Let us now consider a spectrum containing sharp peaks, thus requiring higher resolution. With a monochromator you should close the output slit or use a diffraction grating with higher dispersion. This would in turn reduce the amount of light on the detector.

Monochromatorin UV Spectroscopy

Monochromatordiagram

In this way, only one color is transmitted through the output slit at a given time. Spectra are then recorded wavelength by wavelength, rotating the grating.

Optics is the branch of physics that studies the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light.

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Monochromatorin spectrophotometer

The light intensity at the detector as a function of the delay is called interferogram. It is sufficient to compute a Fourier transform of the interferogram to retrieve the spectrum of the light. In this animation, the GEMINI is first set to zero and then it slowly increases the delay between the two replicas, thus building the interferogram step by step. The measurement is performed until there are no appreciable residual oscillations in the interferogram. In this example, this corresponds to a maximum delay of 300 femtoseconds. At this point, the retrieved spectrum perfectly matches the input spectrum.

Gratingmonochromator

Furthermore, gratings have limited efficiency and narrow spectral bandwidth, so that you often need to use two different gratings and then stitch together two separate measurements to record the spectrum of polychromatic light.

Prismmonochromator

A monochromator is an optical instrument which measures the light spectrum. Light is focused in the input slit and diffracted by a grating.

Monochromatorexample

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The presence of the two slits and the sequential recording of the light reduce the throughput and increase the measurement time considerably.

Types ofmonochromatorin spectrophotometer

Optics definition:Optics is the branch of physics that studies the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light.It studies facts like how light reflects off of objects, or the energy of other forms of electromagnetic waves. The study of optics has huge applications to the technology on earth and is extremely helpful in many ways.

On the other hand, with GEMINI it is sufficient to increase the maximum delay of the scan, in this case up to one picosecond, to increase the spectral resolution, without any loss of throughput.

It studies facts like how light reflects off of objects, or the energy of other forms of electromagnetic waves. The study of optics has huge applications to the technology on earth and is extremely helpful in many ways.

This is the GEMINI’s working principle.  The spectrum of the light at the input of the device is measured using a different approach, based on Fourier-Transform spectroscopy. In fact, GEMINI is an interferometer that creates two replicas of the light with a finely tunable delay.  In this way, the light throughput is much higher than a monochromator because the output spectrum is not filtered and there are no input or output slits. Furthermore, GEMINI has no gratings, thus providing extremely broad spectral coverage, from the ultraviolet to the mid-infrared spectral region.

When high spectral resolution is needed, to resolve sharp features such as this narrow peak, using a monochromator one has to either use a grating with higher dispersion or to close the output slit.