Ananth Z. Subramanian

Fabrication of Submicrometer High Refractive Index Tantalum Pentoxide Waveguides for Optical Propulsion of Microparticles

Design, fabrication, and optimization of tantalum pentoxide (Ta2O5 ) waveguides to obtain low-loss guidance at a wavelength of 1070 nm are reported. The high-refractive index contrast (Deltan ~ 0.65, compared to silicon oxide) of Ta2O5 allows strong confinement of light in waveguides of submicrometer thickness (200 nm), with enhanced intensity in the evanescent field. We have employed the strong evanescent field from the waveguide to propel micro-particles with higher velocity than previously reported. An optical propelling velocity of 50 mum/s was obtained for 8-mum polystyrene particles with guided power of only 20 mW.

Mirrorless buried waveguide laser in monoclinic double tungstates fabricated by a novel combination of ion milling and liquid phase epitaxy

Buried channel waveguides were fabricated by liquid phase epitaxial growth of a lattice-matched KY(0.58)Gd(0.22)Lu(0.17)Tm(0.03)(WO4)2 film on a microstructured KY(WO4)2 substrate. Channels were transferred to the substrates by standard photolithography and Ar-ion milling. The bottom and sidewalls of the milled channels were smooth enough (rms roughness = 70 nm and 20 nm, respectively) to favour the epitaxial growth of the active layer without defects at the boundary of substrate/epitaxial layer. The refractive index contrast was sufficient to enable light confinement and guided modes with low scattering losses were observed at wavelengths between 1440 nm and 1640 nm. CW laser operation at 1840 nm at room temperature was observed with feedback provided only by Fresnel reflection at the end faces, with slope efficiencies of 4% and 9% for TE and TM polarizations, respectively.

Erbium-Doped Waveguide Laser in Tantalum Pentoxide

Tantalum pentoxide (Ta₂O₅) is a promising high index material for dense photonic circuits, with the incorporation of gain substantially increasing its potential functionality. Diode-pumped laser action is demonstrated in 2.3-cm-long Ta₂O₅ rib waveguides doped with 2.7 10²⁰ erbium ions/cm³, which were fabricated by magnetron sputtering on an oxidized silicon wafer. Lasing was observed at wavelengths between 1558 and 1562 nm with a launched diode pump power threshold of 14 mW.

Integrated platform based on high refractive index contrast waveguide for optical guiding and sorting

The high-refractive index contrast (▵n ~0.65 as compared to silicon oxide) of Tantalum pentoxide (Ta2O5) waveguide allows strong confinement of light in waveguides of sub-micron thickness (200 nm). This enhances the intensity in the evanescent field, which we have employed for efficient propelling of micro-particles. The feasibility of opto-fluidics sorting of different sized micro-particles based on their varying optical propulsion velocity is suggested. Optical propulsion of fixed red blood cells (RBC) with velocity higher than previously obtained is also reported. The optical propulsion velocities of RBC in isotonic solution (0.25 M sucrose) and water have been compared.

Spectroscopy, Modeling, and Performance of Erbium-Doped Ta

The design, fabrication, spectroscopic characterization, and performance of an Er:Ta2O5 rib waveguide amplifier is described. Rib waveguides with low loss (<; 0.65 dB/cm at 1600 nm) were obtained. Their absorption spectrum was measured and McCumber theory was employed to obtain the emission spectrum, leading to the absorption and emission cross sections. Numerical modeling for gain optimization in Er:Ta2O5 waveguide amplifiers is presented, employing the experimentally determined parameters. Finally, net optical gain of 2.1 dB/cm at 1531.5 nm is demonstrated in a 2.3 cm long Er:Ta2O5 rib waveguide when pumped with 977 nm laser diode, and compared with simulations to deduce the extent of upconversion.

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Titanium in-diffused lithium niobate index-tapered waveguides have been fabricated using laser-induced forward transfer technique for mode-filtering applications. Details of their fabrication, losses and transmission characterization are presented.

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Design, fabrication and optimization of high refractive index (2.1 @ 1070 nm), sub-micron thickness (200 nm) Tantalum Pentoxide waveguides is reported. Optimization of fabrication parameters reduces the propagation loss to ~ 1 dB/cm @ 1070 nm for Ta2O5 waveguides. Ta2O5 waveguides were found to be stable for high power application with no significant absorption peaks over a large range of wavelengths (600-1700 nm). Ta2O5 waveguides provide high intensity in the evanescent field, which is useful for efficient optical propelling of micro-particles. We have employed Ta2O5 waveguide to propel polystyrene micro-particles with 50 μm/s velocity.

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Tantalum Pentoxide (Ta2O5) films exhibit high refractive index (2.1 @ 1550 nm), transparency between 300 nm and 2000 nm wavelengths, compatibility with silicon processing techniques and high photosensitivity [1], making them ideal for realising compact multifunctional planar lightwave circuits (PLCs).