Preheating laser diodes for HAMR disk drives with reverse bias

Abstract

A data storage device may include one or more disks, an actuator arm assembly including one or more disk heads, at least one laser diode positioned inside a corresponding laser diode cavity, a preamplifier, and one or more processing devices. The one or more processing devices are configured to: generate a reverse bias; applying a reverse bias to the at least one laser diode using a preamplifier to preheat the corresponding laser diode cavity to a target temperature prior to a write operation; controlling a transition of the preamplifier from applying a reverse bias to the at least one laser diode to applying a forward bias; and activating the at least one laser diode to initiate a write operation.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Non-Provisional Application No. 18 / 447,401, filed on August 10, 2023 in the U.S. Patent and Trademark Office, entitled “PREHEATING LASER DIODES WITH REVERSE BIAS FOR HAMRDISK DRIVES,” and is hereby incorporated by reference in its entirety for all purposes, which application claims priority to U.S. Provisional Application No. 63 / 426,176, filed on November 17, 2022. Background Art

[0003] A data storage device such as a disk drive includes one or more disks and one or more read / write heads connected to the distal end of an actuator arm that is rotated by an actuator (e.g., a voice coil motor, one or more fine actuators) to radially position the heads above the surface of the disk at a carefully controlled flying height above the disk surface. The disk surfaces each include a plurality of radially spaced concentric tracks for recording user data sectors and servo wedges or servo sectors. As part of the final stages of disk drive preparation, servo tracks are written on the previously blank disk drive surface. The servo sectors include head positioning information (e.g., track addresses) that is read by the heads and processed by a servo control system to control the actuator arm as the actuator arm seeks from track to track.

[0004] Figure 1A The prior art disk format 2 is shown as comprising a plurality of radially spaced concentric servo tracks 4 consisting of servo wedges 60 to 67 recorded around the circumference of each servo track. N A plurality of concentric data tracks are defined relative to the servo track 4, wherein the data tracks may have the same or different radial density (eg, tracks per inch (TPI)) as the servo track 6. Each servo wedge 6 i A preamble 8 is included for storing a periodic pattern (which allows for proper gain adjustment and timing synchronization of the read signal) and a synchronization mark 10 for storing a special pattern for symbol synchronization to a servo data field 12. The servo data field 12 stores coarse head positioning information, such as a servo track address, used to position the head over a target data track during a seek operation. Each servo wedge (e.g., servo wedge 64) further includes a phase-based servo burst group 14 (e.g., N servo bursts and Q servo bursts) that are recorded at a predetermined phase relative to each other and relative to the servo track centerline.

[0005] The coarse head positioning information is processed to position the head over a target data track during a seek operation, and the servo bursts 14 provide fine head positioning information for centerline tracking when accessing a data track during a write / read operation. A position error signal (PES) is generated by reading the servo bursts 14, where the PES represents the measured position of the head relative to the centerline of the target servo track. The servo controller processes the PES to generate a control signal that is applied to one or more actuators to actuate the head radially over the disk in a direction that reduces the PES.

[0006] The description provided in the Background section should not be considered prior art merely because it is mentioned in or related to the Background section.The Background section may include information describing one or more aspects of the subject technology. Summary of the invention

[0007] An overview of one or more aspects and / or embodiments disclosed herein is presented below. The following overview should not be considered an extensive review of all expected aspects and / or embodiments, nor should it be considered to identify key or important elements related to all expected aspects and / or embodiments or to define the scope associated with any particular aspect and / or embodiment. Therefore, the sole purpose of the following overview is to present certain concepts related to one or more aspects and / or embodiments related to the mechanisms disclosed herein in a simplified form, prior to the detailed description presented below.

[0008] In some cases, laser diodes in heat-assisted magnetic recording (HAMR) drives are susceptible to temperature-induced mode jumps, such as during the start of a write operation. During HAMR writing, the temperature of the laser diode may increase (e.g., by 10°C to 20°C), and may cross several mode jump critical temperatures during this temperature transient. In some cases, one or more mode jump events may be triggered during this transient phase, which may adversely affect write performance. For example, mode jump events during a HAMR write operation may result in recording non-uniformities, which degrade HAMR recording performance. Broadly speaking, aspects of the present disclosure relate to preventing or reducing mode jumps, which helps to enhance HAMR recording performance. In some embodiments, preheating the laser diode cavity to a target temperature (i.e., the temperature used during the write operation) can help eliminate or minimize temperature transients, as described in further detail below.

[0009] In some aspects, the technology described herein relates to a data storage device, the data storage device comprising: one or more disks, an actuator arm assembly including one or more magnetic recording heads, at least one laser diode, a preamplifier, and one or more processing devices, each of the at least one laser diode being positioned inside a corresponding laser diode cavity. The one or more processing devices are configured to: generate a reverse bias voltage; apply the reverse bias voltage to the at least one laser diode using the preamplifier to preheat the corresponding laser diode cavity to a target temperature before a write operation; control the transition of the preamplifier from applying the reverse bias voltage to the at least one laser diode to applying a forward bias voltage to the at least one laser diode; and activate the magnetic recording head corresponding to the at least one laser diode to start the write operation.

[0010] In some aspects, the technology described herein relates to a data storage device, wherein the preamplifier further includes a reverse bias power control circuit coupled to the at least one laser diode and configured to apply the reverse bias to the at least one laser diode.

[0011] In some aspects, the technology described herein relates to a data storage device wherein one or more of the following items: when the reverse bias is applied to the at least one laser diode, no laser is emitted; when the reverse bias is applied to the at least one laser diode, no data writing or rewriting occurs; and the temperature of the corresponding laser diode cavity is configured to remain the same or substantially the same after controlling a transition from the reverse bias to the forward bias for the at least one laser diode.

[0012] In some aspects, the technology described herein relates to a data storage device wherein each of the at least one laser diode dissipates a first power during the preheating period, and wherein each of the at least one laser diode dissipates a second power during the writing operation.

[0013] In some aspects, the technology described herein relates to a data storage device wherein one of the following: the first power is the same or substantially the same as the second power; or the first power is greater than the second power.

