Pseudorandom bit sequences are recorded to a heat-assisted recording medium at a laser power that is stepped while recording the pseudorandom bit sequences. The pseudorandom bit sequences are read from the heat-assisted recording medium to determine timing differences between bits written before and after the laser power is stepped. A thermal gradient of bits written to the heat-assisted recording medium is determined based on the timing differences.

A slider configured for heat-assisted magnetic recording comprises a magnetic writer, a near-field transducer, and an optical waveguide coupling the near-field transducer to a light source. The writer is situated proximate the near-field transducer at an air bearing surface of the slider and comprises a first return pole, a second return pole, and a write pole situated between and spaced apart from the first return pole and the second return pole. A structural element is situated at or near the air bearing surface between the write pole and one of the first and second return poles. The structural element comprises a cavity. A thermal sensor is disposed in the cavity. The thermal sensor is configured for sensing contact between the slider and a magnetic recording medium, asperities of the medium, and output optical power of the light source.

According to one embodiment, a system includes a head, where the head includes: an optical signal source configured to emit a first optical signal, and a near-field transducer (NFT) configured to focus the first optical signal on a moving ferroelectric storage medium positioned below the head. The system also includes a detector operatively coupled to the head, where the detector is configured to detect a second optical signal generated in and reflected from the ferroelectric storage medium, and where the second optical signal has twice the optical frequency as the first optical signal.

A recording head includes a waveguide configured to deliver light from a light source to a media-facing surface of the recording head. A near-field transducer is at the media-facing surface the proximate the waveguide. The near-field transducer includes a plasmonic structure with at least two opposing internal surfaces. A dielectric material fills a region between the at least two opposing internal surfaces. A dielectric slit extends between the at least two opposing internal surfaces. The dielectric slit is substantially parallel to the media-facing surface and includes a transparent material with a refractive index different than that of the dielectric material.

A recording head has a waveguide core with an input facet at an input surface. The waveguide core extends to a near-field transducer at a media-facing surface of the recording head. First and second cladding regions are co-planar with and on either cross-track side of the waveguide core. First and second pseudo-slab regions are co-planar with and on outer cross-track sides of the respective first and second cladding regions. The first and second pseudo-slab regions have an index of refraction higher than that of the first and second cladding regions. The first and second pseudo-slab regions confine and channel stray light away from the near-field transducer.

A recording head has a near-field transducer proximate a media-facing surface of the recording head. A waveguide core overlaps and delivers light from a light source to the near-field transducer. The waveguide core has a dielectric cavity proximate the near-field transducer. The cavity is filled with a cladding material and reduces optical feedback to the light source.

Devices having air bearing surfaces (ABS), the devices including a near field transducer (NFT) that includes a disc configured to convert photons incident thereon into plasmons; and a peg configured to couple plasmons coupled from the disc into an adjacent magnetic storage medium, wherein at least one of a portion of the peg, a portion of the disc, or a portion of both the peg and the disc include a multilayer structure including at least two layers including at least one layer of a first material and at least one layer of a second material, wherein the first material and the second material are not the same and wherein the first and the second materials independently include aluminum (Al), antimony (Sb), bismuth (Bi), boron (B), barium (Ba), calcium (Ca), cerium (Ce), chromium (Cr), cobalt (Co), copper (Cu), erbium (Er), gadolinium (Gd), gallium (Ga), germanium (Ge), gold (Au), hafnium (Hf), indium (In), iridium (Ir), iron (Fe), lanthanum (La), magnesium (Mg), manganese (Mn), molybdenum (Mo), nickel (Ni), niobium (Nb), osmium (Os), palladium (Pd), platinum (Pt), rhenium (Re), rhodium (Rh), ruthenium (Ru), scandium (Sc), silicon (Si), silver (Ag), strontium (Sr), tantalum (Ta), thorium (Th), tin (Sn), titanium (Ti), vanadium (V), tungsten (W), ytterbium (Yb), yttrium (Y), zirconium (Zr), or combinations thereof.

Data is written to data sectors of a heat-assisted magnetic recording (HAMR) medium using a laser of a HAMR head supplied with a sum of an operational current and a threshold current. A service current is supplied to the laser when the head is over servo sectors of the medium, such that a temperature of the medium at the servo sectors is greater than or equal to a temperature of the head when over the servo sectors.

The system and corresponding process includes a system for producing a mechanical image of original audio source media and a system for encoding the mechanical image information into a digital file. A processing system recovers the mechanical image information from the digital file at a receiving end. Audio processing is used to produce the original audio source material without the standard losses associated with digital encoding of audio material.

A folded lasing cavity comprises at least one bend. The folded lasing cavity is disposed on and configured to emit light along a substrate-parallel plane. An etched facet is on an emitting end of the folded lasing cavity and an etched mirror is on another end of the folding lasing cavity. An etched shaping mirror redirects light received from the etched facet in a direction normal to the substrate-parallel plane.