Quantum-optical technologies based on parametric light down-conversion are not yet applied in the terahertz frequency range. This is owing to the complexity of detecting single photons in the terahertz frequency range and the strong entanglement of modes of optical–terahertz biphotons. This study investigates the angular structure of scattered radiation generated by strongly non-degenerate parametric down-conversion when the frequency of the idler radiation does not exceed several terahertz. We demonstrate that under certain approximations, it is possible to obtain azimuthal eigenmodes for the nonlinear interaction operator. The solution of the evolution equations for the field operators in these eigenmodes has the form of the Bogoliubov transformation, which allows a scattering matrix to be obtained for arbitrary values of the parametric gain. This scattering matrix describes both the production of biphoton pairs and the generation of intense fluxes of correlated optical–terahertz fields that form a macroscopic quantum state of radiation in two spectral ranges.

基于参量光下转换的量子光学技术尚未在太赫兹频率范围内应用。这是由于在太赫兹频率范围内检测单个光子的复杂性以及光太赫兹双光子模式的强纠缠。这项研究研究了当惰轮辐射的频率不超过几太赫兹时，由强烈的非退化参数下转换产生的散射辐射的角结构。我们证明，在某些近似下，有可能获得非线性相互作用算子的方位本征模。在这些本征模式下，针对场算符的演化方程的解采用Bogoliubov变换的形式，该变换允许针对参数增益的任意值获得散射矩阵。