Low-power broadband all-optical switching via intermodal cross-phase modulation in integrated optical waveguides

Abstract

We demonstrate the potential of all-optical switches in integrated waveguides based on intermodal cross-phase modulation between transverse modes. For this purpose, the differential phase between two transverse modes of a probe beam was altered by cross-phase modulation with a control beam propagating only in the fundamental mode. A switching behavior was accomplished by spatially filtering the resulting multimode interference of the probe modes, which changed depending on the control beam power. All-optical switching with a contrast of 82% at 1280 nm over a frequency range of 4.4 THz at 1.6 nJ was achieved, representing an improvement of the product of necessary power and waveguide length by a factor of nearly 2000 compared to similar experiments in graded-index fibers. Additionally, we show that the center wavelength of the switch can be tailored by changing the cross-sectional geometry of the waveguide or the involved probe modes.

Numerical and Experimental Demonstration of Intermodal Dispersive Wave Generation

“…Hence, multi-mode integrated waveguides have gained an increasing attention in the recent years, for example, for second-harmonic generation, [32,33] frequency comb generation in the visible, [23,34] quantum optics, [35] or all-optical switching. [28] In this work, we present numerical as well as experimental evidence of a new mechanism for DW generation between different transverse modes, namely intermodal DW generation (iDWG). This process is mediated by iXPM, where HOS formation in one mode induces a DW in a different mode.…”

“…[ 26 ] While iXPM is solely a phase modulation between transverse modes, iFWM includes amplitude modulations, transferring energy between transverse modes. Many multi‐mode interactions were already investigated numerically as well as experimentally, such as multi‐mode SCG, [ 6,13 ] higher‐order mode SCG, [ 16 ] multi‐mode solitons, [ 5 ] iFWM, [ 27 ] all‐optical switching, [ 28 ] intermodal third‐harmonic generation, [ 23 ] geometric parametric instability, [ 29 ] soliton self‐mode conversion, [ 30 ] and beam self‐cleaning. [ 31 ] With the increased number of transverse modes in multi‐mode waveguides, the complexity of the nonlinear dynamics increases but enables new phase‐matching opportunities for frequency generation.…”

“…Hence, multi‐mode integrated waveguides have gained an increasing attention in the recent years, for example, for second‐harmonic generation, [ 32,33 ] frequency comb generation in the visible, [ 23,34 ] quantum optics, [ 35 ] or all‐optical switching. [ 28 ]…”

Optical parametric amplification in silicon nitride waveguides for coherent Raman imaging

“…In contrast to fibers, silicon nitride (Si 3 N 4 ) waveguides offer a versatile, CMOS-compatible, onchip platform with a high nonlinear refractive index and a tight mode confinement [16]. Therefore, nonlinear processes such as FWM can be driven more efficiently [17][18][19][20][21], enabling operation with lower pump energies and shorter interaction lengths. Frequency conversion by spontaneous FWM was already demonstrated in Si 3 N 4 for telecommunications [22], mid-infrared generation [23], and even for broadband CARS applications [24].…”

Spatial-Dependent Hamiltonian Formulation of Cross-Mode Modulation

“…However, the restriction of RMM as well as degenerate mode group limits the applications in other scenario such as integrated photonic circuit where the required interaction length can be made very short due to strong mode confinement [10]. In addition, XMM effect between non-degenerate mode group are also topics of active research interests [2]. Therefore, Hamiltonian approach of linearizing the complex nonlinear dynamics is also very appearing.…”