Search

Ge28Sb12Se60 waveguides and microresonators were fabricated by thermal evaporation and dry etching technology. The low loss waveguides and high-index-contrast Ge28Sb12Se60 microring resonators were developed and demonstrated using the optimal parameters of CF4/CHF3 etching recipe. An intrinsic quality factor (Q-factor) of 2.3 × 105 with propagation loss of 2.4 dB/cm at 1550 nm was obtained in this microring resonator with 800 × 400 nm cross-sectional dimension. Critically coupled resonator showed extinction ratio of >30 dB. Nonlinear refractive index (n 2) of 5.12 × 10−18 m2/W for Ge28Sb12Se 60 glass was measured and nonlinear coefficient (γ) of 24 W−1 m −1 asfabricated waveguide was also estimated. This paper illustrates the potential of Ge28Sb 12Se60 glass as a low loss and large nonlinearity material for integrated photonics applications. [ABSTRACT FROM AUTHOR]

Transverse electric (TE) modes in symmetrical planar slot waveguides are analytically solved, and a comprehensive knowledge about them is provided. It has been shown that there are four types of TE modes in planar slot waveguides just as the TM modes. Their field solutions, characteristic equations and cut-off conditions are derived. The cut-off conditions and the power confinement factors of the TE and TM modes are compared. It is demonstrated that there may be degeneration points between TE and TM modes. Because a three-dimensional waveguide has similar modal characteristics as its planar counterpart, our work presents a foundation of recognizing and utilizing the three-dimensional slot waveguides. [ABSTRACT FROM PUBLISHER]

A simple, compact, low cost and highly sensitive refractive index sensor based on single mode leaky planar waveguide is reported. An optical waveguide fabricated on glass substrate has been proposed to construct the sensor. In this structure Cytop works as guiding layer while Teflon forms the cladding layers. Propagation of light in Cytop layer is strongly affected by the refractive index of external medium placed on top of Teflon layer. If the refractive index of the medium is close to or greater than that of Cytop, there is leakage of power from Cytop layer to external medium which affects the transmittance of the waveguide. The structure can be designed to have strong variation in transmittance with the refractive index of external medium and, thus, can be utilized as a highly sensitive refractive index sensor for biomedical applications. In this paper we have carried out the designs of such refractive index sensor for various biological and chemical applications. We design a sensor having sensitivity of the order of 10 4 dB/RIU. Fabrication of the sensor can be carried out by using spin coating technique. Long sensing range, high sensitivity, simple manufacturing process and compactness make the sensor attractive for diverse applications. [ABSTRACT FROM AUTHOR]

A planar waveguide-based array immunosensor (PWAI) was described, allowing measurements of up to twenty-four analytes in eight separate channels rapidly, sensitively and simultaneously. In this system, a linear laser light created by a line generator was coupled into a planar optical waveguide via a beveled angle, forming eight individual total internal reflection (TIR) lines. A multi-channel microfluidics cell was employed to isolate the parallel TIR lines physically so as to form eight independent flow channels on the same chip, avoiding the cross-reactivity of antibodies and supporting various bioassay conditions. By employing fluorescent detection with fluorophore-labeled antibodies binding to the surface of the waveguide with the analyte derivative covalently attached, the array immunoassays can realize the multi-analyte biosensing. A model was proposed to guide the design of such a planar waveguide-based evanescent wave biosensor. The proposed system was confirmed with the comparable sensitivity with previously reported waveguide biosensor. In addition to being a multi-channel analytical device for the highly sensitive detection of contaminants, the proposed evanescent wave PWAI can provide the dynamic surface-based biomolecular interaction information regarding the affinity and kinetics with high sensitivity. [ABSTRACT FROM AUTHOR]

