Abstract:
An apparatus includes a slider body, a write element, and a laser chip. The write element is disposed on the slider body and is configured to apply a magnetic field to write data on a portion of a heat-assisted magnetic recording media in response to an energizing current. The laser chip has a laser diode with an active region configured to produce light. The laser diode adapted to inject the light to the proximate the read/write element. The laser chip additionally has a photodetector The photodetector is adapted to monitor light from the laser diode. The photodetector shares a same active region as the laser diode and the laser diode and photodetector are integrated together on the same laser chip.

Description:
SUMMARY 
     Examples described herein are directed to a monolithically integrated laser diode and photodetector apparatus and methods of use. The examples can be used with a heat-assisted magnetic recording device. In one embodiment, an apparatus includes a body, a write element, and a laser chip. The write element is disposed on the body and is configured to apply a magnetic field to write data on a portion of a heat-assisted magnetic recording media in response to an energizing current. The laser chip has a laser diode with an active region configured to produce light. The laser diode adapted to inject the light to the proximate the read/write element. The laser chip additionally has a photodetector. The photodetector is adapted to monitor light from the laser diode. The photodetector shares a same active region as the laser diode and the laser diode and photodetector are integrated together on the same laser chip. 
     In another embodiment, an apparatus includes a body, a write element, and a laser chip. The write element is disposed on the body and is configured to apply a magnetic field to write data on a portion of a heat-assisted magnetic recording media in response to an energizing current. The laser chip has segregated first and second contacts. The first contact is reverse biased as a detector and the second contact is forward biased as a laser diode. The detector is monolithically fabricated to have an active region that is continuous with an active region of the laser diode such that a first trench feature does not separate the active regions of the detector and laser diode. 
     In yet another embodiment a method is disclosed. The method includes providing a monolithically integrated laser chip having one contact reverse biased as a photodetector and a second contact forward biased as a laser diode, the photodetector having an active region that is continuous with an active region of the laser diode; generating laser light from the laser diode; coupling the laser light into an optical path having a distal end; directing a first portion of the laser light toward a near field transducer located at the distal end, the first portion of laser light exciting the near field transducer to surface plasmonic resonance; sensing the laser light to monitor an output power of the laser diode; and applying an energizing current to a write element to write data to a portion of a media. 
     These and other features and aspects of various embodiments may be understood in view of the following detailed discussion and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The discussion below makes reference to the following figures, wherein the same reference number may be used to identify the similar/same component in multiple figures. 
         FIG. 1  is a side view of a heat-assisted magnetic recording device with an integrated laser diode and photodetector according to an example embodiment; 
         FIG. 2A  is a cross-sectional view of a laser chip according to an exemplary embodiment; 
         FIG. 2B  is circuit diagram of one embodiment of a circuit that can be used with the laser chip of  FIG. 2A ; 
         FIG. 3  is a cross-sectional view of a particle emitting device and a laser chip according to another exemplary embodiment; 
         FIG. 4A  is a cross-sectional view of a laser chip according to another exemplary embodiment; and 
         FIG. 4B  are circuit diagrams of exemplary embodiments of circuits that can be used with the laser chip of  FIG. 2A . 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure is related to the use of a laser chip with a shared active region for both a laser diode and a photodetector. Such a laser chip can be used in a heat-assisted magnetic recording (HAMR) device among other applications. In one embodiment, the laser chip has segregated first and second contacts with the first contact reverse biased as the photodetector and the second contact forward biased as a laser diode. In one embodiment, the laser chip has a first feature that separates the first contact from the second contact without extending into the shared active region of the photodetector and laser diode. 
     In HAMR devices, also sometimes referred to as thermal-assisted magnetic recording (TAMR) devices, a magnetic recording medium (e.g., hard drive disk) is able to overcome superparamagnetic effects that limit the areal data density of typical magnetic media. In a HAMR recording device, information bits are recorded on a storage layer at elevated temperatures. The heated area in the storage layer determines the data bit dimension, and linear recording density is determined by the magnetic transitions between the data bits. 
     It can be useful to monitor the power of a light source, e.g., laser diode, used with the HAMR recording device. Embodiments discussed herein provide for both lasing and power monitoring of a laser diode used in the HAMR recording device. Current light collection arrangements for power monitoring have led to inefficiencies as photodiodes are located a distance from the energy source on a submount or other structure. This disclosure discusses using a laser chip with a monolithically fabricated laser diode and photodetector to allow power monitoring to be conducted in closer proximity to the laser light. This can increase the power monitor&#39;s light collection efficiency and reduces the overall submount and head size. 
