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A novel hybrid plasmonic (HP) donut resonator integrated with a photothermal plasmonic absorber has been developed, which can be used as a compact all-optical switch or modulator. The radius of the fabricated HP donut resonator is 1.8 $\mu \text{m}$ , with a resonant wavelength around 1550 nm and a quality factor ( ${Q}$ factor) around 600. The photothermal plasmonic absorber is directly integrated above the HP device, which can absorb as much as 75% of impinging optical power at 1064 nm wavelength. Since the absorber is in tight contact to the Si ridge of the HP waveguide, the absorbed optical power can efficiently heat up the Si ridge, and hence change the resonant wavelength of the HP donut resonator by Si thermal expansion effect. Experimental results show that the power used for 15 dB amplitude switch is only 10 mW, with rise and fall response times around 18 and 14 $\mu \text{s}$ , respectively.

Poly-3-hexylthiophene (P3HT) nanofibers are 1D crystalline semiconducting nanostructures, which are known for their application in photovoltaics. Due to the internal arrangement, P3HT nanofibers possess optical anisotropy, which can be enhanced on a macroscale if nanofibers are aligned. Alternating electric field, applied to a solution with dispersed nanofibers, causes their alignment and serves as a method to produce solid layers with ordered nanofibers. The transmission ellipsometry measurements demonstrate the dichroic absorption and birefringence of ordered nanofibers in a wide spectral range of 400–1700 nm. Moreover, the length of nanofibers has a crucial impact on their degree of alignment. Using electric birefringence technique, it is shown that external electric field applied to the solution with P3HT nanofibers can cause direct birefringence modulation. Dynamic alignment of dispersed nanofibers changes the refractive index of the solution and, therefore, the polarization of transmitted light. A reversible reorientation of nanofibers is organized by using a quadrupole configuration of poling electrodes. With further development, the described method can be used in the area of active optical fiber components, lab-on-chip or sensors. It also reveals the potential of 1D conducting polymeric structures as objects whose highly anisotropic properties can be implemented in electro-optical applications.​

We analyze whispering gallery-type disk resonators with radii down to 50 nm. Single interface waveguiding is accomplished by a plasmonic–dielectric interface operating near the surface plasmon polariton (SPP) resonance, employing a hypothetical material with lower loss than what is currently available in metals or negative permittivity media. The disk is immersed in a second dielectric, nonresonant to the plasmonic medium. Due to the high effective index of the disk mode and the concomitant low radiation losses, the quality ( $Q$ ) values of the resonator are solely determined by material losses, in contrast to more conventional nanoscale resonators. We calculate the dependence of the effective indices of the guided mode, the $Q$ values of absorption and radiation, and the Purcell factor on the deviation from the SPP resonance.

Poly-3-hexylthiophene (P3HT) nanofibers are 1D crystalline structures with semiconductor properties. When P3HT nanofi bers are dispersed in nonconducting solvent, they react to external alternate e ...

This paper gives a review of the recent progresses in our research on nanophotonics and hybrid plasmonic geometries, structures and devices. In the first part we present SOI-nanowire-based integrated components. The concept and different configurations of hybrid plasmonic structures will be then discussed. Finally different fabricated devices for applications in optical interconnects and sensing will be presented and characterized.

A Mach-Zehnder interferometer (MZI)-based liquid refractive index sensor, utilizing a hollow hybrid plasmonic (HP) waveguide as the sensing element, has been investigated, showing large sensitivity to the refractive index changes of the tested liquids, as well as lower propagation loss in comparison to typical plasmonic waveguide-based ones. The sensor is fabricated using conventional silicon-on-insulator (SOI) technology; therefore, it is compatible to other standard SOI devices. The waveguide sensitivity, Ssubw/sub, is experimentally demonstrated to be 0.64, with a propagation loss less than 0.25 dB/μm. Using a 20 μm long hollow HP waveguide in the sensing arm, the sensitivity of the MZI sensor (device sensitivity, Ssubd/sub) is about 160 nm/RIU, with an extinction ratio larger than 40 dB.