[0014] In some aspects, the techniques described herein relate to a data storage device in which one or more mode jumps associated with temperature transients at or near the beginning of a write operation are avoided based at least in part on preheating a corresponding laser diode cavity to a target temperature.

[0015] In some aspects, the technology described herein relates to a data storage device, wherein the target temperature comprises a steady-state temperature associated with the write operation and when the at least one laser diode is in a lasing state.

[0016] In some aspects, the technology described herein relates to a data storage device wherein one or more processing devices are further configured to maintain one or more of the at least one laser diode and the corresponding laser diode cavity in a preheated state such that a laser turn-on transition time is kept below a threshold.

[0017] In some aspects, the technology described herein relates to a data storage device, wherein applying the reverse bias voltage includes applying a negative voltage, and wherein the value of the negative voltage is maintained below an avalanche or breakdown voltage of the at least one laser diode.

[0018] In some aspects, the technology described herein relates to a method of operating a data storage device, the method comprising: generating a reverse bias voltage; applying the reverse bias voltage to at least one laser diode of the data storage device through a preamplifier to preheat at least one laser diode cavity to a target temperature prior to a write operation on one or more disks, wherein each of the at least one laser diode is positioned inside a corresponding laser diode cavity; controlling the preamplifier to transition from applying the reverse bias voltage to the at least one laser diode to applying a forward bias voltage to the at least one laser diode; and activating a magnetic recording head corresponding to the at least one laser diode to start the write operation.

[0019] In some aspects, the technology described herein relates to a method wherein one or more of the following: (1) when the reverse bias is applied to the at least one laser diode, no laser is emitted; (2) when the reverse bias is applied to the at least one laser diode, no data writing or rewriting occurs; and (3) the temperature of the corresponding laser diode cavity is configured to remain the same or substantially the same after controlling a transition from the reverse bias to the forward bias for the at least one laser diode.

[0020] In some aspects, the technology described herein relates to a method of operating a data storage device, the method further comprising: (1) selecting a first power, wherein the first power corresponds to the power dissipated by each of the at least one laser diode during the preheating period and when in a non-laser emitting state; and (2) selecting a second power, wherein the second power corresponds to the power dissipated by each of the at least one laser diode during the write operation and when in a lasing state.

[0021] In some aspects, the technology described herein relates to a method of operating a data storage device, wherein one of the following: the first power is the same or substantially the same as the second power; or the first voltage is greater than the second voltage.

[0022] In some aspects, the technology described herein relates to a method of operating a data storage device in which one or more mode jumps associated with temperature transients at the beginning of a write operation are avoided based at least in part on preheating a corresponding laser diode cavity to a target temperature.

[0023] In some aspects, the technology described herein relates to a method of operating a data storage device, wherein the target temperature comprises a steady-state temperature associated with the write operation and when the at least one laser diode is in a lasing state.

[0024] In some aspects, the technology described herein relates to a method of operating a data storage device, the method further comprising: maintaining one or more of the at least one laser diode and the corresponding laser diode cavity in a preheated state so as to keep the laser turn-on transition time below a threshold.

[0025] In some aspects, the technology described herein relates to a method of operating a data storage device, wherein applying the reverse bias voltage includes applying a negative voltage, and wherein the value of the negative voltage is maintained below an avalanche or breakdown voltage of the at least one laser diode.

[0026] In some aspects, the technology described herein relates to a method of operating a data storage device, wherein the preamplifier includes a reverse bias power control circuit, which is coupled to the at least one laser diode and is configured to apply the reverse bias to the at least one laser diode, and wherein the preamplifier further includes one or more multiplexers for isolating the at least one laser diode during application of the reverse bias.

[0027] In some aspects, the technology described herein relates to one or more processing devices, which include: a component for generating a reverse bias; a component for applying the reverse bias to at least one laser diode of a data storage device to preheat at least one laser diode cavity to a target temperature prior to a write operation on one or more disks, wherein each of the at least one laser diode is positioned within a corresponding laser diode cavity; a component for controlling a transition from applying the reverse bias to the at least one laser diode to applying a forward bias to the at least one laser diode; and a component for activating a magnetic recording head corresponding to the at least one laser diode to initiate the write operation.

[0028] In some aspects, the technology described herein relates to one or more processing devices, wherein the data storage device includes a heat-assisted magnetic recording (HAMR) data storage device, and wherein one or more of the following items: when the reverse bias is applied to the at least one laser diode, no laser is emitted; when the reverse bias is applied to the at least one laser diode, no data writing or rewriting occurs; and the temperature of the corresponding laser diode cavity is configured to remain the same or substantially the same after controlling the transition from the reverse bias to the forward bias for the at least one laser diode.

[0029] In some aspects, the technology described herein relates to one or more processing devices, the one or more processing devices further comprising: means for selecting a first power, wherein the first power corresponds to the power dissipated by each of the at least one laser diode during the preheating period and when in a non-lasing state; and means for selecting a second power, wherein the second power corresponds to the power dissipated by each of the at least one laser diode during the writing operation and when in a lasing state. In some implementations, the first power is the same or substantially the same as the second power, or the first power is greater than the second power.

[0030] In some aspects, the technology described herein relates to one or more processing devices, wherein the means for applying the reverse bias voltage includes means for applying a negative voltage. In some implementations, the negative voltage has a value at or below an avalanche or breakdown voltage of the at least one laser diode.

[0031] In some implementations, one or more mode jumps associated with temperature transients at or near the beginning of the write operation are avoided based at least in part on preheating the corresponding laser diode cavity to a target temperature.

[0032] In some implementations, the target temperature comprises a steady-state temperature associated with the write operation and when the at least one laser diode is in a lasing state.

[0033] Various further aspects are depicted in the drawings and described below and will be further apparent based on these. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The various features and advantages of the technology of the present disclosure will become apparent from the following description of specific examples of those technologies and those as shown in the accompanying drawings. The drawings are not necessarily to scale; instead, the emphasis is on illustrating the principles of the technical concepts. In the accompanying drawings, the same reference numerals may refer to the same parts in different views. The drawings depict only illustrative examples of the present disclosure and do not limit the scope.