We have studied supercontinuum generation in a tapered-rib lead-silicate waveguide. The Air-SF57 glass-SiO2 waveguide is 2 cm long, with a varying etch depth to manage the dispersion profile. Numerical simulations are conducted for input sech2 pulses centered at 1.55 μm. Due to continuous modification of the phase matching condition for dispersive wave emission, the proposed waveguide geometry generates broadband output spectrum extending from ~1 μm to ~4.6 μm at −30 dB level. With proper pumping conditions, fully coherent supercontinuum can be obtained. [ABSTRACT FROM AUTHOR]

The single-mode planar waveguides were fabricated on MgF2 crystals by 6.0 MeV carbon ion implantation with the fluence of 1 \times 10^15 ions/cm2. The guiding modes were measured by the prism-coupling method at the wavelength of 632.8 nm. The near-field intensity distributions were obtained by the end-face coupling method, and the simulation of the light propagation process was performed simultaneously for comparison. The thermal stability was investigated by annealing treatment at different temperatures ranging from 260 °C to 400 °C in air. After suitable annealing, the minimum propagation loss of the waveguide can be reduced to 0.4 dB/cm. [ABSTRACT FROM PUBLISHER]

We demonstrate a continuous-wave 460-nm compact visible laser module having a footprint of 75 mm × 25 mm × 25 mm. This blue light source is achieved through single-pass second harmonic generation with a distributed Bragg reflector tapered diode laser as a single-frequency pump source at ~920 nm in a periodically poled MgO-doped lithium niobate crystal with a planar waveguide. The compact blue laser module reached an optical output power of 286 mW with the highest optical conversion efficiency of 11.6% at room temperature. The power stability of the blue light from the laser module is measured at an output power of 268 mW with a variation of ±3.5% during a period of 1 h. [ABSTRACT FROM PUBLISHER]

Abstract: We report on the fabrication of the planar waveguide in x-cut Nd:YVO4 laser crystal formed by 1.98GeV with the fluence of 2×1010 ions/cm2 swift Kr8+ ion irradiation. The investigation of the absorption bands and the photoluminescence spectra demonstrates that the transmission properties of the bulk Nd:YVO4 crystal and the Nd3+ luminescence features have been preserved after ion irradiation. In Raman spectra, the peak positions and peak widths had no obvious change after ion irradiation. The irradiated cross section along with an accurate size measurement of the planar waveguide region buried beneath the surface of the crystal were observed by a microscope with transmitted polarized light. We also measured the near-field intensity distributions of the light in the waveguide by the end-face coupling method. [Copyright &y& Elsevier]

Abstract: In this letter, we report on the fabrication of planar optical waveguide in stoichiometric lithium niobate by four-low-energy Helium ion implantation with relative low doses. The simulated refractive index profile reveals that the index-raised well exists in the near-surface ion implanted region. There are dark modes with positive changes of effective refractive indices measured by the prism coupling technique both at 633 and 1539nm after annealing. Further, the small and homogenous damage depth profile proves that there should be the refractive index with positive change. Large energy of the modes is confined in the guiding region. The light was confined well in the waveguide by broad and homogenous index-raised region. Propagation loss for extraordinary refractive index is estimated to be ∼1.2dB/cm. [Copyright &y& Elsevier]

Abstract: We present a design of a dual-core leaky waveguide that can be used as an integrated-optic polarizer. The proposed polarizer works on the principle of mode filtering. The structure is characterized by two cores, namely core-1 and core-2 and a high index layer in the upper-most region, such a structure supports leaky modes. The leakage losses of the modes have been calculated by using the transfer matrix method (TMM). Single polarization operation is ensured by high differential leakage loss between fundamental TE and TM modes. We show TE-pass operation with 0.5dB/mm loss in TE0 mode and 13dB/mm loss in TM0 mode, and TM-pass operation with 0.36dB/mm loss in TM0 mode and 7.45dB/mm loss in TE0 mode. Besides single-polarization operation, single-mode operation of the structure is ensured by high leakage loss of all the other higher-order modes. [Copyright &y& Elsevier]

