Fiber-Coupled Optical Delay Line ODL, 5 fs Resolution, up to 50 ns Range

Overview

An optical delay line is the component that makes time-domain spectroscopy possible. This is a fibre-coupled, high-speed unit with 5 fs resolution, delay range up to 50 ns, typical insertion loss of 0.8 dB for sub-nanosecond models, return loss above 55 dB and a working band of 1250 to 1650 nm, in a compact package that runs from -10 to +70 C.

Why the delay line is the heart of a TDS system

Terahertz time-domain spectroscopy does not measure the terahertz field directly in real time; it samples it. The probe pulse is scanned in arrival time relative to the terahertz pulse and the detected signal is recorded point by point, so the mechanical delay maps into a time axis through the relation dt = 2dx/c. Everything downstream depends on that axis: the resolution of the delay stage sets the highest frequency you can resolve, and the total travel sets the frequency resolution after the Fourier transform.

Fibre coupling versus a free-space stage

A conventional free-space delay stage needs a retroreflector, careful alignment, and a beam path whose length changes as the stage moves, which means the beam pointing and spot size at the detector both drift during a scan. A fibre-coupled delay line removes all of that: the light stays in fibre, alignment does not change with position, and the polarisation dependent loss below 0.1 dB means the polarisation state at the output is stable across the whole travel. For a fibre-based terahertz spectrometer it is the obvious architecture.

Specifying a unit

Pick delay range from the frequency resolution you need, since the Fourier transform resolution is set by the total scan window. Sub-nanosecond models are the fastest to deliver and cover most standard time-domain work; longer stages extend the resolution but take longer to build. Fibre type and connector are customisable, so state the source and antenna interfaces at the time of enquiry.