Filter harmonics in AC power line
This is clearly any industrial conducted and possibly radiated EMC issue if the unit has a floating SMPS without earth ground, e.g. DC plug.

The solutions may require a properly designed CLC CM and DM "Pi" filter with CM and DM chokes and RF X caps and Y caps to earth for rated current and if laser must withstand the heater current rating.

If earth bonding of Y caps is essential. Also the USB cable if used to host device and its earth bonding is also critical 

I found this out yesterday at a Uni EE POwer Lab when a tower could not even communicate to an Arduino on a USB cable with decent 12V SMPS to Arduino with linear regulator for 5V. One fix was made both ends (host and client) floating, e.g. laptop to Arduino next fix is earth bond Arduino CNC target and Arduino 0Vdc and then all stray local noise is shunted to earth. THen if host noise also conducts earth bonded ground noise an extra line filter is needed.

Caution CLC CM filter cascaded line PI filter can cause anti-resonant issues so ask a professional to design it for DM and CM mode or trial and error. Your choice.  Verify design with earth bonded 10:1 (calibrated with step pulse AND AC Line to both probes for flat line) probes in A-B mode AC coupled with short gnd clips.  If you don't know what a CLC line filter does, then you cannot design it.