An amorphous photoconductive GaAs switch is laser ablated directly onto a superconducting YBa2Cu3Ox coplanar transmission line structure. Illuminating the switch with femtosecond laser pulses generates electrical pulses containing frequency components up to 2 THz. The pulses are detected by photoconductive sampling and have a full width at half maximum of 0.4 ps without deconvolution. Measurements have been performed on both YBa2Cu3Ox and Au/YBa2Cu3Ox transmission lines and we find attenuation and dispersion coefficients to be larger on YBa2Cu3Ox at 77 K than on Au. Furthermore, the integrated photoconductive switch is used to demonstrate that subpicosecond pulses can propagate through small gaps in the transmission lines with minimum attenuation and dispersion. © 1999 American Institute of Physics.