Thorlabs' High-Speed Optical Modulators use deformable mirror technology instead of Pockels cells or acousto-optic modulators to provide high-speed intensity modulation and beam attenuation (see graph at right). The all-reflective design incorporates gold-coated MEMS mirrors that are polarization independent and introduce minimal (<100 fs2) dispersion. This unidirectional device accepts a collimated, 1 to 2 mm (1/e2) diameter input beam with <5 W optical power and is available with either standard (>250:1) or high (>2500:1) contrast ratios.
Transmission, which is a function of both input voltage and wavelength as shown in the graph to the right, is controlled by a 0 to 1 V analog input voltage; this voltage can be easily generated by off-the-shelf data acquisition (DAQ) hardware or other electronics. The device supports continuous DC operation as well as modulation frequencies up to 20 kHz, making it ideal for imaging applications such as fly-back blanking or region of interest (ROI) selection.
The higher contrast achieved with the OM6NH(/M) modulator is made possible by incoporating two MEMS mirrors, the deformation of which behaves like a grating, into the design; one diffracts horizontally and the other vertically to provide enhanced contrast performance.
An internal beam sampler directs a small portion (<1%) of the modulated beam to a separate output port where a photodetector can be used to monitor the transmission. If desired, the included, pre-installed Thorlabs PDA100A2 Si Switchable Gain Detector can be easily removed and replaced with a user-supplied detector; to do so, loosen the 8-32 mounting screw located on the underside of the modulator.
Housing and Mounting Features
The input and output ports of the optical modulator feature internal SM05 (0.535"-40) threading, which can be used to install external SM05-threaded alignment targets or irises (not included). All three ports also have 4-40 threaded holes for compatibility with our 30 mm cage systems. To aid in initial alignment, we recommend using an SM05 slotted lens tube or a 30 mm cage system assembly on the modulator input.
Three slots in the enclosure allow the modulator to be mounted directly to an optical table with table clamps, such as our CL6 clamps (not included), resulting in a minimum beam height of 1.25". The base also includes three 8-32 (M4) mounting holes for attaching pedestal posts, which can be used to elevate the modulator to the desired beam height.
The unit is shipped with a 24 V power supply with an KPJX-4S-S connector for the modulator, as well as a ±12 V supply for the photodetector. For more information, please see the Pin Diagrams tab.
- Offers DC Power Attenuation and High-Speed Modulation
- 700 nm to 1100 nm Operating Range
- <2 µs Response Time
- Polarization Independent
- External Photodetector for Monitoring/Calibrating Output Power
(PDA100A2 Si Detector Included)
- Near-Zero (<100 fs2) Dispersion
- Passively Cooled to Eliminate Vibrations