[0035] Figure 1AThe disk format according to various aspects of the present disclosure is shown to include a plurality of radially spaced concentric servo tracks defined by servo wedges recorded around the circumference of each servo track.

[0036] Figure 1B A block diagram illustration of selected components of a disk drive in accordance with various aspects of the present disclosure is shown.

[0037] Figure 2A and Figure 2B Conceptual block diagrams illustrating top and side views of a data storage device in the form of a disk drive in accordance with various aspects of the present disclosure.

[0038] Figure 2C Methods that may be implemented, performed, and practiced by data storage devices according to various aspects of the present disclosure are illustrated.

[0039] Figure 3 A conceptual graph showing the relationship between temperature transients, mode hopping critical temperature, and laser wavelength according to various aspects of the present disclosure is illustrated.

[0040] Figure 4 Block diagrams showing waveguides, laser diodes, disks, and sliders of a data storage device according to various aspects of the present disclosure are illustrated.

[0041] Figure 5A A conceptual graph of laser diode cavity temperature versus time during a write operation in accordance with various aspects of the present disclosure is illustrated.

[0042] Figure 5B Conceptual graphs of laser diode power versus time for both a warm-up phase and a write phase of a laser diode of a data storage device in accordance with various aspects of the present disclosure are illustrated.

[0043] Figure 6 Examples of IV curves for laser diodes including Joule power dissipated in forward and reverse bias modes are illustrated in accordance with various aspects of the present disclosure.

[0044] Figure 7 is a block diagram illustrating some example components that may be used to implement reverse bias control of a laser diode in accordance with various aspects of the present disclosure. DETAILED DESCRIPTION

[0045] The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other implementations.

[0046] The embodiments described below are not intended to limit the invention to the precise form disclosed, nor are they intended to be exhaustive. Instead, the embodiments are presented to provide a description so that others skilled in the art can utilize their teachings. Technology continues to evolve, and elements of the described and disclosed embodiments may be replaced by improved and enhanced items, however, the teachings of the present disclosure inherently disclose elements used in embodiments of technology available at the time of incorporation into the present disclosure.

[0047] In some cases, laser diodes in heat-assisted magnetic recording (HAMR) drives are susceptible to temperature-induced mode jumps, such as during the start of a write operation. During HAMR writing, the temperature of the laser diode may increase (e.g., by 10°C to 20°C), and may cross several mode jump critical temperatures during this temperature transient. In some cases, one or more mode jump events may be triggered during this transient phase, which may adversely affect write performance. For example, mode jump events during a HAMR write operation may result in non-uniformities in the recording, which degrades HAMR recording performance. Broadly speaking, aspects of the present disclosure relate to preventing or reducing mode jumps, which helps to enhance HAMR recording performance. In some embodiments, preheating the laser diode cavity to a target temperature (i.e., the nominal temperature used during the write operation) can help eliminate or minimize temperature transients, as described in further detail below.

[0048] When the disk rotates under the slider of the hard disk drive (HDD), the slider 103 is said to "fly" above the disk. In some cases, a thermal flying height control (TFC) device (e.g., a heater element) may be disposed within a slider (e.g., slider 103, slider 303) to distort the slider near the read and write transducer (or element), which reduces the flying height of the read and write transducer. In some examples, the read and write element or transducer resides in the slider of the HDD. In some cases, the disk drive may include a flying height control circuit 106 that interfaces with a flying height component in the slider. Thermal flying height control (TFC) is a prior art control technology that uses a heater element (not shown) disposed in the slider. The flying height can be adjusted by heating the slider with a heater. The current supplied to the heater by the flying height control circuit 106 generates heat to thermally expand the slider and adjust the flying height. In addition to the heater, the flying height component 109 may also include other elements. In some cases, the relative temperature at the air bearing surface (ABS) can be used to estimate the resistance R of a resistive thermal detector (RTD) such as an embedded contact sensor (ECS) or a near-field temperature sensor (NTS). RTD. In general, the resistance of a material can be expressed as a function of its intrinsic resistance and its dimension (e.g., length, width, thickness, or height). The fly height control system may also include a near-field temperature sensor (NTS) 108 located in the slider and an associated NTS control circuit 107 located in the arm electronics (AE) 102.

[0049] like Figure 1B As shown, a disk drive 100 according to various aspects of the present disclosure includes a system on a chip (SOC) 101, wherein the SOC 101 includes electronics and firmware for the drive and is used to control the functions of the drive, including providing power and / or control signals to components shown in the AE chip 102. Each disk (in Figure 2B 16A to 16D) may have thin film magnetic material on each flat surface. Each recording surface may include a pair of dedicated read and write heads enclosed in a slider 103, which is moved by an actuator (e.g., Figure 2B 104 and 105. The SOC 101 is shown as an actuator assembly 19 (shown in FIG. 104 ) mechanically positioned above the rotating disk. In some examples, the actuator also provides electrical connections to the slider 103 component. The actuator assembly 19 may also include an arm electronics (AE) chip 102, and the AE 102 includes a preamplifier 104 (e.g., a read or write preamplifier) ​​for a head (e.g., a read head 111, a write head 110), a write driver 105, and a flying height control 106. In some examples, for example, when the disk drive employs heat-assisted magnetic recording (HAMR), the flying height control circuit 106 includes an NTS control circuit 107. It should be noted that according to various aspects, some of the components shown in the AE 102 may be implemented or partially implemented in the SOC 101.

[0050] As shown, a first connection (e.g., a flexible cable) 140-a connects the SOC 101 to the AE 102, while a second connection (e.g., a flexible cable) 140-b connects the AE 102 to the slider 103. The AE 102 typically includes digital and analog circuits that control signals transmitted to components in the slider 103 and process signals received from the slider 103 components. The AE 102 may include registers that are set using serial data from the SOC 101 to provide parameters for the AE function. The write driver 105 generates an analog signal that is applied to an inductive coil in the write head 110 to write data by selectively magnetizing portions of the magnetic material on the surface of the rotating disk 16.

