Electronic-photonic Integrated Circuit Research Articles

A Bi-CMOS electronic photonic integrated circuit quantum light detector.

Complimentary metal-oxide semiconductor (CMOS) integration of quantum technology provides a route to manufacture at volume, simplify assembly, reduce footprint, and increase performance. Quantum noise-limited homodyne detectors have applications across quantum technologies, and they comprise photonics and electronics. Here, we report a quantum noise-limited monolithic electronic-photonic integrated homodyne detector, with a footprint of 80 micrometers by 220 micrometers, fabricated in a 250-nanometer lithography bipolar CMOS process. We measure a 15.3-gigahertz 3-decibel bandwidth with a maximum shot noise clearance of 12 decibels and shot noise clearance out to 26.5 gigahertz, when measured with a 9-decibel-milliwatt power local oscillator. This performance is enabled by monolithic electronic-photonic integration, which goes below the capacitance limits of devices made up of separate integrated chips or discrete components. It exceeds the bandwidth of quantum detectors with macroscopic electronic interconnects, including wire and flip chip bonding. This demonstrates electronic-photonic integration enhancing quantum photonic device performance.

Defect‐Engineered Electrically‐Injected Germanium‐on‐Insulator Waveguide Light Emitters at Telecom Wavelengths

AbstractGe‐on‐insulators (GOIs) have been extensively explored as a potential platform for electronic‐photonic integrated circuits (EPICs), enabling various emerging applications. Although an efficient electrically‐injected light source is highly desirable, realizing such devices with optimal light emission efficiency remains challenging. Here, the first room‐temperature electrically‐injected Ge waveguide light emitters consisting of a lateral p–i–n homojunction on a GOI platform that can be monolithically integrated with EPICs are demonstrated. A high‐quality Ge active layer is transferred onto an insulator layer with the misfit dislocations in the Ge active layer eliminated to suppress unwanted nonradiative recombination. A 0.165% tensile strain is introduced to enhance the directness of the band structure and improve the light emission efficiency. The device comprises a waveguide structure with a significantly improved optical confinement as the optical resonator and a lateral p–i–n homojunction structure as the electrical injection structure. Under continuous‐wave electrical current injection at room temperature, enhanced electroluminescence is successfully observed at telecommunications wavelengths covering the C, L, and U bands, with improved efficiency. Theoretical analysis suggests that the quantum efficiency of Ge light emitters is dramatically affected by the defect density. These results pave the way for developing efficient, room‐temperature, electrically‐injected light emitters for next‐generation GOI‐based EPICs.

Two-dimensional semiconducting SnP2Se6 with giant second-harmonic-generation for monolithic on-chip electronic-photonic integration

Two-dimensional (2D) layered semiconductors with nonlinear optical (NLO) properties hold great promise to address the growing demand of multifunction integration in electronic-photonic integrated circuits (EPICs). However, electronic-photonic co-design with 2D NLO semiconductors for on-chip telecommunication is limited by their essential shortcomings in terms of unsatisfactory optoelectronic properties, odd-even layer-dependent NLO activity and low NLO susceptibility in telecom band. Here we report the synthesis of 2D SnP2Se6, a van der Waals NLO semiconductor exhibiting strong odd-even layer-independent second harmonic generation (SHG) activity at 1550 nm and pronounced photosensitivity under visible light. The combination of 2D SnP2Se6 with a SiN photonic platform enables the chip-level multifunction integration for EPICs. The hybrid device not only features efficient on-chip SHG process for optical modulation, but also allows the telecom-band photodetection relying on the upconversion of wavelength from 1560 to 780 nm. Our finding offers alternative opportunities for the collaborative design of EPICs.

