Is it possible to reduce the spectral bandwidth to decrease the measurement time?

No, due to the employed Fourier-transform approach, there is no trade off between the working spectral range and the measurement time. Therefore, you cannot save time by reducing the spectral bandwidth of interest. In fact, the measurement time is affected by the spectral resolution that you want to achieve, i.e. the better the spectral resolution, the longer the scan of the interferometer and thus the measurement time.

Can the GEMINI select a specific spectral band?

No, the GEMINI does not act as a monochromator, so it is not possible to select a single wavelength at the output, given a broad spectrum in the input.

The GEMINI Interferometer always transmits the entire spectrum of the incoming light, introducing a spectral modulation with a period that depends on the delay of the interferometer. For more information on the working principle of the device, please refer to this video.

Does the GEMINI work with coherent (i.e. lasers) or incoherent (i.e. lamps, fluorescent samples) light sources?

The GEMINI Interferometer can work in both cases, with the very same software and optical alignment.

Can I perform experiments with ultra-short laser pulses using the GEMINI?

If the GEMINI is placed “after the sample” (i.e. when the light has already interacted with the sample), then it is possible to use it with ultra-short laser pulses, as it does not affect the temporal resolution of your experiment. As an example, you can refer to this application in pump-probe spectroscopy.
Instead, if you need to use the interferometer “before the sample”, then the GEMINI-2D is the most suitable device. As an example, the GEMINI-2D is used in bidimensional electronic spectroscopy (2DES), in which it creates two replicas of ultra-short pump pulses with a precise control on the dispersion.

How to choose the most suitable version of GEMINI for my application?

Spectral coverage
The standard model of GEMINI covers the range 250 nm – 2300 nm. There is the option of upgrading it to cover a much broader region (250 nm – 3500 nm).
On request, GEMINI can be customized to cover the 500 nm – 4200 nm range.
Moreover, currently NIREOS is developing a special version of GEMINI, which can work up to 15 microns. Stay tuned for updates on this version!

You can select one out of two versions of the driver that controls the relative delay between the two generated replicas of light (“standard” and “high performance – HP”). With respect to the standard controller, the HP version guarantees a higher speed of the scan (up to 5 time faster: it typically takes 15-20 millisecond per step in a step-scan mode) and a much higher accuracy and stability in the relative delay (on the order of 1 attosecond – that is more than 1000 times better than the optical cycle of visible light). This ultimately translates into a much better signal to noise ratio of the retrieved spectrum of your signal.
When GEMINI is coupled to SPAD, APD or PMT detectors and TCSPC systems to detect time-resolved and very weak signals, we always recommend to go for the HP version.

Spectral resolution
You can select one out of two versions (S, L) with different spectral resolutions:

Please note that this is the minimum achievable spectral resolutions for each version; if sometimes you do not need such a good spectral resolution, you can perform shorter – and thus faster – scans (these parameters can be easily selected via software) and get a worse spectral resolution.

How to couple the GEMINI with time-correlated single-photon counting (TCSPC) modules?

If you are interested in measuring time- and frequency- resolved fluorescence (TRES), we can provide a plug&play software that directly enables the control of both the GEMINI and the TCSPC card, so that you can easily acquire a TRES map without any extra effort for integration.

NIREOS is collaborating with the major TCSPC module providers and the software is compatible with most of the available TCSPC modules on the market.
Contact us to discuss how GEMINI could enrich your time-resolved applications, adding the spectral resolution to your experiments!

Is there a dedicated Software? How does it work?

The GEMINI comes together with a plug&play software, which allows one to easily control the device, acquire the data of interest and retrieve the calibrated spectrum of the light. The software is open access and described by a detailed manual, so that it can be freely modified by the user according to his needs. Moreover, NIREOS team is always available to help the user for customization, if needed.
The software is available in LabVIEW and Python.
For more information concerning the software for TSCPC applications, please refer to the Question “How to couple the GEMINI with time-correlated single-photon counting (TCSPC) modules?”

How does the Optical Alignment work?

The GEMINI Interferometer has a 10 mm clear aperture, and the light inside the device propagates in free space. The most efficient way to use the GEMINI is to enter with collimated light in free space. If one uses optical fibers, then it is possible to use fiber couplers before and/or after the GEMINI.
The optical alignment of the GEMINI is straightforward, as you just need to insert it into the beam path in your setup. There are 2 apertures (1 in the input and 1 in the output surface) with variable diameter, in order to facilitate the optical alignment in the center of the clear aperture; once aligned, the apertures should be completely opened to ensure the maximum throughput.

Which is the provided Spectral Resolution?

The spectral resolution provided by the GEMINI Interferometer is not constant as a function of wavelengths, but it increases at longer wavelengths. This behavior is due to both the Fourier Transformation approach and the birefringence, which depends on the wavelength.
Please refer to the following graph:

The graph above shows the best spectral resolution achievable by the two standard versions of the GEMINI Interferometer. However, the GEMINI offers the ability for customers to adjust the spectral resolution simply via software: the user can even decide to perform faster measurement with poorer spectral resolution. A change in the spectral resolution does not affect the throughput of the device.