     In a number of existing HAMR designs, a laser chip for the laser diode is manufactured separately from the slider that houses the read/write head. The laser can be physically attached to the slider, or attached elsewhere and optically coupled to the slider (e.g., via an optic fiber). The exemplary embodiment described in  FIG. 1  describes a configuration referred to herein as laser-on-slider (LOS) where the laser chip is physically attached to a submount and the submount is attached to the slider. However, other HAMR designs can utilize configurations where the laser chip is formed in or mounted directly on the slider in a configuration referred to as a laser-in-the-slider (LIS) or simply laser-in-slider. Similarly, the laser chip described herein enhances both surface emitting and edge emitting lasers. 
       FIG. 1  illustrates a side view of a HAMR apparatus  100  according to an example embodiment. The slider  102  is coupled to an arm  104  by way of a suspension  106  that allows some relative motion between the slider  102  and arm  104 . The slider  102  includes read/write transducers  108  at a trailing edge that are held proximate to a surface  110  of a magnetic recording medium, e.g., disk  112 . When the slider  102  is located over surface  110  of disk  112 , a flying height  114  is maintained between the slider  102  and the surface  110  by a downward force of arm  104 . This downward force is counterbalanced by an air cushion that exists between the surface  110  and a media facing surface  103  of the slider  102  when the disk  112  is rotating. It is desirable to maintain a predetermined slider flying height  114  over a range of disk rotational speeds during both reading and writing operations to ensure consistent performance. Heating from HAMR optical components can affect the flying height  114 . Example HAMR components that may induce these temperature changes include a laser chip  116 , NFT  118 , and waveguide  120 . 
     In the example embodiment of  FIG. 1 , HAMR apparatus  100  includes optical path components (e.g., waveguide  120 ) that direct light from the laser diode of the laser chip  116  to the recording medium (e.g., disk  112 ). The NFT  118  allows HAMR apparatus  100  to achieve tiny confined hot spots. In one embodiment, the NFT  118  is designed to reach local surface-plasmon at a designed light wavelength. Additionally, part of the field will tunnel into a storage medium and get absorbed, raising the temperature of the medium locally for recording. 
       FIG. 2A  illustrates an exemplary embodiment of the laser chip  116  from  FIG. 1 .  FIG. 2A  is a sectional view of the laser chip  116  that also schematically illustrates an exemplary electrode configuration with three terminals. In the exemplary embodiment, the laser chip  116  includes a laser diode  202  and a photodetector  204  monolithically integrated onto one laser chip. Laser chip  116  additionally includes a p-region  206 , an n-region  208 , a single active region  210 , a front facet  212 , and a rear facet  214 . The n-region  208  includes a n-contact  216  and semiconductor layers  218 . The p-region  206  includes p-contact  220  for the laser diode  202 , an p-contact  222  for the photodetector  204 , semiconductor layers  224  and a cladding  225 . 
     In the embodiment of  FIG. 2A , the laser diode  202  is fabricated on the same chip as the photodetector  204  in a manner such that an optical cavity  226  of the chip is uninterrupted and is used for both the laser diode  202  as well as the photodetector  204 . In the exemplary embodiment, laser diode  202  is forward biased with a connection to an anode terminal  228  at p-contact  220 . Photodetector  204  is reverse biased with a connection to cathode terminal  230  at p-contact  222 . The n-contact  216  for both laser diode  202  and photodetector  204  is connected to ground  232 . P-contacts  220  and  222  are segregated from one another by a feature  234  such as a trench/gap. Thus, feature  234  separates (i.e. interrupts) connection between p-contact  220  and p-contact  222 . 
     In  FIG. 2A , laser diode  202  and photodetector  204  share the same active region  210 , which is disposed between the p-region  206  and the n-region  208 . The active region  210  is continuous (i.e. uninterrupted) in extent. The feature  234  does not have sufficient height (i.e. depth in the direction measured by dimension H) to extend into and separate active region  210  or cladding  225 . Thus, the feature  234  does not have sufficient height to interfere with the quantum wells or impinge upon cladding  225 . However, in the exemplary embodiment the feature  234  does have sufficient height to extend through semiconductor layers  224  adjacent to cladding  225  Semiconductor layers  218  and  224  are disposed adjacent the active region  210 . The front facet  212  and the rear facet  214  are disposed on opposing ends of the laser chip  116 . 
     In one embodiment, the laser chip  116  comprises, for example, a semiconductor injection laser with a gallium arsenide, indium gallium arsenide, aluminum gallium arsenide active region  210 . In one embodiment, laser chip  116  has a total height H of 100 μmeters, a total width (dimension not shown in  FIG. 2A ) of 100 μmeters, and a total length L of between about 100 to 500 μmeters. In one embodiment, the feature  234  has a height of 0.1 to about 10 μmeters, a width that can match the width of contact (e.g., 3 to 10 μmeters), and a length of 0.1 to 10 μmeters. Thus, the first feature can have a height of between about 0.001 to about 0.1% of a total height H of the laser chip  116 . In some embodiments, the feature  234  can have a length of between about 0.0002 and about 0.1% of a total length L of the laser chip. A length of the photodetector  204  can be between 5% to 10% of a length of the laser diode  202 . Thus, the photodetector  204  comprises a smaller section of the laser chip  116  than the laser diode  202 . 
