The FTMC50-SCL is a high efficiency, ultra-broad spectral range, precisely tunable filter for supercontinuum lasers, with a wavelength-independent output bandwidth.

The device can couple directly to the output optic of a variety of high-powered supercontinuum lasers, protecting internal gratings with selectable filters and a dynamic beam expander. It outputs monochromatic light either into a multimode fibre, or through a free-space optic. The latter produces a high intensity collimated monochromatic output beam of constant or dynamically alterable width. A single unit can work from the UV (< 400 nm) to the infrared (>2400 nm) using up to 3 diffraction gratings and 6 filters.


The FTMC50-SCL excels wherever high intensity light of particular spectral parameters is required, including:

  • Photoluminescence spectroscopy
  • Fluorescence imaging
  • Detector responsivity / QE evaluation

With it's dynamically variable wavelength, a single FTMC50-SCL with a suitable driving supercontinuum laser can in many applications replace a large number of different wavelength lasers.


Configurable Powerhouse

The FTMC50-SCL brings the flexibility and precision of monochromators to laser light -- without burned gratings!

  • Precision 

    The wavelength selection mechanism is tried-and-tested. It utilises the same technology as is available in our top-line monochromators, offering incredibly precise and accurate positioning of the internal diffraction grating.

  • Configurability 

    The FTMC50-SCL has room for three diffraction gratings, and due to its dynamic beam expander, can be configured to work with a large variety of conventional gratings. Together with the choice of free-space or fibre output, this great flexibility allows us to configure the FTMC50-SCL to your requirements.

  • Remote Interface 

    If you want to automate your testing or integrate the light source into a bigger system, the FTMC50-SCL has a simple USB text-based remote interface compatible with any modern computer and operating system, without drivers. The protocol is based on the widely-used SCPI syntax. We also provide development tools and libraries including Windows SDK and terminal, and a cross-platform python package (bendev).



Light from the supercontinuum laser enters the FTMC50-SCL through a socket into which the output ferrule of the laser is slotted. A dynamic beam expander increases the beam diameter to a minimum level that prevents damage to the diffraction gratings, or, if required by the user, up to 12mm. This beam is filtered by one of 6 filters on a rotary filter wheel, then diffracted by one of three gratings mounted to monochromator turret, and the chosen diffractive order is captured and focused onto the output slit using a mirror. The output slit sets the bandwidth. The light diverges again beyond the mirror and then is reflected off a final collimating mirror, coupling the light to free space. 

Alternatively, the output slit / collimating optic can be replaced using a precisely positioned fibre mount. The combination of grating ruling density and the aperature diameter of the fibre then determines the bandwidth. 

Beam Expander

The device features an internal dynamic beam expander that compensates for the wavelength dependent beam width of the SCL laser beam. This protects the gratings from laser induced damage, and produces an output beam with a  user-controllable, wavelength-independent output beam diameter. It can also be used to correct for a wavelength-dependent input beam diameter.

The video on the left shows this device by itself.

Software Control

The FTMC50-SCL is a smart device that contains all of its calibration data, as well as the algorithms and calculations required to reconfigure itself for a certain wavelength, so minimal work is required externally. To further simplify the control scheme:

  • The USB device class is HID, which does not require drivers in any modern operating system, as it is the same class of device used by keyboards and mice.
  • The command protocol consists of SCPI-style text-based commands that are very readable. For instance, you can turn your FTMC50-SCL to 555nm using the command "GOTO 555".
  • No Bentham software is required on the host computer, but we do provide some software to simplify things. For instance, we publish a crossplatform Python package bendev, which is open source, available with the permissive MIT license, and can be installed with "pip install bendev". A windows SDK with a simple control library and a terminal is also available.

Typical output characteristics



beam diameter (1)

5mm – 12mm


2× – 9×

divergence (v)

< 1 mrad

divergence (h)

< 3 mrad

output bandwidth

see Configuration page

spectral bandwidth

see Configuration page

spectral efficiency


wavelength speed

0.5 s for a 5 nm step

mechanical resolution (2)

Δλ < 0.02nm

wavelength accuracy (3)

1.2 nm (D=300)

wavelength accuracy (3)

0.6 nm (D=600)

wavelength accuracy (3)

0.3 nm (D=1200)


  1. Depending on the choice of laser, a minimum width may apply to prevent damage to the gratings.
  2. Wavelength change corresponding to a minimal adjustment of the grating motor. Highly grating dependent, upper bound for standard gratings given.
  3. Filtering wavelength accuracy. Features of source laser can distort the spectral shape of the output.

Configuration Options

Main monochromator configuration

grating ruling density

Slit Width

Minimum Wavelength

Maximum Wavelength

Bandwidth, FWHM


50 µm

300 nm

3000 nm

3.2 nm ± 0.1 nm


75 µm

300 nm

3000 nm

4.8 nm ± 0.1 nm


100 µm

300 nm

3000 nm

6.4 nm ± 0.2 nm


150 µm

300 nm

3000 nm

9.8 nm ± 0.1 nm


50 µm

300 nm

2200 nm

1.5 nm ± 0.1 nm


75 µm

300 nm

2200 nm

2.3 nm ± 0.2 nm


50 µm

300 nm

1500 nm

1.0 nm ± 0.1 nm


50 µm

300 nm

1100 nm

0.8 nm ± 0.1 nm

Output Optic




FTMC50-SCL with free-space coupled optic


FTMC50-SCL with fibre-coupled optic. Please let us know the type of fibre and connector type you require.

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