High density vertical optical interconnects for passive assembly.

The co-packaging of optics and electronics provides a potential path forward to achieving beyond 50 Tbps top of rack switch packages. In a co-packaged design, the scaling of bandwidth, cost, and energy is governed by the number of optical transceivers (TxRx) per package as opposed to transistor shrink. Due to the large footprint of optical components relative to their electronic counterparts, the vertical stacking of optical TxRx chips in a co-packaged optics design will become a necessity. As a result, development of efficient, dense, and wide alignment tolerance chip-to-chip optical couplers will be an enabling technology for continued TxRx scaling. In this paper, we propose a novel scheme to vertically couple into standard 220 nm silicon on insulator waveguides from 220 nm silicon nitride on glass waveguides using overlapping, inverse double tapers. Simulation results using Lumerical's 3D Finite Difference Time Domain solver are presented, demonstrating insertion losses below -0.13 dB for an inter-chip spacing of 1 µm; 1 dB vertical and lateral alignment tolerances of approximately 2.6 µm and ± 2.8 µm, respectively; a greater than 300 nm 1 dB bandwidth; and 1 dB twist and tilt tolerances of approximately ± 2.3 degrees and 0.4 degrees, respectively. These results demonstrate the potential of our coupler for use in co-packaged designs requiring high performance, high density, CMOS compatible out of plane optical connections.

Engineering third-order optical nonlinearities in hybrid chalcogenide-on-silicon platform.

We demonstrated a class of highly nonlinear hybrid waveguide structures based on infiltration of As2S3 chalcogenide glass into silicon slot waveguides. The nonlinear properties of the hybrid waveguides were precisely quantified via a bidirectional top-hat D-scan method, enabling a direct comparison between properties measured using different device geometries. We experimentally demonstrate hybrid As2S3-Si slot waveguides with a two-photon absorption (TPA) figure of merit exceeding 2 at near infrared wavelengths. These waveguides largely satisfy the critical criterion for efficient nonlinear integrated photonics (FOMTPAwg>1), allowing phase shifts greater than π with minimal overall losses. These results pave the way for efficient and robust ultrafast all-optical devices and circuits in large-scale silicon photonics technology.

Bi-directional top-hat D-Scan: single beam accurate characterization of nonlinear waveguides.

The characterization of a third-order nonlinear integrated waveguide is reported for the first time by means of a top-hat dispersive-scan (D-Scan) technique, a temporal analog of the top-hat Z-Scan. With a single laser beam, and by carrying two counterdirectional nonlinear transmissions to assess the input and output coupling efficiencies, a novel procedure is described leading to accurate measurement of the TPA figure of merit, the effective two-photon absorption (TPA), and optical Kerr (including the sign) coefficients. The technique is validated in a silicon strip waveguide for which the effective nonlinear coefficients are measured with an accuracy of ±10%.

Silicon nanobeam cavity for ultra-localized light-matter interaction.

In this work, we theoretically and experimentally demonstrate an unusual air mode silicon nanobeam cavity design with dielectric mirrors. This design combines an extremely strong localization of light-matter interaction in the cavity center and a reduced sensitivity of the resonator wavelength to temperature or top cladding material refractive index variations. The proposed approach allows accurate control of the resonator cavity quality factor combined with flexible choice of the cavity effective mode volume. Q-factors higher than 50,000 have been determined for such cavities and mode volumes smaller than (λ/n)3 were achieved in the investigated configurations. Such a cavity design provides a robust approach to study the hybrid integration of various active materials in the silicon platform, including carbon nanotubes, III-V nanowires, graphene, etc., for light emission, modulation, or detection.

Narrow-linewidth carbon nanotube emission in silicon hollow-core photonic crystal cavity.

Polymer-sorted semiconducting single-walled carbon nanotubes (SWNTs) provide room-temperature emission at near-infrared wavelengths, with potential for large volume production of high-quality solutions and wafer-scale deposition. These features make SWNTs a very attractive material for the realization of on-chip light sources. Coupling SWNT into optical microcavities could enhance and guide their emission, while enabling spectral selection by cavity resonance engineering. This could allow the realization of bright, narrowband sources. Here, we report the first demonstration of coupling SWNTs into the resonant modes of Si hollow-core photonic crystal cavities. We exploit the strong evanescent field in these resonators to interact with SWNT emission, coupling it into an integrated access waveguide. Based on this concept, we demonstrate narrowband SWNT emission resonantly coupled into a Si bus waveguide with a full width at half-maximum of 0.34 nm and an off-resonance rejection exceeding 5 dB.

