We report silicon microring transmitter and receiver with monolithically integrated driver and analog front end at up to 64Gbps NRZ. The total die area of the circuits is 0.006 mm 2 , 10x smaller than prior reports.

Over the past decade, photonics research has explored accelerated tensor operations, foundational to artificial intelligence (AI) and deep learning1-4, as a path towards enhanced energy efficiency and performance5-14. The field is centrally motivated by finding alternative technologies to extend computational progress in a post-Moore's law and Dennard scaling era15-19. Despite these advances, no photonic chip has achieved the precision necessary for practical AI applications, and demonstrations have been limited to simplified benchmark tasks. Here we introduce a photonic AI processor that executes advanced AI models, including ResNet3 and BERT20,21, along with the Atari deep reinforcement learning algorithm originally demonstrated by DeepMind22. This processor achieves near-electronic precision for many workloads, marking a notable entry for photonic computing into competition with established electronic AI accelerators23 and an essential step towards developing post-transistor computing technologies.

We experimentally demonstrated V-groove-based self-aligned SiN edge coupler (EC) on a monolithic CMOS-SiPh platform. <0.6/0.8 dB TE/TM SMF-EC transmission efficiency, in conjunction with <-39 dB back reflection and >520 mW power handling capability were achieved.

Photonic system component counts are increasing rapidly, particularly in CMOS-compatible silicon photonics processes. Large numbers of cascaded active photonic devices are difficult to implement when accounting for constraints on area, power dissipation, and response time. Plasma dispersion and the thermo-optic effect, both available in CMOS-compatible silicon processes, address a subset of these criteria. With the addition of a few back-end-of-line etch processing steps, silicon photonics platforms can support nano-opto-electro-mechanical (NOEM) phase shifters. Realizing NOEM phase shifters that operate at CMOS-compatible voltages (≤ 1.2 V) and with low insertion loss remains a challenge. Here, we introduce a novel NOEM phase shifter fabricated alongside 90 nanometer transistors that imparts 5.63 radians phase shift at 1.08 volts bias over an actuation length of 25μm with an insertion loss of less than 0.04 dB and 3 dB bandwidth of 0.26 MHz.

As Moore’s law and Dennard scaling come to an end, new devices and computing architectures are being explored. The development of computing hardware designed to address the rapidly growing need for computational power to accelerate artificial intelligence applications has prompted investigations into both. While silicon photonics is typically viewed as a communications platform, we discuss its application to artificial intelligence and some outstanding challenges to be addressed.

Three-dimensional (3D) photonic crystals can provide access to very interesting and unique properties for ultimate control and manipulation of photons, not possible otherwise. However, widespread implementation of such photonic crystals remains elusive because the fabrication technology available today has either silicon (Si) incompatibility, poor scalability, a large number of undesired defects, challenging or impossible placement of intentional defects, or has advanced nonstandard process steps available only in a few laboratories. In this work, a new methodology of fabricating 3D photonic crystals free of unintentional defects is developed. This methodology is "truly" Si-compatible and uses techniques available in any standard fabrication facility. A broadband omnidirectional reflector on Si is demonstrated using the same method. Introduction of intentional defect sites for fabrication of 3D waveguides and optical cavities is also discussed.

A complementary metal-oxide semiconductor compatible on-chip light source is the holy grail of silicon photonics and has the potential to alleviate the key scaling issues arising due to electrical interconnects. Despite several theoretical predictions, a sustainable, room temperature laser from a group-IV material is yet to be demonstrated. In this work, we show that a particular loss mechanism, inter-valence-band absorption (IVBA), has been inadequately modeled until now and capturing its effect accurately as a function of strain is crucial to understanding light emission processes from uniaxially strained germanium (Ge). We present a detailed model of light emission in Ge that accurately models IVBA in the presence of strain and other factors such as polarization, doping, and carrier injection, thereby revising the road map toward a room temperature Ge laser. Strikingly, a special resonance between gain and loss mechanisms at 4%-5% (100) uniaxial strain is found resulting in a high net gain of more than 400 cm(-1) at room temperature. It is shown that achieving this resonance should be the goal of experimental work rather than pursuing a direct band gap Ge.

