Single-mode Buried Channel Waveguides Research Articles

Three-dimensional mid-infrared photonic circuits in chalcogenide glass

We report the fabrication of single-mode buried channel waveguides for the whole mid-IR transparency range of chalcogenide sulphide glasses (λ ≤ 11 μm), by means of direct laser writing. We have explored the potential of this technology by fabricating a prototype three-dimensional three-beam combiner for future application in stellar interferometry that delivers a monochromatic interference visibility of 99.89% at 10.6 μm and an ultrahigh bandwidth (3-11 μm) interference visibility of 21.3%. These results demonstrate that it is possible to harness the whole transparency range offered by chalcogenide glasses on a single on-chip instrument by means of direct laser writing, a finding that may be of key significance in future technologies such as astrophotonics and biochemical sensing.

Direct laser writing of near-IR step-index buried channel waveguides in rare earth doped YAG

A new (to our knowledge) ultrashort laser pulse irradiation regime that allows us to directly modify and increase the refractive index of rare earth doped YAG polycrystalline ceramics has been identified. Single-mode buried channel waveguides in both Ho:YAG and Er:YAG ceramics at the near-IR wavelengths of 1.55 μm and 1.95 μm are demonstrated by fabricating positive square step-index cores. Minimum propagation losses of 1.5 dB cm(-1) at a 1.51 μm wavelength have been preliminarily obtained. Confocal microluminescence mapping reveals that the increased refractive index regions retain the near-IR spectral properties of Er3+ ions in the YAG crystalline matrix.

Fabrication and optical packaging of an integrated Mach-Zehnder interferometer on top of a movable micromirror

There is a great need for techniques that will permit the evaluation of the micromechanical state of micro-electro-mechanical system (MEMS) devices, at all steps of manufacturing, with respect to material properties, as well as of lifetime and for monitoring mechanical performances of MEMS actuators. We propose a new approach, based on integrated optical read-out using a Mach-Zehnder interferometer (MZI), monolithically integrated on the top of an electrostatically rotatable micromirror loaded with the sensing arm of MZI. The working principle of MZI read-out is based on the local change of the effective refractive index of guided waves of MZI, induced by strains of the deformable structure. A single-mode buried channel waveguide based on the silica/silicon oxinitride/silica structure is used, presenting optical attenuation of 0.6 dB/cm. The coupling of the standard optical fiber to the waveguide is based on the V-groove technique, supplemented by micromechanical sawing of the silicon substrate. For TE polarization, the set of obtained parameters is a coupling efficiency of about 55% with a horizontal misalignment of ±0.5 µm, a vertical misalignment of ±0.7 µm, and angular precision of ±0.2 deg on directions of the silicon substrate.

Mechanically tunable optofluidic distributed feedback dye laser

A continuously tunable optofluidic distributed feedback (DFB) dye laser was demonstrated on a monolithic replica molded poly(dimethylsiloxane) (PDMS) chip. The optical feedback was provided by a phase-shifted higher order Bragg grating embedded in the liquid core of a single mode buried channel waveguide. Due to the soft elastomeric nature of PDMS, the laser frequency could be tuned by mechanically stretching the grating period. In principle, the mechanical tuning range is only limited by the gain bandwidth. A tuning range of nearly 60 nm was demonstrated from a single dye laser chip by combining two common dye molecules Rhodamine 6G and Rhodamine 101. Single-mode operation was maintained with less than 0.1 nm linewidth. Because of the higher order grating, a single laser, when operated with different dye solutions, can provide tunable light output covering the entire spectrum from near UV to near IR in which efficient laser dyes are available. An array of five DFB dye lasers with different grating periods was also demonstrated on a chip. Such tunable integrated laser arrays are expected to become key components in inexpensive advanced spectroscopy chips.

Effect of additional layers on bend loss in buried channel waveguides

The authors propose a new strategy to increase or decrease bend loss in single-mode buried channel waveguides in a predictable manner. This strategy is based on the presence in the cladding of additional layers with different refractive indices on either or both sides of the core in the plane of the bend. It is demonstrated that this approach can lead to significant bend loss reduction when compared to other strategies, and, conversely, can be used to enhance bend loss for a fixed bend radius for application to devices such as optical attenuators.

Direct-UV-written buried channel waveguide lasers in direct-bonded intersubstrate ion-exchanged neodymium-doped germano-borosilicate glass

We report a technique for producing single-mode buried channel waveguide lasers in neodymium-doped SiO2:GeO2:B2O3:Na2O (SGBN) glass. Direct bonding forms the basis of this process, providing a buried waveguide layer in the photosensitive SGBN material into which channel confinement can be directly written with a focused UV beam. Characterization of a 7.5-mm-long device was performed using a Ti:Sapphire laser operating at 808 nm and the resultant 1059 nm channel waveguide laser output exhibited single-mode operation, milliwatt-order lasing thresholds, and propagation losses of <0.3 dB cm−1.

A modal cutoff approach to the study of buried channel waveguide couplers

We investigate the higher-order supermodes of symmetric buried channel waveguide (BCW) couplers with cores of square, rectangular, and trapezoidal geometries. We show how the cutoff wavelengths of these supermodes can be used to interpret the spectral response of a practical single-mode BCW coupler. Our results highlight the design constraints imposed by second-order supermodes. We also compare the behaviour of these couplers with that of circular-core couplers to illustrate how the geometry of each core affects the coupler cutoff characteristics.

