Capacitor-embedded 054 pJ/bit silicon-slot photonic crystal waveguide modulator

Improving the performance of all-optical switching based on nonlinear photonic Crystal microring resonators

The light harvesting efficiency of dye-sensitized photoelectrodes was enhanced by coupling a TiO(2) photonic crystal layer to a conventional film of TiO(2) nanoparticles. In addition to acting as a dielectric mirror, the inverse opal photonic crystal caused a significant change in dye absorbance which depended on the position of the stop band. Absorbance was suppressed at wavelengths shorter than the stop band maximum and was enhanced at longer wavelengths. This effect arises from the slow group velocity of light in the vicinity of the stop band, and the consequent localization of light intensity in the voids (to the blue) or in the dye-sensitized TiO(2) (to the red) portions of the photonic crystal. By coupling a photonic crystal to a film of TiO(2) nanoparticles, the short circuit photocurrent efficiency across the visible spectrum (400-750 nm) could be increased by about 26%, relative to an ordinary dye-sensitized nanocrystalline TiO(2) photoelectrode.

We demonstrate both theoretically and numerically that slow light can enhance the stimulated emission of four-level atomic systems in photonic crystals. By applying the Bloch-Floquet formalism and the semiclassical physical model of harmonic oscillators coupled to electromagnetic fields, we develop a formalism that relates the group velocity of slow light to the conversion rate between the electric field and atomic potential energy. From our numerical study of the stimulated emission in fiber Bragg gratings (FBGs) and nongrating fiber, a ninefold enhancement of stimulated emission is observed in a FBG over the nongrating fiber when pumping at the band edge, while a 20-fold enhancement of is observed when the frequency of the stimulated emission approaches the band edge.

Slow light with electromagnetically induced transparency (EIT) in the core of optical fibre containing three-level atoms is investigated. The guided modes are treated in the weakly guiding approximation which renders the analysis into a manageable form. The transparency window and permittivity profile of the core due to the strong pump field in the EIT scheme is calculated. For a specific permittivity profile of the core due to EIT, the propagation constant of the weak signal field and spatial shape of fundamental guided mode are calculated by solving the vector wave equation using the finite difference method. It is found that the transparency window and slow light field can be controlled via the optical fibre parameters. The reduced group velocity of slow light in this configuration is useful for many technological applications such as optical memories, effective control of single photon fields, optical buffers and delay lines.

Compact and high-speed electro-optic phase modulators play a vital role in various large-scale applications including optical computing, quantum and neural networks, and optical communication links. Conventional electro-refractive phase modulators such as silicon (Si), III-V and graphene on Si suffer from a fundamental tradeoff between device length and optical loss that limits their scaling capabilities. High-finesse ring resonators have been traditionally used as compact intensity modulators, but their use for phase modulation has been limited due to the high insertion loss associated with the phase shift. Here, we show that high-finesse resonators can achieve a strong phase shift with low insertion loss by simultaneous modulation of the real and imaginary parts of the refractive index, to the same extent, i.e., ΔnΔk∼1. To implement this strategy, we demonstrate an active hybrid platform that combines a low-loss SiN ring resonator with 2D materials such as graphene and transition metal dichalcogenide [tungsten disulphide (WSe2)], which induces a strong change in the imaginary and real parts of the index. Our platform consisting of a 25 µm long Gr-Al2O3-WSe2capacitor embedded on a SiN ring of 50 µm radius (∼8% ring coverage) achieves a continuous phase shift of (0.46±0.05)πradians with an insertion loss (IL) of 3.18±0.20 dB and a transmission modulation (ΔTRing) of 1.72±0.15dB at a probe wavelength (λp) of 1646.18 nm. We find that our Gr-Al2O3-WSe2capacitor exhibits a phase modulation efficiency (Vπ2⋅L) of 0.530±0.016V⋅cm and can support an electro-optic bandwidth of 14.9±0.1GHz. We further show that our platform can achieve a phase shift ofπradians with an IL of 5 dB and a minimum ΔTof 0.046 dB. We demonstrate the broadband nature of the binary phase response, by measuring a phase shift of (1.00±0.10)πradians, with an IL of 5.20±0.31dB and a minimal ΔTRingof 0.015±0.006dB for resonances spanning from 1564 to 1650 nm. This SiN–2D hybrid platform provides the design for compact and high-speed reconfigurable circuits with graphene and transition metal dichalcogenide (TMD) monolayers that can enable large-scale photonic systems.