Highly sensitive refractive index sensing by fast detuning the critical coupling condition of slot waveguide ring resonators.

We experimentally investigate refractive index sensing in silicon slot waveguide ring resonators by the detection of the giant shift of the ring transmission spectrum envelope enabled by the following specific conditions: the slot waveguide cross section as well as the ring couplers have been designed to lead to a V-shaped microring resonator spectrum modulated by the classical frequency comb and exhibiting quality factor peaks of 2000-6000 around λ=1.5 µm. By tracking the spectrum envelope wavelength shift, sensitivity up to S=1,300 nm per refraction index unit (RIU) is reported when the slots are filled by liquids with refraction index values close to 1.33.

Enhanced nonlinear interaction in a microcavity under coherent excitation.

The large field enhancement that can be achieved in high quality factor and small mode volume photonic crystal microcavities leads to strengthened nonlinear interactions. However, the frequency shift dynamics of the cavity resonance under a pulsed excitation, which is driven by nonlinear refractive index change, tends to limit the coupling efficiency between the pulse and the cavity. As a consequence, the cavity enhancement effect cannot last for the entire pulse duration, limiting the interaction between the pulse and the intra-cavity material. In order to preserve the benefit of light localization throughout the pulsed excitation, we report the first experimental demonstration of coherent excitation of a nonlinear microcavity, leading to an enhanced intra-cavity nonlinear interaction. We investigate the nonlinear behavior of a Silicon-based microcavity subject to tailored positively chirped pulses, enabling to increase the free carrier density generated by two-photon absorption by up to a factor of 2.5 compared with a Fourier-transform limited pulse excitation of equal energy. It is accompanied by an extended frequency blue-shift of the cavity resonance reaching 19 times the linear cavity bandwidth. This experimental result highlights the interest in using coherent excitation to control intra-cavity light-matter interactions and nonlinear dynamics of microcavity-based optical devices.

Nonlinear optimization of slot Si waveguides: TPA minimization with FOM(TPA) up to 4.25.

The χ(3) nonlinear properties of slotted crystalline silicon photonic waveguides filled with third-order nonlinear materials (NM) are studied by calculating the effective nonlinear susceptibilities associated to the silicon and cladding material, respectively. The adopted approach circumvents the assumptions that the introduced NM dominates the nonlinear behavior of the slotted waveguide and that strong light confinement in the slot allows neglecting the two-photon absorption (TPA) process in the silicon rails. Optimization of the geometry of silicon-slotted waveguides is performed on the basis of the nonlinear figure of merit (FOM(TPA)) of the guided mode, which is related to the balance between the Kerr and the TPA effects, allowing to reach a FOM(TPA)=4.25. The obtained results reveal the importance of properly choosing the waveguide width of the silicon rails in order to minimize the TPA effect even by tolerating a reduced overall nonlinearity.

Analysis of silicon-on-insulator slot waveguide ring resonators targeting high Q-factors.

Vertical slot waveguide micro-ring resonators in silicon photonics have already been demonstrated in previous works and applied to several schemes, including sensing and hybrid nonlinear optics. Their performances, first quantified by the reachable Q-factors, are still perceived to be restrained by larger intrinsic propagation losses than those suffered by simple Si wire waveguides. In this Letter, the optical loss mechanisms of slot waveguide micro-ring resonators are thoroughly investigated with a special focus on the coupler loss contribution that turns out to be the key obstacle to achieving high Q-factors. By engineering the coupler design, slotted ring resonators with a 50 µm radius are experienced with a loaded Q-factor up to 10 times improvement from Q=3,000 to Q=30,600. The intrinsic losses due to the light propagation in the bent slot ring itself are proved to be as low as 1.32±0.87 dB/cm at λ=1,550 nm. These investigations of slot ring resonators open high performance potentials for on-chip nonlinear optical processing or sensing in hybrid silicon photonics.

Crown ether decorated silicon photonics for safeguarding against lead poisoning.

