Software Features

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. For details about the functionality and the usage of the different slit widths, please see the Operation tab.

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.

The beam profilers can work directly with a connected PC with no additional hardware or power supply required. For ease of use, Thorlabs utilizes a Hi-Speed USB2.0 interface to connect the measurement head with the user-supplied PC. Flexible data export options as well as a data interface for National Instruments® software ease the integration of these profilers into customized data processing environments.

Please see the User Interface tab above for more details on the functionality of the software. The operating principles are detailed on the Operation tab.

Pulsed Laser Beams
The beam profile of pulsed laser sources with repetition rates of 10 Hz or higher and of any pulse widths can be measured. Several scans of the XY slit pairs are used to reconstruct the complete beam shape. Synchronization is achieved by manually adjusting the scanning speed so that it is very close to an integer fraction of the laser’s repetition frequency. See the Operations Manual for a detailed description. For M² measurements, the minimum pulse repetition rate is ≥ 300 kHz.

The instrument's saturation level depends on the power density (power per unit area) that hits the sensor. Therefore, the maximum power the device can withstand depends on the total optical beam power and the diameter of the beam being measured. As depicted above, the measurable power range is dependent on both the model of beam profiler used (slit size and sensor material) as well as the beam diameter being measured.

This graph shows the power ranges (vertical axis) that can be measured as a function of the 1/e² beam width (horizontal axis) for the BP209-VIS (green line) and the BP209-IR (red line).

Please note that the maximum average power needs to be kept below 1 W to prevent thermal damage to the measurement head. Levels up to 10 W are acceptable for short-term analysis only (5 s Max).

Rotation Mount
The BP200 Series devices come with a rotation mount, which enables you to manually rotate the X and Y scan axes up to ±60°. Simply take the plug on the top and move it to the left or right (while keeping the mount fixed); the beam profiler rotates within its mount. To aid in getting the desired angle, the rotation mount is engraved with short lines every 10° and longer lines at 0° and 45° in order to measure your beam profile at different directions easily. Refer to the photo of the device located to the right of the above sketch.

The rotation mount is essential for the measurement of the beam's ellipticity. For example, since the major and minor axes of an elliptical beam have arbitrary position in space, the scan axes of the beam profiler need to be aligned with these axes in order to measure the real ellipticity. Without scan axes alignment, the beam profiler will measure erroneous beam ellipticities.

Functionality
A variable average function provides adjustable noise reduction and increases the measurement accuracy. The maximum-hold function allows analysis of pulsed laser sources, while the automatic or manual gain control enables the user to adapt to different beam powers. The power meter readouts can be provided in mW or dBm, depending on the user's preference.. The provided GUI shows all parameters as digital or bar graph readouts, and parameter drifts can be visualized by a trend indicator. All resulting data can be exported as text or spreadsheet files. See the User Interface tab for more details about the included GUI software package.