High-speed modulation of a compact silicon ring resonator based on a reverse-biased pn diode

A Review of Photonic Sensors Based on Ring Resonator Structures: Three Widely Used Platforms and Implications of Sensing Applications

Optical ring resonators (RRs) are a novel sensing device that has recently been developed for several sensing applications. In this review, RR structures based on three widely explored platforms, namely silicon-on-insulator (SOI), polymers, and plasmonics, are reviewed. The adaptability of these platforms allows for compatibility with different fabrication processes and integration with other photonic components, providing flexibility in designing and implementing various photonic devices and systems. Optical RRs are typically small, making them suitable for integration into compact photonic circuits. Their compactness allows for high device density and integration with other optical components, enabling complex and multifunctional photonic systems. RR devices realized on the plasmonic platform are highly attractive, as they offer extremely high sensitivity and a small footprint. However, the biggest challenge to overcome is the high fabrication demand related to such nanoscale devices, which limits their commercialization.

Silicon Photonic Phase Shifters and Their Applications: A Review

With the development of silicon photonics, dense photonic integrated circuits play a significant role in applications such as light detection and ranging systems, photonic computing accelerators, miniaturized spectrometers, and so on. Recently, extensive research work has been carried out on the phase shifter, which acts as the fundamental building block in the photonic integrated circuit. In this review, we overview different types of silicon photonic phase shifters, including micro-electro-mechanical systems (MEMS), thermo-optics, and free-carrier depletion types, highlighting the MEMS-based ones. The major working principles of these phase shifters are introduced and analyzed. Additionally, the related works are summarized and compared. Moreover, some emerging applications utilizing phase shifters are introduced, such as neuromorphic computing systems, photonic accelerators, multi-purpose processing cores, etc. Finally, a discussion on each kind of phase shifter is given based on the figures of merit.

Long cavity photonic crystal laser in FDML operation using an akinetic reflective filter

A novel configuration of a Fourier domain mode locked (FDML) laser based on silicon photonics platform is presented in this work that exploits the narrowband reflection spectrum of a photonic crystal (PhC) cavity resonator. Configured as a linear Fabry-Perot laser, forward biasing of a p-n junction on the PhC cavity allowed for thermal tuning of the spectrum. The modulation frequency applied to the reflector equalled the inverse roundtrip time of the long cavity resulting in stable FDML operation over the swept wavelength range. An interferometric phase measurement measured the sweeping instantaneous frequency of the laser. The silicon photonics platform has potential for very compact implementation, and the electro-optic modulation method opens the possibility of modulation speeds far beyond those of mechanical filters.

CORNERSTONE’s Silicon Photonics Rapid Prototyping Platforms: Current Status and Future Outlook

The field of silicon photonics has experienced widespread adoption in the datacoms industry over the past decade, with a plethora of other applications emerging more recently such as light detection and ranging (LIDAR), sensing, quantum photonics, programmable photonics and artificial intelligence. As a result of this, many commercial complementary metal oxide semiconductor (CMOS) foundries have developed open access silicon photonics process lines, enabling the mass production of silicon photonics systems. On the other side of the spectrum, several research labs, typically within universities, have opened up their facilities for small scale prototyping, commonly exploiting e-beam lithography for wafer patterning. Within this ecosystem, there remains a challenge for early stage researchers to progress their novel and innovate designs from the research lab to the commercial foundries because of the lack of compatibility of the processing technologies (e-beam lithography is not an industry tool). The CORNERSTONE rapid-prototyping capability bridges this gap between research and industry by providing a rapid prototyping fabrication line based on deep-UV lithography to enable seamless scaling up of production volumes, whilst also retaining the ability for device level innovation, crucial for researchers, by offering flexibility in its process flows. This review article presents a summary of the current CORNERSTONE capabilities and an outlook for the future.

