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Optical biosensors with the high sensitivity is an important tool for environment monitoring, disease diagnosis and drug development. Integrating the biosensor could reduce the size and cost and is desirable for home and outdoor use. However, the integrated structure always results in the worsening of sensitivity and narrowing of sensing range, especially for small molecule sensing. In this work, we propose an integrated plasmonic biosensor based on the resonant structure composed of dielectric grating and metal film. With vertically incident light from the grating side, the surface plasmon polariton (SPP) mode could be excited at certain wavelength and the reflected light would vanish. Simulation results indicate that, when varying refractive index (ndet) of detection layer, the energy of reflected light changes dramatically. Assuming the resolution of the power meter is 0.01dB, the sensing resolution could be 4.37×10-6 RIU, which is very close to the bulk lens based SPP biosensor by monitoring the light intensity variation. Since antibody and antigen always have the size of tens of nanometers, it is necessary to check the sensing ability of the sensor in tens of nanometers. Fixing ndet and varying the thickness of detection layer, calculation result demonstrates that the reflected light energy is sensitive to the thickness change with one hundred nanometers. This attributes to the surface mode property of SPP mode.

Optomechanical crystal is a combination of both photonic and phononic crystal. It simultaneously confines light and mechanical motion and results in strong photon-phonon interaction, which provides a new approach to deplete phonons and realize on-chip quantum ground state. It is promising for both fundamental science and technological applications, such as mesoscopic quantum mechanics, sensing, transducing, and so on. Here high optomechanical coupling rate and efficiency are crucial, which dependents on the optical-mechanical mode-overlap and the mechanical frequency (phonon frequency), respectively. However, in the conventional optomechanical-crystal based on the same periodical structure, it is very difficult to obtain large optical-mechanical mode-overlap and high phonon frequency simultaneously. We proposed and demonstrated nanobeam cavities based on hetero optomechanical crystals with two types of periodic structure. The optical and mechanical modes can be separately confined by two types of periodic structures. Due to the design flexibility in the hetero structure, the optical field and the strain field can be designed to be concentrated inside the optomechanical cavities and resemble each other with an enhanced overlap, as well as high phonon frequency. A high optomechanical coupling rate of 1.3 MHz and a high phonon frequency of 5.9 GHz are predicted theoretically. The proposed cavities are fabricated as cantilevers on silicon-on-insulator chips. The measurement results indicate that a mechanical frequency as high as 5.66 GHz is obtained in ambient environment, which is the highest frequency demonstrated in one-dimensional optomechanical crystal structure.

Nanostructure is an effective solution for realizing optoelectronic devices with compact size and high performances simultaneously. This paper reports our research progress on integrated nanophotonic devices for optical interconnections. We proposed a parent-sub micro ring structure for optical add-drop multiplexer (OADM) with compact footprint, large free spectral range, and uniform channel spacing. All eight channels can be multiplexed and de-multiplexed with 2.6 dB drop loss, 0.36 nm bandwidth (>40 GHz), -20 dB channel crosstalk, and high thermal tuning efficiency of 0.15 nm/mW. A novel principle of optical switch was proposed and demonstrated based on the coupling of the defect modes in photonic crystal waveguide. Switching functionality with bandwidth up to 24 nm and extinction ratio in excess of 15 dB over the entire bandwidth was achieved, while the footprint was only 8 μm×17.6 μm. We proposed an optical orbital angular momentum (OAM) coding and decoding method to increase the data-carrying capacity of wireless optical interconnect. An integrated OAM emitter, where the topological charge can be continuously varied from -4 to 4 was realized. Also we studied ultrafast modulated nLED as the integrated light source for optical interconnections using a nanobeam cavity with stagger holes.

