TICO Raman

Time-Encoded (TICO) Raman spectroscopy and microscopy

The TICO-Raman approach uses a wavelength swept Probe laser to record spectral points sequentially in time. With a spectral resolution limited only by the narrowband laser line width and a  broadband coverage, this system has great spectroscopic capabilities but the flexibility also allows for fast imaging applications.


Details of the TICO-Raman concept

The Time-Encoded (TICO)-Raman approach uses rapidly wavelength swept FDML lasers in combination with a narrowband, actively modulated pump laser to encode and detect the Raman spectra directly in time. The FDML probe laser changes its wavelength continuously and repetitively in time. This is indicated in Figure 2A as a rainbow colored line. The blue line shows the single color narrowband pump laser. It is evident that the energy difference between these two light sources changes over time. Therefore, with different timing, different Raman transitions get probed (Figure 2B). When the energy difference matches a Raman transition, pump photons will be converted to probe photons and the FDML laser intensity gets increased at that position. This intensity change can be measured with a fast photodetector (Figure 2C).

To achieve high signal levels, the pump laser is not power on all the time, but modulated to short pulses (Figure 2D). To probe all possible Raman transistions, these pulses get delayed more and more compared to the start of a FDML laser sweep for each new sweep. With the known time-to-wavelenght encoding, the intensity changes can be directly mapped onto a Raman spectrum.


related Publications

Publications about TICO Raman can be found in the publication list.