Ultrafast electro-optical disk modulators for logic, communications, optical repeaters, and wavelength converters

We propose a U-shaped pn junction in a silicon-on-insulator microdisk resonator to effectively double the junction-mode overlap in the state-of-the-art, vertical pn junction microdisk electro-optical (EO) modulators. The U-shaped pn junction promotes the maximum overlap between the junction depletion zone and the whispering gallery optical mode in the microdisk. By fully depleting the p region of the npn-sequenced U-junction, the capacitance is reduced below 3 fF, which significantly improves the speed and power performance. In this work, we implement the high-efficiency, depleted U-junction design to maximize the operating bandwidth of EO modulators, EO logic elements, EO 2 × 2 switches for wavelength-division cross-connects, 2 × 2 reconfigurable optical add-drop multiplexers, optical-to-electrical-to-optical (OEO) repeaters-with-gain, OEO wavelength converters, and 2 × 2 optical-optical logic gates. These devices all operate in the 7.6-to-50 GHz bandwidth range with ultralow energy consumption between 0.4 and 9.8 fJ/bit. By using CMOS-compatible materials and fabrication-feasible design dimensions, our proposed high-performance devices offer a promising potential in next-generation, high-volume electro-optical communications and computing circuits.

Frequency modulated hybrid photonic crystal laser by thermal tuning

We demonstrate frequency modulation (FM) in an external cavity (EC) III-V/silicon laser, comprising a reflective semiconductor optical amplifier (RSOA) and a silicon nitride (SiN) waveguide vertically coupled to a 2D silicon photonic crystal (PhC) cavity. The PhC cavity acts as a tunable narrowband reflector giving wavelength selectivity. The FM was achieved by thermo-optical modulation of the reflector via a p-n junction. Single-mode operation was ensured by the short cavity length, overlapping only one longitudinal laser mode with the reflector. We investigate the effect of reflector modulation theoretically and experimentally and predict a substantial tracking of the resonator by the laser frequency with very small intensity modulation (IM).

High-speed Si/GeSi hetero-structure Electro Absorption Modulator

The ever-increasing demand for integrated, low power interconnect systems is pushing the bandwidth density of CMOS photonic devices. Taking advantage of the strong Franz-Keldysh effect in the C and L communication bands, electro-absorption modulators in Ge and GeSi are setting a new standard in terms of device footprint and power consumption for next generation photonics interconnect arrays. In this paper, we present a compact, low power electro-absorption modulator (EAM) Si/GeSi hetero-structure based on an 800 nm SOI overlayer with a modulation bandwidth of 56 GHz. The device design and fabrication tolerant process are presented, followed by the measurement analysis. Eye diagram measurements show a dynamic ER of 5.2 dB at a data rate of 56 Gb/s at 1566 nm, and calculated modulator power is 44 fJ/bit.

Integrated Optical Modulator Based on Transition between Photonic Bands

An area efficient novel optical modulator with low operation voltage is designed based on integrated Mach-Zehnder Interferometer with a photonic crystal slab structure as the phase shifter. Plasma dispersion effect is utilized so that photonic band-to-band transition occurs at the operating frequency leading to a high index change (Δn = ~4) for π-phase shift on the modulator. This approach reduces the phase shifter length to a few micrometers (~5 µm) in a silicon on insulator platform and operating voltage required is around 1 V. Low voltage together with short optical interaction length decrease optical losses and power consumption during modulation process providing a great opportunity for size and system cost optimization.

Ultracompact CMOS-compatible optical logic using carrier depletion in microdisk resonators

We present a CMOS-compatible optoelectronic directed logic architecture that achieves high computational throughput (number of operations per second per unit area) by its ultracompact form factor. High speed-to-power performance is also achieved, by the low capacitance and high junction-to-mode overlap of low-radii SOI vertical pn junction microdisk switches. By using wavelength-division multiplexing and two electrical control signals per disk, each switch performs (N)OR, (N)AND, and X(N)OR operations simultaneously. Connecting multiple switches together, we demonstrate higher-order scalability in five fundamental N-bit logic circuits: AND/OR gates, adders, comparators, encoders, and decoders. To the best of our knowledge, these circuits achieve the lowest footprint of silicon-based multigigabit-per-second optical logic devices in literature.

