Microwave electro-optic mixer

Claim 1

An electro-optic mixer comprising: (a) means for providing first and second microwave signals having first and second frequencies, respectively; (b) a device for providing a source light; (c) a first modulator responsive to the source light and to the first microwave signal for producing a first modulated optical signal; (d) a second modulator cascade coupled to said first modulator and being responsive to the first modulated signal and to the second microwave signal for producing a second modulated optical signal having a frequency component selected from the class consisting of the sum and difference of the first and second frequencies; each of said first and second modulators comprising: an associated substrate having substrate modes, having electro-optic effects and having first and second optical waveguides adapted to receive and transmit light therethrough in a first direction and with a first phase velocity; an associated buffer layer disposed on said associated substrate; and an associated coplanar waveguide electrode structure having a coplanar mode and being disposed on said associated buffer layer for receiving an electrical signal propagating therethrough in the first direction with a second phase velocity to intensity modulate the light in said optical waveguides at a frequency in a preselected frequency range, said associated coplanar waveguide electrode structure having a sufficiently large thickness so that said second phase velocity of said electrical signal is substantially equal to said first phase velocity; said associated substrate having a sufficiently small thickness so that coplanar mode-substrate mode coupling substantially does not occur upon operation in the preselected frequency range; and (e) means coupled between said first and second modulators for transmitting the first modulated signal from said first modulator to said second modulator.