Silicon-Germanium Electronics and Photonics for Space Systems

Space has been aptly called the “final frontier” (thank you, Star Trek!). The application needs of the global space and aerospace communities are predictably many and varied, ranging from a diverse set of communications and imaging satellites, to the GPS constellation, to microwave and millimeter-wave (mmW) remote sensing to support weather forecasting and climate science, to exploration of other worlds, which include: the mighty James Webb Space Telescope (probing the origins of the universe), the shadowed polar craters of the Moon (the search for water ice), Mars surface (colonization?), and Europa (the search for extraterrestrial life in the water ocean beneath the 10 km ice cap).While classically, orbital satellites were massive, tough to launch, and extremely expensive (a few $Bs), the current (and rapidly accelerating) trend has swung decidedly towards using relatively low-cost (a few $M) and easy to launch constellations of single or multi-U CubeSats (1U = 10x10x10 cm3) to cost-effectively address the plethora of emerging needs. These days, this has been increasingly supported by commercial space ventures (e.g., SpaceX, BlueOrigin et al., vs. the old gang—NASA and DoD), which are proliferating rapidly.As appealing as space is for visioning fun new science and slick applications, it remains a decidedly unfriendly place to visit. Space is the quintessential “extreme environment,” bathed in intense radiation from both our Sun (high energy electrons and protons trapped by the Earth’s magnetosphere in radiation belts) and the cosmos (GeV energy galactic cosmic rays from supernovae). By way of level setting, a satellite in the most benign Earth orbit, Low Earth Orbit (LEO – 160-1000 km up from the surface), experiences 100,000 rad of ionizing radiation dose over mission life. In comparison, 500 rad will do a person in! That is, we are asking a lot of our electronics in such systems, and given the extreme cost constraints of launch weight, adding a few inches of lead shielding is not the ideal solution! In addition, it is mighty chilly in space (2.73 K = -455°F, the cosmic background), and when the sunlight shines on you, it gets uncomfortably warm, very quickly (e.g., on the surface of the Moon, from -180°C to +120°C from darkness to light, within a few moments). Yep, space is a tough place to do business.As I have long argued [1], SiGe HBT BiCMOS technology provides a unique solution for many of the needs of these emerging space systems, including: 1) extreme levels of performance (multi-hundred GHz) with the SiGe HBT and high integration levels with on-board CMOS, for realizing compelling system functionality/unit volume, at low cost; 2) the rapid improvement of all electronic circuit relevant performance metrics with cooling, with operational capability down into the mK quantum regime (SiGe HBTs love chilly weather!); 3) the ability to operate robustly up to 150-200°C, with modest performance loss; 4) the ability to operate robustly over wide temperature ranges (in principle from mK to 150-200°C); 5) built-in robustness to multi-Mrad total ionizing dose radiation; and 6) built-in heavy ion induced latchup immunity (read: those pesky GeV cosmic rays).Long ago (1990s), the notion of creating a low-cost Si-based electronic + photonic integrated circuit (EPIC) “superchip” was envisioned (Soref), which brought together advanced SiGe HBTs (analog, RF-mmW), CMOS (digital), and Si integrated photonics (with the possible exception of a laser, which could be flipped onto the die worse case). In essence, EPICs are a low-cost, high-yielding, reliable, highly integrated Si platform for putting electrons and light into the same conversation! Clearly this represents a paradigm shift to business as usual. Now, with even more compelling system functionality/unit volume, at low cost. Such an EPIC superchip could in principle satisfy all-comers-of-new-needs. While photonics has long been used in space (think solar cells, imagers), EPICs are new to that space game, but possess great potential for the emergent needs in this new vision of CubeSat/SmallSat driven space systems, including, thing like: LIDAR (spacecraft-to-spacecraft positioning); deep space and within-constellation optical communications (huge data rate improvement); and on-spacecraft high bandwidth data transport (think data center in the sky for instruments that spew out tons of data that need to get back home quickly). This field of EPICs in space is only a few years old, but already much has been learned, and results look very encouraging.In this invited talk, I will highlight the current status and the future trends of using SiGe electronic and photonics in space systems.[1] J.D. Cressler, Proc. IEEE, vol. 93, pp. 1559-1582, 2005. Figure 1

Crosstalk suppression for high-density traveling-wave MZM array based on static and dynamic combined analysis and circuit-level designs.

