Silicon-on-insulator Nanowire Research Articles

Enhanced Spectral Broadening of Femtosecond Optical Pulses in Silicon Nanowires Integrated with 2D Graphene Oxide Films.

We experimentally demonstrate enhanced spectral broadening of femtosecond optical pulses after propagation through silicon-on-insulator (SOI) nanowire waveguides integrated with two-dimensional (2D) graphene oxide (GO) films. Owing to the strong mode overlap between the SOI nanowires and the GO films with a high Kerr nonlinearity, the self-phase modulation (SPM) process in the hybrid waveguides is significantly enhanced, resulting in greatly improved spectral broadening of the femtosecond optical pulses. A solution-based, transfer-free coating method is used to integrate GO films onto the SOI nanowires with precise control of the film thickness. Detailed SPM measurements using femtosecond optical pulses are carried out, achieving a broadening factor of up to ~4.3 for a device with 0.4-mm-long, 2 layers of GO. By fitting the experimental results with the theory, we obtain an improvement in the waveguide nonlinear parameter by a factor of ~3.5 and in the effective nonlinear figure of merit (FOM) by a factor of ~3.8, relative to the uncoated waveguide. Finally, we discuss the influence of GO film length on the spectral broadening and compare the nonlinear optical performance of different integrated waveguides coated with GO films. These results confirm the improved nonlinear optical performance of silicon devices integrated with 2D GO films.

Enhanced Kerr Nonlinearity and Nonlinear Figure of Merit in Silicon Nanowires Integrated with 2D Graphene Oxide Films.

Layered two-dimensional (2D) graphene oxide (GO) films are integrated with silicon-on-insulator (SOI) nanowire waveguides to experimentally demonstrate an enhanced Kerr nonlinearity, observed through self-phase modulation (SPM). The GO films are integrated with SOI nanowires using a large-area, transfer-free, layer-by-layer coating method that yields precise control of the film thickness. The film placement and coating length are controlled by opening windows in the silica cladding of the SOI nanowires. Owing to the strong mode overlap between the SOI nanowires and the highly nonlinear GO films, the Kerr nonlinearity of the hybrid waveguides is significantly enhanced. Detailed SPM measurements using picosecond optical pulses show significant spectral broadening enhancement for SOI nanowires coated with 2.2 mm long films of 1-3 layers of GO and 0.4 mm long films with 5-20 layers of GO. By fitting the experimental results with theory, the dependence of GO's Kerr nonlinearity on layer number and pulse energy is obtained, showing interesting physical insights and trends of the layered GO films from 2D monolayers to quasi bulk-like behavior. Finally, we show that by coating SOI nanowires with GO films, the effective nonlinear parameter of SOI nanowires is increased 16-fold, with the effective nonlinear figure of merit (FOM) increasing by about 20 times to FOM > 5. These results reveal the strong potential of using layered GO films to improve the Kerr nonlinear optical performance of silicon photonic devices.

CMOS compatible SOI nanowire FET with charged dielectric for temperature sensing applications

This paper reports a novel concept of a low voltage low power temperature sensor with a 300–370 K operating temperature range, based on a silicon-on-insulator (SOI) nanowire FET with standard SOI CMOS technology. The novel design combines a top-down silicon nanowire and an electrostatically formed nanowire, capacitively coupled to a back-gate electrode. A surface charged silicon nitride layer is used to deplete the upper part of the nanowire, while a back-gate controls the size and location of the electrostatically formed nanowire. The device operates in a regime similar to the subthreshold regime of a nanowire transistor and features a very high temperature response, expressed by the temperature coefficient of current (TCC = 6 % K−1 at 0.4 < IDS < 5 pA for a single nanowire). The device can be easily integrated into a nanowire-based sensor array.

