Long-range Surface Plasmon Polariton Waveguide Research Articles

Nanoimprinted Bragg Gratings for Long-Range Surface Plasmon Polaritons Fabricated via Spin Coating of a Transparent Silver Ink

We designed, fabricated, and characterized novel long-range surface plasmon polariton waveguides based on Bragg gratings (LRSPPW-BGs) via spin coating of a transparent silver ink on nanoimprinted polymeric patterns at low temperature in the absence of a vacuum system. For 20-nm-thick and 8-μm-wide LRSPPW-BGs of lengths in excess of 500 μ <b xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</b> , the measured reflectances are greater than 90% at a Bragg wavelength of ~1532 nm. For a 20-nm-thick, 8- μ <b xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</b> -wide, and 1000-μ <b xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</b> -long LRSPPW-BG, the full width at half maximum of a reflectance is determined to be 1.89 nm. The use of spin-coatable silver ink combined with the nanoimprint technique may represent a viable new route for cost effective and simple fabrication of LRSPPW-BGs.

Hybrid Coupling Between Long-Range Surface Plasmon Polariton Mode and Dielectric Waveguide Mode

In this paper, the hybrid coupling between long-range surface plasmon polariton (LRSPP) waveguide mode and dielectric waveguide mode has been studied theoretically and experimentally in detail by considering its dependence on the structure parameters and wavelength. It is demonstrated that extremely high coupling efficiency (>;99%) has been achieved for TM polarization, while no coupling could happen for TE polarization between these two kinds of waveguides. Based on this hybrid coupler, a polarization splitter with pure TM-mode output from one arm and TE-mode output from the other arm with high TE/TM extinction ratio has been realized. Additionally, this kind of coupling between different waveguides is very significant for providing an effective approach to connect the LRSPP-based devices with the conventional dielectric devices.

Long-range surface plasmon polariton waveguides containing very thin spin-coated silver films

We fabricated very thin solid silver films with thicknesses below 50 nm using a spin coating method. An aqueous silver ionic complex solution was spin-coated and then thermally cured for a few minutes at a low temperature. The properties of the spin-coated silver films were compared to the properties of silver films deposited by thermal evaporation. The spin-coated thin silver films possessed silver crystallinity and a surface roughness of ~ 2.83 nm, while the thermally evaporated thin silver films also possessed silver crystallinity with a surface roughness of ~ 2.44 nm. Long-range surface plasmon polariton (LR-SPP) waveguides fabricated by both spin coating and thermal evaporation were also characterized and compared. The propagation losses of the 23 nm thick spin-coated and the 19 nm thick evaporated LR-SPP waveguides with strip widths of 7 μm were 3.6 and 4.2 dB/cm, respectively, and their coupling losses were 1.4 and 1.0 dB/2facets, respectively. The use of the spin coating method is a very cost effective solution because the films can be formed at low temperature in a short period of time without requiring a vacuum system. In addition, there are many potential applications of using spin-coated very thin solid silver films in LR-SPP waveguides and nano electrical circuit patterns.

Measuring gain and noise in active long-range surface plasmon-polariton waveguides

We describe techniques and an experimental setup to measure the gain and noise characteristics of a long-range surface plasmon-polariton amplifier consisting of a symmetric metallic stripe waveguide incorporating optically pumped dye molecules in the solution as the gain medium. The setup is capable of acquiring absolute power measurements at the amplifier's output over a narrow optical bandwidth. This allows independent characterization of the amplifier's gain via measurements of stimulated emission and via measurements of amplified spontaneous emission (ASE) over a narrow optical bandwidth, both obtained during the same experimental run. In addition, the absolute power measurements of ASE quantify directly the amplifier's noise.

Demonstration of long-range surface plasmon-polariton waveguide sensors with asymmetric double-electrode structures

We demonstrate a long-range surface plasmon-polaritons (LRSPP) refractive-index sensor using an asymmetric double-electrode LRSPP waveguide configuration. The LRSPP sensor is inherently self-referencing by virtue of two Bragg wavelengths in the transmission spectrum generated by a Bragg grating. The measured sensitivity is about 130 nm/RIU and 27 pm/K, which means a sensing resolution of ∼10−6 RIU and a temperature determination with an inaccuracy of 0.04 K under measurement accuracy of the Bragg wavelength of 1 pm. The sensor dimensions of 1.95 mm in total length and submicrometer in fluidic-channel thickness may be desirable for highly integrated sensors based on LRSPP.

