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Plasmonic-multimode-interference-based logic circuit with simple phase adjustment.

Ota M, Sumimura A, Fukuhara M, Ishii Y, Fukuda M - Sci Rep (2016)

Bottom Line: Also, simultaneous operations of XOR and AND gates are substantiated experimentally by combining 1 × 1 MMI based phase adjusters and 2 × 2 MMI based intensity modulators.An experimental on-off ratio of at least 4.3 dB is confirmed using scanning near-field optical microscopy.The proposed structure will contribute to high-density plasmonic circuits, fabricated by complementary MOS-compatible process or printing techniques.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi-shi, Aichi 441-8580, Japan.

ABSTRACT
All-optical logic circuits using surface plasmon polaritons have a potential for high-speed information processing with high-density integration beyond the diffraction limit of propagating light. However, a number of logic gates that can be cascaded is limited by complicated signal phase adjustment. In this study, we demonstrate a half-adder operation with simple phase adjustment using plasmonic multimode interference (MMI) devices, composed of dielectric stripes on a metal film, which can be fabricated by a complementary metal-oxide semiconductor (MOS)-compatible process. Also, simultaneous operations of XOR and AND gates are substantiated experimentally by combining 1 × 1 MMI based phase adjusters and 2 × 2 MMI based intensity modulators. An experimental on-off ratio of at least 4.3 dB is confirmed using scanning near-field optical microscopy. The proposed structure will contribute to high-density plasmonic circuits, fabricated by complementary MOS-compatible process or printing techniques.

No MeSH data available.


Simulated optical intensity distributions of the proposed half adder.(a–d) Optical distributions and output characteristics of “00”, “01”, “10”, “11” input states. Plasmonic signals interfered through the MMI structures, and half-adder operations were confirmed numerically. Upper parts of panels (a–d) are the output characteristics averaged over 1 μm and normalized with respect to the maximum value of AND “11” output.
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f2: Simulated optical intensity distributions of the proposed half adder.(a–d) Optical distributions and output characteristics of “00”, “01”, “10”, “11” input states. Plasmonic signals interfered through the MMI structures, and half-adder operations were confirmed numerically. Upper parts of panels (a–d) are the output characteristics averaged over 1 μm and normalized with respect to the maximum value of AND “11” output.

Mentions: We numerically simulated the SPP fields in the MMI patterns of the half adder and calculated the on-off ratio for the XOR and AND output using a 3D finite-difference time-domain (FDTD) method with electromagnetic wave analysis software (Fujitsu, Poynting for Optics). The refractive indices of SiO2 and Au were set at 1.447 and 0.41 + 8.37i, respectively2627. In the SiO2 single-mode waveguides, the effective wavelength of SPPs (1063 nm) is close to the wavelength of propagating light (1068 nm). Plasmonic signals can therefore propagate along SiO2 patterns with approximate light velocity. The simulated optical intensity distributions of MMI for half-adder operations are shown in Fig. 2a–d. From these numerical results, an on-off ratio of at least 7.43 dB was confirmed, as shown in Tables 1 and 2. In Fig. 2, to carry out the XOR operation, input SPPs interfere with antiphase SPPs at the XOR output as mentioned above, and the XOR output signal therefore has input-dependent phase change π. To carry out the AND operation, the input SPPs interfere with the reference SPPs, and the AND output signal does not change the phase because of the input multiplexing in phase. Hence, the AND output can be connected in a cascaded circuit, although the XOR output cannot be connected to the other logic gates due to the input-dependent phase change. In the proposed half adder, the XOR and AND operation gives a sum and carry output, respectively. If the proposed half adder is used in a cascaded multi-bit adder, only the AND output will be connected to the upper bit adder and the XOR output will be detected as an intensity signal of the sum output.


Plasmonic-multimode-interference-based logic circuit with simple phase adjustment.

Ota M, Sumimura A, Fukuhara M, Ishii Y, Fukuda M - Sci Rep (2016)

Simulated optical intensity distributions of the proposed half adder.(a–d) Optical distributions and output characteristics of “00”, “01”, “10”, “11” input states. Plasmonic signals interfered through the MMI structures, and half-adder operations were confirmed numerically. Upper parts of panels (a–d) are the output characteristics averaged over 1 μm and normalized with respect to the maximum value of AND “11” output.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834483&req=5

f2: Simulated optical intensity distributions of the proposed half adder.(a–d) Optical distributions and output characteristics of “00”, “01”, “10”, “11” input states. Plasmonic signals interfered through the MMI structures, and half-adder operations were confirmed numerically. Upper parts of panels (a–d) are the output characteristics averaged over 1 μm and normalized with respect to the maximum value of AND “11” output.
Mentions: We numerically simulated the SPP fields in the MMI patterns of the half adder and calculated the on-off ratio for the XOR and AND output using a 3D finite-difference time-domain (FDTD) method with electromagnetic wave analysis software (Fujitsu, Poynting for Optics). The refractive indices of SiO2 and Au were set at 1.447 and 0.41 + 8.37i, respectively2627. In the SiO2 single-mode waveguides, the effective wavelength of SPPs (1063 nm) is close to the wavelength of propagating light (1068 nm). Plasmonic signals can therefore propagate along SiO2 patterns with approximate light velocity. The simulated optical intensity distributions of MMI for half-adder operations are shown in Fig. 2a–d. From these numerical results, an on-off ratio of at least 7.43 dB was confirmed, as shown in Tables 1 and 2. In Fig. 2, to carry out the XOR operation, input SPPs interfere with antiphase SPPs at the XOR output as mentioned above, and the XOR output signal therefore has input-dependent phase change π. To carry out the AND operation, the input SPPs interfere with the reference SPPs, and the AND output signal does not change the phase because of the input multiplexing in phase. Hence, the AND output can be connected in a cascaded circuit, although the XOR output cannot be connected to the other logic gates due to the input-dependent phase change. In the proposed half adder, the XOR and AND operation gives a sum and carry output, respectively. If the proposed half adder is used in a cascaded multi-bit adder, only the AND output will be connected to the upper bit adder and the XOR output will be detected as an intensity signal of the sum output.

Bottom Line: Also, simultaneous operations of XOR and AND gates are substantiated experimentally by combining 1 × 1 MMI based phase adjusters and 2 × 2 MMI based intensity modulators.An experimental on-off ratio of at least 4.3 dB is confirmed using scanning near-field optical microscopy.The proposed structure will contribute to high-density plasmonic circuits, fabricated by complementary MOS-compatible process or printing techniques.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi-shi, Aichi 441-8580, Japan.

ABSTRACT
All-optical logic circuits using surface plasmon polaritons have a potential for high-speed information processing with high-density integration beyond the diffraction limit of propagating light. However, a number of logic gates that can be cascaded is limited by complicated signal phase adjustment. In this study, we demonstrate a half-adder operation with simple phase adjustment using plasmonic multimode interference (MMI) devices, composed of dielectric stripes on a metal film, which can be fabricated by a complementary metal-oxide semiconductor (MOS)-compatible process. Also, simultaneous operations of XOR and AND gates are substantiated experimentally by combining 1 × 1 MMI based phase adjusters and 2 × 2 MMI based intensity modulators. An experimental on-off ratio of at least 4.3 dB is confirmed using scanning near-field optical microscopy. The proposed structure will contribute to high-density plasmonic circuits, fabricated by complementary MOS-compatible process or printing techniques.

No MeSH data available.