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Observation of spin Hall effect in photon tunneling via weak measurements.

Zhou X, Ling X, Zhang Z, Luo H, Wen S - Sci Rep (2014)

Bottom Line: Photonic spin Hall effect (SHE) manifesting itself as spin-dependent splitting escapes detection in previous photon tunneling experiments due to the fact that the induced beam centroid shift is restricted to a fraction of wavelength.This photonic SHE is attributed to spin-redirection Berry phase which can be described as a consequence of the spin-orbit coupling.These findings provide new insight into photon tunneling effect and thereby offer the possibility of developing spin-based nanophotonic applications.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Spin Photonics, School of Physics and Electronics, Hunan University, Changsha 410082, China.

ABSTRACT
Photonic spin Hall effect (SHE) manifesting itself as spin-dependent splitting escapes detection in previous photon tunneling experiments due to the fact that the induced beam centroid shift is restricted to a fraction of wavelength. In this work, we report on the first observation of this tiny effect in photon tunneling via weak measurements based on preselection and postselection technique on the spin states. We find that the spin-dependent splitting is even larger than the potential barrier thickness when spin-polarized photons tunneling through a potential barrier. This photonic SHE is attributed to spin-redirection Berry phase which can be described as a consequence of the spin-orbit coupling. These findings provide new insight into photon tunneling effect and thereby offer the possibility of developing spin-based nanophotonic applications.

No MeSH data available.


(a) Experimental setup: The tunneling potential barrier structure is composed of two right angle BK7 prisms (refractive index n = 1.515 at 632.8 mm) embed with Au film. HWP, half-wave plate (for adjusting the intensity). L1 and L2, lenses with effective focal length 50 mm and 250 mm, respectively. P1 and P2, Glan Laser polarizers. CCD, charge-coupled device (Coherent LaserCam-HR). The light source is a 21 mW linearly polarized He-Ne laser at 632.8 nm (Thorlabs HNL210L-EC). The inset describes the preselection and postselection with P1 and P2, respectively. (b) A weak measurement with preselection and postselection. System is preselected in state /ψ1〉. The weak interaction correlates the meter with the eigenstates of the measured observable Â. A postselection on the system in state /ψ2〉 gives rise to an interference in the meter, shifting it to its final position proportional to Aw.
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f2: (a) Experimental setup: The tunneling potential barrier structure is composed of two right angle BK7 prisms (refractive index n = 1.515 at 632.8 mm) embed with Au film. HWP, half-wave plate (for adjusting the intensity). L1 and L2, lenses with effective focal length 50 mm and 250 mm, respectively. P1 and P2, Glan Laser polarizers. CCD, charge-coupled device (Coherent LaserCam-HR). The light source is a 21 mW linearly polarized He-Ne laser at 632.8 nm (Thorlabs HNL210L-EC). The inset describes the preselection and postselection with P1 and P2, respectively. (b) A weak measurement with preselection and postselection. System is preselected in state /ψ1〉. The weak interaction correlates the meter with the eigenstates of the measured observable Â. A postselection on the system in state /ψ2〉 gives rise to an interference in the meter, shifting it to its final position proportional to Aw.

Mentions: Our experimental setup is schematically shown in Fig. 2(a). We construct a three-layer structure which consists of an Au film and two 45° BK7 right angle prisms. When photons enter the potential barrier structure, the photonic SHE happens allowing for the spin-dependent splitting in the transverse direction. The amplified effect can be obtained through the preselection and postselection [Fig. 2(b)]. A Gauss beam generated by a He-Ne laser is firstly focused by a short-focal-length lens (L1). Then, we use the polarizer P1 to get the preselection state /ψ1〉 = /H〉 or /V〉. Finally, the beam passes through the second polarizer P2 to obtain the postselection state /ψ2〉 = /V ± Δ〉 or /H ± Δ〉, with being the postselection angle. The two opposite spin components will undergo destructive interference at the surface of the second polarizer, which makes the amplified displacement in the meter much larger than the initial one. Remarkably, the free evolution of the light beam can also enhance the pointer shift due to the propagation amplification. We use a CCD to measure the total amplified displacement after a long-focal-length lens (L2).


Observation of spin Hall effect in photon tunneling via weak measurements.