Temperature dependence of symmetric and asymmetric structured Au stripe waveguides

The thermal effects on pigtailed 22-nm-thick, 5-μm-wide and 1-cm-long Au stripe long-range surface plasmon polariton (LRSPP) waveguides, embedded in polymer/polymer layers and in polymer/silica layers, are theoretically and experimentally demonstrated. The polymer and silica cladding layers have thermo-optic coefficients of opposite signs. As the temperature varies the Au stripe LRSPP waveguide embedded in the polymer/polymer layers retains its symmetry in the refractive index, but that embedded in the polymer/silica layers becomes asymmetric in the refractive index. The thermal sensitivity in the optical output power of the symmetric structure is smaller than 0.02 dB/°C but the sensitivity of the asymmetric structure is ∼ 0.3 dB/°C. These structures open up potential applications of the LRSPP waveguides for temperature independent/dependent photonic devices.

Modelling of Polarization-Dependent Loss in Plasmonic Nanowire Waveguides

We have investigated the potential of using gold nanowires embedded in a dielectric cladding environment as polarization-independent long-range surface plasmon polariton waveguides at telecom wavelengths. We performed finite-element analysis on various symmetric and close-to-symmetric cross-sectional geometries and evaluated the effects of cladding thickness on the propagation and coupling loss. The calculations confirm that fabrication of polarization-independent waveguides with reasonable tolerances is feasible and that straight-waveguide insertion losses around 1.5 dB for short (0.5 mm) devices can be realized when coupling to and from conventional dielectric waveguide geometries.

Hybrid vertical directional coupling between a long range surface plasmon polariton waveguide and a dielectric waveguide

To investigate light coupling between a long range surface plasmon polariton (LRSPP) waveguide and a conventional integrated optical component, a hybrid vertical directional coupler consisting of a LRSPP waveguides and a dielectric waveguide is investigated and fabricated. In the proposed coupler the dielectric waveguide and LRSPP waveguide are vertically configured for dense integration and strong coupling. The characteristics of the even and odd super-modes of the coupler are also analyzed to design the device. The fabricated device exhibits damped sinusoidal behavior along the coupling length due to propagation loss of the LRSPP waveguide. The maximum power transfer of 86% from the LRSPP waveguide to the dielectric waveguide is achieved at the coupling length of 600 μm. The measured characteristics of the device are in relatively good agreement with a theoretical analysis.

Long-range surface plasmon-polariton waveguide sensors with a Bragg grating in the asymmetric double-electrode structure

We propose a Bragg grating resonance sensor based on long-range surface plasmon-polaritons (LRSPP) excited on an asymmetric double-electrode waveguide structure. The proposed LRSPP waveguide sensor utilizes spectral resonance of the asymmetric double-electrode structure by adding a Bragg grating layer on the top surface of the metal slab. We have numerically estimated the bulk index resolution and thickness detection limit of a target biomolecule layer under 30 dB total propagation loss. The sub-mum fluidic channel between the two metal layers always experiences a highly confined LRSPP mode excited by end-fire coupling with optical fibers, therefore the proposed LRSPP sensor platform can be applied to a variety of integrated sensor-chip scenarios.

Fabrication of surface plasmon waveguides on thin CYTOP membranes

The fabrication of a membrane supported long-range surface plasmon polariton waveguide for use as a biosensor is described. This type of device can be completely immersed in the sensing environments to create symmetrical waveguide surroundings. The membrane is created from the fluoropolymer CYTOP which has strong physical properties and a low index of refraction. The fabrication steps of this device are described along with examples of completed structures.

비대칭 이중-금속 장거리 표면-플라즈몬 도파로를 이용한 파장필터

비대칭 이중-금속 장거리 표면-플라즈몬 구조는 두 금속 사이에 위치한 코어 유전체 층의 굴절률을 임의로 선택하여도 장거리 표면-플라즈몬 모드가 존재한다는 장점이 있다. 도파로의 코어 층에 격자를 형성함으로써 플라즈몬 밴드-갭에 기초한 통신대역 파장에서의 장거리 표면-플라즈몬 파장필터를 구현하였다. Method of Line과 전달행렬방법 등을 통해 장거리 표면-플라즈몬 모드의 유효굴절률, 모드 특성, 투과도 등의 분석을 통해 설계하였으며, 도파로의 코어 층에 홀로그램 리소 방식을 이용하여 523.3 nm 주기의 브래그격자를 형성하여 파장필터를 제작하여 통신대역인 1541 nm 파장에서 대략 2 nm의 반치폭과 50 dB 이상의 파장 소광률을 확인하였다. 본 연구에서 제안한 파장필터는 표면-플라즈몬 집적회로를 구성하는 소자로써 중요한 역할을 할 것이다. We propose a wavelength filter based on long-range surface plasmon-polaritons (LR-SPP) supported by a asymmetric doubleelectrode LR-SPP structure. For the case of the asymmetric double-layered LR-SPP waveguide, LR-SPPs exist with a much broader range of index mismatches between core and clad materials. Thus, the asymmetric double-electrode LR-SPP waveguide is adequate to form a plasmonic band-gap device as we report in this paper by studying Bragg-reflection wavelength filter based on it. The structure for wavelength filter operating telecommunications wavelength is designed by using the method of line (MoL) and the transfer matrix method. The fabricated device shows a relatively high extinction ratio of 50 dB with a bandwidth of 2 nm, and the performance is very consistent with numerical simulations.