Analysis of Nanowire Field-Effect Transistors SET Response: Geometrical Considerations

The single-event transient (SET) response of silicon-on-insulator (SOI) tri-gate silicon nanowires is investigated using direct measurements of current transients. The impact of nanowire geometry is discussed using the major SET characteristics: duration, amplitude, and integrated value. The experimental results demonstrate the key influence of the nanowire width on the generated current transients induced by heavy ion irradiations. Both Monte-Carlo calculations of deposited energy and Technology Computer Aided Design (TCAD) simulations give evidence of the SOI tri-gate silicon nanowires ability to mitigate generated current transients. TCAD calculations are used to discuss the impact of the main nanowire geometrical parameters which include the nanowire width, thickness, and gate length, on transient charge collection mechanisms in SOI nanowire field-effect transistors (NWFET). Thin and narrow NWFET designs enhance the control of the surrounding gate over the electrostatic potential into the nanowire. The onset of floating body effects induced by heavy ion strike is reduced which mitigates the SET generation.

On-chip hybrid demultiplexer for mode and coarse wavelength division multiplexing

We propose a hybrid demultiplexer for mode and coarse wavelength division multiplexing on silicon-on-insulator (SOI) nanowires and photonic crystal (PhC) slab. First, a V-shape waveguide–cavity–waveguide filter based on PhC slab is presented. Coupling of resonant modes is introduced to the filter to suppress the crosstalk caused by connection with nanowires. Then, we cascade and optimize the filter to compose a coarse wavelength division demultiplexer. After that, a hybrid demultiplexer is constructed by combining the coarse wavelength division demultiplexer on PhC slab and mode division demultiplexer on SOI nanowires. The parameters of the hybrid demultiplexer are calculated using three-dimensional finite-difference time-domain (3D-FDTD) method. The numerical results show that the fundamental transverse electric ( $$\hbox {TE}_0$$ ) modes and the first-order TE ( $$\hbox {TE}_1$$ ) modes of 1530 nm and 1550 nm can be demultiplexed. The insertion loss is smaller than 2.0 dB, and the channel crosstalk is less than − 25 dB. The hybrid demultiplexer can be applied in a system that using mode and coarse wavelength division multiplexing simultaneously.

Ultrasensitive Detection of 2,4-Dinitrophenol Using Nanowire Biosensor

The method for the detection of 2,4-dinitrophenol (DNP) in solution is proposed. This method employs the sensors based on silicon nanowire field-effect transistors with protective layers of high-k dielectrics, whose surface is functionalized with an amino silane. Direct highly sensitive detection of DNP has been demonstrated, and the lowest detectable concentration of DNP was determined to be 10−14 M. Silicon-on-insulator nanowire (SOI-NW) sensors can well be employed for the rapid detection of a wide range of toxic and explosive compounds by selection of sensor surface modification techniques.

10‐Channel Mode (de)multiplexer with Dual Polarizations

AbstractA dual‐polarization 10‐channel mode (de)multiplexer is proposed and realized with cascaded dual‐core adiabatic tapers on a silicon‐on‐insulator (SOI) platform. The mode demultiplexer has a 2.3 μm‐wide multimode bus waveguide, which supports six mode‐channels of TE polarization and four mode‐channels of TM polarization. These ten mode‐channels are (de)multiplexed with five cascaded dual‐core adiabatic tapers based on SOI nanowires. The widths for these dual‐cores are chosen optimally according to the dispersion curves of the dual‐core SOI nanowire, so that the desired highest‐order modes of TE‐ and TM‐polarizations are extracted simultaneously. These two extracted mode‐channels are coupled very efficiently to the fundamental modes of TE‐ and TM‐polarizations (TE0 and TM0) in the narrow waveguide, respectively, which are then separated by using a polarization beam splitter based on bent directional couplers. A chip consisting of a pair of 10‐channel mode (de)multiplexers is fabricated and then tested with data transmission of 30Gbps/channel. The measurement results show that all TM‐ and TE mode‐channels have low crosstalks (–15∼–25 dB) and low excess losses (0.2∼1.8 dB) over a broad wavelength band of ∼90 nm, which makes it WDM (wavelength‐division‐multiplexing)‐compatible and thus suitable for high capacity on‐chip optical interconnects.

