Coupled interface modes for nonlinear interaction in periodic layered media

Abstract

and nonlinear properties. Second harmonic generation is adopted for the demonstration of nonlinear interaction, due to its convenient experimental set-up. Three different laser sources are used to pump the waveguides and second harmonic light is generated and characterized. Coupled interface modes in conjunction with other types of modes also existing within the same structures, offer the possibility to explore three-wave mixing processes such as sum and difference frequency generation.ii

Interface modes for monolithic nonlinear photonics

“…Another variation of IMs can occur at the boundary of semiinfinite periodic media with a high refractive index cap layer and a homogeneous medium. Such a structure is capable of guiding TIR modes as well as IMs [19]. A schematic of such structure is shown in Fig.…”

“…In reality, the effective mode index of TIR modes resides somewhere between the core index and the cladding indices and is, hence, confined within the two caps and core layers through TIR. Using the design methodology in [19], given the core thickness, the structure refractive indices, and the thickness of the cap, the thicknesses of the bilayers composing the periodic cladding can be determined for the QtW condition. The following procedure describes the route used for designing phase-matched waveguides that utilize IMs for SH generation:…”

“…4. Use the dispersion relations in [19] to calculate the corresponding cap layer thickness for both TE and TM IMs.…”

“…As seen in these figures, the same structures that accommodate propagation of the TIR modes and Bragg modes discussed, for example, in [18] can also support optical modes that exist at the interface between the periodic cladding and the core. These are based on IMs, which we previously reported [19]. Interface mode waveguides (IMWs) could be utilized in a similar fashion to what has been carried out in the past utilizing BRWs to facilitate efficient three-wave mixing and to provide an additional degree of freedom for alleviating the limitations associated with conventional BRWs when used in PM applications.…”