Integrated double octave-spanning dichroic filters in thin-film lithium niobate

Optical filters are essential for precise wavelength manipulation in various fields, including telecommunication, spectroscopy, nonlinear optics, and quantum photonics. Recent interest has grown in integrated wideband filters for on-chip photonic computing system components, such as optical combs and nonlinear circuits. This work introduces versatile dichroic short-, long-, and band-pass filters with ultrawideband operation (500–2100nm) as well as a 700-nm reconfigurable cutoff using thin-film lithium niobate (TFLN) waveguide structures. Leveraging TFLN's superior electro-optic and nonlinear properties, a monolithic coupler design enables broadband operation over 1600 nm. These filters have applications in optical isolators, optical combs, nonlinear wavelength converters, quantum parametric amplifiers, vacuum squeezers, and spontaneous parametric down-conversion systems.