Backward terahertz difference frequency generation via modal phase-matching in a planar LiNbO₃ waveguide

Abstract

The backward difference frequency generation process is used to produce narrowband terahertz radiation via modal phase-matching in a S i O 2 - L i N b O 3 -air planar waveguide. The T M 0 pump mode, T E 0 signal mode, and T E 0 or T E 2 idler modes are selected to satisfy the backward difference frequency generation phase-matching condition, thus allowing narrowband (i.e., &lt;<!-- 100 G H z linewidth) terahertz radiation generation in the spectral range of 2.4–3.2 THz. To date, this is the first investigation of terahertz radiation generation in a waveguide via the modal phase-matched backward difference frequency generation process.

Nonlinear Photonic Waveguides: A Versatile Platform for Terahertz Radiation Generation (a Review)

“…[ 43 ] The lower‐frequency spectral peaks (i.e., ≈1.7‐2.2 THz) were due to DFG phase‐matching to the TE 0 THz mode and the higher‐frequency spectral peaks (i.e., ≈2.4–3.3 THz) were due to DFG phase‐matching to the TE 2 THz mode. [ 43 ]…”

Propagation and Transformation of Vortexes in Linear and Nonlinear Radio-photon Systems

“…In [46], a modified method of slowly varying envelope approximation was developed based on the factorization of a slowly varying amplitude into two factors, one of which is forced to obey the parabolic equation, and the second one depends only on the coordinate in the propagation direction and obeys a differential equation, which makes it possible to improve accuracy when describing the three-wave mixing process. In this method, in contrast to the search for a solution to equation ( 21) in the form (22), the envelope ( , , ) E x y z  is represented in a more detailed multiplicative form so that ( , , , ) ( ) ( , ,…”

“…In [20], a hybrid lithium niobate/silicon waveguide scheme with a high generation efficiency of the order of 3.5×10 −4 W −1 at 3 THz is used to achieve a terahertz signal by generating a difference frequency. In addition to classical PPLNs, aperiodic PPLNs (APPLNs) are also investigated: in [21], a similar crystal is used for cascade DFG (CDFG), which results in terahertz radiation; the conversion efficiency of this approach is almost 3 times higher, but it is achieved at a low temperature -about 10 K. In [22], the optical pump wave and the incident wave propagate in a lithium niobate crystal not co-directionally, but towards each other, which, according to the authors, allows optical feedback without resonance cavity and helps to generate narrow-band THz radiation. A terahertz signal can also be generated using a 2D InxGa1-xSe crystal [23] using DFG with a conversion efficiency of the order of 10 −5 .…”

Strategies for wideband light generation in nonlinear multimode integrated waveguides

“…However, the single-mode platform is intrinsically limited: either broadband gain is achieved in the nearzero anomalous dispersion regime and close to the pump wavelength; or narrow-band gain is achieved far from the pump in the near-zero normal dispersion regime mediated by 4th-order dispersion [14][15][16][17]. Recently, researchers have started to investigate multimode waveguides [18][19][20][21][22], where several interactions among different spatial modes contribute to the nonlinear dynamics. These pioneering works open the way to the use of intermodal nonlinear interactions in integrated waveguides, however up to date the full potential of these interactions is far from being reached.…”