A graphene-based silicon hybrid plasmonic waveguide modulator with 25GHz 3dB bandwidth is proposed in this work. Due to high optical power density at the graphene layers, modulation depth can reach ...

Hybrid plasmonics can provide a technology solution for lab-on-a-chip applications with nano-scale waveguiding and subwavelength light confinement, keeping the propagation loss on an acceptable level. In this talk we will present some designed and fabricated devices in application to bio-sensing, based on single-slot and double-slot hybrid plasmonic resonant structures on silicon platform that can be integrated to obtain a multi-sensor array on a single chip.

Optical interconnects is today an obvious solution for inter- and intra-data center communication, but is also continuously penetrating the shorter and shorter distances in structures down to chip-to-chip and on-chip data transfer for multi-core processors.

As the age of Moore’s law is drawing to a close, continuing increase in computing performance is becoming increasingly hard‐earned, while demand for bandwidth is insatiable. One way of dealing with this challenge is the integration of active photonic material with Si, allowing high‐speed optical inter‐ and intra‐chip connects on one hand, and the economies of scale of the CMOS industry in optical communications on the other. One of the most essential active photonic materials is InP, stemming from its capability in combination with its related materials to produce lasers, emitting at wavelengths of 1300 and 1550 nm, the two most important wavelengths in data‐ and telecom.However, integrating InP with Si remains a challenging subject. Defects arise due to differences in lattice constants, differences in thermal expansion coefficients, polarity and island‐like growth behavior. Approaches to counter these problems include epitaxial lateral overgrowth (ELOG), which involves growing InP laterally from openings in a mask deposited on a defective InP/Si substrate. This approach solves some of these problems by filtering out the previously mentioned defects. However, filtering may not be complete and the ELOG and mask themselves may introduce new sources for formation of defects such as dislocations and stacking faults.In this work, the various kinds of defects present in InP ELOG layers grown by hydride vapor phase epitaxy on Si, and the reason for their presence, as well as strategies for counteracting them, are investigated. The findings reveal that whereas dislocations appear in coalesced ELOG layers both on InP and InP/Si, albeit to varying extents, uncoalesced ELOG layers on both substrate types are completely free of threading dislocations. Thus, coalescence is a critical aspect in the formation of dislocations. It is shown that a rough surface of the InP/Si substrate is detrimental to defect‐free coalescence. Chemical‐mechanical polishing of this surface improves the coalescence in subsequent ELOG leading to fewer defects.Furthermore, ELOG on InP substrate is consistently free of stacking faults. This is not the case for ELOG on InP/Si, where stacking faults are to some extent propagating from the defective substrate, and are possibly also forming during ELOG. A model describing the conditions for their propagation is devised; it shows that under certain conditions, a mask height to opening width aspect ratio of 3.9 should result in their complete blocking. As to the potential formation of new stacking faults, the formation mechanism is not entirely clear, but neither coalescence nor random deposition errors on low energy facets are the main reasons for their formation. It is hypothesized that the stacking faults can be removed by thermal annealing of the seed and ELOG layers.Furthermore, concepts for integrating an active photonic device with passive Si components are elucidated by combining Si/SiO2 waveguides used as the mask in ELOG and multi‐quantum well (MQW) lasers grown on ELOG InP. Such a device is found to have favorable thermal dissipation, which is an added advantage in an integrated photonic CMOS device.

A short overview of integrated waveguide demultiplexers for different applications in future highly integrated optical communication systems is presented. Some fabricated devices based on amorphous silicon nanowire technology are described.

AC poling allowing to control the orientation of P3HT nanofibers, result in strong optical birefringence with promising implementation in a novel type of optical modulator, without necessary embedd ...

An electro-optic polymer-based hollow hybrid plasmonic phase modulator has been proposed. Estimating from our preliminary experimental results, related to a hollow HP liquid sensor, the proposed device shows unique advantages in high speed modulation applications.

Optical study of two families of poly(propylene imine) (PPI) dendrimers (G = 1-5) are reported. The enlarging of the chain number (generations) of the PPI dendrimer leads to the spectra shift to IR region in solvent until 8 and 19 nm for both families, respectively. The theoretical modelling of the dendrimer structure was performed. The geometric characterization of dendrimer structure demonstrates that the preferable free space for encapsulation is periphery of the PPI dendrimer.

