Simulation Study of Pulse Laser Quality Effects on Recording Performances of Heat Assisted Magnetic Recording by Short Pulse Laser Heating

In heat assisted magnetic recording (HAMR), a higher recording density is pursued. Short pulse laser heating is a good way to improve the thermal distribution in the media and reach the full potential of recording density for HAMR technology. In this paper, the effects of short pulse laser qualities, such as pulse frequency deviation, pulse power deviation and pulse width deviation, on recording performances for HAMR with 100ps pulse laser heating have been analyzed by simulation. The results indicated that frequency jitter has the most significant effect on the recording performance among these three parameters. The decreases of signal to noise ratio (SNR) for 6 % deviations of pulse frequency, pulse power and pulse width are 5 dB, 2 dB and 1.5 dB, respectively. A certain degree phase delay of pulse laser related to magnetic field switching time is beneficial for reducing the effect of pulse frequency deviation on SNR. When the phase delay changes from 0o to 180o, SNR improvement of about 2 dB is obtained. The measurement result of a real laser diode output (pulse width of 97ps and pulse frequency of 2 GHz) by gain-switching technology presents a very low frequency deviation (<0.5%). It indicates that gain-switching technology is a suitable approach for short pulse laser generation for HAMR application.