A hybrid integrated waveguide isolator on a silica-based planar lightwave circuit

La and Ga substituted yttrium iron garnet single-mode buried channel waveguides, prepared using liquid-phase-epitaxial growth and Ar ion beam etching, have been successfully applied as 45/spl deg/ nonreciprocal waveguide rotators (NRWR) for hybrid integrated waveguide isolators at /spl lambda/=1.55 /spl mu/m. The optical and magneto-optical properties of the prepared 45/spl deg/ NRWRs and the epitaxial films are investigated in detail. We describe the assembly procedure and present optical measurement results for the hybrid integrated waveguide isolators. The hybrid isolators are composed of a 45/spl deg/ NRWR, a half-wave plate sheet, thin film-type polarizers, a thin plate-type permanent magnet and a silica-based waveguide on a silicon substrate. We obtained good waveguide isolators with low insertion losses ( 25 dB) in the 1.5 /spl mu/m wavelength band.

Preparation of Magneto-Optic Single-Mode Buried Channel Waveguides of Lanthanum- and Gallium-Substituted Yttrium Iron Garnet

Magneto-optic single-mode buried channel waveguides are prepared using lanthanum- and gallium-substituted yttrium iron garnet [(La, Ga):YIG] liquid-phase-epitaxial film. The film growth conditions, film properties and the core ridge fabrication method are described. The refractive index of the film is controlled with the film growth temperature. The core ridge size is well controlled using ion beam etching. The obtained waveguides provide low loss coupling with a silica-based waveguide, which is a platform waveguide for a hybrid optical integrated circuit. Magneto-optic mode conversion is observed in a weak applied magnetic field, and the conversion efficiency R max and isolation ratio are evaluated. The relationship between R max and the stress-induced birefringence is discussed.

Magneto-optic buried channel waveguides for a 45° nonreciprocal waveguide rotator

An optical isolation ratio of −21.1 dB at λ=1.55 μm is obtained for a LPE-grown La and Ga substituted YIG single-mode buried channel waveguide. Waveguides about 3 mm long end-butted to single-mode fibers show an overall insertion loss of less than 2 dB. The Ar ion-beam etching technique using a three layered etching mask provides sufficient control of both the width (∼4 μm) and height (∼4 μm) of the core ridge. The core and cladding layers are individually grown from melts with different compositions in order to reduce stress-induced birefringence. The good reproducibility with which 45° waveguide rotators exhibiting a circular near-field intensity pattern can be fabricated will enable us to realize optical integration in future systems.

Optical Interconnect: Fully Embedded Etched Passive And Active Polyimide Waveguides And Devices

ABSTRACTElectro-optic polymers are of great interest for inserting photonic elements into electronic systems. Recently Much progress has been made in both materials and processing. These polymers must have low optical loss, high mechanical integrity, low processing cost, and high temperature stability. In the first part of our talk, we present our work to produce etched single mode buried channel waveguides in an all polymide system. We have chosen polyimide because of its high temperature stability. Optical losses and waveguide characteristics are described as a function of waveguide width and index ofrefraction difference between core and cladding.Mach Zehnder Modulators fabricated using a DCM-polymide core are also described The waveguide cores are etched and fully embedded in a polyimide cladding. The active arms of the modulator are poled using parallel plate poling. The electro-optic properties of the Mach Zehnder are described operating at 830nm. Photobleached DCM waveguides are also describe. A new high temperature chromophore is presented.

X-junctions in buried channel waveguides

The excess loss across an acute-angle symmetric X-junction composed of two weakly guiding single-mode buried channel waveguides of square core cross-section is shown to be very small provided the junction angle is greater than a few degrees. Numerical and approximate analytical results are presented, as well as a simple criterion for the onset of cross-talk as the junction angle decreases.

Excess loss in singlemode right-angle X junctions

The excess loss in a right-angle X junction composed of weakly-guiding singlemode buried channel waveguides is quantified numerically and shown to be consistent with a simple physical model based on a Gaussian approximation to the fundamental mode and Fresnel diffraction across the junction.

Light guidance and mode conversion in magneto-optic buried channel waveguides

The optical and magneto-optical properties of weakly guiding single-mode buried channel waveguides in substituted yttrium iron garnet have been investigated experimentally. The propagation constant difference Δβ of the two coupled TE and TM modes, which is of particular interest for waveguide isolator application, is found to be strongly dependent on waveguide geometry. Measured results can be explained by the specific growth of the top cladding layer, which occurs into different crystallographic directions around the etched waveguide core. This leads to a local variation of the refractive index, which effects the guidance of light, and to a local variation of birefringence, which effects Δβ. The measured variation of Δβ is shown to be primarily caused by growth induced birefringence. It is demonstrated that Δβ can be controlled to small values at selectable waveguide widths as required for waveguide isolator application simply by an appropriate setting of fabrication parameters.

Single-mode buried channel waveguide by single-step electromigration technique using silver film

Single-mode buried channel waveguides with circularly symmetric mode field distribution compatible with conventional single-mode fibers at 1.3 μm wavelength were fabricated and characterized for the first time using a novel single-step ion exchange process from silver films. The technique is relatively simple and eliminates the gold electrode deposition used in previously reported fabrication methods.

Yttrium iron garnet single-mode buried channel waveguides for waveguide isolators

Magneto-optic single-mode buried channel waveguides in substituted yttrium iron garnet suitable for waveguide isolators have been prepared. The channels are fabricated in a three-step procedure: starting with multiple-layer planar single-mode waveguides, rib waveguides are wet etched and then overgrown with top cladding. Such waveguides show mode profiles well matched to that of single mode fibers. In mode conversion experiments, an extinction ratio of 20 dB was obtained. Waveguides coupled to single-mode fibers on both sides showed an overall insertion loss of about 4 dB.