We formulate a “Moore’s law” for photonic integrated circuits (PICs) and their spatial integration density using two methods. One is decomposing the integrated photonics devices of diverse types into equivalent basic elements, which makes a comparison with the generic elements of electronic integrated circuits more meaningful. The other is making a complex component equivalent to a series of basic elements of the same functionality, which is used to calculate the integration density for functional components realized with different structures. The results serve as a benchmark of the evolution of PICs and we can conclude that the density of integration measured in this way roughly increases by a factor of 2 per year. The prospects for a continued increase of spatial integration density are discussed.

Passband broadening of an AWG (array waveguide grating) demultiplexer with an MMI (multimode interference) coupler connected at the end of a tapered input waveguide is considered. An explicit formu ...

A new type of wavelength selective filter, based on high differential dispersion between two coupled waveguides, is presented. The Bragg Reflection Waveguide displays high effective refractive index dispersion, due to the interaction of the guided mode with the two confining Bragg reflectors. When coupled with a weakly guided buried channel silica waveguide, a very narrow bandwidth filter (

Ion bombarding conditions were used to modify glass properties in silica-on-silicon systems during plasma enhanced chemical vapour deposition (PECVD). The induced structural modifications in the SiO2/Si system resulted in different photosensitive responses when irradiated by ArF pulsed laser operating at 193 nm wavelength. Fourier transform infrared spectroscopy was used to study the structural modifications triggered by ion bombarding conditions during film growth. The results were further confirmed by additional characterizations with regard to density (etch rate), refractive index and surface topographic measurements. The demonstrated method could be used not only to engineer UV-photosensitivity but also to control and compensate birefringence in planar lightwave devices.

A simple, low-cost spectrophotometer system operating in reflection absorption mode is used to characterize changes in refractive index and thickness of thin films under 193 nm irradiation. The results indicate overall dilation of the glass and are confirmed by additional surface topographic measurements. We also show that in addition to the net relaxation from laser annealing of the interface, in germanosilicate samples local compaction takes place. Since the net relaxation is triggered by remote interactions, it is not spatially confined to the laser-irradiated area. However, a local positive index change is observed. These results are in agreement with previous hypotheses put forward to explain planar waveguide negative index changes. They also bring to attention the great care necessary in both conducting and interpreting measurements that do not take into account spatial variations arising from the combination of remote and local triggers of both index and thickness changes.

We theoretically and experimentally investigate performance of slot hybrid plasmonic rings, with better sensitivity regarding tested liquids than Si-based ones. This component can also be employed as high-efficiency optical modulators with active nonlinear material.

This Letter reports the electro-optical (EO) effect of Poly(3-hexylthiophene-2,5-diyl) (P3HT) nanofibers colloid in a polymer micro-fluidic EO cell. P3HT nanofibers are high aspect ratio semiconducting nanostructures, and can be collectively aligned by an external alternating electric field. Optical transmission modulated by the electric field is a manifestation of the electro-optical effect due to high inner crystallinity of P3HT nanofibers. According to our results, the degree of alignment reaches a maximum at 0.6 V/μm of electric field strength, implying a big polarizability value due to geometry and electrical properties of P3HT nanofibers. We believe that one-dimensional crystalline organic nanostructures have a large potential in EO devices due to their significant anisotropy, wide variety of properties, low actuation voltages, and opportunity to be tailored via adjustment of the fabrication process.

An optically pumped thermo-optic (TO) silicon ring add-drop filter with fast thermal response is experimentally demonstrated. We propose that metal-insulator-metal (MIM) light absorber can be integrated into silicon TO devices, acting as a localized heat source which can be activated remotely by a pump beam. The MIM absorber design introduces less thermal capacity to the device, compared to conventional electrically-driven approaches. Experimentally, the absorber-integrated add-drop filter shows an optical response time of 13.7 μs following the 10%–90% rule (equivalent to a exponential time constant of 5 μs) and a wavelength shift over pump power of 60 pm/mW. The photothermally tunable add-drop filter may provide new perspectives for all-optical routing and switching in integrated Si photonic circuits.

