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25 mm x 36 mm Plate Beamsplitters


  • Ideal for Reflected Light Microscopy
  • Designed for Microscopy Filter Cubes
  • Multiple Wavelength Ranges and Beamsplitting Ratios Available

BSW10R

50:50 for 400 - 700 nm

BSW23R

50:50 for 0.9 - 2.6 μm

BSX12R

10:90 for 1.2 - 1.6 μm

BSW11R Mounted in a
CM1-DCH Cage Cube

Related Items


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Diagram of Beam Reflection and Transmission
Click to Enlarge

Diagram of reflected light microscopy. Cross-polarized linear polarizers are typically used in addition to prevent discarded light from reaching the image plane.
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Wavelength Splitting Ratio
250 - 450 nm 50:50
350 - 1100 nm 50:50
400 - 700 nm 10:90 30:70 50:50 70:30 90:10
600 - 1700 nm 50:50
700 - 1100 nm 10:90 30:70 50:50 70:30 90:10
0.9 - 2.6 μm 50:50
1.2 - 1.6 μm 10:90 30:70 50:50 70:30 90:10

Closeup of Engraving
Click to Enlarge

Each item number is engraved on the beamsplitting surface.

Features

  • 25 mm x 36 mm Rectangular Plate Beamsplitters Designed for our Microscopy Filter Cubes
  • Available for Multiple Wavelength Ranges Between 250 nm and 2600 nm
  • Certain Wavelength Ranges Offer Multiple Split Ratios (R:T) for AOI = 45°
  • 1 mm Thick UV Fused Silica or IR Fused Silica Substrate

When performing reflected light microscopy, a beamsplitter directs light from an illumination source to a sample while simultaneously transmitting the light reflected by the sample onto the image plane. Thorlabs offers Non-Polarizing Plate Beamsplitters at varying wavelengths and beam splitting ratios for ultravoilet (UV), visible, and near infrared (NIR) applications.

These rectangular beamsplitters, measuring 25 mm x 36 mm x 1 mm, have a dielectric beamsplitter coating deposited on the front surface. The beamsplitter dimensions match our dichroic mirrors commonly used in microscopy, making them compatible with our microscopy filter cubes and other rectangular filter holders. Thorlabs also offers a complete selection of non-polarizing plate beamsplitters in round diameters and for additional wavelength ranges.

Each beamsplitter is fabricated using a UV fused silica or an IR fused silica substrate, both of which offer superior homogeneity and a lower coefficient of thermal expansion than N-BK7 glass. In addition, UV fused silica exhibits high transmission deep into the UV with virtually no laser-induced fluorescence, making it an ideal choice for applications from the UV to the near IR.

To reduce the effect of ghost images, an antireflection (AR) coating, which is designed for the same operating wavelength range as the beamsplitter coating on the front surface, has been deposited onto the back surface of each beamsplitter. By applying an AR coating to the back side of the beamsplitter, the percentage of light reflected back through the front surface is reduced to an average of less than 1% over the entire operating range of the coating. To differentiate between the front and back surfaces, the beamsplitter surface is indicated with the Item # engraving, as shown in the image above.

Mounting Option
For customers who wish to use these beamsplitters in microscopy applications, Thorlabs manufactures a family of filter cubes and mounts.


Thorlabs offers a complete line of round non-polarizing plate beamsplitters at additional wavelength ranges. Click here for details.
Click to Enlarge
Schematic of light passing through a beamsplitter. Blue arrows indicate light emitted from the light source and red arrows indicate light reflected from the sample.
Beamsplitter Effect on Light Through a Microscope
Nominal Split Ratio (Reflected:Transmitted) 10:90 30:70 50:50 70:30 90:10
Light Reflected onto Sample Planea 10% 30% 50% 70% 90%
Light Transmitted onto Image Planea 9% 21% 25% 21% 9%
  • Calculations assume perfect reflections across all wavelengths and do not include losses such as transmission loss, reflectivity of the sample, or loss from polarizing elements. Please check transmission and reflectance data for individual beamsplitters at the desired wavelength.

