![]() λ max > 2λ min, optical signals in wavelengths from different diffraction orders may end up at the same spatial position on the detector plane, which will become evident once we take a look at the grating equation. When the required wavelength coverage is broad, i.e. As this example shows, you are able to increase your wavelength coverage at the sacrifice of optical resolution. Comparably, if you were to choose a Exemplar™ with a 600g/mm grating, it would instead give you up to 700nm of wavelength coverage with an optical resolution as low as 1.0nm. Inversely, decreasing the groove frequency decreases the dispersion and increases wavelength coverage at the cost of spectral resolution.įor example, if you were to choose a Exemplar™ spectrometer with a 900g/mm, it would give you a wavelength range of 370 nm, with an optical resolution as low as 0.5nm. However, the greater the dispersion, the greater the resolving power of the spectrometer. The wavelength coverage of a spectrometer is inversely proportional to the dispersion of the grating due to its fixed geometry. The groove frequency of the grating determines the spectrometer’s wavelength coverage and is also a major factor in the spectral resolution. This is commonly referred to as groove density, or groove frequency. The amount of dispersion is determined by the amount of grooves per mm ruled into the grating. Another advantage of holographic gratings is that they are easily formed on concave surfaces, allowing them to function as both the dispersive element and focusing optic at the same time. ![]() Thus, for spectroscopic applications (such as UV spectroscopy) where the detector response is poorer and the optics are suffering more loss, holographic gratings are generally selected to improve the stray light performance of the spectrometer. This is due to surface imperfections and other errors in the groove period. While ruled gratings are the simplest and least expensive gratings to manufacture, they exhibit much more stray light. ![]() This process results in a much more uniform spectral response, but a much lower overall efficiency. Holographic gratings, on the other hand, are created by interfering two UV beams to create a sinusoidal index of refraction variation in a piece of optical glass. ![]() Ruled gratings are created by etching a large number of parallel grooves onto the surface of a substrate, then coating it with a highly reflective material. There are two types of diffraction gratings: ruled gratings and holographic gratings. The grating can be described in two parts: the groove frequency and the blaze angle, which are further explained in the sections below. Gratings will influence your optical resolution and the maximum efficiency for a specific wavelength range. Choosing the correct grating is a key factor in optimizing your spectrometer for the best spectral results in your application. The diffraction grating of a spectrometer determines the wavelength range and partially determines the optical resolution that the spectrometer will achieve.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |