New device for M2 parameter measuring.
In HiLASE laboratory we are developing a new generation of diode pump solid state lasers. We require high accuracy and single-shot information about the laser beam quality, which is characterized by the M2 laser beam propagation ratio parameter. We have therefore developed a new device which delivers exactly what we need – it is smart, simple, and gives us good-quality real-time information about every single-shot laser pulse.
Why we measure the M2?
The laser beam quality and its parameters are crucial for what we can do with the beam, how we can focus on it and how the intensity of the radiation will be laid out in the focal point. Everyone who develops, builds or operates lasers needs to know their laser’s current condition in order to adjust its settings exactly as necessary. The handy criterion of laser beam quality is the M2 parameter.
The M2 quality parameter is counted from the laser’s wavelength, the semi diameter of the waist and the beam’s divergence after focusation. The measuring is described in ISO 11146-1.
Traditional measuring methods
A traditional meter goes along the focal point with a detector and scrutinizes the beam’s profile. For the latest generation of lasers, however, this way is not particularly convenient. How can we observe the beam’s profile with just one shot? Single-shot or repeated mode operated lasers require the same feedback for their settings as the continual ones. The fluctuation in the beam’s profile grows with decreasing frequency of repetition, making the traditional measuring ways unsuitable.
A new device
This is why we at HiLASE developed a solution in the form of a new device for measuring the M2 laser beam quality, which gives us complex information about the beam’s profile both in the waist and along the Rayleigh’s distance from as little as a single shot in real time.
The device does not require any moving parts and has no special requirements for the quality of optical elements processing. It is very easy to adjust to a broad spectrum of wavelengths and any operating mode of the laser.
It measures our ps pulses well. We verified that it is also capable of measuring ns and us pulses as well without trouble; we also tested measuring fs pulses with excellent results. We added a time shutter for continual beam measuring and even here the results are fully valid to the traditional way.