A terahertz device for detecting or for emitting or for both, detecting and emitting electromagnetic waves in the terahertz range, the device comprising on a substrate a first waveguide which is a plasmonic waveguide comprising - a first core comprising a nonlinear material (101, 202, 305, 402), in particular a ferroelectric material; and - a cladding comprising a first cladding portion comprising, at a first interface with the first core, in particular with the nonlinear material, a first cladding material which is an electrically conductive material; the device comprising a first and a second electrode arranged close to the first waveguide, wherein the device comprises an antenna having a first and a second arm (201, 304, 403), for receiving or for emitting or for both, receiving and emitting electromagnetic waves in the terahertz range, wherein the device comprises a second waveguide (103, 302, 401), wherein the second waveguide is a photonic waveguide comprising a second core positioned in proximity to the first waveguide, for enabling coupling between the first and second waveguides, characterized in that - the second waveguide is arranged vertically between the substrate (104, 203, 301) and the first waveguide; and/or - the second waveguide is buried in the substrate; and/or - the device comprises an integrated Mach-Zehnder interferometer by the second waveguide being split in two branches, wherein both branches are arranged to couple evanescently in close proximity with a first waveguide, wherein the device comprises two inner electrodes that function as cladings and two outer electrodes formed by the antenna arms 403. - a first core comprising a nonlinear material (101, 202, 305, 402), in particular a ferroelectric material; and - a cladding comprising a first cladding portion comprising, at a first interface with the first core, in particular with the nonlinear material, a first cladding material which is an electrically conductive material; the device comprising a first and a second electrode arranged close to the first waveguide, wherein the device comprises an antenna having a first and a second arm (201, 304, 403), for receiving or for emitting or for both, receiving and emitting electromagnetic waves in the terahertz range, wherein the device comprises a second waveguide (103, 302, 401), wherein the second waveguide is a photonic waveguide comprising a second core positioned in proximity to the first waveguide, for enabling coupling between the first and second waveguides, characterized in that - the second waveguide is arranged vertically between the substrate (104, 203, 301) and the first waveguide; and/or - the second waveguide is buried in the substrate; and/or - the device comprises an integrated Mach-Zehnder interferometer by the second waveguide being split in two branches, wherein both branches are arranged to couple evanescently in close proximity with a first waveguide, wherein the device comprises two inner electrodes that function as cladings and two outer electrodes formed by the antenna arms 403. - the second waveguide is arranged vertically between the substrate (104, 203, 301) and the first waveguide; and/or - the second waveguide is buried in the substrate; and/or - the device comprises an integrated Mach-Zehnder interferometer by the second waveguide being split in two branches, wherein both branches are arranged to couple evanescently in close proximity with a first waveguide, wherein the device comprises two inner electrodes that function as cladings and two outer electrodes formed by the antenna arms 403.