Cuicui Lu

Tunable ultracompact chip-integrated multichannel filter based on plasmon-induced transparencies

Nanoscale multichannel filter is realized in plasmonic circuits directly, which consists of four plasmonic nanocavities coupled via a plasmonic waveguide etched in a gold film. The feature device size is only 1.35 μm, which is reduced by five orders of magnitude compared with previous reports. The optical channels are formed by transparency windows of plasmon-induced transparencies. A shift of 45 nm in the central wavelengths of optical channels is obtained when the plasmonic coupled-nanocavities are covered with a 100-nm-thick poly(methyl methacrylate) layer. This work opens up the possibility for the realization of solid quantum chips based on plasmonic circuits.

Ultralow power all-optical diode in photonic crystal heterostructures with broken spatial inversion symmetry

We experimentally realize an all-optical diode in a photonic crystal heterostructure with broken spatial inversion symmetry. The physical mechanism is attributed to bandgaps only for certain wavevectors and the transition between different electromagnetic Bloch modes, without any nonlinearity and high power requirement. An ultralow photon intensity of 50 kW/cm2 and an ultrahigh transmission contrast of over 103 are reached simultaneously. Compared with previous reported all-optical diodes, the operating power is reduced by seven orders of magnitude, while the transmission contrast is enlarged by two orders of magnitude. This approach may open a way for the study of integrated photonic devices.

Ultrahigh-contrast and wideband nanoscale photonic crystal all-optical diode.

We experimentally realize a nanoscale all-optical diode in a photonic crystal heterostructure with broken spatial inversion symmetry, performing independent of optical nonlinearity. The physical mechanism lies in unique dispersion relations of the photonic crystal and the transition of incident light between different electromagnetic Bloch modes. An ultrahigh transmission contrast of 10(3) order, a large operating bandwidth of over 50 nm, and an ultralow photon intensity of less than 10 kW/cm(2) are reached simultaneously.

Ferroelectric Hybrid Plasmonic Waveguide for All-Optical Logic Gate Applications

A ferroelectric hybrid plasmonic waveguide, made of a polycrystal lithium niobate waveguide separated from a gold film by a silicon dioxide isolation layer, is fabricated by use of laser molecular beam epitaxy growth, electron beam evaporation, and focused ion beam etching. Strong subwavelength mode confinement and excellent long-range propagation are achieved simultaneously for the hybrid plasmonic mode. An all-optical logic OR gate is also realized based on the ferroelectric hybrid plasmonic waveguide. This may provide a way for the study of all-optical logic gates and integrated photonic circuits.

Chip-integrated ultrawide-band all-optical logic comparator in plasmonic circuits

Optical computing opens up the possibility for the realization of ultrahigh-speed and ultrawide-band information processing. Integrated all-optical logic comparator is one of the indispensable core components of optical computing systems. Unfortunately, up to now, no any nanoscale all-optical logic comparator suitable for on-chip integration applications has been realized experimentally. Here, we report a subtle and effective technical solution to circumvent the obstacles of inherent Ohmic losses of metal and limited propagation length of SPPs. A nanoscale all-optical logic comparator suitable for on-chip integration applications is realized in plasmonic circuits directly. The incident single-bit (or dual-bit) logic signals can be compared and the comparison results are endowed with different logic encodings. An ultrabroad operating wavelength range from 700 to 1000 nm, and an ultrahigh output logic-state contrast-ratio of more than 25 dB are realized experimentally. No high power requirement is needed. Though nanoscale SPP light source and the logic comparator device are integrated into the same plasmonic chip, an ultrasmall feature size is maintained. This work not only paves a way for the realization of complex logic device such as adders and multiplier, but also opens up the possibility for realizing quantum solid chips based on plasmonic circuits.

Integrated all-optical logic discriminators based on plasmonic bandgap engineering

Optical computing uses photons as information carriers, opening up the possibility for ultrahigh-speed and ultrawide-band information processing. Integrated all-optical logic devices are indispensible core components of optical computing systems. However, up to now, little experimental progress has been made in nanoscale all-optical logic discriminators, which have the function of discriminating and encoding incident light signals according to wavelength. Here, we report a strategy to realize a nanoscale all-optical logic discriminator based on plasmonic bandgap engineering in a planar plasmonic microstructure. Light signals falling within different operating wavelength ranges are differentiated and endowed with different logic state encodings. Compared with values previously reported, the operating bandwidth is enlarged by one order of magnitude. Also the SPP light source is integrated with the logic device while retaining its ultracompact size. This opens up a way to construct on-chip all-optical information processors and artificial intelligence systems.

Integrated ultracompact and broadband wavelength demultiplexer based on multi-component nano-cavities

Integrated nanoscale photonic devices have wide applications ranging from optical interconnects and optical computing to optical communications. Wavelength demultiplexer is an essential on-chip optical component which can separate the incident wavelength into different channels; however, the experimental progress is very limited. Here, using a multi-component nano-cavity design, we realize an ultracompact, broadband and high-contrast wavelength demultiplexer, with 2.3 μm feature size, 200 nm operation bandwidth (from 780 nm to 980 nm) and a contrast ratio up to 13.7 dB. The physical mechanism is based on the strong modulation of the surface plasmon polaritons induced by the multi-component nano-cavities, and it can be generalized to other nanoscale photonic devices. This provides a strategy for constructing on-chip photon routers, and also has applications for chip-integrated optical filter and optical logic gates.

All-optical logic binary encoder based on asymmetric plasmonic nanogrooves

We report an all-optical logic binary encoder based on two asymmetric plasmonic nanogrooves etched in a gold film coated a polyvinyl alcohol layer. The physical mechanism originates from the unique capability of plasmonic nanogrooves in modulating the propagation properties of surface plasmon polaritons. The incident signal lights dropping in different wavelength regions are endowed with different logic state encodings. In such an ultracompact device with a feature size of only 2.4 μm, the coupling of free-space signal lights to surface plasmon polaritons and the on-chip encoding are integrated together, which is much suitable for practical integration applications.

Multi-color photon sorting in plasmonic microcavities

Multi-color photon sorting is realized on the basis of plasmonic microcavities etched in a gold film coated with a polyvinyl alcohol layer. Both wide-band unidirectional surface plasmon polariton launchers and plasmonic microcavities are integrated on-chip. The physical mechanism of the multi-color photon sorting function is attributed as the plasmonic stop bands prohibiting the surface plasmon polariton propagation in a broad wavelength range, while the plasmonic microcavities selectively permit several surface plasmon polaritons to pass, on the basis of the photon tunneling effect. Incident continuous wave lasers with wavelengths of 800, 840, and 880?nm are separated, and decoupled from different output ports. The operating wavelength can be tuned by adjusting the refractive index of the covering polymer layer.