In this paper, we proposed and demonstrated a simple ChG waveguide structure, guided by low refractive-index strips on the surfaces of planar ChG films. Theoretical analysis shows that it supports quasi-TE mode transmission in 1.5μm band with high nonlinearity. Samples of this surface guiding ChG waveguides are fabricated. Its transmission properties are measured by the cut-off method, showing a waveguide attenuation of 0.67dB/mm and a coupling loss with optical fibers of ~8dB/facet. It provides a simple way to realize high quality ChG waveguides, which has great potential in developing nonlinear photonic devices.

Here we present investigations on utilizing two kinds of plasmonic nanoparticles (NPs) to enhance the efficiency of dye sensitized solar cells (DSCs). The Au@PVP NPs is proposed and present the specialty of adhesiveness to dye molecules, which could help to localize additional dye molecules near the plasmonic NPs, hence increasing the optical absorption consequently the power conversion efficiency (PCE) of the DSCs by 30% from 3.3% to 4.3%. Meanwhile, an irregular Au-Ag alloy popcorn-shaped NPs (popcorn NPs) with plenty of fine structures is also proposed and realized to enhance the light absorption of DSC. A pronounced absorption enhancement in a broadband wavelength range is observed due to the excitation of localized surface plasmon at different wavelengths. The PCE is enhanced by 32% from 5.94% to 7.85%.

Broadband thermo-optic switch based on an ultra-compact W2 photonic crystal waveguide (PCW) is demonstrated with an integrated titanium/aluminum microheater on its surface. The operating principle relies on shifting a transmission-dip caused by the enhanced coupling between the defect modes in W2 PCW. As a result, broadband switching functionality with larger extinction ratio can be attained. Moreover, microheaters with different width are evaluated by the power consumptions and heating transfer efficiency, and an optimized slab microheater is utilized. Finally, switching functionality with bandwidth up to 24 nm (1557~1581 nm) is measured by the PCW with footprint of only 8μm×17.6 μm, while the extinction ratio is in excess of 15 dB over the entire bandwidth. What’s more, the switching speed is obtained by the measurement of 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.

In particular, the surface plasmon polariton (SPP) is attractive to enhance the spontaneous emission (SE) from active materials due to the larger density of state (DOS) and smaller mode volume comparing with optical wave, namely Purcell effect. Usually, the Purcell factor (PF) is calculated from the reduced form of Fermi’s golden rule, where only the DOS and mode volume of photon (or SPP mode) are involved. Obviously, the PFs calculated with reduced form exclude the influence of active material and only evaluate the effect of cavity or SPP waveguide. However, for a practical emitter, the linewidth could not always be ignored. For example, the ensemble emission linewidth of mass Si- quantum dots (QD) is about 220meV~400meV (90~160nm), which are much wider than the linewidth of the SPP DOS In this work, the PF of SPP mode on Au-Si 3 N 4 grating is calculated with full integration formula of Fermi’s golden rule by taking account of the spontaneous emission linewidth from single Si-QD. The calculated PF is about 1.7~1.4 within the emission range of †hω 0 =1.9~1.6eV. Comparing with the PF value of 266.9~30.1, which is calculated without including the emission linewidth of Si-QD, it could be easily concluded that the impact of rather wide emission linewidth is fatal for applying plasmonic enhancement. To obtain some useful guidelines, we also discuss the necessary linewidth for effective plasmonic enhancement on Si-QDs. It is found that if the emission linewidth could be decreased to several tens of μeV, plasmonic enhancement would be helpful.

We demonstrated and fabricated a 20μm-long ultra-compact variable optical attenuator based on thermo-optical effect with slow light photonic crystal waveguide (PCWG). In simulation, we optimize the line-defect width and radius/period ratio ( r/a ) of the PCWG for deep photonic band gap and large slope photonic band edge. An r/a =140nm/410nm W1 PCWG is selected for its -60dB depth and 36dB variable attenuation range when the tunable refractive index change is 0.01. We also study different shapes of micro-heaters for low power consumption and high heat transfer efficiency. A 24.6mW and 75.9% heat transfer efficiency are achieved in a 2μm-wide right-angle-shaped micro-heater. In experiment, A 4.6nm red shift at the cutoff wavelength of the fundamental mode and a 10dB tunable attenuation range are achieved through tuning the temperature of the W1 PCWG by an 4.7μm-wide aluminum micro-heater with a maximum power consumption as low as 30.7mW.

