Tapered Channel Waveguides Research Articles

Efficient spot size converter for higher-order mode fiber-chip coupling.

We propose and demonstrate a silicon-based spot size converter (SSC), composed of two identical tapered channel waveguides and a Y-junction. The SSC is designed for first-order mode fiber-to-chip coupling on the basis of mode petal separation and the recombination method. Compared with a traditional on-chip SSC, this method is superior with reduced coupling loss when dealing with a higher-order mode. To the best of our knowledge, we present the first experimental observations of a higher-order SSC which is fully compatible with a standard fabrication process. Average coupling losses of 3 and 5.5dB are predicted by simulation and demonstrated experimentally. A fully covered 3dB bandwidth over a 1515-1585nm wavelength range is experimentally observed.

Spatial mapping of refractive index based on a plasmonic tapered channel waveguide.

A tapered plasmonic channel waveguide can be used for index sensing by spatial mapping of the scattering field intensity. A numerical simulation shows that this waveguide reflects the plasmonic channel waveguide mode at various points as the refractive index of an analyte changes, and a strong outgoing scattering wave appears at the reflection point. One can measure the index change by detecting variations in the scattering point. In the case of a unit index change, the scattering point moved 2670 nm, which can be observed by an imaging system. Detection limit of the index change is estimated as 0.12. However, the limit can be further reduced by increasing the tapered length or decreasing the tapered angle of the structure.

Sub-Micrometer-Sized Spectrometer by Using Plasmonic Tapered Channel-Waveguide

It has been a critical issue to reduce the size of spectrometers in many fields such as on-chip chemical and biological sensing. The proposed plasmonic channel-waveguide with a sub-micrometer width has a cutoff frequency which enables us to control wavelength dependent propagation properties. We focused on the capability of the waveguide for spectral-to-spatial mapping when the waveguide width changes gradually. In this paper, we propose a plasmonic tapered channel-waveguide structure as a compact spectrometer with a physical size of <TEX>$0.24{\times}2.0{\times}0.20{\mu}m^3$</TEX>. The scattering point just above the tapered waveguide moves linearly depending on the wavelength of the injecting light. The spectral-to-spatial mapping can be improved by increasing the tapered length.

Engineering lattice matching, doping level, and optical properties of KY(WO4)2:Gd, Lu, Yb layers for a cladding-side-pumped channel waveguide laser

Single-crystalline KY1-x-y-zGdxLuyYbz(WO4)2 layers are grown onto undoped KY(WO4)2 substrates by liquid-phase epitaxy. The purpose of co-doping the KY(WO4)2 layer with suitable fractions of Gd3+ and Lu3+ is to achieve lattice-matched layers that allow us to engineer a high refractive-index contrast between waveguiding layer and substrate for obtaining tight optical mode confinement and simultaneously accommodate a large range of Yb3+ doping concentrations by replacing Lu3+ ions of similar ionic radius for a variety of optical amplifier or laser applications. Crack-free layers, up to a maximum lattice mismatch of ~0.08 %, are grown with systematic variations of Y3+, Gd3+, Lu3+, and Yb3+ concentrations, their refractive indices are measured at several wavelengths, and Sellmeier dispersion curves are derived. The influence of co-doping on the spectroscopy of Yb3+ is investigated. As evidenced by the experimental results, the lattice constants, refractive indices, and transition cross-sections of Yb3+ in these co-doped layers can be approximated with good accuracy by weighted averages of data from the pure compounds. The obtained information is exploited to fabricate a twofold refractive-index-engineered sample consisting of a highly Yb3+-doped tapered channel waveguide embedded in a passive planar waveguide, and a cladding-side-pumped channel waveguide laser is demonstrated.

Compression-molded three-dimensional tapered polymeric waveguides for low-loss optoelectronic packaging

We report for the first time, three-dimensionally tapered polymeric waveguides fabricated by the compression-molding technique. The waveguides presented herein provide a feasible solution to bridge discrete optoelectronic devices having apertures of a few micrometers to hundreds of microns. 1-cm-long tapered channel waveguides with the end cross sections of 5 /spl mu/m/spl times/5 /spl mu/m and 100 /spl mu/m/spl times/100 /spl mu/m were fabricated. These waveguides have a propagation loss of 0.5 dB/cm when the 632.8-nm He-Ne laser light is coupled from the small end and of 1.1 dB/cm when coupled from the large end. By confining the energy to the fundamental mode, when coupling from large end to the small end, a low-loss packaging can be achieved bidirectionally.

Integrated ultrafast saturable absorber

An ultrafast saturable absorber was demonstrated experimentally in AlGaAs, operated with a photon energy below half the band gap, near 1555 nm. Both the saturation intensity and the linear transmission can be independently designed in the structure. The device is based on spatial soliton emission from a tapered channel waveguide with a corresponding increase in transmission of 50%. The experimental data compare favorably with numerically simulated results.

2-D mode tapering via tapered channel waveguide segmentation

A simple and versatile 2-D mode-tapering method for a channel waveguide, which is based on tapered waveguide segmentation, is proposed. The taper can be incorporated into the waveguide at the stage of lateral channel definition. The method is compatible with both mask photolithoography and direct writing techniques, and no modification of the transverse index profile is required. >