A luvetric pulse was type of wide-area blast a personnel phaser could be modified to emit.
In 2369, the crew of USS Enterprise-D were looking for Data and Crosis, a Borg drone, on a planet with naturally high EM interference in its magnetosphere. They had a 20 kilometer radius search zone and the interference made it impossible to use sensors to locate Data.
Captain Jean-Luc Picard suggested they could modify a phaser to send out a luvetric pulse. Such a pulse would have created a resonance fluctuation in Data's power cells. They could have then pinpointed the fluctuation with a tricorder. Geordi La Forge however pointed out that to be effective the pulse would have to be so powerful that it would destroy Data's positronic net in the process. (TNG: "Descent")