NIREOS’ GEMINI interferometer replaces any monochromator or set of bandpass filters in your fluorescence applications!
Having no input/output slits nor grating/prism, it provides unmatched throughput and user-selectable spectral resolution down to better than 1nm. It offers superior signal-to-noise ratios and sensitivity down to single-photon levels for demanding applications such as single-molecule fluorescence, Time-resolved Emission Spectra (TRES) and Excitation/Emission Maps (EEM).
The GEMINI is designed to be added to your setup to extract the spectrum of any light source, coherent or not. It outperforms monochromators, since GEMINI overcomes their main drawbacks in terms of low throughput, fixed spectral resolution and limited spectral coverage.
We performed a direct comparison of the performances of a standard monochromator and NIREOS’ GEMINI system in terms of resolving the spectrum of the fluorescence emitted by a fluorescent sample. The emitted light was collected at 90° by a lens, sent to either a monochromator or NIREOS’ GEMINI interferometer and detected by the same photomultiplier (PMT).
As it can be seen in the following graph, NIREOS’ GEMINI interferometer can reach the same signal to noise (S/N) ratio provided by a monochromator employing ~100 times lower excitation light power, thus preserving the sample against damage. Conversely, for a given excitation power and integration time, NIREOS’ GEMINI interferometer can reach an order of magnitude higher S/N. This also translates in ~100 times faster acquisition time for a given desired S/N and excitation power.
1) Time-Resolved Emission Spectra (TRES)
NIREOS’ compact and ultra-stable GEMINI interferometer can be employed to map a sample’s fluorescence as a function of emission wavelength and decay time with both high temporal and spectral resolution (known under the name TRES).
The sample is illuminated with a pulsed laser in resonance with its optical absorption and the generated fluorescence photons are detected by a single-photon detector, such as a photomultiplier (PMT) or a single-photon avalance detector (SPAD). NIREOS’ GEMINI interferometer provides the spectral resolution, via a Fourier transform (FT) approach, while a time-correlated single photon counting (TCSPC) unit brings the temporal resolution to the table.
This system is remarkably simple, as it only requires the addition of the GEMINI to a standard single-pixel TCSPC system, and it shows a readily adjustable spectral resolution with inherently broad bandwidth coverage.
Excitation-emission matrix (EEM) spectroscopy is a powerful extension of fluorescence spectroscopy, which records emission spectra as a function of excitation frequency, building a two-dimensional map. EEM maps are typically measured in the frequency domain, by selecting a narrowband frequency slice of a broadband excitation light, recording the corresponding fluorescence spectra and finally stacking the data. This generally leads to long acquisition times, due to the need to scan the excitation and/or emission wavelength, and to a bulky setup including two monochromators.
NIREOS’ GEMINI interferometer provides EEM maps using a patented and innovative technology that allows you to excite the sample with many wavelengths simultaneously. This feature greatly enhances the light reaching the sample, improving sensitivity and decreasing integration times with respect to conventional technologies. Moreover, the spectral resolution can be set via software according to the sample to be measured, letting the customer balance the trade-off between measurement time and spectral resolution.
NIREOS’ GEMINI interferometer has been employed to measure EEM maps down to the single-molecule limit, in collaboration with Prof. Tom Vosch from University of Copenhagen.
E. Thyrhaug et al., Proc. Nat. Acad. Sci. USA 116, 4064-4069 (2019)