CMOS compatible photonic integrated circuits have gained great attentions in short haul interconnects applications because of the promises to tackle the issues of traditional copper interconnects. Towards the monolithic integration of electronics and photonics, lots of efforts have been made to decrease the device footprint by using surface plasmon polaritons (SPPs), in order to enhance performances and decrease power consumption. With current metals, this is, however, only true for single or few cascaded devices. This situation can be mitigated by hybridizing SPPs with dielectric modes; hybrid plasmonic waveguides based on silicon platform can provide an alternative to exploit the advantages of both plasmonics and silicon. This paper presents several examples of design, fabrication and characterization of hybrid plasmonic functional components based on silicon nanowire platform, including hybrid plasmonic directional couplers, polarization beam splitters, disks and rings with submicron radii. A proposal of electro-optic polymer modulator based on hybrid plasmonic ring resonator is also discussed. The presented components provide alternative perspectives of novel devices which may be useful in future inter- and intra-core communication systems.

Efficient narrowband light absorption by a metal-insulator-metal (MIM) structure can lead to high-speed light-to-heat conversion at a micro- or nanoscale. Such a MIM structure can serve as a heater for achieving all-optical light control based on the thermo-optical (TO) effect. Here we experimentally fabricated and characterized a novel all-optical switch based on a silicon microdisk integrated with a MIM light absorber. Direct integration of the absorber on top of the microdisk reduces the thermal capacity of the whole device, leading to high-speed TO switching of the microdisk resonance. The measurement result exhibits a rise time of 2.0 μs and a fall time of 2.6 μs with switching power as low as 0.5 mW; the product of switching power and response time is only about 1.3 mW·μs. Since no auxiliary elements are required for the heater, the switch is structurally compact, and its fabrication is rather easy. The device potentially can be deployed for new kinds of all-optical applications.

Silicon nanophotonics became recently a very promising solution for high-speed signal transmission and processing with high bandwidth and very compact size, even for multifunctional integrated structures. With submicron waveguide cross section and bending radius down to 2 mu m with acceptable losses (0.04 dB/90 degrees bend) these structures give promising perspectives for electronic - photonic integration on a common Si platform since they can be realized by conventional planar CMOS techniques. Many research groups, both in academia and the electronics industry, have demonstrated different passive and active components, as well as integrated functional devices. However for more complex optical architectures, for example in optical interconnects for inter-and intra-core data communication, even higher integration density and modal field confinement below the diffraction limit of light, are necessary. For downscaling of photonic components, different solutions based on surface plasmon waveguiding along metal - dielectric interfaces have been proposed including strip-line, slot-line [1] and v-grove [2] structures, as well as some more sophisticated multi-layered systems [3] and quantum dot arrays [4]. Unfortunately, most of them suffer from the high losses always associated with maximum light confinement, resulting in short propagation lengths of the order of several micrometers. Hybrid plasmonic structures, which consist of a low refractive index slot sandwiched between e.g. a gold layer and a silicon material, appear to be a good solution [5-7]. In such structures, light is partly localized in the low-index dielectric and partly in the high-index Si giving relaxed conditions for propagation of the hybrid mode, but still with high confinement. Losses as low as 0.01 dB/mu m (propagation length over 400 mu m) have been obtained experimentally [8]. This is still orders of magnitude higher than those of conventional photonic waveguides, but acceptable for many functional components, not only to decrease the overall size of the structure, but also due to some specific advantages plasmonic components can bring forward, including temperature and production error tolerances, energy efficiency, large Purcell factor and others. So the best choice will probably be to use some kind of hybrid nanoplasmonic-photonic structures with conventional photonic waveguiding and functional plasmonic components. Hybrid plasmonic microring modulators, for example, with sub-micron radius have an intrinsically low quality factor Q, which on one side causes low channel bandwidth of these devices, but simultaneously allows for temperature and production error tolerances. The Q value of a 500 nm radius microring is anyway 8 times higher than the Q of similar Si slot microrings [9]. According to our calculations done for modulators using electrooptic polymer (EOP), even with a moderate electrooptic coefficient of 80 pm/V, due to the small footprint, the device capacitance is very small allowing for RC-limited modulation speed of 190 GHz (modulation speed limited by the cavity photon lifetime is larger than 300 GHz) and giving the average power consumption of only 5 fJ/bit. Similarly for lasers, due to the small cavity volume we should be able to get lower threshold power for lasing than is the case for traditional laser designs.