Beamsplitting Inside a Microscope

A beamsplitter splits an incident beam into two: a reflected beam and a transmitted beam. The split ratio states what portion of the beam gets reflected versus transmitted (reflected:transmitted). In a microscope, the beamsplitter is used in two fashions: to reflect incident light from the light source to the sample plane, and to transmit light from the sample to the imaging plane. To perform this task, the beamsplitter is installed at a 45° angle to both beams (see image to the right). In addition to the beamsplitter, two linear polarizers at orthogonal polarizations are typically used to reduce noise from discarded light (see diagram in Overview tab). Depending upon your imaging requirements, a different beamsplitting ratio than 50:50 may be desirable.

To provide a firmer grasp of beamsplitter functionality inside a microscope, in the table above we give a back of the envelope calculation of the percentage of input light that is directed toward the sample plane and light that is directed towards the imaging plane for different split ratios. This nominal split ratio calculation should only be used as a guideline when choosing between beamsplitters, as it assumes perfect reflections and does not include losses such as transmission loss, reflectivity of the sample, or loss from polarizing elements. Split ratios also vary with incident wavelength, so please check the reflectance and transmission data at the desired wavelength.


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250 - 450 nm Plate Beamsplitter

Item # BSW20R
Nominal Split Ratio (Reflected:Transmitted) 50:50
Coating on Surface 1a 250 - 450 nm
Beamsplitting Coating for 45° AOI
Coating on Surface 2 250 - 450 nm
Antireflection Coating (Ravg < 1%)
Size (L x H) 36.0 mm x 25.0 mm
Thickness 1.0 mm
Dimensional Tolerance ±0.1 mm
Substrate UV Fused Silica
Clear Aperture >22.5 mm x 32.4 mm
Surface Quality 40-20 Scratch-Dig
Transmitted Wavefront Error λ/4 @ 633 nm Over the Clear Aperture
Overall Performance Unpolarized Light Tabs = 50 ± 12%, Rabs = 50 ± 12%, Tabs + Rabs > 99%
Polarization Relationship |Ts-Tp| < 40%, and |Rs-Rp| < 40%
Transmission Plot
50:50 Beamsplitter Reflection
Reflectance Plot
50:50 Beamsplitter Transmission
Raw Transmission and Reflectance Data Raw Data
a. Surface 1 is denoted by an engraving of the item number on the coated surface.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
BSW20R Support Documentation
BSW20RCustomer Inspired!25 x 36 mm 50:50 UVFS Plate Beamsplitter, Coating: 250 - 450 nm, t = 1 mm
$116.00
Today

350 - 1100 nm Plate Beamsplitter

Item # BSW26R
Nominal Split Ratio (Reflected:Transmitted)
50:50
Coating on Surface 1a 350 - 1100 nm
Beamsplitting Coating for 45° AOI
Coating on Surface 2 350 - 1100 nm
Antireflection Coating (Ravg < 2%)
Size (L x H) 36.0 mm x 25.0 mm
Thickness 1.0 mm
Dimensional Tolerance ±0.1 mm
Substrate UV Fused Silica
Clear Aperture >22.5 mm x 32.4 mm
Surface Quality 20-10 Scratch-Dig
Transmitted Wavefront Error λ/2 @ 633 nm Over the Clear Aperture
Overall Performance
Unpolarized Light Tabs = 50 ± 12%, Rabs = 50 ± 12%, Tabs + Rabs > 99%
Polarization Relationship |Ts-Tp| < 40%, and |Rs-Rp| < 40%
Transmission Plot
50:50 Beamsplitter Transmission
Reflectance Plot
50:50 Beamsplitter Reflection
Raw Transmission and Reflectance Data
Raw Data
a. Surface 1 is denoted by an engraving of the item number on the coated surface.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
BSW26R Support Documentation
BSW26R25 mm x 36 mm 50:50 UVFS Plate Beamsplitter, Coating: 350 - 1100 nm, t = 1 mm
$289.00
Today

