Multi-mode signal source

A multimode radiation source, comprising:

• a waveguide radiator constructed and arranged to have a primary mode of operation over a radio frequency (RF) frequency range, the waveguide radiator having a first feed port for receiving an RF signal within the RF frequency range and for providing the RF signal to the waveguide radiator so that the waveguide radiator radiates the RF signal at a first location as a first spherical wave with a first phase center;
• waveguide feed network configured to be coupled to an RF source and that is coupled to the first feed port of the waveguide radiator, the waveguide feed network configured to receive the RF signal from the RF source and to provide the RF signal to the first feed port of the waveguide radiator so as to launch the RF signal in the waveguide radiator;
• and
• a hollow optical pipe disposed at least partially within the waveguide radiator and having a distal end that is disposed substantially at the first location, the hollow optical pipe configured to receive a first optical signal at a first frequency that is a plurality of orders of magnitude above a frequency of the RF signal and that is above the RF frequency range and a second optical signal at a second frequency that is also a plurality of orders of magnitude above the frequency of the RF signal and that is above the RF frequency range, the hollow optical pipe being configured to propagate the first and second optical signals within the waveguide radiator, to radiate the first optical signal from substantially the first location as a second spherical wave with substantially the first phase center,
• and to radiate the second optical signal from substantially the first location as a second spherical wave with substantially the first phase center.