Back to: Beam Characterization

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