Deep-UV Lithography Fabrication of Slot Waveguides and Sandwiched Waveguides for Nonlinear Applications

Abstract

Slot and sandwiched waveguides with silicon nanocrystals were fabricated by means of industrial microelectronic tools, including DUV lithography. Low loss of 4 dB/cm will pave the way to compact all-optical XOR logic gates. IntroductionUsing silicon, oxides, nitrides and other Si-based materials as active means for photonic functionalities is of great interest since it would allow a potential monolithic integration of electrical and optical circuits in a fully compatible CMOS processing. For example, optical interconnects, optical amplifiers and switches integrated in CMOS photonic chips would make it possible to develop low cost and all-optical communication networks without bottlenecks induced by electrical/optical converters. Passive devices (filters, couplers, multiplexers...) that make use of silicon-based waveguides and materials exhibiting non-linear optical properties have already been demonstrated. Nevertheless they use Si thermo-optic effects or refractive index variation due to the free carrier concentration in Si, as bulk Si is a very poor material for non-linear optics. Notwithstanding, nanostructured Si, due to quantum confinement effects, and particularly silicon nanoclusters (Si-nc) embedded in SiO2 (Si-nc/SiO2) are considered very promising materials due to extraordinarily enhanced nonlinear properties in comparison to bulk Si, as its Kerr coefficient is reported in the range

Ultra-high four wave mixing efficiency in slot waveguides with silicon nanocrystals

“…A key role is played by the fine control of the hydrogen content in the top amorphous-Si layer that allows saturating the dangling bonds responsible for mid-bandgap absorption in the infrared wavelength range. 10,11 The nonlinear interactions were studied in both Transversal Magnetic-Field (TM) and Transversal Electric-Field (TE) case. In the TM case (slot confined mode), the measured conversion efficiency exceeds by about 18 dB the one obtained in the previous experiment.…”

Broadband wavelength conversion in a silicon vertical-dual-slot waveguide

“…Using the crossover point of the two curves, we get proposed dimensions of 520-86-54, 540-112-76, 550-129-98, and 570-167-234. Note that small W s helps to avoid the independent beam guidance of side-strip modes, while large S increases the silica filling ratio of the slots [31,32], which further mitigates the uncertainty of the actual GVD induced by partial filling. Therefore, there is a trade-off between W s and S, and we choose a suitable dimension of 550-129-98.…”

“…Therefore, the fabrication procedure of GVD-engineered slot structure is more convenient than that of the sandwich structure, in which multilayers require extra accurate deposition steps. Note that partial filling of the slots may take place due to the nonuniform deposition, which however can be mitigated by using the suitable deposition procedures [31,32].…”

Silicon Nanocrystals as an Enabling Material for Silicon Photonics

“…Examples of such structures are shown schematically in Fig. 11: an SRO slot (100-150 nm) sandwiched by two silicon waveguides (width of 500 nm and height of 200-300 nm) [131]. Both vertical [ Fig.…”