[0051] As shown, slider 103 includes a write head 110 configured to write data to the disk, a read head 111 configured to read data from the disk, a flying height component 109 (as described above) configured to adjust the flying height of the slider, and a resistance temperature detector (RTD) (such as NTS108) for sensing the temperature near the air bearing surface (ABS). It should be noted that ABS is generally used to describe the surface of the slider facing the disk, wherein the disk drive may be filled with a gas other than air (e.g., a gas containing helium, hydrogen, to name just two non-limiting examples), and the use of the "ABS" term to describe various aspects of the present disclosure is not intended to limit the present disclosure to air-filled drives. In some cases, NTS108 is positioned close to ABS and write head 110 (or alternatively, read head 111). NTS108 facilitates detection of the temperature generated by the slider approaching the disk or medium. In various embodiments, NTS108 may include a thermal strip (e.g., a metal or semiconductor strip) located on slider 103.

[0052] In some cases, the HAMR recording head (e.g., write head 110) also includes an optical component that guides light from the laser to the disk. During recording, the write element applies a magnetic field to the heated portion of the storage medium or disk, where the heat reduces the magnetic coercivity of the medium, thereby allowing the applied field to change the magnetic orientation of the heated portion. The magnetic orientation of the heated portion determines whether one or zero is recorded. Therefore, by changing the magnetic field applied to the magnetic recording medium as it moves, data can be encoded onto the medium. The HAMR drive uses a laser diode (LD) to heat the medium to assist the recording process. In some cases, the laser diode is disposed within the laser diode cavity and is close to the HAMR read / write element, where one end of the read / write element is on the ABS of the slider 103. During operation of the HDD, the ABS faces the moving medium surface and remains close to the moving medium surface.

[0053] Laser diode (in Figure 4 403) provides optical-based energy to, for example, heat the surface of the media at a point near the read / write element. In some cases, an optical path component such as a waveguide 401 is integrally formed within the slider 402 to deliver light from the laser diode 403 to the media. For example, Figure 4As shown, the waveguide 401 and the near field transducer (NFT) 404 may be positioned close to the writing element 444 to provide local heating to the medium during the writing operation. In some cases, when the energy generated by the LD 403 is delivered to the magnetic recording medium or disk 16, various components (e.g., the writing element 444, the NFT 404, the LD 403, etc.) may experience significant heating due to the inefficiency of light absorption and electrical to optical energy conversion. In some cases, such as during the start of the writing operation, the temperature of the LD undergoes significant changes, resulting in a shift in the laser emission wavelength. This in turn results in a change in the optical feedback from the optical path in the slider 402 to the LD cavity, resulting in a mode jump (i.e., power instability) of the LD 403. Mode jumps can degrade the performance of the HAMR drive because mode jumps cause shifts / jumps in the laser output power and magnetic transition shifts between data blocks. Large transition shifts in data blocks can increase errors, thereby degrading disk drive performance.

[0054] Now turn to Figure 3 , which illustrates a conceptual graph 300 of laser wavelength 331 (on the vertical axis or y-axis 332) versus temperature transient 333 (on the horizontal axis or x-axis 334) according to various aspects of the present disclosure. Specifically, Figure 3 Depicted is a conceptual graph showing how a laser "mode hops" when the temperature changes transiently. Figure 3 As shown, when the temperature transient is equal to the mode hopping critical temperature, the laser can suddenly switch from operating in one resonator mode (e.g., generating energy having a first wavelength) to operating in another mode (e.g., generating energy having a second, different wavelength). The laser then operates in the new resonator mode (e.g., generating energy having a second wavelength) before switching to a different resonator mode (e.g., generating energy having a third wavelength) to obtain a series of temperature transients.

[0055] Aspects of the present disclosure are directed to eliminating or minimizing temperature transients by preheating the laser diode cavity to a target temperature (ie, the temperature used during write operations), which helps prevent mode hopping and enhances HAMR recording performance.

[0056] Now turn to Figure 2A and Figure 2B , which illustrates a conceptual block diagram of top and side views of a data storage device in the form of a disk drive 15 according to aspects of the present disclosure. The disk drive 15 includes a control circuit 22, an actuator assembly 19, and a plurality of hard disks 16A, 16B, 16C, 16D ("hard disks 16", "disks 16"). Figure 2CA flow chart depicting an example method 80 that the control circuitry 22 of the disk drive 15 according to aspects of the present disclosure may implement or perform in controlling the operation of the disk drive 15, including the operation of the heads 18 (e.g., heads 18A-18H) disposed on the actuator assembly 19, as further described below. Thus, the actuator assembly 19 includes the heads 18 and is configured to position one or more heads 18 over the disk surfaces 17 of one or more disks 16. The heads 18 may each include write and read elements that are configured to write control features and data to and read control features and data from the corresponding disk surfaces 17 of the hard disk 16.

[0057] The actuator assembly 19 includes a main actuator 20 (e.g., a voice coil motor ("VCM")) and a plurality of actuator arms 40 (e.g., a topmost actuator arm 40A, such as Figure 2A and Figure 2B Each of the actuator arms 40 includes a magnetic head 18 at its distal end (e.g., at Figure 2A and Figure 2B 18A is included in the topmost actuator arm 40A). Each of the actuator arms 40 is configured to suspend one of the heads 18 in close proximity above the corresponding disk surface 17 (e.g., head 18A is suspended by the topmost actuator arm 40A above the corresponding topmost disk surface 17A, and head 18H is suspended by the bottommost actuator arm 40H above the corresponding bottommost disk surface 17H). Various examples may include, for example, a wide variety of other numbers of hard disks and disk surfaces, in addition to Figure 2A and Figure 2B Any of a number of actuator arm assemblies and main actuators other than one actuator assembly 19 and one main actuator 20 in the example of FIG. 1 , and a number of other fine actuators on each actuator arm.