Compact microring resonators integrated with grating couplers working at 2 μm wavelength on silicon-on-insulator platform

Compact all-pass and add-drop microring resonators (radius=10  μm) integrated with grating couplers working at 2 μm wavelength are designed, fabricated, and characterized on a commercial 340-nm-thick-top-silicon silicon-on-insulator platform. They are suitable for high-volume integrated optical circuits at 2 μm wavelength as the fabrication process involved are uncomplicated and complementary metal-oxide-semiconductor (CMOS)-process compatible, thus making them more convenient to be utilized. The performance of the grating couplers, based on four most important parameters, has been simulated and optimized. The simulation and experimental results of grating couplers show the lowest coupling loss of 4.5 dB and 6.5 Db, respectively. By utilizing the grating couplers to couple light in and out from the chip, the designed microring resonators have been tested. The experimental results of microring resonators show that an extinction ratio of 12 dB and a quality factor of 11,200 can be achieved. To the best of our knowledge, this is thus far the smallest microring resonator ever demonstrated at this wavelength.

Simplified modeling and optimization of silicon modulators based on free-carrier plasma dispersion effect

In this paper, a simplified model of silicon phase modulators is presented that enables favorable accuracy together with a substantial reduction in computational effort and without the requirement of semiconductor TCAD device simulation software. This permits fast optimization of the different parameters of a modulator. The model was successfully implemented in Phoenix Optodesigner optical software allowing the optimization of silicon phase shifters for different applications. Moreover, this model presents a great potential for the simulation of modulators based on PN interdigitated junctions, which normally require complex and time consuming 3D simulations. Simulation time was reduced by a factor of 6 for the lateral PN junction based modulator, and two orders of magnitude reduction was obtained for interdigitated PN junctions based modulators.

Electromagnetically induced transparency-like effect in microring-Bragg gratings based coupling resonant system

An all-pass microring-Bragg gratings (APMR-BG) based coupling resonant system is proposed and experimentally demonstrated to generate electromagnetically induced transparency (EIT)-like transmission for the first time. The coupling between two light path ways in the micro-ring resonator and the Fabry-Pérot (F-P) resonator formed by two sections of Bragg gratings gives rise to the EIT-like spectrum. This system has the advantage of a small footprint consisting of only one microring resonator and one bus waveguide with Bragg gratings. It also has a large fabrication tolerance as the overlap requirement between the resonance wavelengths of the microring and the F-P resonator is more relaxed. The two most important properties of the EIT-like transmission namely the insertion loss (IL) and the full-width-at-half-maximum (FWHM) have been analytically investigated by utilizing the specially developed model based on the transfer matrix method. The APMR-BG based coupling resonant system was fabricated on a silicon-on-insulator (SOI) platform. The EIT-like transmission with an extinction ratio (ER) of 12 dB, a FWHM of 0.077 nm and a quality factor (Q factor) of 20200 was achieved, which agree well with the simulated results based on our numerical model. A slow light with a group delay of 38 ps was also obtained.

Slot waveguide ring resonators coated by an atomic layer deposited organic/inorganic nanolaminate

In this study, slot waveguide ring resonators patterned on a silicon-on-insulator (SOI) wafer and coated with an atomic layer deposited nanolaminate consisting of alternating layers of tantalum pentoxide and polyimide were fabricated and characterized. To the best of our knowledge, this is the first demonstration of atomic layer deposition (ALD) of organic materials in waveguiding applications. In our nanolaminate ring resonators, the optical power is not only confined in the narrow central air slot but also in several parallel sub-10 nm wide vertical polyimide slots. This indicates that the mode profiles in the silicon slot waveguide can be accurately tuned by the ALD method. Our results show that ALD of organic and inorganic materials can be combined with conventional silicon waveguide fabrication techniques to create slot waveguide ring resonators with varying mode profiles. This can potentially open new possibilities for various photonic applications, such as optical sensing and all-optical signal processing.

