We report on the dispersion of the third-order nonlinear susceptibility ( ͑3͒ or "Chi 3") in planar Ta 2 O 5 waveguides in the telecommunications spectral window. We utilize the observation of third-harmonic generation under ultrashort pulsed excitation as a reference-free characterization method of ͑3͒ and obtain a large nonlinear coefficient, 2 ϫ 10 −13 esu, at 1550 nm. Our observation of efficient third-harmonic generation in Ta 2 O 5 waveguides in the telecoms window reveals the potential of this material system in high-speed integrated nonlinear optical switches. © 2009 Optical Society of America OCIS codes: 160.4330, 230.7390, 190.2620 Fast low-power all-optical switches are a key component for high-bit-rate communication systems. Silica optical fibers are currently used owing to their low loss. However, the small nonlinear refractive index of silica [1-3] requires high switching powers and very long interaction lengths. To achieve compact switching devices, a large nonlinear refractive index ͑n 2 ͒ is required. Although many materials with a higher nonlinear refractive index than silica have been reported [2,4-6], there is a particular interest in those compatible with planar processing technologies, with minimal losses and absorption at a wide range of operating wavelengths, and good thermal and mechanical robustness. Silicon provides one potential candidate [7,8] but exhibits strong free carrier and twophoton absorption limiting device performance. Chalcogenide (e.g., As 2 S 3 ) glass is an alternative that does not exhibit two-photon absorption [9][10][11][12]; however, it has a relatively low damage threshold (9 GW/ cm 2 [13]) compared to Ta 2 O 5 [14]. Both of the above two examples have large normal material dispersion, which can be detrimental to wavelength division multiplexing applications but can be compensated by adjusting the waveguide geometry dimensions [7][8][9][10][11][12]. Here we investigate Ta 2 O 5 rib planar waveguides as an alternative for compact optical devices with a small effective area that could enable the exploitation of nonlinear effects at low light intensity in the telecoms window. Ta 2 O 5 has been widely used as a high dielectric gate material for microelectronic devices, and multilayer dielectric mirrors, and more recently it was shown to possess a high nonlinear refractive index at 800 nm [1,14].Silicon dioxide ͑SiO 2 ͒ clad Ta 2 O 5 planar rib waveguides are grown following the methodology in [15]. We examine the nonlinear optical properties of 5-mm-long waveguides with 750 nm core thickness and 2.5 m (sample A) and 18 m (sample B) width. Figure 1 shows a cross-sectional scanning electron microscope view of two waveguides. The samples are optically excited using an optical parametric amplifier tunable in the near IR (280 fs pulses) with no laser-induced damage to the waveguides.We characterize the nonlinear optical properties of the rib waveguides by spectrally and spatially resolving the guided optical modes at the end face of the rib structure in both the near-IR an...

Abstract:We exploit the large third order nonlinear susceptibility ( Ta O ) planar waveguides and realize broadband optical parametric conversion on-chip. We use a co-linear pumpprobe configuration and observe stimulated four wave parametric conversion when seeding either in the visible or the infrared. Pumping at 800 nm we observe parametric conversion over a broad spectral range with the parametric idler output spanning from 1200 nm to 1600 nm in infrared wavelengths and from 555 nm to 600 nm in visible wavelengths. Our demonstration of on-chip stimulated four wave parametric conversion introduces Thienpont, and B. J. Eggleton, "High-resolution optical sampling of 640-Gb/s data using four-wave mixing in dispersion-engineered highly nonlinear As2S3 planar waveguides," J. Lightwave Technol. 28(2), 209-215 (2010). 13. I.

We utilize analysis of third harmonic generation under femtosecond pulsed excitation as a reference free measurement method for third order nonlinear susceptibility (

Abstract. Limitations of current sensors include large dimensions, sometimes limited sensitivity and inherent single-parameter measurement capability. Surface-enhanced Raman spectroscopy can be utilized for environment and pharmaceutical applications with the intensity of the Raman scattering enhanced by a factor of 10 6 . By fabricating and characterizing an integrated optical waveguide beneath a nanostructured precious metal coated surface a new surface-enhanced Raman spectroscopy sensing arrangement can be achieved. Nanostructured sensors can provide both multiparameter and high-resolution sensing. Using the slab waveguide core to interrogate the nanostructures at the base allows for the emission to reach discrete sensing areas effectively and should provide ideal parameters for maximum Raman interactions. Thin slab waveguide films of silicon oxynitride were etched and gold coated to create localized nanostructured sensing areas of various pitch, diameter, and shape. These were interrogated using a Ti:Sapphire laser tuned to 785-nm end coupled into the slab waveguide. The nanostructured sensors vertically projected a Raman signal, which was used to actively detect a thin layer of benzyl mercaptan attached to the sensors.

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