     The laser chip  116  may be fabricated using solid state batch processing on a larger wafer scale, and after processing the wafer may be diced or otherwise subdivided into a multitude of smaller devices, one of which is the laser chip  116 . The semiconductor layers  218  may be the diced portion of an initial crystalline wafer on which a plurality of thin layers  114  (e.g., layers whose thicknesses are on the order of about one micron or less) are grown, deposited, and/or patterned on a side of the wafer using, for example, photolithography and chemical, plasma, or other etching processes. Feature  234  can be created during an under bump metallization (UBM) process using lithography or etching, for example. Although shown in reference to a dual sided laser, the techniques disclosed herein are also applicable to a single sided laser. 
       FIG. 2B  shows a high level circuit diagram of one embodiment of a circuit  300  that can be used with the three terminal arrangement and laser chip  116  of  FIG. 2A . In  FIG. 2B , a low pass filter  302  is electrically connected to the photodetector  204  as well as a driver  304 . The driver  304 , such as a comparator, is provided (connected to bias  306 ) and is electrically connected to the photodetector  204 . The photodetector  204  and the laser diode  202  are electrically connected to ground  232 , as previously discussed. 
       FIG. 3  illustrates another exemplary embodiment of a laser chip  400 . Laser chip  400  is constructed and operates in a manner similar to laser chip  116  described in reference to  FIG. 2A . However, the embodiment of  FIG. 3 , additionally includes a device  402  capable of bombarding the surfaces  404  of feature  434  with particles such as ions or photons in order to increase the resistance along the surfaces  404 . Additionally, surfaces  404  can be treated with a combination of passivation of the top semiconductor layer and oxidation of the top electrode in the etched  234  region to increase the resistance therealong. These and other applicable processes should avoid introduction of defects to the cladding  225  and quantum wells of active region  210 . 
       FIG. 4A  illustrates another embodiment of a laser chip  500  that schematically illustrates an exemplary electrode configuration with four floating terminals. Laser chip  500  is constructed and operates in a manner similar to laser chip  116  described in reference to  FIG. 2A . However, in  FIG. 4A  both the n-contact and p-contact of the laser diode and photodetector are separated by first feature  534 A and second feature  534 B. In particular, n-contact is now separated into a n-contact  516 A for the laser diode  502  and a n-contact  516 B for the photodiode  504 . Thus, n-contacts  516 A and  516 B are segregated from one another by the second feature  534 B, which can comprise for example a trench/gap in the n-contact and other layers of the laser chip  500 . Similarly, the p-contact  520  for the laser diode  502  is segregated from the p-contact  522  of the photodiode  504  by the first feature  534 A. 
     In the exemplary embodiment of  FIG. 4A , laser diode  502  is forward biased with a connection to an anode terminal  550  at the p-contact  520  and a connection to a cathode terminal  552  at the n-contact  516 A. Photodetector  504  is reverse biased with a connection to a cathode terminal  554  at an p-contact  522  and a connection to an anode terminal  556  at the n-contact  516 B. 
     In  FIG. 4A , laser diode  502  and photodetector  504  share the same active region  510 , which is disposed between the p-region  506  and the n-region  508 . The active region  510  as well as the cladding  225  in the p-region  506  is continuous (i.e., uninterrupted) in extent. The features  534 A and  534 B do not have sufficient depth to extend into and separate active region  510  and/or cladding  225 . The features  534 A and  534 B do not interfere with the cladding or quantum wells of the laser chip  500 . 
       FIG. 4B  shows a high level circuit diagrams of embodiments of a circuits  600  and  602  that can be used with the floating four terminal arrangement and laser chip  500  of  FIG. 4A . As shown in the circuits  600  and  602 , the laser diode  502  and the photodetector  504  are independently driven by a current source  604  and a voltage bias  606 , respectively. The floating terminal arrangement described with reference to  FIGS. 4A and 4B  may be used in instances where a pulsed mode of operation is used in order to electrically isolate the laser diode  502  from the photodetector  504 . 
     The foregoing description of the example embodiments has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the embodiments to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. Any or all features of the disclosed embodiments can be applied individually or in any combination are not meant to be limiting, but purely illustrative. It is intended that the scope of the invention be limited not with this detailed description, but rather determined by the claims appended hereto.