[0058] Figure 2A Also depicted are servo sectors 32 (e.g., servo sectors 321 through 322) written to disk surface 17. N). In some cases, when the disk drive is manufactured, servo sectors 32 may be written to the disk surface 17 to define a plurality of evenly spaced concentric tracks 34. As an example, each servo sector 32 may include a phase locked loop (PLL) field, a servo synchronization mark (SSM) field, a track identification (TKID) field, a sector ID, and a set of servo pulses (e.g., an alternating pattern of magnetic transitions) that are sampled by a servo system of the disk drive to align a movable transducer head (e.g., disk head 18) with and relative to a particular track 34. Each circumferential track 34 includes a plurality of embedded servo sectors 32 for track seeking and track tracking. The plurality of servo sectors 32 are sequentially spaced around the circumference of the circumferential track 34 and extend radially outward from the inner diameter (ID) of the disk surface 17. These embedded servo sectors 32 contain servo information for track seeking and track tracking and are interspersed between data areas on the disk surface 17. Conventionally, data is written in a data area in the form of a plurality of discrete data sector areas. Each data region is typically followed by a servo sector 32. Host 25 may be a computing device such as a desktop computer, a laptop, a server, a mobile computing device (e.g., a smart phone, a tablet, a netbook, to name a few non-limiting examples), or any other suitable computing device. Alternatively, host 25 may be a test computer that performs calibration and testing functions as part of the disk drive manufacturing process.

[0059] In some examples, the control circuit 22 is configured to control actuation of a main actuator (i.e., a VCM). In addition, the VCM is configured to actuate a magnetic head 18 above a disk surface 17. In some examples (80), the control circuit 22 is further configured to: generate a reverse bias voltage (82); apply a reverse bias voltage to at least one laser diode of a data storage device through a preamplifier to preheat at least one laser diode cavity to a target temperature before a write operation on one or more disks, wherein each of the at least one laser diode is positioned inside a corresponding laser diode cavity (84); control the preamplifier to transition from applying a reverse bias voltage to applying a forward bias voltage to at least one laser diode (86); and start a write operation, wherein the write operation includes writing data to one or more disks of the data storage device or rewriting data on the one or more disks (88).

[0060] exist Figure 2AIn an embodiment of the present invention, the control circuit 22 may also process the read signal 36 sent from the head 18 to demodulate the servo data (e.g., servo sector 32) written on the disk to generate a position error signal (PES) representing the error between the actual position of the head and the target position relative to the target track. The control circuit 22 may use a suitable servo control system to process the PES to generate a control signal 38 (e.g., a VCM control signal) that is applied to the VCM 20 to rotate the actuator arm 40 about the pivot so as to actuate the head 18 radially over the disk surface 17 in a direction that reduces the PES. In one embodiment, the disk drive may also include a suitable microactuator, such as a suitable piezoelectric (PZT) element, for actuating the head 18 relative to the suspension, or for actuating the suspension relative to the actuator arm 40.

[0061] In one embodiment, servo data (e.g., servo sectors 32) read from the disk surface 17, i.e., for servoing the head over the disk during an access operation, can be self-written to the disk using the control circuit 22 inside the disk drive. In some examples, a plurality of spiral servo tracks are first written to the disk surface 17, and then the servo sectors 32 are written to the disk while servoing on the spiral servo tracks. To write the spiral servo tracks to the disk surface 17, at least one pilot spiral track is first written to the disk without using position feedback from the servo data (i.e., the actuator or VCM 20 is controlled in an open loop manner relative to the servo data on the disk). Prior to writing the pilot spiral track, a feed-forward compensation is generated by evaluating the BEMF voltage generated by the VCM 20 during a calibration seek (where the BEMF voltage represents an estimated velocity of the VCM). The pilot spiral track is then written to the disk using the feed-forward compensation. In some embodiments, the BEMF voltage representing the velocity of the VCM 20 may be sampled at any suitable sampling rate so that the feed-forward compensation is updated at any suitable frequency during a seek operation.

[0062] Figure 4A block diagram 400 showing a waveguide (WG) 401, a laser diode (LD) 403, a disk 16, a near field transducer (NFT) 404, and a slider 402 of a data storage device according to various aspects of the present disclosure is illustrated. As shown, the WG 401 and the NFT 404 are positioned close to the writing element 444 to provide local heating to the medium (i.e., the disk 16) during the writing operation. In some cases, the LD 403 generates light energy (e.g., having a wavelength between 700nm and 900nm) that is delivered to the magnetic recording medium or the disk 16. In some examples, the LD 403 may be preheated before the writing operation begins by applying a reverse bias (or negative voltage) to the LD 403. When the reverse bias is applied, the LD 403 may not emit laser light. In such cases, data writing, rewriting, and / or erasing does not occur. In this way, when the reverse bias is applied to the LD 403, the laser cavity in which the LD 403 is located is preheated. In order to start writing (or rewriting) data on disk 16, the bias voltage applied to LD 403 is switched from reverse bias to forward bias. In some cases, the temperature of LD 403 is configured to remain the same or substantially the same when the bias voltage is switched to forward bias, which helps to minimize temperature transients compared to the prior art. In some aspects, applying a reverse bias to LD 403 before starting a write operation to preheat it promotes enhanced control of LD steady-state temperature, which helps to avoid mode jumps associated with temperature transients at or near the start of a write operation. In some cases, LD403 is maintained in a preheated state before actually starting a write operation, which helps to minimize or reduce the laser opening transition time.

[0063] In some embodiments, the joule power dissipation selected for the reverse bias condition can be based on the expected joule power dissipation under forward bias conditions. For example, the reverse bias joule power is selected based on the IV characteristics of LD 403 and the forward bias or operating joule power, as described below with respect to Figure 6 described.

[0064] Figure 6 An example of an IV curve 600 for a laser diode such as LD 403 is illustrated in accordance with various aspects of the present disclosure. Specifically, but not limited to, Figure 6The IV curve 600 in FIG. 1 depicts an example of a method for selecting a joule power for preheating a laser diode (i.e., when the laser diode is in a reverse bias condition). As shown, in some embodiments, a reverse bias joule power 612 is selected based on an operating joule power 610 (i.e., an expected joule power when a forward bias is applied to the laser diode). Here, the reverse bias joule power 612, which can be calculated as the product of the reverse bias voltage and the reverse bias current, is equal to the operating joule power 610. Since the reverse bias voltage is equal to the avalanche or breakdown voltage of the LD, the reverse bias current can be calculated based on the reverse joule power 612 and the breakdown voltage (e.g., -10V, -15V, etc.).

