Choose from Uncoated Versions for Beam Sampling or Coated Versions for Beamsplitting
Ø1/2", Ø1", and Ø2" Versions Available
Surface Quality: 40-20 (Scratch-Dig)
Thorlabs' Ø1/2", Ø1", and Ø2" Pellicle Beamsplitters, which are available with models covering wavelengths from 300 nm - 5 µm, are ideal for use in applications where chromatic dispersion must be minimized (i.e., cases where focused beams are necessary). Pellicle beamsplitters virtually eliminate ghosting since the second surface reflection is superimposed on the first one. However, they are extremely fragile due to the nitrocellulose membrane being only a few microns thick. For each size, Thorlabs offers both coated and uncoated versions. When using a coated optic, light should be incident upon the coated surface first (Note: the coated side of these beamsplitters is the side without the engraving). When using an uncoated optic, light can be incident on either surface.
The curves pictured below show each of the different coating types as well as the uncoated beamsplitting ratios over a variety of wavelengths. Data was obtained for unpolarized, S-polarized, and P-polarized light incident at 45°. In general, P-polarized light will be transmitted more than S-polarized light, and sinusoidal oscillation is present, resulting from thin film interference effects. See the Tutorial tab for more information about interference effects.
Mounting Options Each pellicle is mounted in a black anodized frame that has two 2-56 tapped mounting holes on the engraved side for mounting them in either our Fixed or Kinematic Pellicle Mounts. Both the fixed and kinematic pellicle mounts are available in versions that accommodate our Ø1/2", Ø1", or Ø2" pellicles. We also offer cage-cube-mounted pellicle beamsplitters, which are pre-mounted in cage cubes, offer protection to the delicate pellicle surface, and are compatible with our 30 mm cage systems. For a direct comparison of the performance of our non-polarizing beamsplitting cube, plate, and pellicle at 633 nm, see the Lab Facts tab.
Please note that the size of the pellicle beamsplitter (e.g., Ø1") refers to the inner diameter of the aluminum frame, not the outer diameter. Hence, these beamsplitters are not compatible with our standard Ø1/2", Ø1", and Ø2" optic mounts. Refer to the Specs tab for a complete table of dimensions.
Handling Precautions Our pellicle beamsplitters are manufactured from an extremely thin and fragile membrane. Please do not touch the membrane under any circumstances. Compressed or canned air can be used to clean these beamsplitters, but please exercise caution as the force of the air may be large enough to damage the membrane. Aim the stream of air such that it makes a small angle with the surface, and hold the can sufficiently far away to avoid damaging the membrane.
We present laboratory measurements of the polarization angle, split ratio, and total throughput power of a beam transmitted through Thorlabs plate, cube, and pellicle beamsplitters. While all non-polarizing beamsplitters function similarly, the exact performance is different for different types of beamsplitter. Each type of beamsplitter contains its own advantages and disadvantages compared to other types of beamsplitters. Appropriate choice of beamsplitter is essential to sensitive experimental systems. We present a complete analysis and comparison of optical parameters for three common types of non-polarizing beamsplitters.
For our experiment we used the former generation HRS015 stabilized HeNe laser (replaced by the HRS015B) as the light source for our investigation. A linear polarizer is used to set the laser beam's polarization axis to 45° in order to provide equal S- and P-polarized light incident on the beamsplitter. The beamsplitter under investigation was then placed in the beampath, and its split beams directed to appropriate detectors. The total power though the optic, polarization states, split ratios, and angle of incidence effects were investigated under this configuration.
The plots below summarize the measured results for all three types of beamsplitters. From these graphs the performance of each optic can be easily compared to one another. The bottom left plot summarizes the results for the total power throughput for each optic. The total power throughput is measured as the fraction of input power. While the plate and pellicle beamsplitters perform rather similarly, the cube shows signs of absorption inside the optic. Additionally, this plot shows the relative insensitivity of throughput power to angle of incidence. The bottom middle graph summarizes the results for the output polarization angle for each optic. The cube shows the most similar polarization angles between the reflected and transmitted beams, with the plate producing the largest difference in polarization between beams. The bottom right plot summarizes the results for the split ratio, as a fraction of input power, for the beamsplitters. Here it can be shown that the plate beamsplitter demonstrates the most ideal for 50/50 power splitting. For details on the experimental setup employed and the results summarized here, please click here.
The plots below, which show transmission as a function of wavelength, depict a sinusoidal fluctuation that is caused by interference effects. These effects will occur for all pellicle beamsplitters and are sometimes averaged out when data is displayed.
The graph to the right depicts the measured reflectance of an 8:92 beam sampler without averaging the sinusoidal oscillations that result from thin film interference. The frequency and amplitude of the pattern depends several factors, such as the thickness of the film, the thickness of any coating present, the angle of incidence of the incoming light, the polarization of the incoming light, and the bandwidth of the light incident on the pellicle.
What is a Thin Film? A layer of material is referred to as a thin film if the thickness of the layer is on the order of the wavelength of incident radiation in the film medium. The relationship between the wavelength of light in air and that in the film is given by
For the pellicle beamsplitters featured here, the information under the Specs tab states that nfilm = 1.5 at 550 nm. Therefore, for this incident wavelength, the wavelength in the pellicle membrane itself is
Thorlabs' portfolio contains many different kinds of beamsplitters, which can split beams by intensity or by polarization. We offer plate and cube beamsplitters, though other form factors exist, including pellicle and birefringent crystal. Many of our beamsplitters come in premounted or unmounted variants. Below is a complete listing of our beamsplitter offerings. To explore the available types, wavelength ranges, splitting/extinction ratios, transmission, and available sizes for each beamsplitter category, clickMore [+] in the appropriate row below.
Thorlabs offers both fixed and kinematic mounting options for our Ø1/2", Ø1", and Ø2" pellicle beamsplitters. Two 2-56 capscrews included with the mount are used to attach the pellicle. Pellicle mounts are post-mountable via 8-32 or M4 x 0.7 tapped mounting holes (KM05BP and KM05BP/M), or #8 (M4) counterbores (all other pellicle mounts).