1,721,069 research outputs found
Tantalum pentoxide waveguide amplifier and laser for planar lightwave circuits
No full textA planar lightwave circuit (PLC) has been envisioned to provide a new generation of optical networks capable of delivering signal at high speed and bandwidth to the household. High index contrast (HIC) and optical gain in the same material system would substantially enhance integration of different optical devices in a small area and compensate for the losses in the system to realise low cost, dense multi-functional PLCs. This thesis investigates the use of tantala as a HIC material system for realising gain efficient Erbium doped waveguide amplifiers (EDWAs) and lasers to be used at 1.5µm wavelength, towards realising dense multi-functional PLCs.Slab waveguides were fabricated by magnetron sputter deposition under optimised conditions of a powder pressed, Er:Ta2O5 target onto an oxidized silicon substrate. Optimised sputtering process yielded a Er:Ta2O5 thin film with a refractive index of 2.105 @ 1550 nm and a maximum erbium lifetime of 2.3 ms. Single mode rib waveguides were designed and the fabricated using photolithography and argon ion beam milling. A maximum propagation loss of 0.65 ± 0.05 dB/cm at 1600 nm was measured, the peak erbium absorption and emission cross-section was determined to be 4.8 ± 0.2 x 10-21 cm2 and 4.4 ± 0.2 x 10-21 cm2 respectively.Numerical modeling of Er:Ta2O5 based EDWA predicted a maximum gain of 4 dB/cm at 200 mW pump power, in a 5.4cm long waveguide with an erbium concentration of 5.4 x 1020 ions/cm3. Gain measurements were performed on a 2.3cm long rib waveguide with a erbium concentration of 2.7 x 1020 ions/cm3, at a pump power of 200mW, and a net optical gain of 2.25dB/cm peaking at 1531.5 nm was measured in a 2µm wide waveguide. The pump threshold with respect to the launched pump power was measured to be as low as 4.5mW. The cavity was formed by affixing two mirrors at the end facets of the waveguides. Lasing was observed in a single longitudinal and transverse mode peaking between 1556 and 1560nm. The lasing threshold of 14mW with a slope efficiency of 0.3% was measured with respect to the launched power.Finally, a feasibility study for inscribing sub-micron grating structures on the Er:Ta2O5 waveguides were carried out using interferometric ablation. Gratings inscribed with 23 mJ/cm2 energy density and 1000 pulses yielded a maximum reflectivity of 11dB for TE polarisation at 1505nm. This feasibility study shows potential to realise integrated cavity line narrowed lasers and filters. Tantala has long been used for different photonic applications but gain at 1.5 μm is demonstrated for the first time. The results presented in the thesis demonstrate that tantala due to its HIC, net optical gain and other inherent properties that it possesses have the potential to realise low cost, compact PLCs for the short haul networks
Er:Ta<sub>2</sub>O<sub>5</sub> waveguide optimization & spectroscopy
No full textThe optimization of erbium-doped Ta thin film waveguides deposited by magnetron sputtering is described. Background losses below 0.4dB/cm have been obtained before post-annealing. A broad photoluminescence spectrum centered at 1534nm is obtained, and the photoluminescence power and fluorescence lifetime increase with post-annealing, yielding promising results for compact amplifiers
Waveguiding and photoluminescence in Er<sup>3+</sup>-doped Ta<sub>2</sub>O<sub>5</sub> planar waveguides
Get PDFThe optimization of erbium-doped Ta2O5 thin film waveguides deposited by magnetron sputtering onto thermally oxidized silicon wafer is described. Optical constants of the film were determined by ellipsometry. For the slab waveguides, background losses below 0.4dB/cm at 633nm have been obtained before post-annealing. The samples, when pumped at 980nm yielded abroad photoluminescence spectrum (FWHM ~50 nm) centred at 1534nm, corresponding to 4 I 13/2 to the 4 I 15/2 transition of Er3+ ion. The samples were annealed up to 600 °C and both photoluminescence power and fluorescence lifetime increase with post-annealing temperature and a fluorescence lifetime of 2.4ms was achieved, yielding promising results for compact waveguide amplifier
Sub-micron period relief grating structures inscribed on Erbium doped Ta<sub>2</sub>O<sub>5</sub> waveguides using 213 nm, 150 ps laser radiation
No full textTantalum 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)
Er:Ta2O5 waveguide optimization and spectroscopy
No full textThe optimization of erbium-doped Ta2O5 thin film waveguides deposited by magnetron sputtering is described. Background losses below O.4dB/cm have been obtained before post-annealing. A broad photoluminescence spectrum centered at 1534nm is obtained, and the photoluminescence power and fluorescence lifetime increase with post-annealing, yielding promising results for compact amplifiers
Surface transport and stable trapping of particles and cells by an optical waveguide loop
No full textWaveguide trapping has emerged as a useful technique for parallel and planar transport of particles and biological cells and can be integrated with lab-on-a-chip applications. However, particles trapped on waveguides are continuously propelled forward along the surface of the waveguide. This limits the practical usability of the waveguide trapping technique with other functions (e.g. analysis, imaging) that require particles to be stationary during diagnosis. In this paper, an optical waveguide loop with an intentional gap at the centre is proposed to hold propelled particles and cells. The waveguide acts as a conveyor belt to transport and deliver the particles/cells towards the gap. At the gap, the diverging light fields hold the particles at a fixed position. The proposed waveguide design is numerically studied and experimentally implemented. The optical forces on the particle at the gap are calculated using the finite element method. Experimentally, the method is used to transport and trap micro-particles and red blood cells at the gap with varying separations. The waveguides are only 180 nm thick and thus could be integrated with other functions on the chip, e.g. microfluidics or optical detection, to make an on-chip system for single cell analysis and to study the interaction between cells
Spectroscopy, modeling, and performance of Erbium-Doped Ta<sub>2</sub>O<sub>5</sub> waveguide amplifiers
No full textThe 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
High index contrast Er:Ta<sub>2</sub>O<sub>5</sub> waveguide amplifier on oxidised silicon
No full textWe report a high index contrast erbium doped tantalum pentoxide waveguide amplifier. 2.3 cm long waveguides with erbium concentration of 2.7 × 1020 cm-3 were fabricated by magnetron sputtering of Er-doped tantalum pentoxide on oxidised silicon substrates and Ar-ion milling with photolithographically defined mask. A net on-chip optical gain of ~2.25 dB/cm at 1531.5 nm was achieved with 20mW of pump power at 977 nm launched into the waveguide. The pump threshold for transparency was 4.5mW.<br/
Sub-micron period relief grating structures inscribed on erbium doped Ta2O5 waveguides using 213 nm, 150 ps laser radiation
No full textFabrication of submicrometer high refractive index tantalum pentoxide waveguides for optical propulsion of microparticles
No full textDesign, 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 (Δn ~ 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 µm/s was obtained for 8 µm polystyrene particles with guided power of only 20 mW
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