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An energy-time entanglement-based dispersive optics quantum key distribution (DO-QKD) is demonstrated experimentally over optical fibers of 20 km. In the experiment, the telecom band energy-time entangled photon pairs are generated through spontaneous four-wave mixing in a silicon waveguide. The arrival time of photons is registered for key generation and security test. High-dimensional encoding in the arrival time of photons is used to increase the information per coincidence of photon pairs. The bin sifting process is optimized by a three-level structure, which significantly reduces the raw quantum bit error rate (QBER) due to timing jitters of detectors and electronics. A raw key generation rate of 151 kbps with a QBER of 4.95% is achieved, in a time bin encoding format with 4 bits per coincidence. This experiment shows that the entanglement-based DO-QKD can be implemented in an efficient and convenient way, which has great potential for quantum secure communication networks in the future.

An integrated Ge photodetector of very low dark current density is demonstrated in an optoelectronic integrated circuit label-free biosensing system. The sensor system consists of a microring for optical sensing and a monolithically integrated Ge detector. For point-of-care applications, integration of Ge detector increases the reliability of measurement by eliminating mechanical-optical alignment of output signals. Optimizing Ge detector performance will further enhance system signal-noise ratio and reliability. For homogeneous sensing, the system has a sensitivity of ∼18.8 nm/RIU and a detection limit of 3.50 × 10−5.

The two-surface-plasmon-polariton-absorption (TSPPA) at the vacuum wavelength of 400 nm is observed, and the subwavelength lithography, by using this nonlinear phenomenon, is demonstrated. Resist patterns with the period of ∼138 nm have been obtained by exciting the SPP at the Al/resist interface with the 400 nm femtosecond laser. By altering the exposure time, the exposure linewidth reduces from ∼90 nm to ∼55 nm, which explores the ability of the TSPPA based lithography at the short wavelength. The factors limiting the performance of the proposed TSPPA based lithography are discussed in detail.

We propose and demonstrate the two-surface-plasmon-polariton-absorption (TSPPA), which is a nonlinear effect by absorbing two surface-plasmon-polaritons (SPPs), as well as a nanolithography technique based on TSPPA. The TSPPA effect is verified with the plasmonic interference structure to exclude the possibility of two photon absorption. Benefiting from the short wavelength and the field enhancement of SPP as well as the selective transfer of plasmonic patterns into photoresist induced by TSPPA, resist strips with the linewidth of ∼λ0/11 are achieved by a single illumination on the plasmonic mask with the femtosecond laser for only 15 s, which shows great potential for future large-area nanolithography.

Based on a hybrid coupler composed of short-range surface plasmon polariton (SRSPP) and dielectric waveguides, an integrated sensor for ultra-thin layer sensing has been realized. The simulation and experiment results demonstrate that the thickness variation of detection layer (polymer layer) about several nanometers could be detected. The measured thickness-detection sensitivity is as high as 0.67 dB/nm. And the sensitive region for thickness variation of polymer layer can be adjusted widely by varying the thickness of the SRSPP waveguide.

Broadband switching functionality realized by an ultra-compact W2 photonic crystal waveguide (PCW) is demonstrated with an integrated titanium/aluminum microheater on its surface. Due to the enhanced coupling between the defect modes in W2 PCW, switching functionality with bandwidth up to 24 nm is achieved by the PCW with footprint of only 8 μm × 17.6 μm, while the extinction ratio is in excess of 15 dB over the entire bandwidth. Moreover, the switching speed is measured by alternating current modulation. Response time for this thermo-optic switch is 11.0 ± 3.0 μs for rise time and 40.3 ± 5.3 μs for fall time, respectively.

The Purcell factor (PF) of the propagating surface plasmon polariton (SPP) mode on metallic grating is evaluated with full integration formula of Fermi's golden rule, while both spontaneous emission linewidth of single quantum dot and the spectrum broadening of photonic density of state (DOS) due to the propagation loss of SPP mode are involved. It is found that the PF would be degraded by taking account of the emission linewidth. For emitters with narrow linewidth, the DOS broadening is dominant while it would be helpful to some degree for wide-linewidth emitters.

Optical switch based on an ultra-compact double-slot photonic crystal waveguide (DS-PCWG) with a titanium/aluminum microheater is demonstrated. The operating principle relies on shifting a transmission-dip caused by the defect mode coupling in photonic band gap (PBG). Based on the unique mode coupling in PBG, low switching power of 9.2 mW and high extinction ratio of 17 dB are achieved experimentally while the length of DS-PCWG is only 16 μm.

An integrated sensor based on a vertical hybrid coupler composed of a short-range surface plasmon polariton (SRSPP) waveguide and a SiNx dielectric waveguide has been realized. The output power of the sensor is observed to change drastically with the refractive index of the detection liquid, and the sensing region can be adjusted by varying the width of the SiNx waveguide. The resolution is estimated to be as high as 7.3 × 10−6 refractive index units. This sensor is expected to have significantly high effective sensitivity for detecting a hundred-nanometer-thick layer owing to the highly bounded field of the SRSPP mode.

