How to know your laser specifications so you can choose the right measurement solution
Monday, July 19, 2021
If you want to measure the power of your laser, you need a detector and a power meter. There is a wide variety of detectors and power meters available and not all of them are compatible with each other.
They are also all designed to accommodate specific laser systems, therefore it is crucial that you select the right measurement tools.
When selecting a laser power measurement tool, it is important to know some of the finer points of your system. Getting these wrong could cause you to use the wrong tool, resulting in ineffective measurements and potential damage to the measurement device.
It is important to know both the beam size and the shape of your beam. The shape can be either circular, elliptic or rectangular. This refers to the physical shape of your laser beam when focused, along the axis, on a flat surface. The size measurements characterize the approximate size of this shape.
If you aren’t sure about these characteristics of your beam, you should be able to find them in the manual that came with your laser. Alternatively, the best way to check this is through the use of a beam profiler, if the beam profile of your laser has been measured before, then this information should be available in the report.
Lasers can be continuous wave or pulsed. Continuous Wave (CW) means that when your laser is turned on, the beam remains at the same approximate intensity, until it is programmed or manually turned off. Pulsed means that the laser is turned on for a very short time period, usually milliseconds or less, and may be fired as a single pulse or multiple pulses. Some pulsed lasers allow the user to program in pulse shaping, where you can select the time and number of pulses, how long you have between pulses, etc.
There is a good chance that your laser can be used in both pulsed and CW modes, in this case it is important to consider which mode is most important for you and your power measurement. Consider which mode that you will be using the most.
Warning: If you decide that a CW measurement is the most useful for you, then it is important that you do not operate the laser in pulsed mode when using your power meter, unless you have been advised to do so. With pulsed lasers, the very high concentration of power in a short period of time can affect matter differently from continuous power. Therefore, it is important to also check the damage thresholds of your detector in terms of both power density and energy density, to avoid permanent damage.
Laser type can also be characterized by wavelength. This is normally inherent to the laser and the active medium that is used to produce the beam. Again, you should be able to look this up in your laser manual, alternatively you may be able to discern the wavelength from the laser’s variety. For example, an Nd:YAG fiber laser would have a predominant wavelength of 1064nm.
For a CW laser you will need to know the average power (as opposed to peak power), whilst for pulsed lasers you need to know the energy per pulse (can be calculated from power and repetition rate), repetition rate and pulse width (duration of pulse in seconds).
Generally, these are all variable for a laser system, depending on what is programmed. Therefore, it is important that you know what variables you would most like to measure the power for. If you are unsure, it is advisable to be cautious and select the highest values that you expect to test for, as underestimating could result in damaging the detector.
There are three options for beam profile, gaussian or flat-top, your laser manual should help to answer whether your laser is gaussian or flat-top. However, ideally you want to measure your beam profile to know this answer with certainty.
If you know your laser’s M2 value, then this can be a big help, as a value near 1 suggests that your laser is gaussian, whereas a value much higher suggests that your laser is more likely to be top-hat.
If you know the answers to these questions, you can use Gentec-EO’s product finder tool to quickly find a detector and power meter that meets your needs.
On the other hand, if you are having trouble finding out your laser specifications and you require any assistance, please do not hesitate to get in touch with us.