What is a spectrometer?
A fiber-optic spectrometer is an instrument used to measure properties of light (often using a light source, a fiber-optic cable and software) over a specific part of the electromagnetic spectrum. In the case of fiber-optic spectroscopy, the focus lies on ultraviolet radiation, the visible spectrum, and near-infrared radiation, as is pictured in Figure 1. The spectrum is often displayed in wavelengths which, in the area of interest for a spectrometer, are measured in nanometers (nm) or micrometers (µm), as is shown in Figure 2. Avantes spectrometers operate in the range of 200-2500 nm.
The technique spectrometers utilize to break up light into separately measurable wavelengths is often compared to dispersive prisms. A prism is a transparent, triangular object that refracts white light into the different wavelengths of the visible spectrum (colors of the rainbow), as shown in Figure 3.
A spectrometer utilizes this same basic technique of refracting light to then measure its properties with a so-called grating. A grating is a refractive element in which every line is essentially a miniature prism, as shown in detail in Figure 4. Though similar, prisms and gratings are not exactly the same. A regular prism uses the principle of transmission, since the light passes through it, while the gratings we use in our spectrometers are reflective gratings. With reflection gratings, the light is refracted by the grating and then reflected by the coating at an angle equal to the diffraction angle.
How does a spectrometer work?
Our spectrometers generally consist of an entrance slit, which is where the light enters the spectrometer via a fiber-optic cable, a collimating mirror that causes the light to concentrate into a parallel beam, a grating (refractive element), focusing optics that deflect the refracted light to reach the electronics and a detector that converts the measured light into comprehensible data in our software. Every one of our spectrometers is optimized with light traps and filters to make sure the detector captures the minimal amount of stray light to make your measurement as accurate as possible.
A variety of spectrometer models are available, each offering unique advantages to optimize your measurement, such as compact sizing, ultra-sensitivity, cooling for higher performance, speed or the ability to measure in ranges besides the standard UV and visible range. Visit our product page to see the different lines of spectrometers we offer and their benefits.
For more detailed information on spectrometers and tips on how to select the right spectrometer for your application, please visit our background theory page.
What does a spectrometer do?
A spectrometer is used in a variety of applications using various techniques, such as absorbance spectroscopy to measure the absorption of wavelengths by materials diluted in e.g. fluids and powders and reflectance spectroscopy to measure the intensity of reflected light off an object or surface. Other popular spectroscopy techniques are LIBS (laser-induced breakdown spectroscopy) and Raman.
These are some techniques for spectroscopy, but the applications for these techniques are virtually endless. Spectrometers are used in agriculture to determine crop health, sort fruits based on their ripeness or color and to optimize fertilizer components. The biomedical sector uses spectroscopy to measure certain levels in blood and to non-invasively research samples. Spectroscopy is used in the semiconductor industry for applications such as end-point detection for plasma ion etching, ion beam etching, photoresist stripping, and chemical/mechanical polishing.
Of course, these are only examples, find out what else spectroscopy can be utilized for here!