Low V(π) Silicon photonics modulators with highly linear epitaxially grown phase shifters

We report on the design of Silicon Mach-Zehnder carrier depletion modulators relying on epitaxially grown vertical junction diodes. Unprecedented spatial control over doping profiles resulting from combining local ion implantation with epitaxial overgrowth enables highly linear phase shifters with high modulation efficiency and comparatively low insertion losses. A high average phase shifter efficiency of VπL = 0.74 V⋅cm is reached between 0 V and 2 V reverse bias, while maintaining optical losses at 4.2 dB/mm and the intrinsic RC cutoff frequency at 48 GHz (both at 1 V reverse bias). The fabrication process, the sensitivity to fabrication tolerances, the phase shifter performance and examples of lumped element and travelling wave modulators are modeled in detail. Device linearity is shown to be sufficient to support complex modulation formats such as 16-QAM.

Hybrid Si-VO(2)-Au optical modulator based on near-field plasmonic coupling

We present a computational design for an integrated electro-optic modulator based on near-field plasmonic coupling between gold nanodisks and a thin film of vanadium dioxide on a silicon substrate. Active modulation is achieved by applying a time-varying electric field to initiate large changes in the refractive index of vanadium dioxide. Significant decrease in device footprint (200 nm x 560 nm) and increase in extinction ratio per unit length (9 dB/µm) compared to state-of-the-art photonic and plasmonic modulators are predicted.

Recent advances in silicon-based passive and active optical interconnects

Silicon photonics has experienced phenomenal transformations over the last decade. In this paper, we present some of the notable advances in silicon-based passive and active optical interconnect components, and highlight some of our key contributions. Light is also cast on few other parallel technologies that are working in tandem with silicon-based structures, and providing unique functions not achievable with any single system acting alone. With an increasing utilization of CMOS foundries for silicon photonics fabrication, a viable path for realizing extremely low-cost integrated optoelectronics has been paved. These advances are expected to benefit several application domains in the years to come, including communication networks, sensing, and nonlinear systems.

Reconfigurable electro-optical directed-logic circuit using carrier-depletion micro-ring resonators

Here we demonstrate a reconfigurable electro-optical directed-logic circuit based on a regular array of integrated optical switches. Each 1×1 optical switch consists of a micro-ring resonator with an embedded lateral p-n junction and a micro-heater. We achieve high-speed on-off switching by applying electrical logic signals to the p-n junction. We can configure the operation mode of each switch by thermal tuning the resonance wavelength. The result is an integrated optical circuit that can be reconfigured to perform any combinational logic operation. As a proof-of-principle, we fabricated a multi-spectral directed-logic circuit based on a fourfold array of switches and showed that this circuit can be reconfigured to perform arbitrary two-input logic functions with speeds up to 3  GB/s.

Silicon microring modulator for 40 Gb/s NRZ-OOK metro networks in O-band

A microring-based silicon modulator operating at 40 Gb/s near 1310 nm is demonstrated for the first time to our knowledge. NRZ-OOK signals at 40 Gb/s with 6.2 dB extinction ratio are observed by applying a 4.8 Vpp driving voltage and biasing the modulator at 7 dB insertion loss point. The energy efficiency is 115 fJ/bit. The transmission performance of 40 Gb/s NRZ-OOK through 40 km of standard single mode fiber without dispersion compensation is also investigated. We show that the link suffers negligible dispersion penalty. This makes the modulator a potential candidate for metro network applications.

Optical peaking enhancement in high-speed ring modulators

Ring resonator modulators (RRM) combine extreme compactness, low power consumption and wavelength division multiplexing functionality, making them a frontrunner for addressing the scalability requirements of short distance optical links. To extend data rates beyond the classically assumed bandwidth capability, we derive and experimentally verify closed form equations of the electro-optic response and asymmetric side band generation resulting from inherent transient time dynamics and leverage these to significantly improve device performance. An equivalent circuit description with a commonly used peaking amplifier model allows straightforward assessment of the effect on existing communication system architectures. A small signal analytical expression of peaking in the electro-optic response of RRMs is derived and used to extend the electro-optic bandwidth of the device above 40 GHz as well as to open eye diagrams penalized by intersymbol interference at 32, 40 and 44 Gbps. Predicted peaking and asymmetric side band generation are in excellent agreement with experiments.