We report the first experimental observation of low-threshold lasing in strained germanium nanowires. The lasing threshold is ~3.0 kW cm -2 which is more than one order of magnitude lower than the state-of-the-art germanium-tin Fabry-Perot laser.

We experimentally study III-V/Ge heterostructure and demonstrate InGaAs hetero-contacts to n-Ge with a wide range of In % and achieve low contact resistivity ($\rho_C$) of $5\times10^{-8} \Omega\cdot cm^2$ for Ge doping of $3 \times 10^{19} cm^{-3}$. This results from re-directing the charge neutrality level (CNL) near the conduction band and benefiting from low effective mass for high electron transmission. For the first time, we observe that the heterointerface presents no temperature dependence despite the two different conduction minimum valley locations of III-V ($\Gamma$-valley) and Ge (L-valley), which potentially stems from elastic trap-assisted tunneling through defect states at the interface generated by dislocations. The hetero-interface plays a dominant role in the overall $\rho_C$ below $\approx 1 \times 10^{-7} \Omega \cdot cm^2$, which can be further improved with large active dopant concentration in Ge by co-doping.

The integration of efficient, miniaturized group IV lasers into CMOS architecture holds the key to the realization of fully functional photonic-integrated circuits. Despite several years of progress, however, all group IV lasers reported to date exhibit impractically high thresholds owing to their unfavourable bandstructures. Highly strained germanium with its fundamentally altered bandstructure has emerged as a potential low-threshold gain medium, but there has yet to be a successful demonstration of lasing from this seemingly promising material system. Here we demonstrate a low-threshold, compact group IV laser that employs a germanium nanowire under a 1.6% uniaxial tensile strain as the gain medium. The amplified material gain in strained germanium can sufficiently overcome optical losses at 83 K, thus allowing the observation of multimode lasing with an optical pumping threshold density of ~3.0 kW cm −2 . Our demonstration opens new possibilities for group IV lasers for photonic-integrated circuits.

A dramatic and previously overlooked interaction of parasitic absorption with strain in germanium (Ge) is demonstrated through extensive simulations and experiments. Uniaxial strain of 4-5% and biaxial strain greater than 1% are the best candidates for a room temperature Ge laser.

A silicon-compatible light source is the final missing piece for completing high-speed, low-power on-chip optical interconnects. In this paper, we present a germanium nanowire light emitter that encompasses all the aspects of potential low-threshold lasers: highly strained germanium gain medium, strain-induced pseudoheterostructure, and high-Q nanophotonic cavity. Our nanowire structure presents greatly enhanced photoluminescence into cavity modes with measured quality factors of up to 2000. By varying the dimensions of the germanium nanowire, we tune the emission wavelength over more than 400 nm with a single lithography step. We find reduced optical loss in optical cavities formed with germanium under high (>2.3%) tensile strain. Our compact, high-strain cavities open up new possibilities for low-threshold germanium-based lasers for on-chip optical interconnects.

We theoretically investigate the impact of the defect-limited carrier lifetime on the performance of germanium (Ge) light sources. For Ge LEDs, we show that improving the material quality can offer even greater enhancements than techniques such as tensile strain, the leading approach for enhancing Ge light emission. For Ge lasers, we show that the defect-limited lifetime becomes increasing important as tensile strain is introduced, and that defect-limited lifetime must be improved if the full benefits of strain are to be realized. We conversely show that improving the material quality supersedes much of the utility of n-type doping for Ge lasers.

We theoretically investigate the effect of <100> uniaxial strain on a Ge-on-Si laser. We predict a dramatic ~200x threshold reduction upon applying sufficient uniaxial tensile strain to Ge. This anomalous reduction is explained by how the topmost valence bands split and become anisotropic with uniaxial tensile strain. Approximately 3.2% uniaxial strain is required to achieve this anomalous threshold reduction for 1×1019 cm−3 n-type doping, and a complex interaction between strain and n-type doping is observed. Achieving this critical uniaxial strain level for the anomalous threshold reduction is dramatically more relevant to practical devices than realizing a direct band gap.

Extensive modeling and experiments demonstrate a dramatic reduction in parasitic absorption with strain due to a previously overlooked mechanism. A special resonance at 4-5% uniaxial strain indicates that this is the optimal strain level for a room temperature Ge laser.

