Broadband heterodyne electro-optic sampling using a lithium niobate ridge-waveguide

We demonstrated the bandwidth broadening of terahertz waves detected by heterodyne electro-optical sampling by implementing a ridge waveguide structure in a lithium niobate (LiNbO3) crystal. Such an approach effectively reduces absorption loss, eases the phase matching condition and enhances the nonlinear interaction length through the optical confinement effect. As a result, we have more than doubled the bandwidth and improved the signal-to-noise ratio compared with an equivalent approach in a bulk LiNbO3 crystal. Heterodyne electro-optic sampling in a ridged-waveguide structure is only marginally dependent on the probe beam wavelength, suggesting its potential as a versatile method for broadband terahertz detection.