Cascaded uncoupled dual-ring modulator

We demonstrate, by coherent driving two uncoupled rings in same direction, that the effective photon circulating time in the dual-ring modulator is reduced, with increased modulation quality. The inter-ring detuning-dependent photon dynamics, Q factor, extinction ratio, and optical modulation amplitude of two cascaded silicon ring resonators are studied and compared with that of a single-ring modulator. Experimentally measured eye diagrams, together with coupled mode theory simulations, demonstrate the enhancement of the dual-ring configuration at 20 Gbps with a Q∼20,000.

Ultracompact (3 μm) silicon slow-light optical modulator

Wavelength-scale optical modulators are essential building blocks for future on-chip optical interconnects. Any modulator design is a trade-off between bandwidth, size and fabrication complexity, size being particularly important as it determines capacitance and actuation energy. Here, we demonstrate an interesting alternative that is only 3 μm long, only uses silicon on insulator (SOI) material and accommodates several nanometres of optical bandwidth at 1550 nm. The device is based on a photonic crystal waveguide: by combining the refractive index shift with slow-light enhanced absorption induced by free-carrier injection, we achieve an operation bandwidth that significantly exceeds the shift of the bandedge. We compare a 3 μm and an 80 μm long modulator and surprisingly, the shorter device outperforms the longer one. Despite its small size, the device achieves an optical bandwidth as broad as 7 nm for an extinction ratio of 10 dB, and modulation times ranging between 500 ps and 100 ps.

12.5 pm/V hybrid silicon and lithium niobate optical microring resonator with integrated electrodes

We present a silicon microring resonator with a lithium niobate top cladding and integrated tuning electrodes. Submicrometer thin films of z-cut lithium niobate are bonded to silicon microring resonators via benzocyclobutene. Integrated electrodes are incorporated to confine voltage controlled electric fields within the lithium niobate thin film. The electrode design utilizes thin film metal electrodes and an optically transparent electrode wherein the silicon waveguide core serves as both an optical waveguide medium and as a conductive electrode medium. The hybrid material system combines the electro-optic functionality of lithium niobate with the high index contrast of silicon waveguides, enabling compact low tuning voltage microring resonators. Optical characterization of fabricated devices results in a measured loaded quality factor of 11,500 and a free spectral range of 7.15 nm in the infrared. The demonstrated tunability is 12.5 pm/V, which is over an order of magnitude greater than electrode-free designs.

Linearized silicon modulator based on a ring assisted Mach Zehnder inteferometer

We demonstrate a Linearized Ring Assisted Mach-Zehnder Interferometer (L-RAMZI) modulator in a miniature silicon device. We measure a record high degree of linearization for a silicon device, with a Spurious Free Dynamic Range (SFDR) of 106dB/Hz²/³ at 1GHz, and 99dB/Hz²/³ at 10GHz.

Design of a silicon Mach-Zehnder modulator with a U-type PN junction

We have developed a silicon depletion-mode modulator featuring a novel U-type PN junction that enables a substantial improvement in electro-optical modulation efficiency. Through electrical, optical, and manufacturing process simulations, an ultralow V_πL of 0.63  V·cm is exhibited with 3 V reverse bias. The high modulation efficiency enables a high extinction ratio (ER) of >17  dB with only a 1 mm phase shifter when the excess loss at the "on" state is 2 dB. The ER can maintain >12  dB at ∼28  GHz operation with a 3 V peak-to-peak voltage due to the small voltage attenuation of the short phase shifter.

50-Gb/s ring-resonator-based silicon modulator

We achieved 50-Gb/s operation of a ring-resonator-based silicon modulator for the first time. The pin-diode phase shifter, which consists of a side-wall-grating waveguide, was loaded into the ring resonator. The forward-biased operation mode was applied, which exhibited a V(π)L as small as 0.28 V · cm at 25 GHz. The driving voltage and optical insertion loss at 50-Gb/s were 1.96 V(pp) and 5.2 dB, respectively.

