Gemini Interferometer – Broadband Spectroscopy

Broadband spectroscopy with high throughput

GEMINI is the ultimate interferometer providing unrivaled accuracy and reproducibility in controlling the temporal delay between the two replicas of the input light. It can be employed in combination with our included drivers and software to measure the spectrum of the input light (either coherent or incoherent source) based on the Fourier-transform approach, as in any FTIR spectrometer.

  • Rugged, robust, and insensitive to vibrations, thanks to our patented common-path geometry.
  • Factory assembled and aligned for easy and turn-key integration in any existing setup, requiring no particular optical alignment procedure.
  • Compact (176 x 44 x 54.5 mm) and lightweight (approx.400 gm)
  • Broad spectral coverage from 400nm to 2300nm, with optional ultra-broadband coverage from 250 to 3500 nm.
  • It provides continuous spectra, with a virtually unlimited number of spectral bands.
  • High throughput: featuring a 1-cm clear aperture without any grating nor input/output aperture slits.
  • Scan range and spectral resolution selectable by the user, who can start with quick measurements to have an initial look at the spectra, and then prolong the data acquisition to increase both the signal-to-noise ratio and the spectral resolution, down to <1 nm in the visible, see below.
  • Drivers included, with intuitive examples and a complete user manual.
  • Worldwide quick support.

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NIREOS’ GEMINI interferometer replaces any monochromator or set of bandpass filters in your fluorescence and broadband spectroscopy 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 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.

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