Zhou X, Ling X, Zhang Z, Luo H, Wen S - Sci Rep (2014)

(a) Experimental setup: The tunneling potential barrier structure is composed of two right angle BK7 prisms (refractive index n = 1.515 at 632.8 mm) embed with Au film. HWP, half-wave plate (for adjusting the intensity). L1 and L2, lenses with effective focal length 50 mm and 250 mm, respectively. P1 and P2, Glan Laser polarizers. CCD, charge-coupled device (Coherent LaserCam-HR). The light source is a 21 mW linearly polarized He-Ne laser at 632.8 nm (Thorlabs HNL210L-EC). The inset describes the preselection and postselection with P1 and P2, respectively. (b) A weak measurement with preselection and postselection. System is preselected in state /ψ1〉. The weak interaction correlates the meter with the eigenstates of the measured observable Â. A postselection on the system in state /ψ2〉 gives rise to an interference in the meter, shifting it to its final position proportional to Aw.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4260228&req=5

f2: (a) Experimental setup: The tunneling potential barrier structure is composed of two right angle BK7 prisms (refractive index n = 1.515 at 632.8 mm) embed with Au film. HWP, half-wave plate (for adjusting the intensity). L1 and L2, lenses with effective focal length 50 mm and 250 mm, respectively. P1 and P2, Glan Laser polarizers. CCD, charge-coupled device (Coherent LaserCam-HR). The light source is a 21 mW linearly polarized He-Ne laser at 632.8 nm (Thorlabs HNL210L-EC). The inset describes the preselection and postselection with P1 and P2, respectively. (b) A weak measurement with preselection and postselection. System is preselected in state /ψ1〉. The weak interaction correlates the meter with the eigenstates of the measured observable Â. A postselection on the system in state /ψ2〉 gives rise to an interference in the meter, shifting it to its final position proportional to Aw.
Mentions: Our experimental setup is schematically shown in Fig. 2(a). We construct a three-layer structure which consists of an Au film and two 45° BK7 right angle prisms. When photons enter the potential barrier structure, the photonic SHE happens allowing for the spin-dependent splitting in the transverse direction. The amplified effect can be obtained through the preselection and postselection [Fig. 2(b)]. A Gauss beam generated by a He-Ne laser is firstly focused by a short-focal-length lens (L1). Then, we use the polarizer P1 to get the preselection state /ψ1〉 = /H〉 or /V〉. Finally, the beam passes through the second polarizer P2 to obtain the postselection state /ψ2〉 = /V ± Δ〉 or /H ± Δ〉, with being the postselection angle. The two opposite spin components will undergo destructive interference at the surface of the second polarizer, which makes the amplified displacement in the meter much larger than the initial one. Remarkably, the free evolution of the light beam can also enhance the pointer shift due to the propagation amplification. We use a CCD to measure the total amplified displacement after a long-focal-length lens (L2).

Bottom Line: Photonic spin Hall effect (SHE) manifesting itself as spin-dependent splitting escapes detection in previous photon tunneling experiments due to the fact that the induced beam centroid shift is restricted to a fraction of wavelength.This photonic SHE is attributed to spin-redirection Berry phase which can be described as a consequence of the spin-orbit coupling.These findings provide new insight into photon tunneling effect and thereby offer the possibility of developing spin-based nanophotonic applications.

View Article: PubMed Central - PubMed

Affiliation: Laboratory for Spin Photonics, School of Physics and Electronics, Hunan University, Changsha 410082, China.

ABSTRACT
Photonic spin Hall effect (SHE) manifesting itself as spin-dependent splitting escapes detection in previous photon tunneling experiments due to the fact that the induced beam centroid shift is restricted to a fraction of wavelength. In this work, we report on the first observation of this tiny effect in photon tunneling via weak measurements based on preselection and postselection technique on the spin states. We find that the spin-dependent splitting is even larger than the potential barrier thickness when spin-polarized photons tunneling through a potential barrier. This photonic SHE is attributed to spin-redirection Berry phase which can be described as a consequence of the spin-orbit coupling. These findings provide new insight into photon tunneling effect and thereby offer the possibility of developing spin-based nanophotonic applications.

No MeSH data available.