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 slider and a laser diode configured to facilitate heat assisted magnetic recording (HAMR), the slider comprising:
a read element and a write element respectively situated at an air bearing surface (ABS) of the slider;
a near-field transducer (NFT) situated at the ABS proximate the write element;
an optical waveguide configured to couple light from the laser diode to the NFT;
a temperature sensing arrangement configured to determine a temperature at a junction of the laser diode; and
a heater arrangement configured to heat the junction of the laser diode; and
a controller coupled to the slider and the laser diode, the controller comprising:
a laser control coupled to the laser diode and configured to control operation of the laser diode; and
a heater control coupled to the heater arrangement and configured to control operation of the heater arrangement, the heater control configured to control the heater arrangement to heat the laser diode junction during a non-lasing state of the laser diode or during at least a portion of the non-lasing state and at least a portion of the lasing state of the laser diode.
2. The apparatus of claim 1 , wherein the heater control is configured to control the heater arrangement to heat the laser diode junction during the non-lasing state.
3. The apparatus of claim 1 , wherein the heater control is configured to control the heater arrangement to heat the laser diode junction during at least the portion of the non-lasing state and at least the portion of the lasing state.
4. The apparatus of claim 1 , wherein the laser control and the heater control define independent circuits.
5. The apparatus of claim 1 , wherein the heater control is configured to heat the laser diode junction to achieve a junction temperature associated with a reduced likelihood of mode hopping occurring for the laser diode.
6. The apparatus of claim 1 , wherein the heater control is configured to maintain a junction temperature within a predetermined temperature range associated with a reduced likelihood of mode hopping occurring for the laser diode.
7. The apparatus of claim 1 , wherein the temperature sensing arrangement and the heater arrangement are coupled to a sensor configured to sense temperature and produce heat.
8. The apparatus of claim 1 , wherein the temperature sensing arrangement is configured to:
determine a voltage differential between a non-steady lasing state of the laser diode and a steady state lasing state of the laser diode; and
calculate the temperature of the laser diode junction based on the voltage differential.
9. The apparatus of claim 1 , wherein the heater arrangement comprises a heating element disposed proximate or along the laser diode.
10. The apparatus of claim 1 , wherein the heater arrangement comprises a heating element disposed within the laser diode.
11. The apparatus of claim 1 , wherein:
the heater arrangement comprises a heating element; and
a spatial proximity of the heater element to the laser diode junction is such that heat produced by the heating element diffuses to the laser diode junction in less than about 1 μs.
12. The apparatus of claim 1 , wherein the laser diode is mounted on a submount, and the submount is mounted on the slider.
13. The apparatus of claim 1 , wherein the controller is configured to implement rewriting a sector of data recorded on a magnetic recording medium in response to determining that mode hopping was likely to have occurred.
14. An apparatus, comprising:
a slider and a laser diode configured to facilitate heat assisted magnetic recording (HAMR), the slider comprising:
a read element and a write element respectively situated at an air bearing surface (ABS) of the slider;
a near-field transducer (NFT) situated at the ABS proximate the write element;
an optical waveguide configured to couple light from the laser diode to the NFT;
a temperature sensing arrangement configured to determine a temperature at a junction of the laser diode; and
a heater arrangement configured to heat the junction of the laser diode; and
a controller coupled to the slider and the laser diode, the controller comprising:
a laser control coupled to the laser diode and configured to control operation of the laser diode;
a heater control coupled to the heater arrangement and configured to control operation of the heater arrangement, the heater control configured to control the heater arrangement to heat the laser diode junction during a non-lasing state of the laser diode or during at least a portion of the non-lasing state and at least a portion of the lasing state of the laser diode; and
a processor coupled to the controller and configured to determine a likelihood of mode hopping occurring for the laser diode during the lasing state based on a comparison of the junction temperature of the laser diode and an injection current relative to stored combinations of junction temperature and injection current.
15. The apparatus of claim 14 , wherein controller is configured to communicate with the processor and vary a current supplied to the heater arrangement for varying a temperature of the laser diode junction to reduce the likelihood of mode hopping occurring during the lasing state.
16. The apparatus of claim 14 , wherein the heater control is configured to control the heater arrangement to heat the laser diode junction during the non-lasing state.
17. The apparatus of claim 14 , wherein the heater control is configured to control the heater arrangement to heat the laser diode junction during at least the portion of the non-lasing state and at least the portion of the lasing state.
18. The apparatus of claim 14 , wherein the laser control and the heater control define independent circuits.
19. The apparatus of claim 14 , wherein the temperature sensing arrangement and the heater arrangement are coupled to a sensor configured to sense temperature and produce heat.
20. The apparatus of claim 14 , wherein the temperature sensing arrangement is configured to:
determine a voltage differential between a non-steady lasing state of the laser diode and a steady state lasing state of the laser diode; and
calculate the temperature of the laser diode junction based on the voltage differential.