Measuring laser diode temperature and predicting mode hops using laser diode resistance
A data storage device may include a disk, an actuator arm assembly comprising a magnetic recording head, a laser diode, and one or more processing devices configured to: initiate a write operation, wherein the write operation is associated with a first temperature of the laser diode; measure a resistance of the laser diode, wherein the resistance corresponds to a temperature of the laser diode; detect, based at least in part on measuring the resistance, a change in the temperature of the laser diode relative to the first temperature; and in response to detecting the change, adjust the temperature of the laser diode during the write operation.
1. A data storage device, comprising:
a disk;
an actuator arm assembly comprising a magnetic recording head;
a laser diode; and
one or more processing devices configured to:
initiate a write operation, wherein the write operation is associated with a first temperature of the laser diode;
determine self-heating induced by the laser diode for one or more of a transient condition and a steady-state condition of the laser diode, wherein determining the self-heating induced by the laser diode comprises measuring a resistance of the laser diode, and wherein the resistance corresponds to a temperature of the laser diode;
detect, based at least in part on measuring the resistance, a change in the temperature of the laser diode relative to the first temperature; and
in response to detecting the change, adjust the temperature of the laser diode during the write operation.
2. The data storage device of claim 1 , wherein the one or more processing devices are further configured to measure the resistance of the laser diode in real-time or substantially real-time.
3. The data storage device of claim 1 , wherein the temperature of the laser diode is based at least in part on a voltage across the laser diode and a laser current flowing through the laser diode.
4. The data storage device of claim 1 , wherein the resistance of the laser diode is based at least in part on a laser current flowing through the laser diode.
5. The data storage device of claim 1 , wherein, during the steady-state condition, the first temperature corresponds to a steady-state temperature associated with the write operation and when the laser diode is in a lasing state.
6. The data storage device of claim 1 , wherein, during the transient condition, the temperature of the laser diode is different from the first temperature, wherein the first temperature corresponds to a steady-state temperature associated with the write operation.
7. The data storage device of claim 1 , wherein adjusting the temperature comprises adjusting the temperature of the laser diode to prevent encountering one or more mode hops during the write operation.
8. The data storage device of claim 1 , further comprising a preamplifier, and wherein prior to initiating the write operation, the one or more processing devices are further configured to:
apply, using the preamplifier, a reverse bias to the laser diode to preheat the laser diode such that the temperature is at or near the first temperature;
control transition of the preamplifier from applying the reverse bias to applying a forward bias to the laser diode; and
wherein a temperature of the laser diode is configured to stay the same or substantially the same after controlling the transition from the reverse bias to the forward bias for the laser diode.
9. The data storage device of claim 8 , wherein, when the reverse bias is applied to the laser diode,
the laser diode is in a non-lasing state, and
no data writing or rewriting occurs.
10. The data storage device of claim 9 , wherein applying the reverse bias comprises applying a negative voltage, and wherein a value of the negative voltages is kept below an avalanche or breakdown voltage for the laser diode.
11. The data storage device of claim 1 , wherein the data storage device comprises a heat assisted magnetic recording (HAMR) data storage device, and wherein the one or more processing devices further comprise a system on chip (SoC), and wherein the one or more processing devices are further configured to:
calibrate firmware (FW) to allow measurement of the resistance of the laser diode, adjustment of the temperature of the laser diode, or a combination thereof.
12. A method of operating a data storage device, the method comprising:
initiating a write operation, wherein the write operation is associated with a first temperature of a laser diode;
determining self-heating induced by the laser diode for one or more of a transient condition and a steady-state condition of the laser diode, wherein determining the self-heating induced by the laser diode comprises at least measuring a resistance of the laser diode, and wherein the resistance corresponds to a temperature of the laser diode;
detecting, based at least in part on measuring the resistance, a change in the temperature of the laser diode relative to the first temperature; and
in response to detecting the change, adjusting the temperature of the laser diode during the write operation.
13. The method of claim 12 , wherein the resistance of the laser diode is measured in real-time or substantially real-time, and wherein,
the temperature of the laser diode is based at least in part on a voltage across the laser diode and a laser current flowing through the laser diode.
14. The method of claim 12 ,
wherein:
during the steady-state condition, the laser diode is in a lasing state and the temperature of the laser diode is equal to or substantially equal to the first temperature;
during the transient condition, the temperature of the laser diode is different from the first temperature; and
the first temperature corresponds to a steady-state temperature associated with the write operation.
15. The method of claim 12 , wherein adjusting the temperature comprises adjusting the temperature of the laser diode to prevent encountering one or more mode hops during the write operation.
16. The method of claim 12 , wherein the data storage device comprises a heat assisted magnetic recording (HAMR) data storage device, the method further comprising:
calibrating firmware (FW) to allow one or more of the measurement of the resistance of the laser diode and adjustment of the temperature of the laser diode.
17. One or more processing devices comprising:
means for determining self-heating induced by a laser diode of a data storage device for one or more of a transient condition and a steady-state condition of the laser diode, wherein the means for determining the self-heating induced by the laser diode comprises at least means for measuring a resistance of the laser diode, and wherein the resistance corresponds to a temperature of the laser diode;
means for detecting, based at least in part on measuring the resistance, a change in the temperature of the laser diode relative to a first temperature; and
in response to detecting the change, means for adjusting the temperature of the laser diode.
18. The one or more processing devices of claim 17 , wherein the means for measuring are configured to measure the resistance of the laser diode when a magnetic recording head of the data storage device is flying over a disk surface of a disk of the data storage device.
19. The one or more processing devices of claim 17 , wherein the means for measuring are configured to measure the resistance of the laser diode when a magnetic recording head of the data storage device is parked on a ramp of the data storage device.