400 - 700 nm Plate Beamsplitters

Item # BSN10R BSS10R BSW10R BST10R BSX10R
Nominal Split Ratio (Reflected:Transmitted) 10:90 30:70 50:50 70:30 90:10
Coating on Surface 1a 400 - 700 nm Beamsplitting Coating for 45° AOI
Coating on Surface 2
400 - 700 nm Antireflection Coating (Ravg < 1%)
Size (L x H) 36.0 mm x 25.0 mm
Thickness 1.0 mm
Thickness Tolerance ±0.1 mm
Substrate Uv Fused Silica
Clear Aperture >22.5 mm x 32.4 mm
Surface Quality 20-10 Scratch-Dig
Transmitted Wavefront Error λ/4 @ 633 nm
Overall Performance
Unpolarized
Light
Tabs = 90 ± 8%
Rabs = 10 ± 8%
Tabs+Rabs > 99%
Tabs = 70 ± 8%
Rabs = 30 ± 8%
Tabs+Rabs > 99%
Tabs = 50 ± 8%
Rabs = 50 ± 8%
Tabs+Rabs > 99%
Tabs = 30 ± 8%
Rabs = 70 ± 8%
Tabs+Rabs > 99%
Tabs = 10 ± 8%
Rabs = 90 ± 8%
Tabs+Rabs > 99%
Polarization
Relationship
|Ts - Tp| < 35% and |Rs - Rp| < 35%
Transmission Plot
10:90 Beamsplitter Transmission
30:70 Beamsplitter Transmission
50:50 Beamsplitter Transmission
70:30 Beamsplitter Transmission
90:10 Beamsplitter Transmission
Reflectance Plot
10:90 Beamsplitter Reflection
30:70 Beamsplitter Reflection
50:50 Beamsplitter Reflection
70:30 Beamsplitter Reflection
90:10 Beamsplitter Reflection
Raw Transmission and Reflectance Data Raw Data Raw Data Raw Data Raw Data Raw Data
a. Surface 1 is denoted by an engraving of the item number.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
BSN10R Support Documentation
BSN10R25 x 36 mm 10:90 (R:T) UVFS Plate Beamsplitter, Coating: 400 - 700 nm, t = 1 mm
$124.00
Today
BSS10R Support Documentation
BSS10R25 x 36 mm 30:70 (R:T) UVFS Plate Beamsplitter, Coating: 400 - 700 nm, t = 1 mm
$113.00
Today
BSW10R Support Documentation
BSW10RCustomer Inspired!25 x 36 mm 50:50 UVFS Plate Beamsplitter, Coating: 400 - 700 nm, t = 1 mm
$113.00
Today
BST10R Support Documentation
BST10R25 x 36 mm 70:30 (R:T) UVFS Plate Beamsplitter, Coating: 400 - 700 nm, t = 1 mm
$113.00
Today
BSX10R Support Documentation
BSX10R25 x 36 mm 90:10 (R:T) UVFS Plate Beamsplitter, Coating: 400 - 700 nm, t = 1 mm
$124.00
Today

600 - 1700 nm Plate Beamsplitter

Item # BSW29R
Nominal Split Ratio (Reflected:Transmitted) 50:50
Coating on Surface 1a 600 - 1700 nm
Beamsplitting Coating for 45° AOI
Coating on Surface 2 600 - 1700 nm
Antireflection Coating (Ravg < 1.5%)
Size (L x H) 36.0 mm x 25.0 mm
Thickness 1.0 mm
Dimensional Tolerance ±0.1 mm
Substrate UV Fused Silica
Clear Aperture >22.5 mm x 32.4 mm
Surface Quality 20-10 Scratch-Dig
Transmitted Wavefront Error λ/2 @ 633 nm Over the Clear Aperture
Overall Performance Unpolarized Light Tabs = 50 ± 10%, Rabs = 50 ± 10%, Tabs + Rabs > 99%
Polarization Relationship |Ts-Tp| < 40%, and |Rs-Rp| < 40%
Transmission Plot
50:50 Beamsplitter Transmission
Reflectance Plot
50:50 Beamsplitter Reflection
Raw Transmission and Reflectance Data Raw Data
a. Surface 1 is denoted by an engraving of the item number.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
BSW29R Support Documentation
BSW29R25 mm x 36 mm 50:50 UVFS Plate Beamsplitter, Coating: 600 - 1700 nm, t = 1 mm
$113.00
Today

