn when measured on a 5 mm radius bend at 1625 nm and bend losses that are less than or equal to 1.5 dB/turn when measured on a 5 mm radius bend at 1650 nm.

Abstract: We present predicted relative scattering losses from sidewall roughness in a strip waveguide compared to an identical waveguide surrounded by a photonic crystal with a complete or incomplete gap in both 2d and 3d. To do so, we develop a new semi-analytical extension of the classic “volume-current method” (Green’s functions with a Born approximation), correcting a longstanding limitation of such methods to low-index contrast systems (the classic method may be off by an order of magnitude in high-contrast systems). The resulting loss predictions show that even incomplete gap structures such as photonic-crystal slabs should, with proper design, be able to reduce losses by a factor of two compared to an identical strip waveguide; however, incautious design can lead to increased losses in the photonic-crystal system, a phenomena that we explain in terms of the band structure of the unperturbed crystal.

Abstract: In general, in one aspect, the invention features systems, including a photonic crystal fiber including a core extending along a waveguide axis and a dielectric confinement region surrounding the core, the dielectric confinement region being configured to guide radiation along the waveguide axis from an input end to an output end of the photonic crystal fiber. The systems also includes a handpiece attached to the photonic crystal fiber, wherein the handpiece allows an operator to control the orientation of the output end to direct the radiation to a target location of a patient.

Abstract: A new model is presented for the calculation of passive intermodulation (PIM) in waveguide connections. The model considers the roughness of interconnecting waveguide surfaces and the presence of an insulator layer (oxide and contaminants) on these metal surfaces. This results in the generation of a contact resistance, which can excite the PIM level. In particular, the case in which metal-insulator-metal regions are the PIM source is especially investigated. The intermodulation level response is calculated for different waveguide junction parameters like applied mechanical load, surface finish, or metal properties showing qualitative agreement with the measured data published by previous authors.

Abstract: Virtually all electromagnetic waveguiding structures support a multiplicity of modes. Nevertheless, to date, an experimental method for unique decomposition of the fields in terms of the component eigenmodes has not been realized. The fundamental problem is that all current attempts of modal decomposition do not yield phase information. Here we introduce a noninterferometric approach to achieve modal decomposition of the fields at the output of a general waveguiding structure. The technique utilizes a mapping of the two-dimensional field distribution onto the one-dimensional space of waveguide eigenmodes, together with a phase-retrieval algorithm to extract the amplitudes and phases of all the guided vectorial modes. Experimental validation is provided by using this approach to examine the interactions of 16 modes in a hollow-core photonic-band gap fiber.

Abstract: Index-guided two-dimensional (2D) optical waveguides are numerically studied to investigate propagation properties of guided optical waves. The 2D optical waveguide consists of a dielectric thin film sandwiched between two semi-infinite metals. We demonstrate that vertically localized 2D optical waves can be laterally confined and guided by index guiding when the dielectric film has a high-refractive-index core and claddings of a lower index. The index guiding provides good optical power transmittance, otherwise optical power is rapidly attenuated due to lateral beam divergence.

Abstract: We demonstrate that stress engineering is an effective tool to modify or eliminate polarization dispersion in silicon-on-insulator (SOI) waveguide devices, for a wide range of waveguide cross-section shapes and dimensions. The stress-induced effects on the modal birefringence of SOI waveguides are investigated numerically and experimentally. Finite-element simulations show that while the birefringence of ridge waveguides with both slanted and vertical sidewalls can be effectively modified using cladding stress, the birefringence becomes much less sensitive to dimension fluctuations with decreasing sidewall slope. To efficiently simulate the stress-induced effects we propose a normalized plane-strain model which can achieve comparable accuracy as a fully generalized plane-strain model but requires significantly less computational resources. Excellent agreement is achieved between the calculated and measured birefringence tuning using SiO/sub 2/ cladding induced stress. Finally, both calculations and experiments confirm that cladding induced stress can be used to eliminate the birefringence in SOI waveguides of arbitrary shapes, for typical SiO/sub 2/ film stress values (/spl sigma//sub film//spl ap/-100 to -300 MPa) and cladding thicknesses of the order of 1 /spl mu/m or less.

Abstract: We introduce a rigorous theory of third-harmonic generation in optical waveguides and apply it to design a micro-fiber waveguide for efficient generation of third-harmonic radiation from infrared lasers. Phase-matching with efficient mode overlap is achieved in micro-fibers having a diameter roughly equal to half of the fundamental wavelength. Using a typical solid-state or fiber laser for pumping, high conversion efficiency is possible in only a few centimeters of a micro-fiber.

Abstract: We report on the fabrication, by a 26 MHz stretched-cavity femtosecond Ti:sapphire oscillator, of optical waveguides in different glass substrates, and their optical characterization. Operation of these waveguides in the telecom range at 1.55 microm is demonstrated. Digital holography microscopy is used to measure their refractive index profile. The results evidence a strong dependence of the fabrication process on the glass matrix.