A new integration technique of a 45-degree micromirror providing a vertical coupling between a free-space wave and a guided wave in a dielectric-glass waveguide for high-density intra-board optical interconnection was described. A planar waveguide consisting of a 4-μm-thickness GeO :SiO guiding core layer and a 2-μm-thickness SiO cladding layer on an SiO substrate was used for characterization of the micromirror. A trench with 8-μm depth and 8-μm width was formed in the waveguide by using a dry etching technique. A photoresist filling the trench was exposed at an angle of 45 degrees in the water to give a 45-degree taper in the trench. Au was evaporated on the taper to give high-reflection micromirror. An excess loss due to the micromirror insertion was estimated to be about 2 dB by comparing insertion losses of waveguides with and without the micromirror. [ABSTRACT FROM PUBLISHER]

Abstract: An athermal metal-free planar waveguide concave grating demultiplexer is proposed. We designed the dielectric mirror at the grating facet instead of coating with the metal on the back wall of the grating facet. The transfer-matrix method is introduced to design the dielectric mirror and the reflectance spectral responses of the 2D waveguide structure are simulated using the FDTD software (RSoft, Inc.). To reduce the temperature sensitivity of the device, the three-focal-point method is introduced. We use the design example to show the high-reflectance bandwidth of the dielectric mirror. The fabrication errors are also taken into consideration. By using the numerical model of the scalar diffraction theory, the flat-top spectral responses of the channels are simulated. [ABSTRACT FROM AUTHOR]

Abstract: Chiral nihility meta-material is a special case of chiral medium, in which both the permittivity and permeability are equal to zero. The feature of surface wave modes (or surface polaritons) in the planar chiral nihility waveguides which the core or cladding consist of chiral nihility meta-materials is investigated. The dispersion curves, electromagnetic fields, energy flow distribution and the power of surface wave modes in the planar chiral nihility waveguides are presented for typical parameters. Some novel peculiarities such as anomalous dispersion curves, the power flows opposite to the wave vector propagation direction in the planar chiral nihility waveguides have been found. [Copyright &y& Elsevier]

Abstract: In this paper, we present an interferometric method to determine the refractive index profile in graded-index planar waveguides. To begin, part of the soda-lime glass substrate surface was coated with aluminum and then was immersed in molten AgNO3 to fabricate a planar waveguide on the uncoated part of the surface. After the ion exchange, the coating was removed. Then, the sample was polished obliquely along the boundary between the ion-exchanged and non-ion-exchanged regions, to form a wedge. Thereafter, it was placed inside a Mach–Zehnder interferometer. The fringe pattern was analyzed using the well-known Fourier method and the refractive index profile was determined. The sample preparation, data analysis and experimental results are presented. [Copyright &y& Elsevier]

A novel analytical method for solution of planar optical structure with arbitrary refractive index profile is proposed. This new method is founded on differential-transfer-matrices, whose field solutions are based on Airy's trial functions. In contrast to conventional Wentzel, Kramers, and Brillouin (WKB) solutions, which diverge around the turning points, this approach can be successfully used for exact calculation of various functions, including eigenvalues of optical waveguides with arbitrary index profiles, and complex reflection and transmission coefficients, even at the presence of turning points. The method is rigorous and can be applied for both major polarizations. [ABSTRACT FROM AUTHOR]

we present here a simple numerical method to obtain the mode effective indices as well as field distributions of modes of any arbitrary profile planar optical waveguide. The method is based on the solutions of scalar and semivectorial Helmoltz’s equation by finite difference algorithm and devised with a field convergence technique. This approach is quite general and can be applied straightforwardly to calculate the guided as well as quasi- or leaky modes of any arbitrary planar structure without the need to solve any eigenvalue equation or any complex matrix formalism. Besides providing the ease of application, the algorithm is particularly useful for waveguides with any graded index profile or with irregular multilayered structure and multilayered waveguides with a localised arbitrary nonlinear film. The performance of our method is verified against typical problems with analytical solutions or having results known otherwise, and is shown to yield results with good accuracy. [ABSTRACT FROM AUTHOR]