700 - 1100 nm Plate Beamsplitters

Item # BSN11R BSS11R BSW11R BST11R BSX11R
Nominal Split Ratio (Reflected:Transmitted) 10:90 30:70 50:50 70:30 90:10
Coating on Surface 1a 700 - 1100 nm Beamsplitting Coating for 45° AOI
Coating on Surface 2 700 - 1100 nm Antireflection Coating (Ravg < 1%)
Size (L x H) 36.0 mm x 25.0 mm
Thickness 1.0 mm
Thickness Tolerance ±0.1 mm
Substrate UV Fused Silica
Clear Aperture >22.5 mm x 32.4 mm
Surface Quality 20-10 Scratch-Dig
Transmitted Wavefront Error λ/4 @ 633 nm
Overall Performance
Unpolarized
Light
Tabs = 90 ± 8%
Rabs = 10 ± 8%
Tabs+Rabs > 99%
Tabs = 70 ± 8%
Rabs = 30 ± 8%
Tabs+Rabs > 99%
Tabs = 50 ± 8%
Rabs = 50 ± 8%
Tabs+Rabs > 99%
Tabs = 30 ± 8%
Rabs = 70 ± 8%
Tabs+Rabs > 99%
Tabs = 10 ± 8%
Rabs = 90 ± 8%
Tabs+Rabs > 99%
Polarization
Relationship
|Ts - Tp| < 35% and |Rs - Rp| < 35%
Transmission Plot
10:90 Beamsplitter Transmission
30:70 Beamsplitter Transmission
50:50 Beamsplitter Transmission
70:30 Beamsplitter Transmission
90:10 Beamsplitter Transmission
Reflectance Plot
10:90 Beamsplitter Reflection
30:70 Beamsplitter Reflection
50:50 Beamsplitter Reflection
70:30 Beamsplitter Reflection
90:10 Beamsplitter Reflection
Raw Transmission and Reflectance Data Raw Data Raw Data Raw Data Raw Data Raw Data
a. Surface 1 is denoted by an engraving of the item number.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
BSN11R Support Documentation
BSN11R25 x 36 mm 10:90 (R:T) UVFS Plate Beamsplitter, Coating: 700 - 1100 nm, t = 1 mm
$124.00
Today
BSS11R Support Documentation
BSS11R25 x 36 mm 30:70 (R:T) UVFS Plate Beamsplitter, Coating: 700 - 1100 nm, t = 1 mm
$113.00
Today
BSW11R Support Documentation
BSW11RCustomer Inspired!25 x 36 mm 50:50 UVFS Plate Beamsplitter, Coating: 700 - 1100 nm, t = 1 mm
$113.00
Today
BST11R Support Documentation
BST11R25 x 36 mm 70:30 (R:T) UVFS Plate Beamsplitter, Coating: 700 - 1100 nm, t = 1 mm
$113.00
Today
BSX11R Support Documentation
BSX11R25 x 36 mm 90:10 (R:T) UVFS Plate Beamsplitter, Coating: 700 - 1100 nm, t = 1 mm
$124.00
Today

