A waveguide structure for use in a balanced push-pull Mach Zehnder modulator. The waveguide structure comprises a plurality of layers. The layers comprise, in order: an insulating or semi-insulating substrate; an lower cladding layer; an waveguide core layer; and an upper cladding layer. The lower cladding layer, waveguide core layer, and upper cladding layer are etched to form: a signal waveguide and a ground waveguide, which are connected via the lower cladding layer; and a signal line and a ground line, each located adjacent to the respective waveguide, and each connected to the respective waveguide via one or more respective resistive structures connected in the plane of the lower cladding layer.

A source of femtosecond pulses at center wavelengths of about 940 nm and about 1140 nanometers (nm) includes a mode-locked fiber MOPA delivering pulses having a center wavelength of about 1040 nm. The 1040-nanometer pulses are spectrally spread into a continuum spectrum extending in range between about 900 nm and about 1200 nm and having well defined side-lobes around the 940-nm and 1140-wavelengths. Radiation is spatially selected from these side-lobes and delivered as the 940-nm and 1140-nm pulses.