Tingting Wu

Efficient phase-matched third harmonic generation in an asymmetric plasmonic slot waveguide

An asymmetric plasmonic slot waveguide (APSW) for efficient phase-matched third harmonic generation (THG) is proposed and demonstrated theoretically. Nonlinear organic material DDMEBT polymer is integrated into the bottom of the metallic slot, while silicon is used to fill the top of the slot. We introduce the rigorous coupled-mode equations of THG in the lossy APSW and apply them to optimize the waveguide geometry. Taking advantage of the surface plasmon polaritons (SPPs), the electric fields can be tightly confined in the metallic slot region and the nonlinear effect is greatly enhanced accordingly. Then, we investigate the relationships between THG efficiency and parameters such as slot width and height, phase matching condition (PMC), modal overlap related nonlinear parameter, figure-of-merit, pump power and detuning. With the proposed asymmetric waveguide, we demonstrate a high THG conversion efficiency of 4.88 × 10(-6) with a pump power of 1 W and a detuning constant of -36 m(-1) at a waveguide length of 10.65 ����m.

Coupling-length phase matching for efficient third-harmonic generation based on parallel-coupled waveguides.

We study third-harmonic generation (THG) in parallel-coupled waveguides where the spatial modulation of the mode intensity provides quasi-phase matching, called coupling-length phase matching (CLPM), for efficient nonlinear frequency conversion. Different types of CLPM are investigated for THG, and it is found that two sets of CLPM conditions can be practically implemented with traditional waveguides. These two CLPM conditions are further investigated by considering nonlinear phase modulations, which can degrade the CLPM-based THG conversion. However, up to 45% efficiency is still possible in this scheme. The greatest significance of this approach is that the requirement of perfect phase matching in a single waveguide is no longer necessary, leading to an alternative waveguide design for THG.

Efficient Third-Harmonic Generation From 2

We propose the asymmetrical plasmonic slot waveguide (APSW) design for third-harmonic generation (THG) from 2.25 μm. In this configuration, the phase-matching condition is fulfilled between the zeroth-order mode at fundamental frequency (FF) and the first-order mode at third-harmonic frequency (THF). Due to the asymmetrical geometry, the mode overlap between the two involved modes is significantly enhanced, leading to an efficient THG process. According to the numerical calculation, the conversion efficiency is predicted up to 1.4% with 1-W pump power. The proposed APSW has the potential to realize an integrated efficient THG device in nanometer scale.

\mu \hbox{m}

The conversion efficiency of third harmonic generation (THG) from mid-IR (3600 nm) to near-IR (1200 nm) regions in a silicon-silicon-nanocrystal hybrid plasmonic waveguide (SSHPW) was calculated. The required modal phase-matching condition (PMC) between the 0-th mode at fundamental wave (FW) and the 2-nd mode at third harmonic (TH) is achieved by carefully designing the waveguide geometry. Benefiting from the hybridized surface plasmon polariton (SPP) nature of the two guided modes, the SSHPW is capable of achieving both high THG nonlinear coefficient |I₆| and reasonable linear propagation loss, thereby resulting in large figure-of-merits (FOMs) for both FW and TH. According to our simulation, THG conversion efficiency up to 0.823% is achieved at 62.9 ����m SSHPW with pump power of 1 W.

in Asymmetric Plasmonic Slot Waveguide

We provide a comprehensive study on the efficient third harmonic generation (THG) in a lossy metal-hybrid-metal asymmetric plasmonic slot waveguide (MHM) to develop a method for efficient THG by focusing on the modal phase-matching condition (PMC), the third-order nonlinear susceptibility of the nonlinear interactive material, and the pump-harmonic modal overlap in conjunction with reasonable linear propagation loss. In addition to the PMC and the nonlinear material, the stimulated THG process can be greatly enhanced by the large pump-harmonic modal overlap. With 1 W pump power, simulation results present that THG conversion efficiency up to 2.79 × 10(-4) within 4.5 ����m MHM can be achieved.

Third harmonic generation from mid-IR to near-IR regions in a phase-matched silicon-silicon-nanocrystal hybrid plasmonic waveguide.

Tunable resonant surface plasmons based on graphene nanoribbon are studied to detect nanoscale protein molecules in mid-infrared region. High sensitivity in the detection of the refractive index and the protein chemical vibrations is achieved.

Study on the crucial conditions for efficient third harmonic generation using a metal-hybrid-metal plasmonic slot waveguide

We demonstrate an efficient third harmonic generation (THG) with the effect of nonlinear loss based on a proposed double-hybrid plasmonic slot waveguide structure. Silicon nanocrystal is integrated into the two parallel slots acting as the main interactive nonlinear material. To achieve phase matching condition, we analyze the relation between the guided mode dispersions and the waveguide geometrical parameters. The effect of nonlinear loss, which is contributed by the two-photon-absorption (TPA) effect, on the THG conversion efficiency is investigated numerically. The simulation results reveal that the THG conversion efficiency can be significantly enhanced by the field confinement and enhancement, whereas it is greatly impeded in the presence of the TPA effect (a decrement of 17.6% on the THG conversion efficiency with a pump power of 4 W). According to our calculation, the THG conversion efficiency of 0.91% without the consideration of the TPA effect and 0.75% with the TPA effect under a 4-W input pump power condition is achieved.

Tunable resonant graphene plasmons for mid-infrared biosensing

We report a lithography-free method for large-area plasmonic nano-patterning on ultrathin plastic films through a polymer cold-drawing process. We further transfer the ultra-flexible nano-patterned films onto the curved surfaces of plant leaves and apples to work as conformal SERS sensors.

Third Harmonic Generation With the Effect of Nonlinear Loss

We study the tunable plasmons based on a graphene integrated gold grating structure to sense the vibrational modes of nanometric molecules. The greatly enhanced light-matter interaction and the broadband tunability of the localized graphene plasmonic resonance enable accurate label-free identification of the molecular vibrational modes at subwavelength scale. Our results may accelerate the further development of novel cost-effective biosensors with superior molecular chemical fingerprint sensitivity in an active graphene plasmonic device.

Formation of ultra-flexible, conformal, and nano-patterned photonic surfaces via polymer cold-drawing

Recent years, the research of mid-infrared (mid-IR) photonics has inspired increasingly interest due to their potential applications in a wide variety of areas, including free-space communications, chemical or biological sensors, environmental monitors, thermal imaging, IR countermeasures and medical procedures. On the other hand, third harmonic generation (THG) has been demonstrated to be a versatile tool to realize high speed optical performance monitoring of in-band OSNR and residual dispersion. The mid-IR light sources based third-order frequency conversion opens an entirely new realm of nonlinear interactions. Nevertheless, rare experimental or analytical THG modeling has been published. In this work, we theoretically investigate the possible efficient phase-matched THG in a double symmetric plasmonic slot waveguide (DAPSW) based on a mid-IR light source. Nonlinear organic material DDMEBT with thirdorder susceptibility of χ(3) = 1×10-19 m2/V2 is integrated into the top metallic slot region as the main slot core medium. Silicon (Si) is used to fill the bottom metallic slot region. Silver (Ag) is considered to be the metal medium due to its low Ohmic loss. The needed phase-matching condition (PMC) is satisfied between the zeroth mode at fundamental frequency (FF) and the first mode at third harmonic (TH) by appropriate designing the waveguide geometrical parameters. The associated parameters such as the width and height of the slot, pump-harmonic modal overlap, figureof- merit (FOM), pump power and detuning have been numerically investigated in detail. Finally, the conversion efficiency comes up to 1.69×10-5 with pump power of 1 W and the corresponding waveguide length is 10.8 μm.