Harmonic distortion analysis of triple gate SOI nanowire MOSFETS down to 100 K

The linearity of triple gate nanowire transistors (NWs) implemented on a Silicon-On-Insulator (SOI) substrate is investigated in this work considering temperature (T) influence. The analysis is performed in long channel nanowire MOSFETs with different fin width (WFIN), from quasi-planar structures (WFIN=10μm) to narrow devices (9.5nm), operating as single-transistor amplifiers from room temperature down to 100K. The total, second and third order harmonic distortions (THD, HD2 and HD3, respectively) are extracted using the Integral Function Method (IFM). The analysis is divided in two parts. First, a fixed input signal is applied at the gate of the single-transistor amplifiers and, then, the output signal is fixed. Transport parameters such as effective mobility (μeff), mobility degradation coefficient (θ) and series resistance (RS) have been extracted down to 100K and correlated to the distortion to explain linearity peaks behavior with temperature and fin width. Narrow transistors have shown improved linearity mainly due to higher intrinsic voltage gain (AV) considering the entire temperature range. Low temperature operation has shown to degrade the linearity characteristics of both wide and narrow NW MOSFETs.

Analysis of Self Heating Effect(SHE) according to Buried Oxide Thickness in SOI Nanowire FET

In this paper, the Self Heating Effect (SHE) is investigated in silicon on insulator (SOI) nanowire MOSFETs. A comprehensive study of SHE in Nanowire FET (NWFET) was implemented by Technology Computer-Aided Design (TCAD) simulation. Through analysis of on-current (ISUBon/SUBSUB/SUB), thermal resistance (RSUBTH/SUB), and heat flux, the DC characteristics of SHE were investigated according to the increase of buried oxide thickness (Tbox). The results indicate that leakage current is not changed according to Tbox so that it is not necessary to increase TSUBbox/SUB. In conclusion, in case that TSUBbox/SUB was optimized by 1 nm, temperature and RSUBTH/SUB were reduced by 152 K and 54.5% respectively. Also, ISUBon/SUB was increased by 5.84% maintaining leakage current compared with Tbox of 20 nm.

Compact polarization beam splitter for silicon photonic integrated circuits with a 340-nm-thick silicon core layer.

A polarization beam splitter (PBS) is proposed and realized for silicon photonic integrated circuits with a 340-nm-thick silicon core layer by introducing an asymmetric directional coupler (ADC), which consists of a silicon-on-insulator (SOI) nanowire and a subwavelength grating (SWG) waveguide. The SWG is introduced to provide an optical waveguide which has much higher birefringence than a regular 340-nm-thick SOI nanowire, so that it is possible to make the phase-matching condition satisfied for TE polarization only in the present design when the waveguide dimensions are optimized. Meanwhile, there is a significant phase mismatching for TM polarization automatically. In this way, the present ADC enables strong polarization selectivity to realize a PBS that separates TE and TM polarizations to the cross and through ports, respectively. The realized PBS has a length of ∼2 μm for the coupling region. For the fabricated PBS, the extinction ratio (ER) is 15-30dB and the excess loss is 0.2-2.6dB for TE polarization while the ER is 20-27dB and the excess loss is 0.3-2.8dB for TM polarization when operating in the wavelength range of 1520-1580nm.

Crosstalk analysis of silicon-on-insulator nanowire-arrayed waveguide grating**Project supported by the National High Technology Research and Development Program of China (Grant No. 2015AA016902), the National Natural Science Foundation of China (Grant Nos. 61274047, 61435013, 61307034, and 61405188), and the National Key Research and Development Program of China (Grant No. 2016YFB0402504).

The factors influencing the crosstalk of silicon-on-insulator (SOI) nanowire arrayed waveguide grating (AWG) are analyzed using the transfer function method. The analysis shows that wider and thicker arrayed waveguides, outsider fracture of arrayed waveguide, and larger channel space, could mitigate the deterioration of crosstalk. The SOI nanowire AWGs with different arrayed waveguide widths are fabricated by using deep ultraviolet lithography (DUV) and inductively coupled plasma etching (ICP) technology. The measurement results show that the crosstalk performance is improved by about 7 dB through adopting 800 nm arrayed waveguide width.