A one-dimensional grating serving both as a polarization beam splitter and a vertical coupler for silicon photonic circuits is designed, fabricated, and characterized. Bragg reflectors are employed to improve greatly the coupling efficiency. Over 50% efficiency for both polarizations are achieved experimentally, and the extinction ratio between them is also high ( -20 dB).

A polarization-insensitive design of an echelle grating (or etched diffraction grating) demultiplexer based on silicon nanowires is proposed in the present letter, by introducing a polarization compensation area in its free propagation region. The polarization-dependent wavelength shift of the present device has been compensated at the whole spectral range. For a design with nine channels and 10-nm channel spacing, when the wavelength shift at the central channel 1550 nm is completely compensated, the wavelength shifts of the two edge channels are only 0.14 and 0.15 nm, which are acceptable.

We present a structural and optical study of solid-state dispersions of Ge nanocrystals prepared by plasma-enhanced chemical vapor deposition. Structural analysis shows the presence of nanocrystalline germanium inclusions embedded in an amorphous matrix of Si-rich SiO(2).Optical characterization reveals two prominent emission bands centered around 2.6 eV and 3.4 eV, and tunable by excitation energy. In addition, the lower energy band shows an excitation power-dependent blue shift of up to 0.3 eV. Decay dynamics of the observed emission contains fast (nanosecond) and slow (microseconds) components, indicating contributions of several relaxation channels. Based on these material characteristics, a possible microscopic origin of the individual emission bands is discussed.

Si-based metallic whispering gallery mode disks with 0.5 μm and 1 μm radii are theoretically analyzed and experimentally demonstrated. Estimated Purcell factor is around 127±42. Thermo-tuning of the device is also presented.

An ultracompact polarization beam splitter (PBS) is proposed based on an asymmetrical directional coupler consisting of a silicon hybrid plasmonic waveguide (HPW) and a silicon nanowire. The widths of the two coupling waveguides are chosen so that the phase-matching condition is satisfied for TE polarization only while the phase mismatch is significant for TM polarization. A sharply bent silicon HPW is connected at the thru port to play the role of polarizer by utilizing its polarization-dependent loss. With the present principle, the designed PBS has a footprint as small as only ~1.9 μm × 3.7 μm, which is the shortest PBS reported until now, even when large waveguide dimensions (e.g., the waveguide widths w(1,2) = ~300 nm and the gap width w(gap) = ~200 nm) are chosen to simplify the fabrication process. The numerical simulations show that the designed PBS has a very broad band (~120 nm) with an extinction ratio12 dB and a large fabrication tolerance to allow a waveguide width variation of ± 30 nm.

Silicon-based integrated photonics became a very attractive technology for guiding and manipulating of light in highly integrated structures due to the large index contrast between silicon and cladding materials allowing for very high mode confinement. Moreover, these structures can be realized by conventional planar CMOS techniques. Different passive devices based on Si nanowire waveguides have been realized using SOI technology or amorphous silicon deposition with applications in highly integrated communication systems for optical networking, bio and sensing, as well as for computer interconnects in data centers. Nevertheless for future use, especially for inter-core and intra-core computer communication, structures allowing for subwavelength light confinement based on surface plasmon waveguiding are an attractive solution. Different methods to decrease or compensate the intrinsic high losses of these structures have been proposed. Here we report our work on design and experimental realization of hybrid plasmonic waveguides and devices that allow for considerable decrease of losses, still keeping sub-wavelength light confinement.

