Laser power optimization for heat assisted interlaced magnetic recording

• US 9,741,363 B2
• Filed: 07/22/2015
• Issued: 08/22/2017
• Est. Priority Date: 11/24/2014
• Status: Active Grant

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Inventors: Ma, Minjie, Gao, Kaizhong, Gage, Edward, Rausch, Tim
• Primary Examiner(s): BUTCHER, BRIAN M
• Application Number:
  US14/806,358
• Publication Number:
  US 20160148636A1
• Time in Patent Office: 762 Days
• Field of Search: None
• CPC Class Codes: G11B 11/10506 by modulating only the light beam of the transducer
• CPC Class Codes: G11B 11/10515 Reproducing compensating pit shift G11B11/1053
• CPC Class Codes: G11B 11/10521 using a single light spot
• CPC Class Codes: G11B 11/10595 Control of operating function
• CPC Class Codes: G11B 20/12 Formatting, e.g. arrangement of data block or words on the record carriers within interface between computers and data recorders G06F3/06
• CPC Class Codes: G11B 20/1217 on discs
• CPC Class Codes: G11B 20/1833 by adding special lists or symbols to the coded information G11B20/1806, G11B20/1866 take precedence
• CPC Class Codes: G11B 20/1889 with discs
• CPC Class Codes: G11B 2005/0021 Thermally assisted recording using an auxiliary energy source for heating the recording layer locally to assist the magnetization reversal
• CPC Class Codes: G11B 2020/1222 ECC block, i.e. a block of error correction encoded symbols which includes all parity data needed for decoding pure error correction aspects G11B20/18
• CPC Class Codes: G11B 2020/1232 sector, i.e. the minimal addressable physical data unit
• CPC Class Codes: G11B 2020/1238 track, i.e. the entire a spirally or concentrically arranged path on which the recording marks are located
• CPC Class Codes: G11B 2020/1292 Enhancement of the total storage capacity
• CPC Class Codes: G11B 27/3027 used signal is digitally coded
• CPC Class Codes: G11B 5/012 Recording on, or reproducing or erasing from, magnetic disks G11B17/00, G11B19/00 take precedence
• CPC Class Codes: G11B 5/09 Digital recording
• CPC Class Codes: G11B 5/59633 Servo formatting G11B5/59627, G11B5/59677, G11B5/59683, G11B5/59688 take precedence
• CPC Class Codes: G11B 5/59638 Servo formatting apparatuses, e.g. servo-writers
• CPC Class Codes: G11B 5/6088 Optical waveguide in or on flying head

Abstract

A storage device disclosed herein stores data on a storage media using interlaced magnetic recording (IMR) and it includes a storage controller configured to determine power levels applied to the power source such that power levels applied to heat various tracks can be different from each other. An implementation of the storage device determines the track density, linear densities and power levels for even and odd tracks in IMR HAMR for the storage media.

Claims

1. A storage device comprising:

a storage media configured to store data using interlaced magnetic recording (IMR) having at least two different track densities (kilotracks per inch (ktpi));

a power source configured to heat the storage media; and

a storage device controller configured to determine power levels applied to the power source such that power levels applied to heat various tracks j of different track densities ktpi_j are different from each other by;

writing triple adjacent tracks at a given linear density and a given track density;

determining an optimized power level for the given track density based on an observed best center track bit error rate (BER) of the triple adjacent tracks.

2. The storage device of claim 1, wherein the power source is a laser power source.

3. The storage device of claim 1, wherein the storage device controller is further configured to determine the power levels applied of the power source such that the total area density capacity (ADC) of the storage device is maximized.

4. The storage device of claim 3, wherein the storage device is further configured to determine a power level for a given track density by:

if the observed best center track BER is less than a predetermined BER threshold, increasing the given track density and repeating the writing and the determining operations until the observed best center track BER is greater than the predetermined BER threshold.

5. The storage device of claim 4, wherein writing the triple adjacent tracks further comprises writing a center track first and then writing adjacent outer tracks.