The enhancement effect of optical absorption with core-shell goldnanoparticles on the surface of wafer-based siliconphotovoltaic devices has been studied. The obvious enhanced photocurrent is observed, especially when the wavelength is above 800 nm, and the highest enhancement value is about 14% around the wavelength of 1100 nm. The simulation results indicate that the presence of dielectric coating shell could improve the surface plasmon based scattering effect at longer wavelength range, which provides a good understanding of the experiment results.

The short range surface plasmon polariton (SRSPP) mode, which has an antisymmetric field profile on the two sides of a thin metal film, has been excited efficiently based on an integrated vertical hybrid coupler. The coupler is composed of an Au (SRSPP) waveguide and a SiNx (dielectric) waveguide. Highly efficient coupling between the SRSPP mode and conventional dielectric waveguide mode was demonstrated. A compact (less than 90 μm long) polarizer with a low TE insertion loss and high TM extinction ratio up to 30 dB was realized by utilizing different characteristics of the TE and TM modes in the hybrid coupler.

The photonic crystal (PC) is an important structure for realizing optical integrative circuits. Nowadays, most PC based passive devices operate by utilizing the coupling either between several PC waveguides or between PC waveguides and resonance cavities. In this letter, we present a coupling mechanism between even- and oddlike modes in a single asymmetric PC waveguide. Switches based on this coupling phenomenon were validated experimentally. By adjusting the temperature controlled by the thermal resistor, an extinction ratio of 9.1 dB was realized. Our researches provide a potential way of not only guiding but also controlling light in a simple single PC waveguide.

To connect the surface plasmon polariton (SPP) based devices with the conventional dielectric devices is a significant issue for the further development of SPP and related applications. In this paper, extremely high efficient coupling (>99%) between long range SPP (LRSPP) waveguide mode and TM mode of dielectric waveguide has been demonstrated from a hybrid coupler, which composed of an Au (LRSPP) waveguide and a SiN (dielectric) waveguide. Based on this hybrid coupler, a polarization splitter with pure TM mode output from one arm and TE mode output from the other arm with high TE/TM extinction ratio has been realized.

Coupling performance between a short range surface plasmon polariton (SRSPP) mode and a conventional dielectric waveguide mode is demonstrated numerically. Simulation results show that the coupling length, as short as tens of microns, can be realized because the field of SRSPP extremely concentrates to the metal surface. SRSPP-based hybrid coupler provides not only an approach to realize highly compact functional devices, such as the TE-pass polarizer with high performance, but also an integratable route for efficiently exciting SRSPP mode, which is very useful in the SRSPP-based biosensor or SRSPP-assisted emission enhancement devices.

To improve the quantum efficiency from silicon nanocrystals, a structure with Ag∕Ag-poor cermet layers is proposed. Due to large permittivity of Ag-poor cermet and its dispersion characteristic, density of states can be enhanced at the energy much lower than the plasmon energy of Ag. By properly choosing the component of the Ag-poor cermet, the dispersion of surface plasmons can be engineered to increase radiative emission rate significantly at the emission energy of silicon nanocrystals. Effective enhancement is theoretically demonstrated using Ag, which was generally recognized as nonideal material for emission enhancement in silicon nanocrystals due to its high plasmon energy.

The characteristics of hybrid three-arm coupler, which consists of the middle long range surface plasmon polariton waveguide and two outside conventional dielectric waveguides, are analyzed numerically with finite element method. Since the middle arm can only transfer the TM mode from one dielectric arm to the other one, this structure is promising for realizing integrated polarization splitter. Compared with the two-arm hybrid coupler, the loss of three-arm hybrid coupler based device can be reduced. Furthermore, different from conventional three-arm dielectric coupler, the authors find that the three-arm hybrid coupler with asymmetric structure can reach a much higher extinction ratio.

Coupling of TM mode between long range surface plasmon polariton (LRSPP) mode and conventional dielectric waveguide mode is demonstrated numerically with finite element method. The characteristics of a hybrid coupler, which consists of the LRSPP waveguide and conventional single mode dielectric waveguide, are analyzed. The high efficient coupling shows a possible route for integrating the SPP device and conventional dielectric optical devices together and a method to excite LRSPP mode with dielectric waveguide. Because the coupling just occurs on TM mode, this kind of the hybrid coupler can be used as polarization mode splitter and combiner.

By introducing a defect layer into the periodic cladding of Bragg fiber, the core mode and the defect mode may anticross near their cutoff inside band gap. The defect location suppresses and flattens dramatically the group velocity (vg) of coupled core mode and the defect thickness changes gradually its dispersion. Theoretical investigation reveals zero dispersion and zero dispersion slope at various low vg’s can be achieved simultaneously at arbitrary wavelengths. Specially, the proper defect in the sixth bilayer leads to the lowest vg of 0.074 of light speed in vacuum at 1550nm. The optical energy is confined well in the core and the leakage loss is sufficiently low.

Aimed at improving the quantum efficiency from nanoporous silicon, a device structure with a metal-rich Au (1−α)–SiO2 (α) cermet nanowaveguide is proposed. By properly choosing the component of the cermet, the surface-plasmon-like dispersion of the nanowaveguide can be engineered so that the density of states for photon is very large at the luminescent frequencies of nanoporous silicon. Consequently, spontaneous emission is greatly enhanced and radiative recombination of the careers becomes the dominating process in a nanoporous silicon layer. The internal quantum efficiency is largely improved.