Abstract: A Golay sampling receiver is used for optical sampling of voltage and charge at the internal nodes of analog and digital integrated circuits. The sampling receiver uses very high sampling rates together with narrow banding to recover very small signals in the presence of noise. The sampling system is based on harmonic mixing, which is the interaction of a laser sampling train with the electro-optic modulator formed in the GaBs substrate of the device under test. The application of the Golay sampling receiver to an electro-optic sampling system allows the flexibility of running the signal under test at a subharmonic of the laser pulse repetition rate, as well as any harmonic of these subharmonics. The subharmonics are determined by the length code used in the Golay receiver. For a given signal to be sampled, the fundamental frequency is chosen to be a function of the fixed sample rate divided by the code length, and the baseband offset.