We report a Germanium waveguide electro-absorption modulator with electro-optic bandwidth substantially beyond 50 GHz. The device is implemented in a fully integrated Si photonics platform on 200 mm silicon-on-insulator wafers with 220 nm top Si thickness. Wide open eye diagrams are demonstrated at 1610 nm operation wavelength for nonreturn-to-zero on-off keying (NRZ-OOK) modulation at data rates as high as 56 Gb/s. Dynamic extinction ratios up to 3.3 dB are obtained by applying drive voltages of 2 V peak-to-peak, along with an optical insertion loss below 5.5 dB. The device has a low junction capacitance of just 12.8 fF, resulting in 12.8 fJ/bit of dynamic and ~1.2 mW of static power consumption in typical operating conditions. Wafer-scale performance data are presented and confirm the manufacturability of the device. The demonstrated modulator shows great potential for realizing high-density and low-power silicon photonic transceivers targeting short-reach optical interconnects at serial data rates of 56 Gb/s and beyond.

We theoretically investigate the methodology involved in the minimization of the threshold of a Ge-on-Si laser and maximization of the slope efficiency in the presence of both biaxial tensile strain and n-type doping. Our findings suggest that there exist ultimate limits beyond which no further benefit can be realized through increased tensile strain or n-type doping. In this study, we quantify these limits, showing that the optimal design for minimizing threshold involves approximately 3.7% biaxial tensile strain and 2 × 10 18 cm −3 n-type doping, whereas the optimal design for maximum slope efficiency involves approximately 2.3% biaxial tensile strain with 1 × 10 19 cm −3 n-type doping. Increasing the strain and doping beyond these limits will degrade the threshold and slope efficiency, respectively.

We investigate the interaction of tin alloying with tensile strain and n-type doping for improving the performance of a Ge-based laser for on-chip optical interconnects. Using a modified tight-binding formalism that incorporates the effect of tin alloying on conduction band changes, we calculate how threshold current density and slope efficiency are affected by tin alloying in the presence of tensile strain and n-type doping. Our results show that while there exists a negative interaction between tin alloying and n-type doping, tensile strain can be effectively combined with tin alloying to dramatically improve the Ge gain medium in terms of both reducing the threshold and increasing the expected slope efficiency. Through quantitative modeling, we find that the best design is to include large amounts of both tin alloying and tensile strain but only moderate amounts of n-type doping, if researchers seek to achieve the best possible performance in a Ge-based laser.

BACKGROUNDCarotid intima media thickness is used as a safe, noninvasive, surrogate endpoint to measure severity and progression of generalised atherosclerosis. The basis of almost all cardiovascular diseases is atherosclerosis, which is almost invariably present in all adults. Two vascular beds, coronary artery and carotid artery share same atherosclerosis risk factors and anatomically, first immediate closest branches which originate from aorta, so intima media thickness of carotid artery can be used as golden markers in prediction of atherosclerosis, presence of coronary artery disease and risk of developing disease in later life.MATERIALS AND METHODSThis study compares angiography proved CAD (Coronary artery disease) and non-CAD cases, CAD patients served as outcome variables in subjects without CAD. Carotid intima media thickness was measured in all subjects and correlated with risk factors measured by SMART risk score. Noninvasive measurement of the intima media thickness of the common and internal carotid artery was made with high resolution B-mode ultrasonography in 100 cases.RESULTSThe mean IMT of internal carotid artery of both sides of 100 cases was 0.84 mm. The IMT is significantly higher in CAD proved cases than non- CAD cases. Mean IMT of CAD cases was (0.88 mm +/- 0.11 SD) more than the mean IMT of non CAD cases (mean 0.67 mm+ 0.04 SD) which is highly significant. Intima Media Thickness and Risk factors value are well correlated and there is significant association between two variables with correlation coefficient.02144 [r = 0.2144] respectively. Relative risk of CAD for the quantile with the highest thickness as compared to the lowest quintile was highly significant i. e. infinity (95% CI - 1.081 - infinity).CONCLUSIONIncreased intima media thickness is a predictor and golden marker for presence and severity of CAD.