[0065] When in the forward bias mode, the thermal signal (e.g., from the ECS, NFT that senses thermal changes) and the optical signal (e.g., from the laser diode or photodiode) increase after exceeding the threshold current. Additionally, when in the reverse bias mode, as expected, only the thermal signal increases beyond the breakdown voltage of the laser diode (and not the optical signal). In some cases, when in the reverse bias mode, the current and power of the laser diode are controlled so that the maximum threshold current and power are not exceeded (i.e., the same as the maximum threshold current and power specified for the forward bias mode), which helps prevent the laser diode from being damaged and / or degraded in the reverse bias mode.

[0066] Figure 7 7 is a block diagram 700 showing some example components that may be used to implement reverse bias control of a laser diode of a HAMR data storage device according to various aspects of the present disclosure. As shown, Figure 7 The control circuit 22 including the SOC controller 741, the preamplifier 750 having one or more LD drivers 761 (e.g., LD driver 761-a, LD driver 761-b), one or more laser diodes 703 (e.g., laser diode 703-a, laser diode 703-b), and one or more switches (e.g., shown as reverse bias switch 777, write switch 778). In some embodiments, the preamplifier 750 further includes an optional preamplification logic control module 743 electronically and / or communicatively coupled to the SOC controller 741.

[0067] In some cases, the control circuit 22 may be configured to generate a negative voltage 779 for applying a reverse bias to the laser diode 703. A reverse bias switch 777 connected in series with the corresponding laser diode may be closed to enable a negative voltage 779 to be applied to the LD 703. As noted above, when the laser diode 703 is in a reverse bias state, it generates heat but does not emit laser light, which prevents data writing, rewriting or erasing on the magnetic recording medium. In this way, the laser diode cavity (in which the laser diode is disposed) is preheated, which helps to minimize temperature transients at or near the beginning of a write operation. In some cases, the control circuit 22 (or alternatively, the SOC controller 741) determines to which head (not shown) the reverse bias voltage is applied. In some embodiments, the preamplifier 750 includes one or more internal multiplexers (mux) to isolate the laser diode 703 in a reverse bias mode. Once the laser diode and the laser diode cavity are preheated, the laser diode bias is switched from a reverse bias condition to a forward bias condition. In one non-limiting example, the control circuit 22 opens the reverse bias switch 777 coupled to the corresponding laser diode in the laser diode 703. In addition, a forward bias (shown as a laser bias) is applied, and the write switch 778 connected in series with the driver 761 is closed, which causes the forward current (I LD ) flows through the laser diode 703.

[0068] In some embodiments, the laser diode 703 is switched from the reverse bias condition to a low power laser condition (e.g., forward bias power below a threshold to prevent data writing) for a brief duration before switching to a final operating mode (or final forward bias operating power), which facilitates a fast turn-on characteristic of the laser diode 703. That is, rather than switching directly from 100% reverse bias power to 100% forward bias power, a brief intermediate duration (e.g., a few nanoseconds) can be provided where the laser diode 703 is operated using a low power laser emission condition.

[0069] Figure 5AA conceptual graph 500-a of a normalized temperature 515 of a LD cavity (on a vertical axis or y-axis 502) versus time 510 (on a horizontal axis or x-axis 501) according to various aspects of the present disclosure is illustrated. As shown, when a forward bias is applied at or near the beginning of a write operation, the normalized temperature 515 of the LD cavity undergoes a sharp / exponential increase. After this exponential portion, the normalized temperature curve increases in a linear manner before the normalized temperature reaches a steady-state value. In some cases, the steady-state temperature is the nominal / operating temperature of the laser diode when forward biased during the write operation. Various aspects of the present disclosure are directed to preheating a laser diode cavity by applying a negative voltage (or reverse bias) to the laser diode so that the temperature of the LD cavity (or LD) is at or near the steady-state temperature before the write operation begins. In this way, unwanted LD cavity temperature transients (i.e., by Figure 5A 5 (shown in the exponential and linear increasing portions of graph 500 in FIG. 5 ), which also helps avoid mode hopping associated with temperature transients at the start of writing.

[0070] In some examples, the present disclosure may also support a "boost" or "overshoot" mode of operation, which further helps reduce LD cavity warm-up time, as described below with respect to Figure 5B described.

[0071] Figure 5B A conceptual graph 500-b of LD power 575 (on a vertical axis or y-axis 502) versus time 510 (on a horizontal axis or x-axis 501) according to various aspects of the present disclosure is illustrated. Graph 500-b depicts forward bias LD power 569 corresponding to LD steady-state temperature during a write phase (or write operation). In some examples, setting the reverse bias LD power to reverse bias LD power 565-a results in a desired LD steady-state temperature at the beginning of the write phase. In some cases, reverse bias LD power 565-a (e.g., at Figure 6 565-b) is selected to be similar or substantially similar in magnitude to the forward bias LD power 569 (e.g., also shown as operating joule power 610). In some cases, an overshoot (or boosted) LD reverse bias power (shown as reverse bias LD power 565-b) may be applied to the LD during the preheat phase to reduce the preheat time, as further described below.

[0072] According to aspects of the present disclosure, the warm-up time can be reduced by selecting a higher joule power for the reverse bias condition (shown by reverse bias LD power 565-b). Specifically, reverse bias LD power 565-b corresponds to a higher reverse bias joule power compared to reverse bias LD power 565-a. Figure 5BAs shown, reverse bias LD power 565-a is applied during a first preheating time 540-a, wherein the preheating time corresponds to the time required for the LD cavity to reach the desired steady-state temperature. In other words, the first preheating time 540-a corresponds to the amount of time that the LD spends under reverse bias conditions in order to ensure that it reaches the LD steady-state temperature of the writing phase. In addition, reverse bias LD power 565-b is applied during a second preheating time 540-b, wherein the duration of the preheating time 540-b is shorter than the duration of the preheating time 540-a. That is, reverse bias LD power 565-b is used to reduce the preheating time to reach the same laser diode steady-state temperature as the laser diode steady-state temperature reached by applying reverse bias LD power 565-a for a longer duration (i.e., preheating time 540-a).