High-speed silicon modulator based on cascaded microring resonators

A high-speed silicon modulator based on cascaded double microring resonators is demonstrated in this paper. The proposed modulator experimentally achieved 40 Gbit/s modulation with an extinction ratio of 3.9 dB. Enhancement of the modulator achieves with an ultra-high optical bandwidth of 0.41 nm, corresponding to 51 GHz, was accomplished by using cascaded double ring structure. The described modulator can provides an ultra-high-speed optical modulation with a further improvement in electrical bandwidth of the device.

Linearity of silicon ring modulators for analog optical links

We study the nonlinear distortions of a silicon ring modulator based on the carrier depletion effect for analog links. Key sources of modulation nonlinearity are identified and modeled. We find that the most important source of nonlinearity is from the pn junction itself, as opposed to the nonlinear wavelength response of the ring modulator. Spurious free dynamic range for intermodulation distortion of as high as 84 dB.Hz²/₃ is obtained.

Energy consumption in optical modulators for interconnects

We analyze energy consumption in optical modulators operated in depletion and intended for low-power interconnect applications. We include dynamic dissipation from charging modulator capacitance and net energy consumption from absorption and photocurrent, both in reverse and small forward bias. We show that dynamic dissipation can be independent of static bias, though only with specific kinds of bias circuits. We derive simple expressions for the effects of photocurrent on energy consumption, valid in both reverse and small forward bias. Though electroabsorption modulators with large reverse bias have substantial energy penalties from photocurrent dissipation, we argue that modulator diodes with thin depletion regions and operating in small reverse and/or forward bias could have little or no such photocurrent energy penalty, even conceivably being more energy-efficient than an ideal loss-less modulator.

25 Gbit/s silicon microring modulator based on misalignment-tolerant interleaved PN junctions

A high-speed depletion-mode silicon-based microring modulator with interleaved PN junctions optimized for high modulation efficiency and large alignment tolerance is demonstrated. It is fabricated using standard 0.18 μm complementary metal-oxide-semiconductor processes and provides low V(π)L(π)s of 0.68 V·cm to 1.64 V·cm with a moderate doping concentration of 2 × 10(17) cm(-3). The measured modulation efficiency decreases by only 12.4% under ± 150 nm alignment errors. 25 Gbit/s non-return-zero modulation with a 4.5 dB extinction ratio is experimentally realized at a peak-to-peak driving voltage of 2 V, demonstrating the excellent performance of the novel doping profile.

High speed silicon electro-optical modulators enhanced via slow light propagation

While current optical communication networks efficiently carry and process huge amounts of digital information over large and medium distances, silicon photonics technology has the capacity to meet the ceaselessly increasing demand for bandwidth via energy efficient, inexpensive and mass producible short range optical interconnects. In this context, handling electrical-to-optical data conversion through compact and high speed electro-optical modulators is of paramount importance. To tackle these challenges, we combine the attractive properties of slow light propagation in a nanostructured periodic waveguide together with a high speed semiconductor pn diode, and demonstrate a highly efficient and mass manufacturable 500 µm-long silicon electro-optical device, exhibiting error free modulation up to 20 Gbit/s. These results, supported by modulation rate capabilities reaching 40 Gbit/s, pave a foreseeable way towards dense, low power and ultra fast integrated networks-on-chip for future chip-scale high performance computing systems.

Ten Gbit/s ring resonator silicon modulator based on interdigitated PN junctions

10 Gbit/s silicon modulator based on carrier depletion in interdigitated PN junctions is experimentally demonstrated. The phase-shifter is integrated in a ring resonator, and high extinction ratio larger than 10 dB is obtained in both TE and TM polarizations. VπLπ of about 2.5 V × cm and optical loss lower than 1 dB are estimated. 10 Gbit/s data transmission is demonstrated with an extinction ratio of 4 dB.