Electrical crosstalk severely degrades the performance of Mach-Zehnder modulator (MZM) array. However, conventional crosstalk suppression techniques incur losses of large amounts of chip area for signal isolation, which becomes a bottleneck of high-density electronic-photonic integrated circuit. In this paper, the electrical crosstalk of Traveling-Wave MZM array is originally analyzed with static and dynamic combined crosstalk coefficients. Circuit-level suppression techniques of differential dual-drive electrode schemes with tightly coupled electrode pairs and a virtual ground structure with full-matching termination circuit are investigated for noise-removing effects. Simulation results show that the dynamic electrical crosstalk coefficient between two adjacent modulators is reduced to below 1.5%, which is five times lower than the baseline. The electro-optical link measurements show that the BER is significantly reduced from 1E-3 to 1E-12 for multi-channel operation, which confirms the effectiveness of the crosstalk suppression techniques.

A 50-GHz Bandwidth Traveling-Wave Mach-Zehnder Modulator With Built-In Feedback Equalization

A 50–GHz bandwidth traveling-wave Mach-Zehnder modulator (TWMZM) was designed with a new equalization technique, which takes advantage of the intrinsic delay in a traveling-wave electrode (TWE) and a local negative-feedback circuit. With this idea, given the availability of flip-chip bonding, a long TWE can be equalized as a single stage or be segmented into a few stages, each being equalized separately to optimize the performance of the entire device. The detailed analysis of this equalization technique is presented. As a demonstration, a 1.6–mm long equalized TWMZM was designed using a commercial silicon photonic process and a 0.13 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu \mathrm{m}$</tex-math></inline-formula> SiGe process. A 2–stage cascaded design with equal equalization was adopted and optimized for high bandwidth and high extinction ratio. The circuit was designed using the multi-physics electronic-photonic integrated circuit (EPIC) design flow we developed recently, wherein both electronic and photonic parts were modeled and the EPIC circuit was simulated for system level performance evaluation. Simulation results showed that the equalization technique increased the 3-dB EO bandwidth of the TWMZM from 28 to 50.4 GHz, an 80% increase. Large signal performance with non-return to zero signals upto 100 Gb/s was evaluated and the results showed significant improvements in the eye quality with equalization. The performance evaluation with pulse amplitude modulation (PAM)-4 signal was also carried out and the results showed successful operation at 106 Gbaud PAM-4 for the equalized TWMZM, makes it a promising candidate for future 200 Gbps-per-lambda optical transceivers.

Design and Optimization of GeSn Waveguide Photodetectors for 2-µm Band Silicon Photonics.

Silicon photonics is emerging as a competitive platform for electronic–photonic integrated circuits (EPICs) in the 2 µm wavelength band where GeSn photodetectors (PDs) have proven to be efficient PDs. In this paper, we present a comprehensive theoretical study of GeSn vertical p–i–n homojunction waveguide photodetectors (WGPDs) that have a strain-free and defect-free GeSn active layer for 2 µm Si-based EPICs. The use of a narrow-gap GeSn alloy as the active layer can fully cover entire the 2 µm wavelength band. The waveguide structure allows for decoupling the photon-absorbing path and the carrier collection path, thereby allowing for the simultaneous achievement of high-responsivity and high-bandwidth (BW) operation at the 2 µm wavelength band. We present the theoretical models to calculate the carrier saturation velocities, optical absorption coefficient, responsivity, 3-dB bandwidth, zero-bias resistance, and detectivity, and optimize this device structure to achieve highest performance at the 2 µm wavelength band. The results indicate that the performance of the GeSn WGPD has a strong dependence on the Sn composition and geometric parameters. The optimally designed GeSn WGPD with a 10% Sn concentration can give responsivity of 1.55 A/W, detectivity of 6.12 × 1010 cmHz½W−1 at 2 µm wavelength, and ~97 GHz BW. Therefore, this optimally designed GeSn WGPD is a potential candidate for silicon photonic EPICs offering high-speed optical communications.

GeSn lateral p-i-n waveguide photodetectors for mid-infrared integrated photonics.

In this Letter, we demonstrate mid-infrared (MIR) lateral p-i-n GeSn waveguide photodetectors (WGPDs) on silicon, to the best of our knowledge for the first time, as a key enabler of MIR electronic-photonic integrated circuits (EPICs). Narrow-bandgap GeSn alloys were employed as the active material to enable efficient photodetection in the MIR region. A lateral p-i-n homojunction diode was designed and fabricated to significantly enhance the optical confinement factor of the guided modes and thus enhance the optical responsivity. Thus, a photodetection range of up to 1950 nm and a good responsivity of 0.292 A/W at 1800 nm were achieved. These results demonstrate the feasibility of planar GeSn WGPDs for monolithic MIR EPICs on silicon.