Hybrid Three-Arm Coupler Consisted of Long Range Surface Plasmon Polariton and Dielectric Waveguides

The hybrid three-arm coupler, which consists of the middle long range surface plasmon polariton (LRSPP) waveguide and two outside conventional dielectric waveguides, is proposed and analyzed numerically with finite element method. The characteristics, including coupling length, coupling loss, extinction ratio and frequency dependence, are discussed in detail with different structure parameters. Compared with the two-arm hybrid coupler, the coupling loss of the three-arm hybrid coupler based devices can be reduced, especially with wider middle LRSPP waveguide. Extra transmission loss on the metal strip can be avoided because of the lossless input and output arms. Furthermore, different from conventional three-arm dielectric coupler, we find that the three-arm hybrid coupler with asymmetric structure can reach a much higher extinction ratio by introducing a middle arm offset. Since the middle arm can only transfer the TM mode from one dielectric arm to the other one within the TM mode coupling length, this structure is promising for realizing integrated polarization splitter or other functional devices.

Chip-to-chip optical interconnect using gold long-range surface plasmon polariton waveguides

We demonstrate a novel on-board chip-to-chip optical interconnect using long-range surface plasmon polariton (LR-SPP) waveguides that feature 2.5-cm-long gold strips embedded in a low loss polymer cladding. A TM-mode vertical-cavity surface-emitting laser (VCSEL) operating at a wavelength of 1.3 microm was butt-coupled into the waveguides in order to excite a fundamental LR-SPP mode and then the transmitted light was received with a photo-diode (PD). The waveguide width is varied in the range of 1.5-5.0 microm in order to optimize the insertion loss where the 3-microm-wide waveguide provides a minimum insertion loss of -17 dB, consisting of 6 dB/cm propagation loss and 2 dB coupling loss. An interconnect system based on the optimized waveguide with a 4-channel array is assembled with the arrayed optoelectronic chips. It shows the feasibility of 10 Gbps (2.5 Gbps x 4 channels) signal transmission indicating that the LR-SPP waveguide is a potential transmission line for optical interconnection.

Long-range surface plasmon polariton waveguides embedded in fluorinated polymer

Low-attenuation waveguides based on the propagation of long-range surface plasmon polaritons (LRSPPs) along thin Au stripes embedded in low absorption perfluorocyclobutane (PFCB) polymer are presented. A new low in propagation loss of <2.0 dB/cm was achieved for a 4 microm wide waveguide by optimizing the cladding material and fabrication process. The coupling efficiency between the LRSPP waveguide and the optical fiber is studied theoretically and experimentally for different widths of Au stripes and various cladding thicknesses. Lower coupling loss is found when the cladding thickness is close to the mode diameter of the butt-coupled fiber. Based on the 2D distribution of SPP modes calculated by a finite-difference mode solver, a symmetric structure of multilayer claddings with different refractive indices is proposed to optimize device insertion loss.

Polymer-Based Long-Range Surface Plasmon Polariton Waveguides for 10-Gbps Optical Signal Transmission Applications

We present characteristics of very thin Au strip waveguides based on long-range surface plasmon polaritons (LR-SPPs) along thin Au strips embedded in polymers. We also report a 10 Gbps optical signal transmission via LR-SPPs with the pig-tailed Au strip waveguide at a telecommunication wavelength of 1.55 mum. We limited the thickness, width, and length up to ~20 nm, ~ 10 mum, and ~5 cm, respectively, for practical applications. At 1.55 mum, loss properties of the Au strip waveguides were theoretically and experimentally evaluated with thickness, width and cladding material. The lowest propagation loss of ~1.4 dB/cm was experimentally obtained with the 14-nm-thick and 2-mum-wide Au strip. With a single-mode fiber, the lowest coupling loss of less than 0.1 dB/facet was achieved with the 14-nm-thick and 7.5-mum-wide Au strip. The lowest insertion loss was obtained 7.7 dB with the 14-nm-thick, 5-mum-wide, and 1.5-cm-long Au strip. The propagation loss was improved approximately 30% for the 17-nm-thick Au strip with lowering the refractive index of the cladding polymer by 0.01. In the 10 Gbps optical signal transmission experiment, the LR-SPP waveguide exhibits an excellent eye opening and a 2.2 dB power penalty at 10-12 bit error rate. These all results indicate that the LR-SPP waveguide is a potential transmission line for optical interconnects to overcome inherent problems in electric interconnects.