A high speed electro-optic phase shifter based on a polymer-infiltrated P-S-N diode capacitor

A polymer-infiltrated P-S-N diode capacitor configuration is proposed and a high speed electro-optic phase shifter based on a silicon organic hybrid platform is designed and modeled. The structure enables fast carrier depletion in addition to the second order nonlinearity so that a large electro-optic overlapped volume is achievable. Moreover, the device speed can be significantly improved with the introduction of free carriers due to a reduced experienced transient capacitance. The advantages of the diode capacitor structure are highly suitable for application to a class of low aspect ratio slot waveguides where the RC limitation of the radio frequency response is minimized. According to our numerical results, by optimizing both the waveguide geometry and polarization mode, at least 269 GHz 3-dB bandwidth with high efficiency of 5.5 V-cm is achievable. More importantly, the device does not rely on strong optical confinement within the nano-slot, a feature that gives considerable tolerance in the use of nano-fabrication techniques. Finally, the high overlap and energy efficiency of the device can be applied to slow light or optical resonance media for realizing photonic integrated circuits-based green photonics.

Defect-mediated resonance shift of silicon-on-insulator racetrack resonators

We present a study on the effects of inert ion implantation of Silicon-On-Insulator (SOI) racetrack resonators. Selective ion implantation was used to create deep-level defects within a portion of the resonator. The resonant wavelength and round-trip loss were deduced for a range of sequential post-implantation annealing temperatures from 100 to 300 °C. As the devices were annealed there was a concomitant change in the resonance wavelength, consistent with an increase in refractive index following implantation and recovery toward the pre-implanted value. A total shift in resonance wavelength of ~2.9 nm was achieved, equivalent to a 0.02 increase in refractive index. The excess loss upon implantation increased to 301 dB/cm and was reduced to 35 dB/cm following thermal annealing. In addition to providing valuable data for those incorporating defects within resonant structures, we suggest that these results present a method for permanent tuning (or trimming) of ring resonator characteristics.

40 Gb/s silicon photonics modulator for TE and TM polarisations

A key device in future high speed short reach interconnect technology will be the optical modulator. These devices, in silicon, have experienced dramatic improvements over the last 6 years and the modulation bandwidth has increased from a few tens of MHz to over 30 GHz. However, the demands of optical interconnects are significant. Here we describe an approach based on a self-aligned wrap around p-n junction structure embedded in a silicon waveguide that can produce high-speed optical phase modulation, whilst at the same time, capable of a high extinction ratio. An all-silicon optical modulator using a CMOS compatible fabrication process with a data rate of 40 Gb/s and extinction ratio up to approximately 6.5 dB for TE and TM polarisations is demonstrated. This technology is not only compatible with conventional complementary MOS (CMOS) processing, but is also intended to simplify and improve the reliability of, the fabrication process.

High contrast 40Gbit/s optical modulation in silicon

Data interconnects are on the verge of a revolution. Electrical links are increasingly being pushed to their limits with the ever increasing demand for bandwidth. Data transmission in the optical domain is a leading candidate to satisfy this need. The optical modulator is key to most applications and increasing the data rate at which it operates is important for reducing power consumption, increasing channel bandwidth limitations and improving the efficiency of infrastructure usage. In this work silicon based devices of lengths 3.5mm and 1mm operating at 40Gbit/s are demonstrated with extinction ratios of up to 10dB and 3.5dB respectively. The efficiency and optical loss of the phase shifter is 2.7V.cm and 4dB/mm (or 4.5dB/mm including waveguide loss) respectively.

High extinction ratio 10 Gbit/s silicon optical modulator

High speed and high extinction ratio silicon optical modulator using carrier depletion is experimentally demonstrated. The phase-shifter is a 1.8 mm-long PIPIN diode which is integrated in a Mach Zehnder interferometer. 8.1 dB Extinction Ratio at 10 Gbit/s is obtained simultaneously with optical loss as low as 6 dB.

