Broadband 200-nm second-harmonic generation in silicon in the telecom band

Abstract

Silicon is well known for its strong third-order optical nonlinearity, exhibiting efficient supercontinuum and four-wave mixing processes. A strong second-order effect that is naturally inhibited in silicon can also be observed, for example, by electrically breaking the inversion symmetry and quasi-phase matching the pump and the signal. To generate an efficient broadband second-harmonic signal, however, the most promising technique requires matching the group velocities of the pump and the signal. In this work, we utilize dispersion engineering of a silicon waveguide to achieve group velocity matching between the pump and the signal, along with an additional degree of freedom to broaden the second harmonic through the strong third-order nonlinearity. We demonstrate that the strong self-phase modulation and cross-phase modulation in silicon help broaden the second harmonic by 200 nm in the O-band. Furthermore, we show a waveguide design that can be used to generate a second-harmonic signal in the entire nearinfrared region. Our work paves the way for various applications, such as efficient and broadband complementarymetal oxide semiconductor based on-chip frequency synthesizers, entangled photon pair generators, and optical parametric oscillators.

Thirty Years in Silicon Photonics: A Personal View

“…As a result a large SHG efficiency dependent on the applied reverse bias was observed (Figure 13H). Similar results have been reported by [199,200] with a 200 nm wide spectral SHG band demonstrated in [201] by group velocity engineering.…”

Supercontinuum Generation Assisted by Wave Trapping in Dispersion-Managed Integrated Silicon Waveguides

“…The low power threshold to get broadband SC in DM structures and the high coherence of the resulting frequency comb is promising for robust chip-scale frequency-comb sources. With the recent demonstration of silicon-based second-harmonic generation [77] and integrated thulium mode-locked laser sources [78], our results could be of benefit, for instance, to the development of fully integrated optical-frequency synthesizers. The generation of a strong dispersive wave far from the pump, which is needed for the comb stabilization of the carrier offset frequency by f -2f interferometry, could indeed be combined with a flat and smooth coherent spectrum between this latter wavelength and the pump one, as seen in Fig.…”

Efficient type II second harmonic generation in an indium gallium phosphide on insulator wire waveguide aligned with a crystallographic axis

“…In particular, many novel integrated platforms for integrated SHG have recently emerged [2][3][4]. Conversions as high as 47,000%/(W • cm 2 ) have been demonstrated in III-V semiconductors [5], and ultra-wide tuning was recently shown in silicon waveguides [6]. The large intrinsic nonlinearity in addition to the high-index contrast of sub-wavelength structures leads to very large effective nonlinearities.…”