6. The storage device of claim 5, further comprising finding a maximum linear density for each track density.

7. The storage device of claim 6, wherein finding the maximum linear density for each track density further comprises:

at each particular track density ktpi_j, writing a single track with optimized laser power for that particular track density over a range of linear density values (kilobits per inch (kbpi_i,j),

determining the single track BER;

increasing kbpi_i,j until the single track BER is greater than the predetermined BER −

0.15; and

increasing the ktpi_j and repeating the operations of determining single track BER and increasing until ktpi_j=ktpi_max.

8. The storage device of claim 3, further comprising:

finding power levels for each of the different track densities ktpi_j;

finding a maximum linear density (kilobits per inch (kbpi_max_j)) for each of the different track densities ktpi_j;

determining IMR track density ktpi, IMR even track linear densities kbpi, and IMR even track operating power levels; and

determining IMR odd track linear densities kbpi and IMR odd track operating power levels.

9. The storage device of claim 8, further comprising determining area density capacity ADC_j for each given track density ktpi_j as a product of given track density ktpi_j and maximum linear density kbpi_max_j for the given track density ktpi_j.

10. The storage device of claim 9, wherein the linear density of even track is the maximum linear density kbpi_max_j where the ADC value is equal to maximum value of ADC max_ADC_j.

11. The storage device of claim 8, wherein determining IMR odd track linear densities kbpi further comprises:

writing an odd track with laser power of Iop_n=0 and odd track linear density of kbpi_m=0,n=0;

writing two adjacent even tracks with IMR track density ktpi, IMR even track linear densities kbpi, and IMR even track operating power levels;

increasing odd track linear density until odd track BER>

BER₃ and repeating the operations of writing an odd track and writing two adjacent even tracks, wherein the BER₃ is a predetermined BER threshold.

12. The storage device of claim 8, wherein determining IMR odd track operating power levels further comprises:

writing two background odd tracks with interval of 2*IMR track pitch with laser power of Iop_n;

writing an even track between the two background odd tracks with laser power of Iop_n; and

decreasing the laser power until even track BER>

BER₁ and repeating the writing of the two background odd tracks and the even track between the two background odd tracks, wherein the BER₁ is a predetermined BER threshold.

13. A method comprising:

determining laser power levels applied to a laser power source of a storage device storing data on storage media using interlaced storage recording (IMR) such that laser power levels applied to heat various tracks can be different from each other;

by;

writing triple adjacent tracks at a given linear density and a given track density; and

determining an optimized power level for each of a plurality of track densities based on observed best center track bit error rate (BER) of the triple adjacent tracks.

14. The method of claim 13, wherein determining the laser power levels further comprises determining the laser power levels such that the total area density capacity (ADC) of the storage device is optimized.

15. The method of claim 13, further comprising determining a power level of a given track density by:

if the observed best center track BER is less than a predetermined BER threshold, increasing the given track density and repeating the writing and the determining operations until the observed best center track BER is greater than the predetermined BER threshold.

16. The method of claim 15, wherein writing the triple adjacent tracks further comprises writing a center track first and them writing adjacent outer tracks.

17. The method of claim 16, further comprising finding a maximum linear density for each track density.

18. The method of claim 17, wherein finding the maximum linear density for each track density further comprises:

at each particular track density (kilotracks per inch (ktpi_j)), writing a single track with optimized laser power for that particular track density over a range of linear density values (kilobits per inch (kbpi_i,j)),

measuring the single track BER;

increasing kbpi_i,j until the single track BER is greater than the predetermined BER−

0.15; and

increasing the ktpi and repeating the operations of determining single track BER until ktpi_j=ktpi_max.

19. The method of claim 14, further comprising:

finding power levels for each of the different track densities kilotracks per inch (ktpi_j);

finding a maximum linear density kilobits per inch (kbpi_max_j) for each of the different track densities ktpi_j;

determining IMR track density ktpi, IMR even track linear densities kbpi, and IMR even track operating power levels; and

determining IMR odd track linear densities kbpi and IMR odd track operating power levels.

20. The method of claim 19, further comprising determining area density capacity for each given track density ktpi_j as a product of given track density ktpi_j and maximum linear density kbpi_max_j for the given track density ktpi_j.