Abstract: We have developed a sensor surface for optical detection of organophosphates based on reversible inhibition of organophosphorus hydrolase (OPH) by copper complexed meso-tri(4-sulfonato phenyl) mono(4-carboxy phenyl) porphyrin (CuC1TPP). OPH immobilized onto glass microscope slides retains catalytic activity for more than 232 days. CuC1TPP is a reversible, competitive inhibitor of OPH, binding at the active site of the immobilized enzyme. The absorbance spectrum of the porphyrin–enzyme complex is measured via planar waveguide evanescent wave absorbance spectroscopy using a blue LED as a light source and an Ocean Optics USB2000 as the spectrophotometer. The characteristics of the absorbance spectrum of CuC1TPP are specific and different when the porphyrin is bound to the enzyme or is bound non-specifically to the surface of the slide. Addition of a substrate of OPH such as one of the organophosphates paraoxon, coumaphos, diazinon, or malathion displaces the porphyrin from the enzyme resulting in reduced absorbance intensity at 412nm. Absorbance changes at 412nm show log-linear dependence on substrate concentration. Paraoxon concentrations between 7 parts per trillion (ppt) and 14 parts per million (ppm) were investigated and a 3:1 S/N detection limit of 7ppt was determined. Concentrations of 700ppt to 40ppm were investigated for diazinon, malathion, and coumaphos with detection limits of 800ppt, 1 part per billion, and 250ppt, respectively. This optical technique does not require the addition of reagents or solutions other than the sample and absorbance spectra can be collected in less than 6s. [Copyright &y& Elsevier]

• Photonic-crystal planar waveguides (PCPWs) with advanced elliptic features proposed. • Endless single-polarization single-mode (SPSM) PCPWs achieved with ultra-large mode area. • Ultra-low transmission loss condition in PCPW arrays under SPSM operation has been studied. In this paper, single-polarization single-mode (SPSM) optical waveguides of ultra-broad bandwidth and very large mode areas are proposed and analyzed based on photonic crystal planar waveguides (PCPWs) and arrays with advanced elliptic features. The multi-unit PCPW arrays have been found particularly effective in achieving ultra-broadband operation with substantially expanded modal areas, as an optimized five-unit PCPW array offers an unprecedentedly broad SPSM spectrum of 4310 nm (from 0.11 to 4.42 μm). In addition, near-zero transmission loss conditions have also been identified for PCPW arrays at various resonant wavelengths. Such very-large-mode-area (VLMA), ultra-broadband, SPSM optical waveguides with "lossless" transmission conditions are highly desirable for basic waveguide research as well as related application fields. [ABSTRACT FROM AUTHOR]

A novel scheme for the control of microwave signals carried at optical wavelengths by use of PbS colloidal quantum dots embedded in PMMA waveguides is presented. When these structures are pumped at wavelengths where PbS has efficient absorption (980 or 1310 nm), a phase shift in a signal carried at 1550 nm is induced. Optimal conditions have been analyzed by studying the influence of the microwave signal and the waveguide structure. In a proof-of-concept experiment, a continuous phase shift up to 35 ° at 25 GHz has been demonstrated, with good thermal stability ( at 25 GHz) when the samples are heated 20 °C above room temperature. The potential benefits of the use of this active-waveguide technology in microwave photonics are due to the continuous scan of the phase delay, its high tuning speed, and its small size, which leads to the possibility of integration. [ABSTRACT FROM PUBLISHER]