[0073] Any suitable control circuit may be used (e.g. Figure 2A The flowcharts in the above examples may be implemented using control circuitry 22 in the read channel integrated circuit, such as any one or more suitable integrated circuits. For example, the control circuit may be implemented within a read channel integrated circuit, or in a component separate from the read channel, such as a data storage controller, or some of the operations described above may be performed by the read channel while other operations may be performed by the data storage controller. In one example, the read channel and the data storage controller are implemented as separate integrated circuits, and in another example, they are fabricated into a single integrated circuit or system on a chip (SOC), such as Figure 1B SOC 101 in Figure 7 In addition, the control circuit 22 may include a preamplifier circuit such as Figure 1B The preamplifier 104 and / or Figure 7 The preamplifier 750 in the embodiment of the present invention is implemented as a separate integrated circuit, integrated into a read channel or data storage controller circuit, or integrated into a SOC.

[0074] In some examples, control circuitry (such as, but not limited to, control circuitry 22) includes a microprocessor that executes instructions that are operable to cause the microprocessor to perform the flowcharts described herein (e.g., Figure 2C). The instructions may be stored in any computer-readable medium. In some examples, the instructions may be stored on a non-volatile semiconductor memory device, component, or system external to the microprocessor or integrated with the microprocessor in the SoC. In some examples, the instructions are stored on a disk and are read into the volatile semiconductor memory when the disk drive is powered on. In some examples, the control circuit includes suitable logic circuits, such as state machine circuits. In some examples, at least some of the flowchart blocks may be implemented using analog circuits (e.g., analog comparators, timers, etc.), and in other examples, at least some of the blocks may be implemented using digital circuits or a combination of analog and digital circuits.

[0075] In various examples, one or more processing devices may include or constitute the control circuit 22 as described herein, and / or may perform one or more of the functions of the control circuit as described herein. In various examples, the control circuit 22 or other one or more processing devices that perform one or more of the functions of the control circuit as described herein may be abstracted from being physically close to the disk and disk surface. In various examples, the control circuit or other one or more processing devices that perform one or more of the functions of the control circuit as described herein may be part of or close to a rack or single product including multiple data storage devices, or may be part of or close to one or more physical or virtual servers, or may be part of or close to one or more local area networks or one or more storage area networks, or may be part of or close to a data center, or may be hosted in one or more cloud services.

[0076] In various examples, a disk drive, such as disk drive 15, may include a magnetic disk drive, an optical disk drive, a hybrid disk drive, or other types of disk drives. Additionally, some examples may include electronic devices, such as computing devices, data server devices, media content storage devices, or other devices, components, or systems that may include storage media and / or control circuits as described above.

[0077] The various features and processes described above may be used independently of one another, or may be combined in various ways. All possible combinations and sub-combinations are intended to fall within the scope of the present disclosure. In addition, certain methods, events, or process blocks may be omitted in some specific implementations. The methods and processes described herein are also not limited to any particular order, and the blocks or states associated therewith may be performed in other orders. For example, the tasks or events described may be performed in an order different from that specifically disclosed, or a plurality may be combined in a single block or state. Exemplary tasks or events may be performed serially, in parallel, or in another manner. Tasks or events may be added to or deleted from the disclosed examples. The exemplary systems and components described herein may be configured differently from those described. For example, elements may be added, deleted, or rearranged compared to the disclosed examples.

[0078] Although certain exemplary embodiments are described herein, these embodiments are presented only as examples and do not limit the scope of the invention disclosed herein. Therefore, nothing in the foregoing description implies that any particular feature, characteristic, step, module or block is necessary or indispensable. The novel methods and systems described herein may be embodied in various other forms. Various omissions, substitutions and changes may be made to the form of the methods and systems described herein without departing from the spirit and scope of the present disclosure.

[0079] Method 80 and other methods of the present disclosure may include other steps or variations in various other embodiments. Part or all of any method 80 may be implemented or embodied in hardware, and / or implemented or executed by a controller, CPU, field programmable gate array (FPGA), SOC, multi-processor system on chip (MPSOC) (which may include both CPU and FPGA, as well as other elements together in an integrated SOC), or other processing device or computing device that processes executable instructions to control other associated hardware, devices, systems or products when executing, implementing or embodying the various themes of the method.

[0080] Thus, data storage systems, devices, and methods are shown and described in various basic aspects and in various selected illustrative applications, architectures, techniques, and methods, and other aspects of the present disclosure, which are used to preheat laser diodes and / or laser diode cavities for data storage devices (such as HAMR drivers). From this disclosure, those skilled in the relevant art will have a full understanding and be able to put into practice with knowledge the further applications, architectures, techniques, and methods covered by the present disclosure and the claims set forth below, and other aspects of the present disclosure.

[0081] As used herein, the expression "at least one of A, B, and C" is intended to mean "A, B, C, or any combination of A, B, and C". The description of the disclosed examples is provided to enable any person skilled in the relevant art to understand how to make or use the subject matter of the present disclosure. Various modifications to these embodiments will be apparent to those skilled in the art based on the present disclosure, and the general principles defined herein may be applied to other examples without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure is not limited to the embodiments shown herein, but should be given the widest scope consistent with the principles and novel features disclosed herein.

[0082] The present disclosure and its many attendant advantages will be understood from the foregoing description, and various changes may be made in the form, construction, and arrangement of parts without departing from the disclosed subject matter or without sacrificing all of its substantial advantages. The forms described are illustrative only, and the appended claims encompass and include a wide range of embodiments, including examples of a wide range of any such changes in the form, construction, and arrangement of parts as described herein.

