Abstract: A mathematical extended bandwidth algorithm method (MEB) is used for acquiring real-time thickness profile measurements of a multi-layer sample of unknown layer thicknesses each above about 10 ?m. A statistical based thickness profile algorithm method (SBTP) is used for acquiring real-time thickness profile measurements of a multi-layer sample of unknown layer thicknesses each above about 1 ?m.

Abstract: Disclosed is a method for a phase-insensitive single-sampling point (SSP) data collection system. A rotated 90° infrared (IR) THz signal from a step-tunable IR laser is passed though the fast axis of a 90° polarizing rotator. The polarizing rotator and a second IR signal are coupled to free space through an electro-optic phase modulator (EO-PM), where the EO-PM only retards the phase of along the slow-axis. The polarization angle is rotated by 45° to form a beat frequency in each arm. The light is passed through a polarizer aligned with the slow axis of the PM fiber. Lastly, a resultant IR beat signal is fiber coupled back into the system and an erbium doped fiber amplifier (EDFA) in each arm amplifies the IR power prior to pump the THz emitter and detector.