Due to abrupt increment of the interconnect length in the 65nm-node ASICs, the total interconnect parasitic capacitance is not ignored relative to the total transistor capacitance on the chip. Therefore, by replacement of the conventional SiO/sub 2/ interlayer dielectric (ILD, k=4.2) film to a porous low-k film (k=2.5) in 65nm-nodes, the chip performance such as "multi-functionality and low-power consumption" is estimated to achieve 20-40% improvement. From a view point of the chip fabrication, however, the porous low-k films have difficulties in process integration due to their mechanical and electrical weaknesses. The pore size control in sub-nanometer scales and the pore scaling at the side-walls of line trenches and vias are key technologies to improve the interconnect reliability. For 45nm-node ASICs and beyond, molecular-level controls in the pore structure and the chemical composition of ultra low-k, porous films will be needed to keep the interconnect reliability.

A novel multirate double-sampling sigma delta modulator is proposed for the low power A/D converter for multi-standard wireless applications. A cascade 2-2 structure is designed for the modulator. The multirate technique reduces the sampling rate of the 1st stage integrator to relax the performance requirements of the operational amplifiers(OPAMP), which in turn results in low power consumption. The double-sampling technique is adopted to update the integrator output of the switched capacitor circuit during the both clock phases of the master clock. The sampling frequency is twice of the master clock frequency. The clock frequency can be halved to relax the settling time of the OPAMPs to achieve the similar performance concerning the signal to noise ratio with the conventional sigma delta modulator, which decreases the power dissipation. In comparison with the conventional double-sampling sigma delta modulator topology, the proposed modulator architecture obtains the similar performance with a low slewrate requirement of the 1st stage integrator. The power dissipation is effectively decreased.

An ultra-compact silicon Mach-Zehnder interferometer (MZI) modulator featuring p-i-n-diode-embedded photonic crystal waveguides has been fabricated. As carrier injection is the only practical option for optical modulation in silicon, a lower limit of current density (~10⁴A/cm²) exists for achieving gigahertz modulation in the widely employed p-i-n diode configuration. Electrical simulations have been performed to design and analyze the device. The device interaction length was reduced by one order of magnitude compared to the conventional waveguide based MZI modulators by taking advantage of the slow group velocity exhibited by photonic crystal waveguides (PCWs). A maximum modulation depth of 93% has been obtained under an injected current of 7.1 mA. High-speed optical modulation at 1 Gbit s^-1 in the 1.55 micron wavelength region was experimentally demonstrated. To our knowledge, this is the fastest speed ever achieved for a p-i-n diode based integrated silicon MZI modulator.

Laser diodes are being utilized with increasing frequency in optical remote sensing applications. Their attractive features include small size, low cost, low power consumption, good output power, high modulation speed, good reliability, and good wavelength tunability. However, their optical properties vary significantly even during the same manufacturing run. Therefore, when the application places stringent requirements on their optical properties, diodes need to be individually characterized and evaluated. This paper discusses our present efforts to characterize laser diodes for use in a Differential Absorption Lidar (DIAL) instrument which imposes very tight requirements on diode behavior.