Ge-on-insulator lateral p-i-n waveguide photodetectors for optical communication.

We report high-performance lateral p-i-n Ge waveguide photodetectors (WGPDs) on a Ge-on-insulator (GOI) platform that could be integrated with electronic-photonic integrated circuits (EPICs) for communication applications. The high-quality Ge layer affords a low absolute dark current. A tensile strain of 0.144% in the Ge active layers narrows the direct bandgap to enable efficient photodetection over the entire range of C- and L-bands. The low-index insulator layer enhances optical confinement, resulting in a good optical responsivity. These results demonstrate the feasibility of planar Ge WGPDs for monolithic GOI-based EPICs.

(Invited) Directly Silicon Nitride Waveguide Coupled Ge Photodiode for Non-SOI PIC and Epic Platforms

We demonstrate a Ge photodiode that is directly coupled to a silicon nitride waveguide and shows more than 67 GHz bandwidth. This device paves the way for utterly new SiN waveguide platform based applications. By light feeding through SiN waveguides, the new photodiode can also be a key enabler for a bulk-Si based, monolithically integrated electronic-photonic integrated circuit platform.Silicon nitride (SiN) waveguides (WGs) outperform silicon-on-insulator (SOI) based waveguides in various aspects: they offer an enhanced optical bandwidth, allowing for low loss waveguides in the classic communication bands (C- and O- bands), widely addressed by SOI based photonics, as well as in the visible wavelength range, were Si WGs have already become opaque. Moreover, due to the absence of two-photon absorption in SiN, the optical power handling is superior compared to Si WGs [1–3]. Various platforms with outstanding optical loss performance have been demonstrated over the last years and are meanwhile offered for commercial purposes, as summarized in [1]. However, despite all these advantages, so far, commercially offered SiN based photonic integrated circuit (PIC) platforms neither provide monolithically integrated high speed modulators, nor fast SiN WG coupled detectors. In this work we focus on the detector side of a high-speed SiN PIC platform.Communication applications for upcoming 400 Gbps standards require 56 Gbd symbol rates, which makes photodiodes (PDs) with more than 40 GHz opto-electrical (OE) bandwidth indispensable. Previous works with focus on Ge PDs in SiN platforms have either shown devices directly SiN WG fed or indirectly coupled via multi-layers (SiN on SOI WGs) where the Ge PDs are actually still located on SOI. However, the former ones showed only inferior bandwidth of less than 10 GHz [4] while the latter ones provide at least a bandwidth of about 30 GHz [5]. Here, we demonstrate for the first time a bulk-Si based, directly SiN WG coupled Ge PD with very high OE -3 dB bandwidth of more than 67 GHz which opens new perspectives for opto-electronic platform technologies:(1) The combination of truly high-speed PDs with SiN waveguides could be the start for a novel active SiN platform e.g. aiming at integrated coherent receivers at wavelengths far below the O-band.(2) The demonstrated devices are in principle compatible for co-integration with IHP’s photonic BiCMOS process [6], which opens various opportunities for novel sensing or spectroscopic applications as well.(3) This work could pave the way towards a non-SOI based technology as an alternative to established SOI based PIC or electronic-photonic integrated circuit (ePIC) platforms, e.g. IHP’s photonic BiCMOS technology. Circuit fabrication on pure bulk-Si wafers would significantly relieve process complexity, time and thus costs.We show that the new devices, fabricated on bulk-Si, provide the same bandwidths as Si waveguide coupled SOI based reference Ge photodiodes. However, their O-band responsivity is 0.3 A/W, which is about three times lower compared to the SOI waveguide coupled devices. We attribute this effect to substrate losses and few specific layout features but see some potential for improvement by design and technological optimizations. We further demonstrate that the diodes can be fabricated with high yield and low metrics tolerances. Figure 1 shows SEM cross-sections (perpendicular to the light incidence direction) of Ge photodiodes fabricated on SOI waveguide (left) as well as on bulk-Si (right).[1] P. Muñoz et al., “Silicon Nitride Photonic Integration Platforms for Visible, Near-Infrared and Mid-Infrared Applications,” Sensors, vol. 17, no. 9, 2017.[2] A. Rahim et al., “Expanding the Silicon Photonics Portfolio With Silicon Nitride Photonic Integrated Circuits,” J. Lightwave Technol., vol. 35, no. 4, pp. 639–649, 2017.[3] K. Ikeda et al, “Thermal and Kerr nonlinear properties of plasma-deposited silicon nitride/ silicon dioxide waveguides,” Optics express, vol. 16, no. 17, pp. 12987–12994, 2008.[4] D. Ahn et al., “High performance, waveguide integrated Ge photodetectors,” Optics express, vol. 15, no. 7, pp. 3916–3921, 2007.[5] W. D. Sacher et al., “Monolithically Integrated Multilayer Silicon Nitride-on-Silicon Waveguide Platforms for 3-D Photonic Circuits and Devices,” Proc. IEEE, vol. 106, no. 12, pp. 2232–2245, 2018.[6] D. Knoll et al. “(Invited) SiGe BiCMOS for Optoelectronics,” ECS Transactions, vol. 75, no. 8, pp. 121–139, 2016. Figure 1