The plasmonic enhanced absorption for thin film solar cells with silver nanoparticles (NPs) deposited on top of the amorphous silicon film (a-Si:H) solar cells and embedded inside the active layer of organic solar cells (OSCs) has been simulated and analyzed. Obvious optical absorption enhancement is obtained not only at vertical incidence but also at oblique incidence. By properly adjusting the period and size of NPs, an increased absorption enhancement of about 120% and 140% is obtained for a-Si:H solar cells and OSCs, respectively.

Coupling between long range surface plasmon polariton (LRSPP) waveguide mode and dielectric waveguide (DW) mode has been studied theoretically and experimentally. It is demonstrated that the fundamental and second-order TM-polarized mode of dielectric waveguide could couple with LRSPP mode efficiently, respectively.

The enhanced optical absorption in solar cells using nanoscale structure and novel physical effect has received a lot of attention in recent years. One of the promising methods is to utilize the noble metal nanoparticles with plasmonic effect for increasing the light absorption, consequently the conversion efficiency of photovoltaic devices. While the bare metal nanoparticles may suffer from the energy loss introduced by themselves due to the recombination of electro-hole pairs. Here, we propose to apply the plasmonic metal-dielectric core-shell nano-particles to improve the optical absorption efficiency of thin film solar cells. It is expected that the metal core could increase the optical absorption of thin film solar cells due to the filed enhancement effect of localized surface plasmon (LSP), and meanwhile the dielectric shell could avoid the metal core to become a new recombination center of the light-induced excitons. Further, varying the refractive index of the dielectric shell could adjust the enhancement region of LSP in a large range to cover the whole wavelength range of solar cells. Simulations are carried out by means of the finite element method in a three-dimensional model. The results show that the absorption enhancement up to 110% could be obtained when the active layer of thin film organic solar cells is 30nm thick. Then, some initial experiments have been done. The Au-citrate core-shell nanoparticles synthesized by the sodium citrate reduction method are deposited on the solar cells. And the obvious photocurrent enhancement has been observed.

Spontaneous four-wave mixing (SFWM) in optical fibers is an important way to generate correlated/entangled photon pairs. When the pulsed pump light passes through the optical fiber, two kinds of SFWM will take place simultaneously. One is scalar scattering processes, in which two annihilated pump photons and generated photon pair are all polarized along the same fiber polarization axis. The other is vector scattering processes, in which two annihilated pump photons are polarized along different fiber polarization axes, either to the two photons of the generated pair. If the fiber has large group birefringence, the intensity of vector scattering processes will be suppressed at the phase matching frequencies of the scalar scattering processes. On the other hand, the walk-off effect of the pump pulse components polarized along the two fiber polarization axes also suppresses the vector scattering processes. Hence, by proper pump polarization and signal/idle frequency selection, photon pairs can be generated only by the two independent scalar scattering processes in optical fibers with birefringence, which provide a simple way to realize polarization entangled photon pair generation. In this paper, related experiments based on the high nonlinearity microstructure fiber (HN-MSF) with group birefringence and polarization maintained dispersion shifted fiber (PM-DSF) are introduced, showing their potential on developing practical quantum light sources.

Our recent experimental results of hollow core Bragg fiber fabrication and measurement are shown in this paper. Using a hollow-core Bragg fiber with the fundamental band around 3000 cm−1, the absorption peak of methane can be observed clearly, showing its potential as a compact sample cell for trace gas sensing.