We demonstrate a fully independent differential-drive capable of traveling-wave modulator in silicon using slow-wave transmission line electrode. The reported 3.5-mm device achieves a bandwidth of 27 GHz at $-$ 1 V bias with 7.8-V small signal $V_\pi$ and 50- $\Omega$ impedance. Raising the impedance to this extent requires effectively expanding the RF mode size and radically changes the RF phase velocity, but we show that this can be done with minimal crosstalk effects between the two arms and overall velocity mismatch, and thus, with a high EO bandwidth achieved. 40-Gb/s operation is demonstrated with 1.6-Vpp differential-drive, and performance comparisons to Lithium Niobate modulators are made.

The ability to directly modulate a nanocavity laser with ultralow power consumption is essential for the realization of a CMOS-integrated, on-chip photonic network, as several thousand lasers must be integrated onto a single chip. Here, we show high-speed direct modulation (3-dB modulation bandwidth of 5.5 GHz) of an ultracompact InP/InGaAsP buried heterostructure photonic-crystal laser at room temperature by optical pumping. The required energy for transmitting one bit is estimated to be 13 fJ. We also achieve a threshold input power of 1.5 µW, which is the lowest observed value for room-temperature continuous-wave operation of any type of laser. The maximum single-mode fibre output power of 0.44 µW is the highest output power, to our knowledge, for photonic-crystal nanocavity lasers under room-temperature continuous-wave operation. Implementing a buried heterostructure leads to excellent device performance, reducing the active region temperature and effectively confining the carriers inside the cavity. Advanced on-chip photonic networks require integrated nanoscale lasers with low power consumption. Researchers have now demonstrated high-speed modulation of a compact heterostructure photonic crystal laser at room temperature with an unprecedented low required energy of ∼13 fJ per bit transmitted.

A high speed and low loss silicon optical modulator based on carrier depletion has been made using an original structure consisting of a p-doped slit embedded in the intrinsic region of a lateral pin diode. This design allows a good overlap between the optical mode and carrier density variations. Insertion loss of 5 dB has been measured with a contrast ratio of 14 dB for a 3 dB bandwidth of 10 GHz.

We propose and analyze theoretically an asymmetric Ge/SiGe coupled quantum well (CQW) for silicon based optical phase modulator. An 8-band k⋅p model is used to calculate the eigenstates and absorption spectra of the CQWs. The simulation results exhibit unique physical characteristics owing to the coupling between the two wave functions through the thin barriers. We can achieve an electro-refractive index variation as high as 9 × 10-3 at the wavelength of about 1461 nm under the electric field of 30 kV/cm. The product VπLπ of half-wave voltage and length of phase shift region is estimated to be 0.01 V cm. The proposed asymmetric Ge/SiGe CQW scheme provides a promising candidate for high speed, low voltage, low power consumption and compact optical phase modulators in silicon-based integrated optoelectronic devices.

In this article, we demonstrate a silicon-based carrier-injection optical single-sideband (OSSB) modulator featuring a double-parallel Mach-Zehnder interferometer architecture. This design simultaneously achieves ultra-low driving voltage and high sideband suppression ratio (SSR). By optimizing the p- and n-doping profiles, the device achieves a V<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">π</sub>·L of approximately 0.0375 V·cm. In OSSB operation, the unwanted sideband is suppressed by around 33 dB, highlighting the modulator’s exceptional sideband suppression. These characteristics—low driving voltage, low loss, and high suppression—make the device highly suitable for homodyne phase-locking, on-chip sensing, and other integrated photonic applications.

In this paper, 16-Phase Shift Keying modulator is designed, by using various PSK modulation schemes which is designed for the wireless communication systems using MIC techniques. Sixteen-Phase Shift Keying (16-PSK) designed at the S-band that allows achieving a very high accuracy in phase with very low power consumption. The isolation between the carrier input port and the output port is very high and the phase error is less than 1o. The substrate used for the PSK modulator is FR-4 and the specification for substrate is dielectric thickness (h) =0.08mm, conductor thickness (t) =0.035mm, dielectric constant (e) =4.4 and tangent loss=0.001