Polarization Difference Probing: A New Phase Detection Scheme for Laser Voltage Probing

A novel laser based technique for waveform probing of integrated circuits is presented. This new technique exploits polarization-dependent opto-electronic effects in silicon integrated circuits to give phase sensitivity via a simple common-path interferometer design. The system utilizes a 10 ps pulse-width mode-locked laser to generate equivalent-time sampling pulses. A custom wavelength-tunable and spectrally matched external-cavity laser diode source is used for noise cancellation. A 20-GHz intrinsic system bandwidth with a 2x lower noise-floor, in comparison to current laser voltage probing technology, is shown.