System and method for reading data recorded on ferroelectric storage medium by means of a near-field transducer
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.
1. A system, comprising:
a head, comprising:
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; and
a detector operatively coupled to the head, the detector being configured to detect a second optical signal generated in and reflected from the ferroelectric storage medium, the second optical signal having twice the optical frequency as the first optical signal.
2. The system as recited in claim 1 , wherein the NFT includes one or more materials and/or has a geometry configured to facilitate resonance with the first and second optical signals.
3. The system as recited in claim 2 , wherein an upper surface of the NFT includes a first material resonant with the first optical signal, and wherein a bottom surface of the NFT includes a second material resonant with the second optical signal.
4. The system as recited in claim 3 , wherein the first material includes gold, and wherein the second material includes silver.
5. The system as recited in claim 1 , wherein the first optical signal is red or infrared light.
6. The system as recited in claim 1 , wherein an optical electric field component of the first optical signal and/or the second optical signal is oriented perpendicular to an upper surface of the ferroelectric storage medium.
7. The system as recited in claim 1 , wherein the optical signal source is a pulsed laser.
8. The system as recited in claim 1 , wherein the head comprises at least one optical waveguide configured to direct the first optical signal from the optical signal source to the NFT.
9. The system as recited in claim 8 , wherein the head includes a ferroelectric reference layer configured to frequency double the first optical signal, thereby generating a reference optical signal at twice the optical frequency of the first optical signal.
10. The system as recited in claim 9 , wherein the ferroelectric reference layer comprises one or more ferroelectric materials selected from the group consisting of: LiNbO3, LiTaO3, BaTiO3, SrTiO3, KTiOPO4, PbTiO3, KH2PO4, β-BaB2O4, LiB3O5.
11. The system as recited in claim 9 , wherein the detector is configured to detect the sum of the reference optical signal and the second optical signal.
12. The system as recited in claim 9 , comprising at least one optical component operatively coupled to the head and positioned between the head and the detector, the optical component being configured to only allow the second optical signal and the reference optical signal to pass through to the detector.
13. The system as recited in claim 12 , wherein the optical component is selected from the group consisting of: an optical filter, an optical grating, and a selective directional coupler.
14. The system as recited in claim 9 , wherein the optical waveguide is configured to direct the reference optical signal generated in and reflected from the ferroelectric reference layer to the detector, and the second optical signal generated in and reflected from the ferroelectric storage medium to the detector.
15. The system as recited in claim 9 , wherein the head comprises a second optical waveguide configured to direct the reference optical signal generated in and reflected from the ferroelectric reference layer to the detector, and the second optical signal generated in and reflected from the ferroelectric storage medium to the detector.
16. The system as recited in claim 9 , comprising a processing device operatively coupled to the detector, the processing device configured to demodulate a phase of the second optical signal with respect to the reference optical signal.
17. The system as recited in claim 1 , comprising the ferroelectric storage medium, wherein the ferroelectric storage medium comprises: a substrate; an electrically conductive layer positioned above the substrate; and a ferroelectric layer positioned above the electrically conductive layer.
18. The system as recited in claim 17 , wherein the ferroelectric layer comprises one or more ferroelectric materials configured to configured to frequency double the first optical signal, thereby generating the second optical signal.
19. A ferroelectric data storage system, comprising:
at least one head as recited in claim 1 ;
a ferroelectric medium;
a drive mechanism for passing the ferroelectric medium over the at least one head; and
a controller electrically coupled to the at least one head for controlling operation of the at least one head.