Chi 3 dispersion in planar tantalum pentoxide waveguides in the telecommunications window

Abstract

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...

Broadband stimulated four-wave parametric conversion on a tantalum pentoxide photonic chip

“…, where the proportionality coefficient A relates to (3) χ [18]. Figure 3c shows the output wavelength dependence on the seed wavelength satisfying energy conservation in the parametric process.…”

“…the effective mode index), of the waveguides is also obtained from simulations by Finite Element Method. We use RSoft CAD to simulate the waveguide dispersion of 12 supported modes, numbered as mode 0 -11, which incorporates the 2 5 Ta O material dispersion [17,18] in waveguide G2. Figure 8a shows the measured waveguide output mode images generated by the stimulated four-wave parametric process, and Fig.…”

“…2 5 Ta O also has the advantage that the fabrication process is well-known as it is commonly used as a high-k material in the microelectronics industry [17][18][19][20].…”

Optimization of reactive-ion etching (RIE) parameters for fabrication of tantalum pentoxide (Ta2O5) waveguide using Taguchi method

“…The planar waveguide and the PC slab structure are a desirable structure to realize a compact optical components device (e.g., tunable laser source). Among the available materials, the tantalum pentoxide (Ta 2 O 5 ) has received much attention due to its high refractive index (n > 2), low absorption over a wide wavelength region 0.3 to 10 m [4], high nonlinear refractive index n 2 = (7.23±0.36)×10 -19 m 2 /W [5], large value of chi 3 [6] and high optical damage threshold [7]. Recently, researchers have shown optical non-linear behaviour and demonstrated supercontinuum generation [8] and OPO [9] in Ta 2 O 5 waveguides, suggesting a good stability and high damage threshold limits.…”

Low-loss and high index-contrast tantalum pentoxide microring resonators and grating couplers on silicon substrates

“…Furthermore, Ta 2 O 5 has the potential to become an attractive material for third-order (χ 3 effects) nonlinear integrated optics [4,5]. It is noted that silicon has a very high nonlinear index coefficient, n 2 , and has been aggressively pursued.…”