(Invited) Directly Silicon Nitride Waveguide Coupled Ge Photodiode for Non-SOI PIC and Epic Platforms

A Ge photodiode, directly coupled to a silicon nitride waveguide, showing more than 67 GHz bandwidth is demonstrated. This paves the way for utterly new SiN waveguide platform based applications. By light feeding through SiN waveguides, the new photodiode can also be a key enabler for a bulk-Si based, monolithically integrated electronic-photonic integrated circuit platform. We show that the new devices, fabricated on bulk-Si, provide the same bandwidths as Si waveguide coupled SOI based reference Ge photodiodes. However, their O-band responsivity is 0.3 A/W, which is about three times lower compared to the SOI wave-guide coupled devices. We attribute this effect mainly to substrate leakage, being confirmed by simulations. We demonstrate that bulk-Si based diodes can be fabricated with high yield and low metrics tolerances.

Light effect transistors for high speed and low energy switching and beyond

A semiconductor nanowire based photo-conductive device, referred to as light effect transistor (LET), is demonstrated for replicating the field effect transistor (FET) functions with potentially higher speed and lower switching energy, and offering novel, beyond FET functionalities, e.g., optical logic gates and optical amplification. In an integrated photonic circuit, photonic components are typically used for interconnection between electronic subsystems. A hybrid electronic-photonic integrated circuits with LETs with FETs on one chip can take the advantages of the two worlds and mitigate their shortcomings, which will offer major improvement in performance over the pure electronic version.

Thick film hydrogen silsesquioxane planarization for passive component technology associated with electronic-photonic integrated circuits

Migrating electronic-photonic integrated circuits (EPICs) to higher data rates requires efficient electrical interfaces. This can be achieved with microwave technologies such as coplanar and microstrip transmission lines, but these can be difficult to apply in EPICs because of the complexity of the fabrication processes associated with monolithic integration. In this work, the authors report a novel method for planarizing a thick, low-κ film based on multiple-spins of layers of hydrogen silsesquioxane without a need for thermal curing. Films of total thicknesses of 5 and 6μm were planarized on a heavily doped InP substrate and used to realize coplanar waveguide transmission lines. The film shape is defined as an integral part of the fabrication process without any need for etching. A coplanar waveguide with a characteristic impedance of between 48 and 56Ω over the frequency range 10 MHz–67 GHz was demonstrated.

(Keynote) Silicon-Organic Hybrid Photonics: Integration of Electro-Optical Polymers in a Photonic Integrated Circuit Technology