In this paper, correlated photon pairs at 1.55µm are generated in a silicon wire waveguidewith a length of 1.6 mm. The ratio between coincidence count rate and accidental coincidence count rate under room temperature is 19, showing the property of low Raman noise and strong quantum correlation. Moreover, the experiment shows that photon pair generation isstrongly dependent on pump polarization direction. Using quantum perturbation theory, we analyze the contribution of scalar and vectorspontaneous four-wave mixing processes to the generated photon pairs. Due tohigh nonlinear coefficient and high coupling efficiency, the generation rate in quasi-TE mode is much larger than that in quasi-TM mode. The combination of calculated photon pair generation rates through scalar and vector spontaneous four-wave mixing processes agrees well with the experimental result.

A hybrid coupler comprised of a slot plasmonic waveguide and a dielectric waveguide is proposed and its coupling characteristics were analyzed. The simulation results show that the slot plasmonic mode can be excited efficiently by the dielectric waveguide mode and a highly integrated refractive index sensor could be realized.

Layer-thickness dependence of Si-nanocrystal formation in amorphous Si/SiO 2 multilayers during thermal annealing is experimentally demonstrated with RF-sputtered samples, and further explained by a modified model. The theoretical calculation shows that there is a lower limit (1.5nm) of Si layer thickness and lateral growth of Si-nanocrystal is unconstrained in such multilayers.

Near-infrared silicon solar cell response enhanced by gold nanoparticles with core-shell structure has been studied experimentally. The obvious enhancement on photocurrent response was observed when λ 0 > 800nm and the highest value 12% near λ 0 =1160nm was obtained.

The photoluminescence spectra of amorphous silicon rich silicon nitride films with various compositions were investigated. Two main luminescence peaks were identified for all samples and blueshift of photoluminescence were observed after annealing treatment. With the help of X-ray photoelectron spectroscopy and Fourier transform infrared measurement, the chemical composition and bonding environment of samples, which were grown with different reactant gases flow rates of plasma enhanced chemical vapor deposition, were analyzed. According to all these measurement results, it is confirmed that the main luminescence centers are radiative recombination defects, such as silicon and nitride dangling bonds. With proper deposition conditions, all these radiative recombination defects could be activated at the same time, so that ultra-wide photoluminescence spectra with full width at half maximum of about 250nm ∼ 300nm were obtained in visible region.

Spontaneous parametric down-conversion in two-dimensional photonic crystal made of semiconductor material with large quadratic nonlinear susceptibility is proposed to generate polarization entangled photon pairs. On one hand, the large quadratic nonlinear susceptibility of AlGaAs crystal insures the high nonlinear conversion efficiency; on the other hand, the abnormal dispersion property of two-dimensional photonic crystal causes the satisfaction of the phase-matching condition. In particular, the dispersion property sensitively depends on the structure of photonic crystal. Then the walk-off between the down-converted photons with orthogonal polarizations can be minimized through appropriate structure parameter design; hence compensation measures to mitigate labeling effect on polarization entangled photon pairs can be eliminated.

In this paper, the ability of Bragg fiber array to guide optical mode is investigated theoretically. Simulation shows that Bragg fiber array can be looked as a good waveguide to guide inter-fiber modes, which are supported by the external reflection of the 1-D photonic crystal claddings of the Bragg fibers. The mechanism of leakage loss of the inter-fiber is analyzed, showing that the TM01-like mode has the lowest leakage loss and less than 1dB/m leakage loss can be achieve under the wavelength of 10.6μm. As an open waveguide or 2-D microcavity, the Bragg fiber array has wide potential applications including processes of interaction between light and atoms or molecules.

The influences of the Ge doped core to the properties of holey fibers are investigated in this paper. Numerical simulation shows that for holy fibers with conventional triangular transverse structure, proper-doped core can enhance the nonlinear coefficient and shift the near zero flattened dispersion region to long wavelength. By introducing a Ge doped core, a high nonlinearity holey fiber design for 1.55μm is proposed, with a nonlinear coefficient of 22 W -1 km -1 and a wavelength region of 165nm in which the dispersion value is within ±1 ps/km/nm.