Abstract: We demonstrate the characterization of optical sources with high sensitivity, high temporal resolution, and phase sensitivity using linear optical sampling. Eye diagrams and constellation diagrams are reconstructed using the interference of the source under test with a train of sampling pulses. This concept is implemented using a waveguide optical hybrid, which splits and recombines the sources and adjusts the phase between the recombined signals to provide optimal detection. This diagnostic is used to characterize on-off keyed (OOK) waveforms at rates up to 640 Gb/s and various phase-shift keyed (PSK) signals at 10 and 40 Gb/s.

Abstract: We demonstrate how a Y-branched optical waveguide can be used for microparticle sorting. Polystyrene microparticles, optically guided in the waveguide’s evanescent field, are directed down the desired, more strongly illuminated, output branch. The output of a fibre laser at a wavelength of 1066 nm is coupled to the waveguide by direct butting. The power distribution between the two output branches is selected by the relative position of the fibre to the waveguide input facet. This provides a simple method for reliable particle sorting with very high probability of success under appropriate conditions. The method can be easily combined with other particle manipulation techniques of interest for micro total analysis systems of the future.

Abstract: an optical pulse controlled all-optical logic gate with multifunctional performance and asymmetric structure has been designed theoretically in SiGe/Si materials using multimode interference principle. By switching the optical signal to different input waveguide ports, the device can function as OR, NOT, NAND, and NOR gates simultaneously or individually. It is a kind of promising device for next generation logic optical circuits, ultrahigh speed signal processing, and future Si-based all-optical integrated circuits.

Abstract: The quality factor (Q), mode volume (Veff), and room-temperature lasing threshold of microdisk cavities with embedded quantum dots (QDs) are investigated. Finite element method simulations of standing wave modes within the microdisk reveal that Veff can be as small as 2(lambda/n)^3 while maintaining radiation-limited Qs in excess of 10^5. Microdisks of diameter D=2 microns are fabricated in an AlGaAs material containing a single layer of InAs QDs with peak emission at lambda = 1317 nm. For devices with Veff ~2 (lambda/n)^3, Qs as high as 1.2 x 10^5 are measured passively in the 1.4 micron band, using an optical fiber taper waveguide. Optical pumping yields laser emission in the 1.3 micron band, with room temperature, continuous-wave thresholds as low as 1 microWatt of absorbed pump power. Out-coupling of the laser emission is also shown to be significantly enhanced through the use of optical fiber tapers, with laser differential efficiency as high as xi~16% and out-coupling efficiency in excess of 28%.

Abstract: Si3N4∕SiO2 waveguides have been fabricated by low pressure chemical vapor deposition within a complementary metal–oxide–semiconductor fabrication pilot line. Propagation losses for different waveguide geometries (channel and rib loaded) have been measured in the near infrared as a function of polarization, waveguide width, and light wavelength. A maximum thickness of single Si3N4 of 250 nm is allowed by the large stress between Si3N4 and SiO2. This small thickness turns into significant propagation losses at 1544 nm of about 4.5dB∕cm because of the poor optical mode confinement factor. Strain release and control is possible by using multilayer waveguides by alternating Si3N4 and SiO2 layers. In this way, propagation losses of about 1.5dB∕cm have been demonstrated thanks to an improved optical mode confinement factor and the good quality of the interfaces in the waveguide.

Abstract: In this letter, a very low-profile planar horn antenna is proposed. It consists of a subwavelength aperture placed into a "Bull's Eye" concentric periodic corrugated conducting plate that produces good return losses and a narrow radiated beam. The antenna is excited by means of a waveguide whose flange has been properly mechanized in the rear part of the structure. The mechanism explaining this phenomenon is similar to the enhanced transmission observed at optical wavelengths in similar structures. In this work, the circularly corrugated structure has been scaled into the microwave frequency range and, moreover, the plane wave excitation has been replaced by a subwavelength aperture excited by a conventional closed metallic waveguide. This transforms the original focusing structure into a new concept of a very low-profile feeder with potential applications.

Abstract: A rigorous classical analytic frequency domain model of con?ned optical wave propagation along 2D bent slab waveguides and curved dielectric interfaces is investigated, based on a piecewise ansatz for bend mode profiles in terms of Bessel and Hankel functions This approach provides a clear picture of the behaviour of bend modes, concerning their decay for large radial arguments or effects of varying bend radius Fast and accurate routines are required to evaluate Bessel functions with large complex orders and large arguments Our implementation enabled detailed studies of bent waveguide properties, including higher order bend modes and whispering gallery modes, their interference patterns, and issues related to bend mode normalization and orthogonality properties