Photonic integrated circuits (PIC) based on silicon-on-insulator technologies play a crucial role for the development of large-scale on-chip optical devices [1]. They address a variety of applications in optical sensing [2] and signal processing [3]. Many research efforts have been undertaken to develop a wafer-scale PIC platform by making use of well-established semiconductor fabrication processes. Active photonic devices based on standard silicon-on-insulator based PICs rely typically on the plasma dispersion effect in silicon to induce a refractive index change as function of an applied voltage. In this case, the silicon waveguide is doped in such a way that it forms a pn-junction. This is, however, accompanied by optical losses due to absorption and fundamental speed restrictions are related to carrier injection and removal. To overcome these limitations, it is desirable to integrate materials with large off-resonant electro-optical (EO) effect, which allows a change of refractive index by applying a dc or modulated electric field. In this way, no carrier transport is necessary giving rise to ultra-high speed data communication. Here, the silicon waveguide is structured like a capacitor. It consists of two silicon rails in which the active EO material is located in between. Functionalized organic materials are from great interest since they exhibit extraordinary high EO effects. In particular, they can exhibit both, a linear and quadratic EO effect [4]. The advantage of organic EO materials is twofold. First, they exhibit strong EO effects and are highly transparent in the telecommunication wavelength range. Second, they exhibit off-resonant EO effects avoiding unwanted non-parametric processes like two photon absorption and free carrier absorption. The combination of organic materials with silicon-on-insulator based waveguides is known as silicon-organic hybrid (SOH) technology. Recent research has demonstrated a high-speed SOH phase shifter having bandwidths above 100 GHz [5]. Besides that, EO modulators with energy consumption in the atto-Joule per-bit regime have been realized, and also higher modulation formats have been demonstrated [6]. These results show clearly the potential of SOH devices for a next generation of signal processing. However, the integration of organic materials into a well-established silicon-on-insulator technology is still challenging because typical semiconductor fabrication processes are used with relatively high process-temperatures destroying the organic materials. To tackle this issue, an integration approach was proposed in which the organic material is deposited in a post-process. In this work, we review recent results on the hybrid integration of organic EO materials in a silicon-on-insulator technology. We outline some of the identified challenges regarding process compatibility and present preliminary results on the integration of organic materials in a photonic integrated circuit (PIC) technology. Here, we are focusing on EO applications for high speed data transfer employing the linear and quadratic EO effect. As an example, we demonstrate an intensity modulator fabricated in a 0.25 µm SiGe BiCMOS pilot line using 200 mm silicon-on-insulator wafers. This approach gives perspective for monolithically hybrid-integrated photonic devices in an electronic PIC (EPIC)-technology.

Compact Silicon Electro-Optical Modulator Using Hybrid ITO Tri-Coupled Waveguides

Silicon based electro-optical modulators are essential for optical communication systems. In this paper, we present a silicon electro-optical modulator, which is based on tri-coupled waveguides. Two of these waveguides are silicon-on-insulator slot waveguides separated by a hybrid Indium Tin Oxide intermediate waveguide. The silicon-on-insulator slot waveguides reaps the advantages of the high mode confinement. The power-splitting mechanism can be electrically tuned through applying external electric field to the intermediate plasmonic waveguide. The tuning mechanism is designed such that it will both change the coupling conditions and introduces additional intrinsic losses at the telecommunication wavelength (1550 nm). The modulator was optimized by three-dimensional full finite difference time domain electromagnetic simulations. Extinction ratio of 6.14 dB and insertion losses of 0.06 dB are realized at 21 μm modulator length; as well as, extinction ratio of 11.43 dB and insertion losses of 1.65 dB are realized at 34 μm modulator length. The proposed silicon electro-optical modulator can potentially play a key role in the next generation of the onchip electronic-photonic integrated circuits.

Graphene-based plasmonic waveguide devices for electronic-photonic integrated circuit

Graphene is a one-atom thick carbon film packed in a honeycomb structure, and because it has extraordinary optoelectronic properties, it has attracted a great deal of attention in the field of photonics. Graphene-based plasmonic photonic devices have been developed which are capable of emitting, transmitting, modulating, and detecting light wave signals using a single material. In this paper, we propose the concept of on-chip graphene electronic-photonic integrated circuits (EPICs) architecture, and present developments and perspectives on the essential graphene plasmonic-based photonic components, including the plasmonic waveguide, modulator, and photodetector, which are based on the graphene EPICs. The optical characteristics and design considerations of the graphene-based photonic devices are discussed based on experimental and theoretical investigations at telecommunications wavelengths. In parallel, we provide new device design concepts and a potential solution for further improving their operating characteristics. We also performed a numerical investigation of the characteristics of the photonic devices to explain their operating principles and to predict their operating performances. The proposed photonic components were fabricated on an organic photonic chip using an optimized fabrication process, and their optical characteristics were experimentally demonstrated. Based on these results and demonstrations, we hope to introduce new perspectives on the future direction of graphene-EPICs in graphene plasmonics and the optical telecom field.

