Thermal management of laser diode mode hopping for heat assisted media recording
A method and apparatus provide for determining a temperature at a junction of a laser diode when the laser diode is operated in a lasing state that facilitates heat-assisted magnetic recording, comparing the junction temperature and an injection current supplied during the lasing state to stored combinations of junction temperature and injection current, and determining a likelihood of mode hopping occurring for the laser diode during the lasing state based on the comparison to stored combinations of junction temperature and injection current.
1. An apparatus, comprising:
a laser diode configured to facilitate heat assisted magnetic recording in a lasing state;
a sensor, coupled in parallel with the laser diode, configured to measure a temperature of a junction of the laser diode and to heat the junction, the sensor configured to heat the junction at least during a non-lasing state of the laser diode; and
a controller configured to activate the sensor to heat the junction and maintain the junction temperature within a predetermined temperature range associated with a reduced likelihood of mode hopping occurring for the laser diode.
2. The apparatus of claim 1 , wherein the sensor comprises at least a diode.
3. The apparatus of claim 1 , wherein the sensor comprises a diode in series with a resistive element.
4. The apparatus of claim 3 , wherein the resistive element comprises a thermistor.
5. The apparatus of claim 1 , wherein the sensor comprises at least a diode configured to be reverse biased during the lasing state and forward biased during the non-lasing state.
6. The apparatus of claim 1 , wherein the sensor comprises at least a diode configured to heat the junction of the laser diode during the non-lasing state and during a portion of the lasing state.
7. The apparatus of claim 1 , wherein the sensor is configured to be forward biased during the non-lasing state, reverse biased during a first portion of the lasing state, and forward biased during a second portion of the lasing state following the first portion.
8. The apparatus of claim 1 , wherein the controller is configured to facilitate rewriting of data recorded on a magnetic recording medium in response to determining that mode hopping was likely to have occurred.
9. The apparatus of claim 1 , wherein the controller is configured to modify one or more of an injection current, a laser diode power output, and a head position relative to a magnetic recording medium to compensate for a laser diode power variation due to the mode hopping.
10. The apparatus of claim 1 , wherein the controller is configured to adjust heating of the junction via the sensor and adjust an injection current to achieve a junction temperature for which mode hopping is less likely to occur.
11. An apparatus, comprising:
a laser diode configured to facilitate heat assisted magnetic recording in a lasing state;
a sensor comprising at least a diode and coupled in parallel with the laser diode, the sensor configured to measure a temperature of a junction of the laser diode and to heat the junction during a non-lasing state of the laser diode and at least a portion of the lasing state; and
a controller coupled to the laser diode and the sensor, the controller configured to generate a drive signal having an energizing portion and a non-energizing portion to cause the laser diode to operate in the lasing state and a non-lasing state, respectively, the energizing portion comprising a negative-going portion for forward biasing the diode of the sensor during at least the portion of the lasing state;
wherein the controller facilitates heating of the junction to maintain the junction temperature within a predetermined temperature range associated with a reduced likelihood of mode hopping occurring for the laser diode.
12. The apparatus of claim 11 , wherein the sensor comprises a diode in series with a resistive element.
13. The apparatus of claim 12 , wherein the resistive element comprises a thermistor.
14. The apparatus of claim 11 , wherein the diode of the sensor is configured to be reverse biased during most of the lasing state and forward biased during the non-lasing state.
15. The apparatus of claim 11 , wherein the diode of the sensor is configured to heat the junction during the non-lasing state and the portion of the lasing state.
16. The apparatus of claim 11 , wherein:
the sensor comprises the diode coupled in series with a resistive element; and
the resistive element is configured to heat the junction during the non-lasing state and the portion of the lasing state.
17. The apparatus of claim 11 , wherein the diode of the sensor is configured to be forward biased during the non-lasing state, reverse biased during a first portion of the lasing state, and forward biased during a second portion of the lasing state following the first portion.
18. The apparatus of claim 11 , wherein the controller is configured to facilitate rewriting of data recorded on a magnetic recording medium in response to determining that mode hopping was likely to have occurred.
19. The apparatus of claim 11 , wherein the controller is configured to modify one or more of an injection current, a laser diode power output, and a head position relative to a magnetic recording medium to compensate for a laser diode power variation due to the mode hopping.
20. The apparatus of claim 11 , wherein the controller is configured to adjust heating of the junction via the sensor and adjust an injection current to achieve a junction temperature for which mode hopping is less likely to occur.