Long-range surface plasmon polaritons on asymmetric double-electrode structures

An asymmetric double-electrode structure composed of metal strips separated by a dielectric core layer, all on a metal slab, is proposed as a long-range surface plasmon-polariton (LR-SPP) waveguide. LR-SPP modes on asymmetric structures, including straight, S-bended, and Y-branched strips, are found by far-field measurement to be consistent with theoretical estimates. The proposed structure is inherently free from a symmetry requirement on dielectric constants between the core and cladding materials, therefore, an asymmetric double-electrode waveguide which substitutes a nonlinear medium or biofluid for the core dielectric may be essential to realization of SPP nonlinear devices or biosensors in a long-range manner.

10 Gbps Optical Signal Transmission via Long-Range Surface Plasmon Polariton Waveguide

We demonstrate 10 Gbps optical signal transmission via long-range surface plasmon polaritons (LR-SPPs) in a very thin metal strip-guided geometry. The LR-SPP waveguide was fabricated as a 14 nm thick, 2.5 μm wide, and 4 cm long gold strip embedded in a polymer and pigtailed with single-mode fibers. The total insertion loss of 16 dB was achieved at a wavelength of 1.55 μm as a carrier wave. In a 10 Gbps optical signal transmission experiment, the LR-SPP waveguide exhibits an excellent eye opening and a 2.2 dB power penalty at 10−12 bit error rate. We confirm, for the first time, that LR-SPPs can efficiently transfer data signals as well as the carrier light.

Long range surface plasmon polariton waveguides at 1.31 and 1.55 μm wavelengths

We investigate characteristics of gold metal strip waveguides based on long range surface plasmon polaritons (LRSPPs) along thin metal strips embedded in a polymer for practical applications at the telecommunication wavelengths of 1.31 and 1.55μm. Guiding properties of the gold strip waveguides are theoretically and experimentally evaluated with the limited thickness and width up to ∼20nm and ∼10μm, respectively. The lowest propagation loss of ∼1.4dB/cm is obtained with a 14.5-nm-thick and 2-μm-wide gold strip at 1.55μm. With a single-mode fiber, the lowest coupling loss of ∼0.4dB/facet is achieved with a 14.5-nm-thick and 5-μm-wide gold strip at 1.55μm. The lowest insertion losses are obtained 8–9dB with 1.5cm-long gold strips of a limited thickness and width at both the wavelengths. We demonstrate a 10Gbps optical signal transmission via the LRSPP waveguide with a 14nm-thick, 2.5μm-wide, and 4cm-long gold strip. These LRSPP waveguides have potential applications for optical interconnects and communications.

40 Gbit ∕ s light signal transmission in long-range surface plasmon waveguides

We demonstrate a high bit-rate optical signal transmission by using long-range surface plasmon polariton (LRSPP) waves in a guided geometry. With a 40Gbit∕s optical communication signal, eye patterns and bit-error-rates were measured to access the quality of the transmission properties of the LRSPP mode. A thin gold strip line embedded in a low loss optical polymer supports a LRSPP mode, which propagates with a 2dB∕cm loss, and couples to standard single mode fibers at 1.55μm with a 2dB coupling loss. A 40Gbit∕s optical signal was transmitted via a 4cm long LRSPP waveguide without any distortion of the eye patterns. The experiment also showed error-free transmissions. These results indicate that the LRSPP waveguide is a potential transmission line for optical interconnections overcoming the inherent problems in electric interconnections.

Low-Loss Polymer-Based Long-Range Surface Plasmon-Polariton Waveguide

To improve the propagation loss of polymer-based long-range surface-plasmon-polariton (LR-SPP) waveguide devices at the telecom wavelength range, low-loss LR-SPP waveguides were fabricated in an ultraviolet-curable acrylate polymer with a low refractive index and absorption loss. A propagation loss of 1.72 dB/cm at a wavelength of 1.55 mum was achieved with a 14-nm-thick and 3-mum-wide metal stripe.