In heat-assisted magnetic recording (HAMR), optical power from a laser diode mounted on the slider is used to heat up a nanometer scale area on the disk surface to approximately 450°C, facilitating the writing process. Controlling optical power or current that is applied to the laser diode in HAMR is a critical task. In this study, a fully integrated system of HAMR heads and disks is used to study laser current as a function of the magnetic write width (MWW), the operating radius, and the head-disk clearance. Our experimental results show that the laser current is a linear function of the magnetic write width and the head-disk clearance. As the operating radius increases from the inner diameter to the outer diameter of the disk, the laser current increases by approximately 20%.