Sensitivity Enhancement in Si Nanophotonic Waveguides Used for Refractive Index Sensing

A comparative study is given for the sensitivity of several typical Si nanophotonic waveguides, including SOI (silicon-on-insulator) nanowires, nanoslot waveguides, suspended Si nanowires, and nanofibers. The cases for gas sensing (ncl ~ 1.0) and liquid sensing (ncl ~ 1.33) are considered. When using SOI nanowires (with a SiO2 buffer layer), the sensitivity for liquid sensing (S ~ 0.55) is higher than that for gas sensing (S ~ 0.35) due to lower asymmetry in the vertical direction. By using SOI nanoslot waveguides, suspended Si nanowires, and Si nanofibers, one could achieve a higher sensitivity compared to sensing with a free-space beam (S = 1.0). The sensitivity for gas sensing is higher than that for liquid sensing due to the higher index-contrast. The waveguide sensitivity of an optimized suspended Si nanowire for gas sensing is as high as 1.5, which is much higher than that of a SOI nanoslot waveguide. Furthermore, the optimal design has very large tolerance to the core width variation due to the fabrication error (∆w ~ ±50 nm). In contrast, a Si nanofiber could also give a very high sensitivity (e.g., ~1.43) while the fabrication tolerance is very small (i.e., ∆w < ±5 nm). The comparative study shows that suspended Si nanowire is a good choice to achieve ultra-high waveguide sensitivity.

Silicon-on-Insulator Nanowire Based Optical Waveguide Biosensors

Optical waveguide biosensors based on silicon-on-insulator (SOI) nanowire have been developed for label free molecular detection. This paper reviews our work on the design, fabrication and measurement of SOI nanowire based high-sensitivity biosensors employing Vernier effect. Biosensing experiments using cascaded double-ring sensor and Mach-Zehnder- ring sensor integrated with microfluidic channels are demonstrated

Silicon nanowire hot carrier electroluminescence

Avalanche electroluminescence from silicon pn junctions has been known for many years. However, the internal quantum efficiencies of these devices are quite low due to the indirect band gap nature of the semiconductor material. In this study we have used reach-through biasing and SOI (silicon-on-insulator) thin film structures to improve the internal power efficiency and the external light extraction efficiency. Both continuous silicon thin film pn junctions and parallel nanowire pn junctions were manufactured using a custom SOI technology. The pn junctions are operated in the reach-through mode of operation, thus increasing the average electric field within the fully depleted region. Experimental results of the emission spectrum indicate that the most dominant photon generating mechanism is due to intraband hot carrier relaxation processes. It was found that the SOI nanowire light source external power efficiency is at least an order of magnitude better than the comparable bulk CMOS (Complementary Metal Oxide Semiconductor) light source.

SOI nanowire transistor for detection of D-NFATc1 molecules

Nanowire (NW) detection is one of the fast and highly sensitive methods. An NW biosensor based on silicon-on-insulator (SOI) structures are used in the reported study for real-time label-free biospecific detection of the NFATc1 (D-NFATc1) cancer marker. For this purpose, the SOI NWs are functionalized with NFATc1 aptamers used as macromolecular probes. It is demonstrated that such a biosensor can ensure a detection limits up to 10−15 M, which is comparable with the sensitivity ensured by an NW biosensor with immobilized antibodies used as macromolecular probes. The results of this study demonstrate that such approaches to the development of sensor elements for highly sensitive diagnostics of diseases are really promising.

