Abstract: Techniques dual-frequency comb sources are disclosed. In the illustrative embodiment, a whispering-gallery-mode resonator supports a family of radially-polarized modes and a family of axially-polarized modes. A laser excites one radially-polarized mode and one axial-polarized mode. A microwave field is applied at a free spectral range for each family of modes, coupling the radially-polarized and axially-polarized mode excited by the laser with other modes in the family, creating a dual-frequency comb in the resonator.

Abstract: A trailer having a frame, a hitch apparatus (6) including a tow head adaptor securable to the tow bar of a towing vehicle, universal joint means extending between and linking the tow head adaptor and a tow head bracket attached to the trailer frame in a manner permitting an extended range of towing angles and the tow head bracket being pivotal on the trailer frame between a forwardly extending operative position for the hitch apparatus and an inoperative space saving storage position. In another embodiment the trailer is collapsible, including a removable cargo tray. In a further embodiment the trailer includes a wheel trough (1) for carrying a motorcycle.