[0083] Although the present disclosure has been described with reference to various examples, it should be understood that these examples are illustrative and the scope of the present disclosure is not limited thereto. All themes described herein are presented in the form of illustrative, non-limiting examples, and are not presented as exclusive specific implementations, whether or not they are explicitly pointed out as described examples. Within the scope of the examples of the present disclosure, many changes, modifications and additions are possible. More generally, examples according to the present disclosure have been described in the context of specific specific implementations. Without departing from the essence and scope of the present disclosure and the appended claims, functions can be separated or combined in blocks in different ways in various examples of the present disclosure, or the functions can be described in different terms. These and other changes, modifications, additions and improvements may fall within the scope of the present disclosure as defined by the appended claims.

Claims

1. A data storage device, comprising: one or more disks; an actuator arm assembly including one or more magnetic recording heads; at least one laser diode, each laser diode of the at least one laser diode being positioned within a corresponding laser diode cavity; Preamplifier; and One or more processing devices, the one or more processing devices being configured to: generating a reverse bias voltage; applying the reverse bias voltage to the at least one laser diode using the preamplifier to preheat the corresponding laser diode cavity to a target temperature prior to a write operation; controlling a transition of the preamplifier from applying the reverse bias voltage to the at least one laser diode to applying a forward bias voltage to the at least one laser diode; as well as A magnetic recording head corresponding to the at least one laser diode is activated to initiate the write operation.

2. The data storage device of claim 1, wherein the preamplifier further comprises a reverse bias power control circuit coupled to the at least one laser diode and configured to apply the reverse bias to the at least one laser diode.

3. The data storage device according to claim 1, wherein: When the reverse bias voltage is applied to the at least one laser diode, no laser light is emitted, When the reverse bias is applied to the at least one laser diode, no data writing or rewriting occurs, or The temperature of the corresponding laser diode cavity is configured to remain the same or substantially the same after controlling the transition from the reverse bias to the forward bias for the at least one laser diode.

4. The data storage device of claim 1, wherein each of the at least one laser diode dissipates a first power during the preheating period, and wherein each of the at least one laser diode dissipates a second power during the writing operation.

5. The data storage device according to claim 4, wherein: The first power is the same or substantially the same as the second power; or The first power is greater than the second power.

6. The data storage device of claim 1, wherein one or more mode jumps associated with temperature transients at or near the beginning of the write operation are avoided based at least in part on preheating a corresponding laser diode cavity to the target temperature.

7. The data storage device of claim 6, wherein the target temperature corresponds to a steady-state temperature associated with the write operation and when the at least one laser diode is in a lasing state.

8. The data storage device of claim 1 , wherein the one or more processing devices are further configured to: One or more of the at least one laser diode and the corresponding laser diode cavity are maintained in a preheated state such that a laser on transition time is kept below a threshold.

9. The data storage device of claim 1, wherein applying the reverse bias voltage comprises applying a negative voltage, and wherein a value of the negative voltage is maintained below an avalanche or breakdown voltage of the at least one laser diode.

10. A method of operating a data storage device, the method comprising: generating a reverse bias voltage; applying the reverse bias voltage to at least one laser diode of the data storage device through a preamplifier to preheat at least one laser diode cavity to a target temperature prior to a write operation on one or more disks, wherein each of the at least one laser diode is positioned inside a corresponding laser diode cavity; controlling a transition of the preamplifier from applying the reverse bias voltage to the at least one laser diode to applying a forward bias voltage to the at least one laser diode; as well as A magnetic recording head corresponding to the at least one laser diode is activated to initiate the write operation.

11. The method according to claim 10, wherein: When the reverse bias voltage is applied to the at least one laser diode, no laser light is emitted, When the reverse bias is applied to the at least one laser diode, no data writing or rewriting occurs, or The temperature of the corresponding laser diode cavity is configured to remain the same or substantially the same after controlling the transition from the reverse bias to the forward bias for the at least one laser diode.

12. The method according to claim 10, further comprising: selecting a first power, wherein the first power corresponds to the power dissipated by each of the at least one laser diode during the preheating period and when in a non-lasing state; and A second power is selected, wherein the second power corresponds to a power dissipated by each of the at least one laser diode during the write operation and when in a lasing state.

13. The method of claim 12, wherein one of the following: The first power is the same or substantially the same as the second power; or The first power is greater than the second power.

14. The method of claim 10, wherein one or more mode jumps associated with temperature transients at the beginning of the write operation are avoided based at least in part on preheating a corresponding laser diode cavity to the target temperature.

15. The method of claim 14, wherein the target temperature comprises a steady-state temperature associated with the write operation and when the at least one laser diode is in a lasing state.

16. The method according to claim 10, further comprising: One or more of the at least one laser diode and the corresponding laser diode cavity are maintained in a preheated state such that a laser on transition time is kept below a threshold.

17. The method of claim 10, wherein applying the reverse bias voltage comprises applying a negative voltage, and wherein a value of the negative voltage is maintained below an avalanche or breakdown voltage of the at least one laser diode.

18. The method of claim 10, wherein the preamplifier comprises a reverse bias power control circuit coupled to the at least one laser diode and configured to apply the reverse bias to the at least one laser diode, and wherein the preamplifier further comprises one or more multiplexers for isolating the at least one laser diode during application of the reverse bias.

19. One or more processing devices, the processing devices comprising: means for generating a reverse bias voltage; means for applying the reverse bias voltage to at least one laser diode of a data storage device to preheat at least one laser diode cavity to a target temperature prior to a write operation on one or more disks, wherein each of the at least one laser diode is positioned inside a corresponding laser diode cavity; means for controlling a transition from applying the reverse bias to the at least one laser diode to applying a forward bias to the at least one laser diode; and Means for activating a magnetic recording head corresponding to the at least one laser diode to initiate the writing operation.

20. The one or more processing devices of claim 19, wherein the data storage device comprises a heat-assisted magnetic recording (HAMR) data storage device, and wherein: When the reverse bias voltage is applied to the at least one laser diode, no laser light is emitted, When the reverse bias is applied to the at least one laser diode, no data writing or rewriting occurs, or The temperature of the corresponding laser diode cavity is configured to remain the same or substantially the same after controlling the transition from the reverse bias to the forward bias for the at least one laser diode.

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