Lead (Pb2+) toxification is a concerning, unaddressed global public health crisis that leads to 1 million deaths annually. Yet, public policies to address this issue have fallen short. This work harnesses the unique abilities of crown ethers, which selectively bind to specific ions. This study demonstrates the synergistic integration of highly-scalable silicon photonics, with crown ether amine conjugation via Fischer esterification in an environmentally-friendly fashion. This realizes an integrated photonic platform that enables the in-operando, highly-selective and quantitative detection of various ions. The development dispels the existing notion that Fischer esterification is restricted to organic compounds, facilitating the subsequent amine conjugation for various crown ethers. The presented platform is specifically engineered for selective Pb2+ detection, demonstrating a large dynamic detection range, and applicability to field samples. The compatibility of this platform with cost-effective manufacturing indicates the potential for pervasive implementation of the integrated photonic sensor technology to safeguard against societal Pb2+ poisoning.

When Two Worlds Collide: A Rare Case of Multiple Myeloma With Extramedullary Plasmacytoma.

In this case report, we discuss the presentation, diagnosis, and management of a 67-year-old gentleman with stage II multiple myeloma with concurrent biopsy-proven bone plasmacytoma and why it is important to understand the molecular intricacies of these disorders. We emphasize the critical role of radiology in identifying, characterizing, and managing these lesions. Furthermore, we shed light on the critical differentiation between solitary extramedullary plasmacytoma and multiple myeloma and discuss treatment modalities for both conditions.

When Sight and Cancer Collide: A Rare Case of Paraneoplastic Bilateral Optic Neuritis.

Bilateral acute optic neuritis is a rare and challenging clinical presentation, often associated with conditions like multiple sclerosis or neuromyelitis optica spectrum disorder. We present the case of a 40-year-old woman with a complex medical history, including poorly differentiated squamous cell carcinoma of the cervix (stage IIIC), who presented with a swift and profound bilateral vision loss. Despite initial treatment with high-dose methylprednisolone and therapeutic plasma exchange, her optic nerve enhancement on MRI and negative autoantibody results raised suspicion of paraneoplastic optic neuritis. This prompted consultation with oncology, and the patient initiated chemotherapy. The rapid onset and progression of bilateral optic neuritis in the context of cervical carcinoma emphasize the importance of considering paraneoplastic syndromes in such cases. A multidisciplinary approach involving neurology, ophthalmology, and oncology specialists is vital for the diagnosis and management of these complex presentations. This case underscores the need for heightened awareness of paraneoplastic etiologies in patients with malignancies and unexplained neurological symptoms.

A Case Report on May-Thurner Syndrome: Beyond the Usual Suspects.

May-Thurner syndrome (MTS), also known as iliocaval venous compression syndrome, is a vascular condition characterized by extrinsic venous compression within the iliocaval territory. While traditionally considered a condition predominantly affecting women, this case report presents an atypical presentation in a middle-aged male patient. The patient initially presented with left lower extremity pain and swelling, which was attributed to deep venous thrombosis (DVT) in the left calf and femoral vein. Despite anticoagulation therapy, his symptoms persisted, leading to further diagnostic evaluation and the identification of MTS. This report highlights the clinical presentation, diagnostic challenges, and successful management of MTS in a male patient. Endovascular interventions, including balloon dilation and stent placement, were employed to address refractory stenosis and thrombus burden. The case emphasizes the importance of considering MTS as a potential diagnosis in patients with unexplained lower limb symptoms, irrespective of traditional risk factors or gender. Early identification and appropriate interventions can lead to symptom relief, obstruction resolution, and improved long-term outcomes for patients with MTS. This case underscores the need for heightened clinician awareness regarding MTS and its potential impact on patient care.

A Case Report of Candida-Induced Emphysematous Gastritis.

Emphysematous gastritis is a rare entity that has not much literature available. It is known to manifest as a diffused wall inflammation and air within the wall of the stomach and has been associated with gas-forming organisms. We present a complex case of a middle-aged woman with a previous history of fulminant Clostridium difficile complicated with colectomy and diverting colostomy. She was admitted due to diabetic ketoacidosis, later complicated with worsening abdominal pain, and a CT scan of the abdomen and pelvis without contrast revealed findings consistent with ischemic bowel, severe pneumatosis intestinalis, and extensive portal venous gas. A stomach biopsy revealed hemorrhagic necrosis; a Gomori methenamine silver stain was compatible with fungal organisms, Candida species, correlating with Candida emphysematous gastritis. This case highlights the importance of early diagnosis of this syndrome in order to provide appropriate management, and early identification, to improve survival.

Tailoring carbon nanotubes optical properties through chirality-wise silicon ring resonators.