We report the superbroadband photoluminescence extending from 1.3 to 1.7 μm in Neodymium(Nd3+)/Thulium(Tm3+)/Erbium(Er3+) codoped fluorotellurite glasses under 793 nm excitation. This superbroadband luminescence is contributed by the Nd3+:4F3/2→4I13/2, Tm3+:3H4→3F4, and Er3+:4I13/2→4I15/2 transitions that lead to broadband emissions located at 1.34, 1.47, and 1.53 μm, respectively. Broadband emission spectrum is also obtained in the ion-exchanged planar waveguide fabricated on Nd3+/Tm3+/Er3+ codoped fluorotellurite glass. The results indicate that other than active Bismuth (Bi), Chromium (Cr), Nickel (Ni), and other chemical elements, Nd3+/Tm3+/Er3+ codoping is a promising alternative for the broadband luminescence sources covering the expanded low-loss window. [ABSTRACT FROM PUBLISHER]

Detuning of a coupled planar waveguide pair through surface loading of the top waveguide that is in contact with the analyte serves as a transducer for a Stacked Planar Affinity-Regulated Resonant Optical Waveguide (SPARROW) sensor. Here we investigate the surface loading detection sensitivity of a SPARROW transducer composed of a stack of two planar alumina waveguides grown using ion beam assisted e-beam deposition. Using a sucrose analyte solution introduced to the stack surface in a poly-di-methyl-siloxane (PDMS) microfluidic channel, the change in optical output power through the coupled waveguide pair as a function of sucrose analyte solution concentration was experimentally determined. Based on the analyte in the evanescent field penetration depth volume, the effective minimum detectable surface loading of the stack was determined to be 20 with a bulk index sensitivity of 5.6 refractive index units (RIU) for this stack configuration and experimental setup. [ABSTRACT FROM PUBLISHER]

Abstract: In advanced optical fiber communication systems where reflection light might cause degradation of the signal quality, optical waveguide isolators play an important role. The effect of a metal layer with negative permittivity on the behavior of nonlinear-magnetooptic isolator is studied. The isolator consists of metal film, nonlinear cladding, and magnetooptic substrate. It is found that difference between forward and backward propagation for TM0 mode increases with increasing the absolute value of the tuning parameter which is the permittivity of the metal film, ɛ f . It is also found that the maximum cut-off thickness of the isolator occurs in self-defocusing case around η =0.65 and at the highest assumed value of ɛ f =−8. These results are helpful in fabricating an isolator with high performance. [ABSTRACT FROM AUTHOR]

In this letter, the broadband notch filter exhibiting a flattened bandstop spectral response is experimentally demonstrated for the first time by using the guided-mode resonance associated with the periodic subwavelength structure possessing asymmetric binary grating profiles. The proposed filter consisting of grating and waveguide structures is realized by utilizing a single-layer poly-silicon film deposited on a quartz substrate. The asymmetric grating profile is carried out by dividing the one-filling-factor binary structure into the one with two distinct filling factors within one identical period. A flat bandstop spectral response at the central wavelength of 1.22 mum is obtained under normal incidence for transverse-electric polarization. Its transmittance of bandstop spectrum can be suppressed as low as -20dB within a broad spectral range of 85 nm and its corresponding Deltalambda/lambda is larger than 6%. The spectra under oblique incidence are demonstrated to verify the proposed filter has a high immunity for the angular deviation up to 20deg [ABSTRACT FROM PUBLISHER]

In this paper, novel single-mode (SM) photonic-crystal planar waveguides (PCPW) and linear arrays have been proposed and systematically studied. Advanced elliptic features are embedded into the basic photonic crystal design to differentiate leakage losses between the fundamental and high-order modes, which ensures SM propagation property. Furthermore, linear arrays of PCPWs are proposed to generate fundamental supermodes with ultra-large SM areas. Our study shows that these multi-unit PCPW linear arrays can perform equivalently as ultra-wide planar waveguides that are possible to achieve SM modal areas as large as over 10,000 μm2 with preferable Gaussian-shaped far-field intensity patterns, readily supporting optical powers well over 100 kW. The presented study can be inspiring for designs of single-waveguide solid-state lasers and amplifiers to generate laser beams of extremely high power and high brightness. [ABSTRACT FROM AUTHOR]