Polarization management for silicon photonic integrated circuits

AbstractPolarization management is very important for photonic integrated circuits (PICs) and their applications. Due to geometrical anisotropy and fabrication inaccuracies, the characteristics of the guided transverse‐electrical (TE) and transverse‐magnetic (TM) modes are generally different. Polarization‐dependent dispersion and polarization‐dependent loss are such manifestations in PICs. These issues become more severe in high index contrast structures such as nanophotonic waveguides made of silicon‐on‐insulator (SOI), which has been regarded as a good platform for optical interconnects because of the compatibility with CMOS processing. Recently, polarization division multiplexing (PDM) with coherent detection using silicon photonics has also attracted much attention. This trend further highlights the importance of polarization management in silicon PICs. The authors review their work on polarization management for silicon PICs using the polarization independence and polarization diversity methods. Polarization issues and solutions in PICs made of SOI nanowires and ridge waveguides are discussed.

The BOOM Project: Towards 160 Gb/s Packet Switching Using SOI Photonic Integrated Circuits and Hybrid Integrated Optical Flip-Flops

We present a 160 Gb/s optical packet switching architecture that performs label detection and packet wavelength con- version using photonic components integrated on silicon-on-insulator (SOI) waveguide boards. For label detection, we report the fabrication of a 4-channel tunable, second-order microring resonator demultiplexer using the SOI nanowire waveguide platform. For all-optical wavelength conversion we report the integration and packaging of a cascaded SOI delay interferometer (DI) structure using SOI rib waveguides. Both components were assembled with an optical flip-flop to enable 160 Gb/s optical packet switching. The power penalty after the wavelength conversion process was ~4.5 dB with error performance well above the FEC limit. This work is part of the European ICT-BOOM project which aims at building a Tb/s photonic router using hybrid and heterogeneous integration on SOI substrates. The preliminary results reported here is the initial step before the final project demonstrator.

Fabrication of Silicon Nanowire for Detecting &lt;I&gt;β&lt;/I&gt;-Amyloid (1-42) by Nanoimprint Lithography

Ultraviolet nanoimprint lithography (UV-NIL) is a high volume and cost-effective patterning technique with sub-10 nm resolution. It has great potential as a candidate for next generation lithography. Using UV-NIL, nanowire patterns were successfully fabricated on a four-inch silicon-on-insulator (SOI) wafer under moderate conditions. The fabricated nanowire patterns were characterized by FE-SEM. Its electrical properties were confirmed by semiconductor parameter analysis. Monoclonal antibodies against beta-amyloid (1-42) were immobilized on the silicon nanowire using a chemical linker. Using this fabricated silicon nanowire device, beta-amyloid (1-42) levels of 1 pM to 100 nM were successfully determined from conductance versus time characteristics. Consequently, the nanopatterned SOI nanowire device can be applied to bioplatforms for the detection of proteins.

Top-Down Processed SOI Nanowire Devices for Biomedical Applications

We present silicon nanowire (SiNW) devices, which were fabricated in a top-down process from silicon-on-insulator (SOI) substrates with a high yield. Electronic characterization proved reliable electronic properties. Here we report the versatile use of the devices in different applications like label-free sensing of DNA hybridization, electronic detection of cellular signals, and detection of proteins. Compared to micro-sized devices, the SiNWs show an improved sensitivity. Analyses of the electronic cell-nanowire contact showed that the important seal resistance is largely increased, which is a prerequisite for highly-sensitive detection of cellular activity. In all applications the SiNW devices show a reliable performance and are highly interesting for future biomedical products.

Ultra compact triplexing filters based on SOI nanowire AWGs

An ultra compact triplexing filter was designed based on a silicon on insulator (SOI) nanowire arrayed waveguide grating (AWG) for fiber-to-the-home FTTH. The simulation results revealed that the design performed well in the sense of having a good triplexing function. The designed SOI nanowire AWGs were fabricated using ultraviolet lithography and induced coupler plasma etching. The experimental results showed that the crosstalk was less than −15 dB, and the 3 dB-bandwidth was 11.04 nm. The peak wavelength output from ports a, c, and b were 1455, 1510 and 1300 nm, respectively, which deviated from our original expectations. The deviation of the wavelength is mainly caused by 45 nm width deviation of the arrayed waveguides during the course of the fabrication process and partly caused by material dispersion.