Lidar System Architectures and Circuits

3D imaging technologies are applied in numerous areas, including self-driving cars, drones, and robots, and in advanced industrial, medical, scientific, and consumer applications. 3D imaging is usually accomplished by finding the distance to multiple points on an object or in a scene, and then creating a point cloud of those range measurements. Different methods can be used for the ranging. Some of these methods, such as stereovision, rely on processing 2D images. Other techniques estimate the distance more directly by measuring the round-trip delay of an ultrasonic or electromagnetic wave to the object. Ultrasonic waves suffer large losses in air and cannot reach distances beyond a few meters. Radars and lidars use electromagnetic waves in radio and optical spectra, respectively. The shorter wavelengths of the optical waves compared to the radio frequency waves translates into better resolution, and a more favorable choice for 3D imaging. The integration of lidars on electronic and photonic chips can lower their cost, size, and power consumption, making them affordable and accessible to all the abovementioned applications. This review article explains different lidar aspects and design choices, such as optical modulation and detection techniques, and point cloud generation by means of beam-steering or flashing an entire scene. Popular lidar architectures and circuits are presented, and the superiority of the FMCW lidar is discussed in terms of range resolution, receiver sensitivity, and compatibility with emerging technologies. At the end, an electronic-photonic integrated circuit for a micro-imaging FMCW lidar is presented as an example.

A Monolithically Integrated Segmented Linear Driver and Modulator in EPIC 0.25- $\mu$ m SiGe:C BiCMOS Platform

In this paper, a monolithically integrated segmented linear driver and Mach–Zehnder modulator (MZM) are presented. The transmitter is fabricated in electronic-photonic integrated circuit 0.25- $\mu \text{m}$ SiGe:C BiCMOS technology, with $f_{T}/f_{\text {max}}=190$ GHz. The driver and the modulator are divided into 16 segments and the MZM phase shifter has a total length of 6.08 mm. The segmented driver delivers a maximum of 4 $\text{V}_{\text {pp}}$ differentially, featuring a gain of 13 dB and total harmonic distortion below 5%. Electro-optical time-domain measurements using PAM-4 modulation format are performed, demonstrating optical eye-diagrams up to 25 Gbaud. The electro-optical bandwidth of the transmitter is 18 GHz. The power dissipation of the driver is 1.5 W, resulting in an energy per bit of 30 pJ/bit at 50 Gb/s. The reported optical transmitter demonstrates for the first time an implementation of a linear driver integrated with an MZM in a Si monolithic process.

A Review of Electronic-Photonic Heterogeneous Integration at DARPA

The Defense Advanced Research Projects Agency (DARPA) has developed programs in integrated photonics for over a decade. From the Electronic-photonic Integrated Circuits (EPIC) program to the more recent Electronic-photonic Heterogeneous Integration (E-PHI) program, DARPA programs have established a library of high-performance silicon photonic devices and have demonstrated heterogeneous integration processes. These components and integration techniques, combined with automated design software tools, form the basis of the new American Institute for Manufacturing Integrated Photonics which will establish a photonics manufacturing ecosystem in the United States through a combination of public and private funds.

Multi-function Mach-Zehnder modulator for pulse shaping and generation.

We present a multi-function electronic-photonic integrated circuit (EPIC) design which exploits a new operation mode of a Mach-Zehnder modulator (MZM). Different from the conventional design, the two arms of the modulator are driven by time-shifted signals of tunable amplitude. We study its operation in the linear and quadratic regions where the MZM is biased at π/2 and π initial phase difference, respectively. In the linear region, the modulator sums the waveforms of the driving signals in the two arms, which can be used to add pre-emphasis function to the modulator, and hence it obviates an electrical pre-emphasis driver. Furthermore, when operating in the quadratic region, the modulator can produce optical pulses with tunable pulse width at double clock rate. Prototype circuits are designed first using a suit of device, electromagnetic simulators to build compact models, and then importing into a photonic circuit simulator for complete circuit performance evaluation.