Rotating Slit Beam Profiler


Scanning Slit Optical Beam Profilers

  • Wavelength Range Covering 200 to 1700 nm
  • For Beam Diameters from 2.5 µm to 9 mm
  • Additional Knife-Edge Mode


  • High-Precision Analysis of Beam Quality and Spatial Power Distribution
  • Single Stand-Alone Measurement Head
  • For Characterization of Continuous or Pulsed Laser Beams with a Repetition Rate >10 Hz
  • Scanning Speeds from 2 to 20 Hz
  • Additional Knife-Edge Mode
  • Power Meter Integrated (Not Calibrated)
  • Dynamic Range of 78 dB
  • Low Noise Amplifier
  • 2D or Pseudo 3D Diagrams
  • High-Speed USB 2.0 Interface to PC

Software Features

  • Image and Text File Output with Sequential Saving Option
  • Pass/Fail Analysis
  • Module for Automated M² Beam Quality Measurements
  • Hotpixel and Ambient Light Corrections for Higher Accuracy
  • Configurable Profile Colors
  • Versatile Graphical Interface with Easy-to-Adjust Sub-Windows
  • Cross-Sectional X and Y Profiles at Adjustable Locations
  • 2D Power Density Diagram with Elliptical Beam Fit, Flexible 3D Graph
  • Plots of Total Beam Power as a Function of Time
  • Analysis of Centroid Position Drifts

Thorlabs' Dual Scanning Slit Beam Profilers are ideal for analyzing laser beam profiles that have a close-to-Gaussian beam shape. For non-Gaussian beam shapes, we recommend our camera beam profilers. These scanning slit profilers allow fast, simultaneous measurements of both the X and Y profiles with a high dynamic range of 78 dB and a variable scanning speed from 2 to 20 Hz without the need of attenuators in the beam path. There are two models available, one for use with light in the 200 - 1100 nm range and a second for use with light in the 900 - 1700 nm range. Both versions are equipped with a physical aperture measuring 9 mm in diameter. This design offers two slit widths, low noise electronics, and the additional knife-edge mode, making it possible to analyze an extended range of beam diameters (2.5 µm to 9 mm) with a single device. The beam diameter is measured in accordance with the ISO11146 standard. It can be displayed using a number of industry-standard clip levels, such as 1/e2 (13.5%), 50%, or an arbitrary clip level set by the user. 

The brushless rotation motor incorporated into these profilers extends the lifetime and makes them ideal for quality control in production environments. A variable scan rate of up to 20 Hz allows for real-time optical system alignment. Both beam parameters and spatial power distribution can be monitored in dynamically changing systems. To obtain absolute optical power measurements, the user can record a calibration measurement at the wavelength of interest using the integrated power meter and software.


Key Specifications

Item #BP209-VISBP209-VIS/MBP209-IRBP209-IR/M
Wavelength Range 200 - 1100 nm 900 - 1700 nm
Detector Material Si - UV Enhanced InGaAs
Aperture Diameter 9 mm
Scan Method Scanning Slits
Slit Size 5 µm and 25 µm
Minimum Beam Diameter 2.5 µm
Maximum Beam Diameter 9 mm


Item #BP209-VISBP209-VIS/MBP209-IRBP209-IR/M
Wavelength Range 200 - 1100 nm 900 - 1700 nm
Detector Material Si - UV Enhanced InGaAs
Aperture Diameter 9 mm
Scan Method Scanning Slits
Slit Size 5 µm and 25 µm
Minimum Beam Diameter 2.5 µm
Maximum Beam Diameter 9 mma
Scan Rate 2.0 - 20.0 Hz (Continuously Variable)
Sampling Resolution 0.12 - 1.24 µm (Depending on Scan Rate)
Power Range 10 nW - 10 W (Depending on Beam Diameter and Model)
Amplifier Bandwidth 16 to 1000 kHz in 11 Steps (@ -1 dB)
Sample Frequency 0.2872 - 2.0 MHz
Dynamic Range 78 dB (Amplifier Switchable)
PD Reverse Bias Voltage 0 / -1.5 V (Switchable)
Signal Digitization 15 Bit
Head Size Ø79 mm x 60 mm (Ø3.13" x 2.36") Including Rotation Mount
Minimum Pulse Rate 10 Hzb
Displayed Parameters/Features X-Y-Profile, Centroid Position, Peak Position, Pseudo 3D Profile, Beam Width Clip Level/Second Moment (4σ),
Gaussian Fit Applicable, Colored Pass/Fail Test
Compliant to Norm ISO11146 (Beam Widths, Divergence Angle and Beam Propagation Factor)
General System Requirements Windows™ 2000/XP/Vista or Later, USB2.0 Port Required, 120 MB HD, 512 MB RAM
M² Analysis System
Compatible M² Options BP1M2-xx Series, M2SET-xxx Series
Compliant to Norm ISO11146
Measured Parametersc M², Waist Width, Waist Position, Rayleigh Length, Divergence, Beam Pointing, Waist Asymmetry, Astigmatism
  • Beam Diameter Error <10% for 9 mm Diameter
  • 300 kHz using M² Option
  • Using M² Option


Our Mission is to accelerate the advancement of optical technology for precision measurements and their applications from the table tops of research laboratories to standard use in communication and high technology industries. Our aim is to serve our customers. Our hope is to create a place for highly skilled people in an open environment

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