In this paper, we present our theoretical and experimental work on hybrid plasmonic microdisks. The 170 nm wide access waveguide is first simulated and characterized, and shows a propagation loss about 0.08 dB/μm. 3-D FDTD simulations are then used to investigate the lower limit of the bending radius of the hybrid plasmonic microdisk. Microdisks with radius around 500 nm are fabricated, characterized, and analyzed. The 5th and 4th order resonances are experimentally observed around 1412 nm and 1625 nm. The extinction ratios of the two resonances are measured to be 5.5dB and above 10dB, respectively. The measured intrinsic quality factors are 350 and 110, respectively. Comparisons are also made between the theoretical and experimental results. The demonstrated ultra-small hybrid plasmonic microdisk may find applications in low-power-consumption modulators, nano laser cavities with large Purcell-factor, molecule sensors, and others.

Development in photonics for communications and interconnects pose increasing requirements on reduction of footprint, power dissipation and cost, as well as increased bandwidth. Nanophotonics integrated photonics has been viewed as a solution to this, capitalizing on development in nanotechnology and an increased understanding of light matter interaction on the nanoscale. The latter can be exemplified by plasmonics and low dimensional semiconductors such as quantum dots (QDs). In this scenario the development of improved electrooptic materials is of great importance, the electrooptic polymers being an example, since they potentially offer superior properties for optical phase modulators in terms of power and integratability. Phase modulators are essential for e.g. the rapidly developing advanced modulation formats, since phase modulation basically can generate any type of modulation. The electrooptic polymers, in combination with plasmonics nanoparticle array waveguides or nanostructured hybrid plasmonic media can give extremely compact and low power dissipation modulators. Low-dimensional semiconductors, e.g. in the shape of QDs, can be employed for modulation or switching functions, offering possibilities for scaling to 2 or 3 dimensions for advanced switching functions. In both the high field confinement plasmonics and QDs, the nanosizing is due to nearfield interactions, albeit being of different physical origin in the two cases. Epitaxial integration of III-V structures on Si plays an important role in developing high-performance light sources on silicon, eventually integrated with silicon electronics. A brief remark on all-optical vs. electronically controlled optical switching systems is also given.

The current development in photonics for communications and interconnects pose increasing requirements on reduction of footprint, power dissipation and cost, as well as increased bandwidth. Integrated nanophotonics has been viewed as one solution to this, capitalizing on development in nanotechnology as such as well as on increased insights into light matter interaction on the nanoscale. The latter can be exemplified by plasmonics and low-dimensional semiconductors such as quantum dots (QDs). In this scenario the development of better electrooptic materials is also of great importance, the electrooptic polymers being an example, since they potentially offer improved properties for optical phase modulators in terms of power and probably cost and general flexibility. Phase modulators are essential for e.g. the rapidly developing advanced modulation formats for telecom, since phase modulation basically can generate any type of modulation. The electrooptic polymers, e.g. in combination with plasmonics nanoparticle array waveguides or nanostructured hybrid plasmonic media can theoretically give extremely compact and low power dissipation modulators, still to be demonstrated. The low-dimensional semiconductors, e.g. in the shape of QDs, can be employed for modulation or switching functions, offering possibilities in the future for scaling to 2 or 3 dimensions for advanced switching functions. In both the plasmonics and QD cases, nanosizing and low power dissipation are generally due to near-field interactions, albeit being of different physical origin in the two cases. A comparison of all-optical and electronically controlled switching is given.

An ultracompact polarization beam splitter (PBS) based on a dielectric-hybrid plasmonic-dielectric coupler is proposed. The device utilizes the polarization-dependent nature of hybrid plasmonic waveguides. By choosing proper waveguide parameters, a 2×5.1 μm2 PBS (including S-bends) with extinction ratios over 15 dB and insertion losses below 1.5 dB in the full C-band should be achievable. The effect of fabrication errors is also investigated.

Electromagnetically induced transparency (EIT) effect has been theoretically demonstrated using hybrid plasmonic waveguide system, composed of two stripe-shaped resonators in form of resonant stubs with different lengths located on each side of the HP waveguide.

Hybrid plasmonic waveguide structures allows for sub-wavelength light confinement while keeping propagation losses on an acceptable level. Design and experimental realization of ultra-compact hybrid plasmonic devices based on a silicon platform are presented.