Breakdown delay-based depletion mode silicon modulator with photonic hybrid-lattice resonator

A compact silicon electro-optic modulator that operates in the breakdown delay based depletion mode is introduced. This operation mode has not previously been utilized for optical modulators, and represents a way to potentially achieve much higher modulation speeds and carrier extraction efficiencies without sacrificing energy efficiency, which is a critical criterion for realizing miniaturized sub-THz modulation components in silicon. Our study shows a speed of at least 238 GHz modulation is achievable along with an ultra-low energy consumption of 26.6 fJ/bit in a simple planar P+PNN+ diode example structure, which is embedded in a 2D hybrid photonic lattice mode gap resonator. The optical resonator itself is only 69 µm2 in footprint and is designed for optimized electro-optic sensitivity and conversion efficiency with reduced carrier scattering. Both the static and dynamic device performance are backed up by fully integrated 3D optical and 3D electrical numerical results. The compact device dimensions and low energy consumption are favorable to high density photonic integration.

Analytical model for depletion-based silicon modulator simulation

An original method to simulate depletion-based silicon modulators based on an analytical description of the active region is presented. This method is fast and efficient in particular for performance optimization. It is applied for a lateral diode integrated in a rib waveguide, and a comparison is performed with classical 2D numerical simulation. A very good agreement is obtained, showing the accuracy and efficiency of this analytical method.

Silicon-polymer hybrid slot waveguide ring-resonator modulator

We demonstrate a ring-resonator modulator based on a silicon-polymer hybrid slot waveguide with a tunability of 12.7 pm/V at RF speeds and a bandwidth of 1 GHz, for optical wavelengths near 1550 nm. Our slot waveguides were fabricated with 193 nm optical lithography, as opposed to the electron beam lithography used for previous results. The tunability is comparable to some of the best ring-based modulators making use of the plasma dispersion effect. The speed is likely limited only by resistance in the strip-loading section, and it should be possible to realize significant improvement with improved processing.

High speed silicon optical modulator with self aligned fabrication process

With the imminent commercialisation of silicon photonic devices comes the requirement for a fabrication process capable of high yield and device performance repeatability. The precise alignment of the different elements of a device can be a major fabrication challenge for minimising performance variation or even device failure. In this paper a new design of high speed carrier depletion silicon optical modulator is introduced which features the use of a self-aligned fabrication process to form the pn junction. Experimental results are presented from an initial fabrication run, which has demonstrated a 6 dB modulation depth at 10 Gbit/s from a 3.5 m long device.

An integrated optic ethanol vapor sensor based on a silicon-on-insulator microring resonator coated with a porous ZnO film

Optical structures fabricated on silicon-on-insulator technology provide a convenient platform for the implementation of highly compact, versatile and low cost devices. In this work, we demonstrate the promise of this technology for integrated low power and low cost optical gas sensing. A room temperature ethanol vapor sensor is demonstrated using a ZnO nanoparticle film as a coating on an SOI micro-ring resonator of 5 microm in radius. The local coating on the ring resonators is prepared from colloidal suspensions of ZnO nanoparticles of around 3 nm diameter. The porous nature of the coating provides a large surface area for gas adsorption. The ZnO refractive index change upon vapor adsorption shifts the microring resonance through evanescent field interaction. Ethanol vapor concentrations down to 100 ppm are detected with this sensing configuration and a detection limit below 25 ppm is estimated.

Wavelength-tunable silicon microring modulator

We present a wavelength-tunable, compact, high speed and low power silicon microring modulator. With a ring radius of 5 microm, we demonstrate a modulator with a high speed of 12.5 Gbps and a driving voltage of 3 V to achieve approximately 6 dB extinction ratio in high speed measurement. More importantly, tunability of the resonant wavelength is accomplished by means of a microheater on top of the ring, with an efficiency of 2.4 mW/nm (2.4 mW is needed to tune the resonant wavelength by 1 nm). This device aims to solve the narrow bandwidth problem of silicon microcavity modulators and increase the data bandwidth in optical interconnect systems.