Abstract

In recent years, the development of supercontinuum sources in the mid-infrared has attracted a lot of attention. The unique properties of mid-infrared supercontinuum sources show great potential for applications within spectroscopy. However, supercontinuum sources often suffer from amplitude and polarization fluctuations. These fluctuations are seeded stochastically, and an averaging scheme is often required to achieve an applicable signal-to-noise ratio. If noise cancelling is carried out by pulse-to-pulse normalization, care must be taken to avoid an entanglement of the amplitude and polarization noise. Here, we use a 30 kHz repetition rate supercontinuum source ranging from 2000 nm to 4200 nm. A polarization independent pulse-to-pulse normalization scheme is applied, enhancing the sensitivity by a factor of 18 for a full spectrum, recorded on a few-second basis [1]. This is achieved by splitting the pulses in a reference and signal arm. The splitting is ensured to be polarization independent across the spectrum by minimizing the incident angle on the beam splitter. The signal arm is sent through/into a sample, depending on whether the setup is in a diffuse reflectance or the transmission configuration. The spectral resolution is determined by introducing a monochromator before the splitting.

© 2015 IEEE