0.9 - 2.6 µm Plate Beamsplitter

Item # BSW23R
Nominal Split Ratio (Reflected:Transmitted) 50:50
Coating on Surface 1a 0.9 - 2.6 μm
Beamsplitting Coating for 45° AOI
Coating on Surface 2 0.9 - 2.6 μm
Antireflection Coating (Ravg < 1.5%)
Size (L x H) 36.0 mm x 25.0 mm
Thickness 1.0 mm
Dimensional Tolerance ±0.1 mm
Substrate IR Fused Silica
Clear Aperture >22.5 mm x 32.4 mm
Surface Quality 20-10 Scratch-Dig
Transmitted Wavefront Error λ/2 @ 633 nm Over the Clear Aperture
Overall Performance Unpolarized Light Tabs = 50 ± 10%, Rabs = 50 ± 10%, Tabs + Rabs > 99%
Polarization Relationship |Ts-Tp| < 40%, and |Rs-Rp| < 40%
Transmission Plot
50:50 Beamsplitter Transmission
Reflectance Plot
50:50 Beamsplitter Reflection
Raw Transmission and Reflectance Data Raw Data
a. Surface 1 is denoted by an engraving of the item number.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
BSW23R Support Documentation
BSW23R25 mm x 36 mm 50:50 IR Fused Silica Plate BS, Coating: 0.9 - 2.6 µm, t = 1 mm
$281.00
Today

1.2 - 1.6 µm Plate Beamsplitters

Item # BSN12R BSS12R BSW12R BST12R BSX12R
Nominal Split Ratio (Reflected:Transmitted) 10:90 30:70 50:50 70:30 90:10
Coating on Surface 1a 1.2 - 1.6 μm Beamsplitting Coating for 45° AOI
Coating on Surface 2 1.2 - 1.6 μm Antireflection Coating (Ravg < 1%)
Size (L x H) 36.0 mm x 25.0 mm
Thickness 1.0 mm
Thickness Tolerance ±0.1 mm
Substrate UV Fused Silica
Clear Aperture >22.5 mm x 32.4 mm
Surface Quality 20-10 Scratch-Dig
Transmitted Wavefront Error λ/4 @ 633 nm
Overall Performance
Unpolarized
Light
Tabs = 90 ± 8%
Rabs = 10 ± 8%
Tabs+Rabs > 99%
Tabs = 70±8%
Rabs = 30±8%
Tabs+Rabs > 99%
Tabs = 50 ± 8%
Rabs = 50 ± 8%
Tabs+Rabs > 99%
Tabs = 30 ± 8%
Rabs = 70 ± 8%
Tabs+Rabs > 99%
Tabs = 10 ± 8%
Rabs = 90 ± 8%
Tabs+Rabs > 99%
Polarization
Relationship
|Ts - Tp| < 35% and |Rs - Rp| < 35% |Ts - Tp| < 15% and
|Rs - Rp| < 15%
|Ts - Tp| < 35% and |Rs - Rp| < 35%
Transmission Plot
10:90 Beamsplitter Transmission
10:90 Beamsplitter Transmission
50:50 Beamsplitter Transmission
70:30 Beamsplitter Transmission
90:10 Beamsplitter Transmission
Reflectance Plot
10:90 Beamsplitter Reflection
10:90 Beamsplitter Reflection
50:50 Beamsplitter Reflection
70:30 Beamsplitter Reflection
90:10 Beamsplitter Reflection
Raw Transmission and Reflectance Data Raw Data Raw Data Raw Data Raw Data Raw Data
a. Surface 1 is denoted by an engraving of the item number.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
BSN12R Support Documentation
BSN12R25 mm x 36 mm 10:90 (R:T) UVFS Plate Beamsplitter, Coating: 1.2 - 1.6 µm, t = 1 mm
$255.00
Today
BSS12R Support Documentation
BSS12R25 mm x 36 mm 30:70 (R:T) UVFS Plate Beamsplitter, Coating: 1.2 - 1.6 µm, t = 1 mm
$113.00
Today
BSW12R Support Documentation
BSW12R25 mm x 36 mm 50:50 UVFS Plate Beamsplitter, Coating: 1.2 - 1.6 µm, t = 1 mm
$113.00
Today
BST12R Support Documentation
BST12R25 mm x 36 mm 70:30 (R:T) UVFS Plate Beamsplitter, Coating: 1.2 - 1.6 µm, t = 1 mm
$113.00
Today
BSX12R Support Documentation
BSX12R25 mm x 36 mm 90:10 (R:T) UVFS Plate Beamsplitter, Coating: 1.2 - 1.6 µm, t = 1 mm
$153.00
Today
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