Intermodal four-wave mixing in silicon waveguides

Abstract

In this work, we report the modeling and the experimental demonstration of intermodal spontaneous as well as stimulated four-wave mixing (FWM) in silicon waveguides. In intermodal FWM, the phase-matching condition is achieved by exploiting the different dispersion profiles of the optical modes in a multimode waveguide. Since both the energy and the wave vectors have to be conserved in the FWM process, this leads to a wide tunability of the generated photon wavelength, allowing us to achieve a large spectral conversion. We measured several waveguides that differ by their widths and demonstrate large signal generation spanning from the pump wavelength (1550 nm) down to 1202 nm. A suited setup evidences that the different waves propagated indeed on different order modes, which supports the modeling. Despite observing a reduced efficiency with respect to intramodal FWM due to the decreased modal overlap, we were able to show a maximum spectral distance between the signal and idler of 979.6 nm with a 1550 nm pump. Our measurements suggest the intermodal FWM is a viable means for large wavelength conversion and heralded photon sources.

Silicon Photonics Chip for Inter-modal Four Wave Mixing on a Broad Wavelength Range

“…The increased flexibility provided by the waveguide modes allows broadband and tunable wavelength conversion. This has been already demonstrated in a multimode silicon waveguide [6], with the generated idler photons spanning from 1,200 to 1,500 nm. The broadband operation is one of the most interesting and exploited properties of inter-modal FWM in the integrated platform [7][8][9].…”

“…As an example, in Figure 1 (right) the mode profiles involved in the 1221 TE (transverse electric polarization) combination in a rib waveguide are shown. Each waveguide mode has a different effective index and is affected differently by the waveguide engineering [6]. According to Equation (3), by properly choosing the waveguide geometry and the involved modes, k can be made equal to zero (i.e., maximum generation efficiency) in the desired spectral position.…”

“…With respect to the first demonstration of inter-modal FWM on the silicon-on-insulator (SOI) platform, where simple multimode waveguides have been used [6], in this work we report the results obtained with an optimized design where the different modes are handled directly on the chip. In fact, inter-modal FWM requires efficient mode couplers to selectively route/couple different modes along the chip.…”

Perspectives for Applications of Quantum Imaging

“…Spontaneous four wave mixing can be an expedient. Its successful application for photon pair generation was already demonstrated, but more progress with respect to imaging applications involving UV light needs to be done.…”

Design and performance analysis of integrated focusing grating couplers for the transverse-magnetic TM00 mode in a photonic BiCMOS technology

“…Furthermore, highly stable frequency comb generation can be supported by TM, as shown in [8]. Signal regeneration enabled by four-wave-mixing (FWM) involving the TM mode was demonstrated in a single-mode regime [9] and more recently, intermodal FWM [10] allowed for a large wavelength conversion. Novel on-chip components like optical isolators and circulators [11] require an operation with the TM polarization as well.…”