This paper describes grating design of distributed feedback laser diodes (DFB-LDs) for use in metropolitan area and access networks and demonstrates improved performance of DFB-LDs with new gratin structures. Dynamic behaviors of DFB-LDs under the external optical feedback were analyzed for conventional uniform grating DFB-LDs and partially corrugated waveguide laser diodes (PC-LDs). A high-resistant characteristic against external optical feedback was achieved by PC-LD with optimized grating structure. The increase of RIN was suppressed to as low as -126 dB/Hz with the external optical feedback of -20 dB. It was also found that feedback effect of mirror loss (FEML) plays an important role in external optical feedback resistance. Furthermore, negative FEML, which suppresses relaxation oscillation, reduces transient chirp under high-bit-rate modulation. FEML is successfully controlled by adjusting phase shift value in phase-shifted DFB-LDs, and very low power penalty transmission was demonstrated by (lambda) /8 phase-shifted DFB-LDs. After 100-km transmissions, a power penalty of less than 1 dB within a wide extinction ratio region form 8.5 to 14.5 dB was demonstrated with 2.5 Gb/s direct modulation. These DFB-LDs with new grating structure is promising for intermediate transmission applications.

A high-yield and high-performance single longitudinal mode laser diode (LD) is essential for implementing a low-cost optical module for high capacity access networks. We have realized novel partially corrugated waveguide (PC) LDs and shown that they are cost-effective. Because of a unique resonance feature in a mirror loss profile, the PC-LD has higher yield in single longitudinal mode operation than that of a conventional distributed feedback (DFB) LD. The yield of the PC-LD with single-mode stability ((Delta) (alpha) L > 0.3) was theoretically predicted to be as high as > 65%, which is 1.5 to 2 times higher than that of a conventional DFB-LD. Side-mode suppression ratio was experimentally as high as 40 to 50 dB. Uncooled high-efficiency characteristics have been realized for a cavity with asymmetrical reflectivity facets. The threshold current and slope efficiency were 16 mA and 0.26 W/A at 85 degree(s)C. By introducing a spot-size converted waveguide with chirped corrugation, butt-coupling efficiency was improved by 3 dB higher than that of the conventional straight waveguide. Furthermore, excellent optical feedback resistant 622 Mb/s operation has been demonstrated over a wide temperature range of -40 to 85 degree(s)C. The power penalty was as low as 1 dB under the optical feedback level of -8.5 dB. Isolator-free 2.5 Gb/s-70 km transmission was also demonstrated. The PC-LDs with this performance are very promising for realizing cost-effective optical modules for use in high capacity optical access networks.

This paper clarifies superior external optical feedback resistant characteristics in partially-corrugated-waveguide laser diodes (PC-LDs), compared to conventional distributed feedback laser diodes (DFB-LDs). Based on a novel large single dynamic analysis by using the van der Pol equations in single-mode laser diodes (LDs), it is found that the external optical feedback resistance in single-mode LDs is dominated by the transient fluctuation of mirror loss (total net threshold gain), and depends on the grating phases at the cleaved facets. Theoretical results predict that in the PC-LDs, mirror loss is insensitive to the grating facet phases due to a unique waveguide, which consists of a corrugated waveguide near the antireflection-coated front facet and an uncorrugated waveguide near the high- reflection-coated rear facet. Therefore the variation of phase conditions for oscillation caused by the external optical feedback gives rise to a relative low transient fluctuation of the mirror loss that suppresses the positive feedback effect of mirror loss, as well as the optical output fluctuations. Furthermore, optimum-grating length, i.e. 150 micrometers for 250 micrometers cavity length, was derived by the calculations. The relative intensity noise (RIN) caused by external optical feedback was measured for PC-LDs with different grating length over a wide feedback level range from -40 dB to -20 dB. Experimental results show that, for the cavity length of 250 micrometers , the PC-LDs with a grating length of 150 micrometers have the most excellent external optical feedback resistant characteristics. The increase of RIN was suppressed to as low as -126 dB/Hz with the external optical feedback of -20 dB. These results agreed well with the theoretical analysis.