Bentham has been designing and manufacturing monochromators for over 40 years, developing a comprehensive portfolio built for precision and measurement confidence across the ultraviolet, visible, and infrared.
Several models are also made available as spectroradiometers featuring integrated detection electronics, to represent a complete measurement solution.
The monochromators in this section are customisable and can be outfitted for a large variety of applications by choice of diffraction gratings, mirror coatings (such as aluminium, protected silver, and gold), slit mechanism (motorised, manual micrometer adjustable, and interchangable fixed), order-sorting filters, dynamically movable entrance and exit port switching mirrors, as well as entrance and exit optics.
600mm focal length double monochromator with internal motorised slits and triple grating turret
The monochromators in this section have embedded measurement electronics, using which they can measure the output currents of photodetectors or even generate high voltages to drive photomultiplier tubes. Read by a computer over the same standard USB cable with which the monochromator is controlled, these devices can replace dedicated acquisition electronics and provide a compact but powerful measurement solution.
300mm focal length compact double monochromator, integrated picoammeter and HV supply
600mm focal length double monochromator with internal motorised slits and triple grating turrets, integrated picoammeters and HV supply
The guidance on this page only provides a brief overview. Detailed guidance is available in our monochromator selection guide.
A single monochromator is capable of dispersing light by means of a diffraction grating, and will emit a small bandwidth of wavelengths around the dynamically selectable central wavelength. This light can be shone into a second monochromator for further processing:
- Additive Mode Double: The second monochromator further disperses the light, increasing the wavelength resolution
- Subtractive Mode Double: The second monochromator counteracts the dispersion of the first, reducing dispersion and path length differences at the exit for applications where this is desirable.
Single monochromators are more compact systems, but double monochromators bring additional capability.
For more details see the selection guide.
A monochromator's size dictates its limiting resolution. The bandwidth of a monochromator is directly proportional to the widths of its slits, and inversely proportional to its grating line density and its focal length. To maximise the resolution (minimise the bandwidth), the slit width has to be minimised at the cost of signal strength, the grating line density has to be maximised at the cost of spectral range and efficiency, or the focal length has to be maximised at the cost of size.
Monochromators most typically are used either immediately after the light source or immediately prior to the detectors. A typical monochromator will function in either configuration but there are some differences in optimisation.
- Detection Monochromator: The light to be investigated is shone into the monochromator. One or more exit ports of the monochromator are connected to detectors. The monochromator selects a wavelength of light to pass onto the relevant detector. This approach is useful for systems where the sample under investigation is emitting its own light or is remote.
- Tunable Light Source: One or more light sources are attached directly to the monochromator, which selects between them and produces monochromatic light. This approach is useful for systems where the sample reacts differently to different wavelengths of light. These monochromators may be optimised to a particular light source, for example in our range of tuneable light sources.
- Grating: The choice of grating determines the dispersion and core spectral characteristics of the monochromator. Higher ruling densities result in increased dispersion.
- Coatings: Mirrors and gratings can be coated with different materials such as aluminium, silver, or gold for use in different spectral regions. As light is reflected from a minimum of three surfaces inside a monochromator, the throughput of the monochromator is proportional to at least the cube of the reflectance of the coating material.
- Slits: If your application requires dynamically adjustable bandwidth, many of our monochromators are available with motorised slits, micrometer-adjustable slits, or replaceable slits.
- Ports: many monochromators can be configured to dynamically select between different output ports. In this way multiple detectors can be used if one detector does not function over the entire required spectral range.
- Order sorting filters: To prevent light from higher diffractive orders from passing through the monochromator at the same time as that of the desired diffractive order, a different order sorting filter is required approximately every time the wavelength doubles. These are mounted on a filter selection wheel inside the monochromator.