Nonlinear optical properties of low temperature annealed silicon-rich oxide and silicon-rich nitride materials for silicon photonics

Minissale, S.; Yerci, Selçuk; Negro, Luca Dal

doi:10.1063/1.3675882

Cited by 31 publications

(19 citation statements)

References 26 publications

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“…Unexpectedly, CMOS-compatible amorphous silicon nitride films (SiN) have been shown to possess a bulk second-order nonlinearity by measuring strong second-harmonic generation (SHG) from thin films [9][10][11]. Although the exact reason for this strong SHG response remains unclear, it is believed that the complicated composition, crystalline phase, and defects in the film during the deposition may be responsible [10,[12][13][14][15][16].…”

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confidence: 99%

Enhancement of bulk second-harmonic generation from silicon nitride films by material composition

et al. 2017

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We present a comprehensive tensorial characterization of second-harmonic generation from silicon nitride films with varying compositions. The samples were fabricated using plasma-enhanced chemical vapor deposition, and the material composition was varied by the reactive gas mixture in the process. We found a six-fold enhancement between the lowest and highest second-order susceptibility, with the highest value of approximately 5 pm/V from the most silicon-rich sample. Moreover, the optical losses were found to be sufficiently small (below 6 dB/cm) for applications. The tensorial results show that all samples retain in-plane isotropy independent of the silicon content, highlighting the controllability of the fabrication process. High-performance complementary metal oxide semiconductor (CMOS) compatible materials are essential elements for advanced on-chip photonic devices to realize the future progress in all-optical processing. The ultra-fast speed and high bandwidth of integrated photonic networks continuously require new materials possessing excellent linear and nonlinear optical properties [1,2]. Although silicon (Si) is still the most commonly used CMOS material, the intrinsic drawbacks of Si, such as its narrow bandgap and centrosymmetric structure, highly limit its future applications especially in the visible and ultraviolet spectral regimes [2,3]. Thus, exploring novel CMOScompatible materials with wide bandgap and strong optical nonlinearities is very important for future integrated devices.Many photonic applications rely on nonlinear optical effects. One of the limitations of many nonlinear materials for CMOS-compatible platforms is the lack of second-order nonlinearity due to centrosymmetry. The problem can be overcome by poling [4,5], straining the material [3] or by using multilayer composites [6][7][8]. Unexpectedly, CMOS-compatible amorphous silicon nitride films (SiN) have been shown to possess a bulk second-order nonlinearity by measuring strong second-harmonic generation (SHG) from thin films [9][10][11]. Although the exact reason for this strong SHG response remains unclear, it is believed that the complicated composition, crystalline phase, and defects in the film during the deposition may be responsible [10,[12][13][14][15][16].In this Letter, we show that the strong second-harmonic signal from SiN films can be further enhanced by varying the composition of the films prepared with plasma-enhanced chemical vapor deposition (PECVD). Furthermore, we demonstrate that such composition tuning does not compromise the linear optical properties or optical losses of the material for applications. Our results are crucial for the comprehensive understanding of the linear and nonlinear optical properties in SiN films with different structures, opening the path for further optimization of SiN for on-chip devices.We recognize that there have been previous studies yielding different values for the SHG susceptibility of SiN [9,10,11,17,18]. Samples prepared by sputtering can yield very high values of the su...

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Enhancement of bulk second-harmonic generation from silicon nitride films by material composition

et al. 2017

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“…We include one data point (n 2 = 4.8 × 10 -17 m 2 /W) from [38] in Figure 3. Extremely high n 2 and FOM by 3~4 orders have been obtained experimentally [41] with large silicon excess (note that the FOM in [41] is defined as the reciprocal of ours here).…”

Section: Methodsmentioning

confidence: 99%

“…Silicon nano-crystals in silicon dioxide and silicon nitride have also been investigated as a nonlinear material, exhibiting higher nonlinear indices than crystalline silicon by an order of magnitude or more [36][37][38][39][40][41]. The values of n 2 , β TPA , and nonlinear FOM are also highly variable, if silicon excess, annealing temperature and wavelength change.…”

Section: Methodsmentioning

confidence: 99%

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Nonlinear Group IV photonics based on silicon and germanium: from near-infrared to mid-infrared

et al. 2014

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Group IV photonics hold great potential for nonlinear applications in the near-and mid-infrared (IR) wavelength ranges, exhibiting strong nonlinearities in bulk materials, high index contrast, CMOS compatibility, and cost-effectiveness. In this paper, we review our recent numerical work on various types of silicon and germanium waveguides for octave-spanning ultrafast nonlinear applications. We discuss the material properties of silicon, silicon nitride, silicon nano-crystals, silica, germanium, and chalcogenide glasses including arsenic sulfide and arsenic selenide to use them for waveguide core, cladding and slot layer. The waveguides are analyzed and improved for four spectrum ranges from visible, near-IR to mid-IR, with material dispersion given by Sellmeier equations and wavelength-dependent nonlinear Kerr index taken into account. Broadband dispersion engineering is emphasized as a critical approach to achieving on-chip octavespanning nonlinear functions. These include octave-wide supercontinuum generation, ultrashort pulse compression to sub-cycle level, and mode-locked Kerr frequency comb generation based on few-cycle cavity solitons, which are potentially useful for next-generation optical communications, signal processing, imaging and sensing applications.

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“…Compared to silicon waveguides fabricated on expensive SOI wafers, the guiding layer made of SiN can be easily deposited in standard CMOS lines using plasma-enhanced vapor deposition (PECVD) or low pressure vapor deposition (LPCVD) on silicon wafers at very low cost. Unlike silicon, low propagation losses at both visible and near infrared are achievable in both PECVD and LPCVD deposited SiN waveguides [4,5]. These waveguides were generally fabricated by using E-beam lithography and stepper.…”

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Sub-micron silicon nitride waveguide fabrication using conventional optical lithography

Huang

Zhao

Kamyab

et al. 2014

Advanced Photonics for Communications

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We demonstrate fabrication of sub-µm SiN waveguides using contact lithography with MEMS-grade photomasks for nonlinear optics and sensing applications that can provide 0.8dB/cm propagation loss, γ=0.3W -1 /m nonlinearity, and <100ps/nm.km dispersion.OCIS codes: 130.2790 Guided waves, 220.3740 Lithography, 230.7370 Waveguides. IntroductionRecently, silicon nitride (SiN) has emerged as an alternative to silicon on insulator (SOI) platform for integrated photonic circuits [1][2][3]. Compared to silicon waveguides fabricated on expensive SOI wafers, the guiding layer made of SiN can be easily deposited in standard CMOS lines using plasma-enhanced vapor deposition (PECVD) or low pressure vapor deposition (LPCVD) on silicon wafers at very low cost. Unlike silicon, low propagation losses at both visible and near infrared are achievable in both PECVD and LPCVD deposited SiN waveguides [4,5]. These waveguides were generally fabricated by using E-beam lithography and stepper. It would be very attractive if the highly accessible UV contact lithography can be accommodated to fabricate low loss waveguides. However, the resolution limit of direct contact lithography is larger than 1µm due to optical diffraction limit. Even for large waveguides with dimension greater than 1µm, high quality photomasks with smooth edges are still necessary in order to deliver low loss waveguides. In this report, we present such a fabrication technique that enables fabrication of sub-micron SiN waveguides using i-line UV contact lithography with very low cost MEMS grade photomasks. We show that a sequence of photolithography steps followed by KOH wet etching, thermal oxidation, and LPCVD SiN deposition can produce sub-micron trench like low loss waveguides that is suitable for microfluidic sensing and nonlinear optical applications. The process is also CMOS compatible. With this technique, we successfully fabricated SiN waveguide with a width of 0.8µm and effective mode area of A eff =1.9µm 2 . We achieved a low propagation loss of 0.8±0.26dB/cm. We also measured the nonlinear refractive index, effective nonlinearity and group velocity dispersion as n 2 =1.39×10 -19 m 2 /W, γ=0.3W -1 /m, and D<100ps/nm.km, respectively.

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Nonlinear optical properties of low temperature annealed silicon-rich oxide and silicon-rich nitride materials for silicon photonics

Cited by 31 publications

References 26 publications

Enhancement of bulk second-harmonic generation from silicon nitride films by material composition

Enhancement of bulk second-harmonic generation from silicon nitride films by material composition

Nonlinear Group IV photonics based on silicon and germanium: from near-infrared to mid-infrared

Sub-micron silicon nitride waveguide fabrication using conventional optical lithography

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