Semiconducting single walled carbon nanotubes (s-SWNT) have an immense potential for the development of active optoelectronic functionalities in ultra-compact hybrid photonic circuits. Specifically, s-SWNT have been identified as a very promising solution to implement light sources in the silicon photonics platform. Still, two major challenges remain to fully exploit the potential of this hybrid technology: the limited interaction between s-SWNTs and Si waveguides and the low quantum efficiency of s-SWNTs emission. Silicon micro-ring resonators have the potential capability to overcome these limitations, by providing enhanced light s-SWNT interaction through resonant light recirculation. Here, we demonstrate that Si ring resonators provide SWNT chirality-wise photoluminescence resonance enhancement, releasing a new degree of freedom to tailor s-SWNT optical properties. Specifically, we show that judicious design of the micro-ring geometry allows selectively promoting the emission enhancement of either (8,6) or (8,7) SWNT chiralities present in a high-purity polymer-sorted s-SWNT solution. In addition, we present an analysis of nanometric-sized silicon-on-insulator waveguides that predicts stronger light s-SWNT interaction for transverse-magnetic (TM) modes than for conventionally used transverse-electric (TE) modes.

Nonlinear Properties of Ge-rich Si1-xGex Materials with Different Ge Concentrations.

Silicon photonics is a large volume and large scale integration platform for applications from long-haul optical telecommunications to intra-chip interconnects. Extension to the mid-IR wavelength range is now largely investigated, mainly driven by absorption spectroscopy applications. Germanium (Ge) is particularly compelling as it has a broad transparency window up to 15 µm and a much higher third-order nonlinear coefficient than silicon which is very promising for the demonstration of efficient non-linear optics based active devices. Si1-xGex alloys have been recently studied due to their ability to fine-tune the bandgap and refractive index. The material nonlinearities are very sensitive to any modification of the energy bands, so Si1-xGex alloys are particularly interesting for nonlinear device engineering. We report on the first third order nonlinear experimental characterization of Ge-rich Si1-xGex waveguides, with Ge concentrations x ranging from 0.7 to 0.9. The characterization performed at 1580 nm is compared with theoretical models and a discussion about the prediction of the nonlinear properties in the mid-IR is introduced. These results will provide helpful insights to assist the design of nonlinear integrated optical based devices in both the near- and mid-IR wavelength ranges.

Experimental GVD engineering in slow light slot photonic crystal waveguides.

The use in silicon photonics of the new optical materials developed in soft matter science (e.g. polymers, liquids) is delicate because their low refractive index weakens the confinement of light and prevents an efficient control of the dispersion properties through the geometry. We experimentally demonstrate that such materials can be incorporated in 700 µm long slot photonic crystal waveguides, and hence can benefit from both slow-light field enhancement effect and slot-induced ultra-small effective areas. Additionally, we show that their dispersion can be engineered from anomalous to normal regions, along with the presence of multiple zero group velocity dispersion (ZGVD) points exhibiting Normalized Delay Bandwidth Product as high as 0.156. The reported results provide experimental evidence for an accurate control of the dispersion properties of fillable periodical slotted structures in silicon photonics, which is of direct interest for on-chip all-optical data treatment using nonlinear optical effects in hybrid-on-silicon technologies.

Evaluation of a model to predict poor survival in patients undergoing elective TIPS procedures.

PURPOSE: To validate a previously published model to predict the probability of patient death within 3 months after an elective transjugular intrahepatic portosystemic shunt (TIPS) procedure. The model is implemented with use of a nomogram or a formula. MATERIALS AND METHODS: Patients who underwent an elective TIPS procedure between May 1, 1999, and May 1, 2001, were selected. Patients who underwent emergency TIPS creation and patients with serum creatinine levels greater than 3.0 mg/dL were excluded. A total of 72 patients met the inclusion criteria. The patients were divided into two groups: group A (ethanol-induced cirrhosis; n = 23) and group B (non-ethanol-induced cirrhosis; n = 49). The model was applied and the predicted probability of death was compared to actual patient survival. A high risk score (R > or = 1.8) is associated with a high risk of death within 3 months after TIPS creation. Survival curves were estimated with use of Kaplan-Meier product limit estimates and were compared with use of the log-rank test. The model's accuracy was evaluated with use of the c-statistic. P values lower than.05 indicated statistical significance. RESULTS: The technical success rate was 98.7%. The 3-month survival rate for the whole group was 79.7%. The predicted mortality rate was higher than the observed mortality rate. The c-statistic was 0.65 for the formula and 0.66 for the nomogram. Patients with a risk score of at least 1.8 had a 3-month survival rate of 54.6% and patients with a risk score lower than 1.8 had a 3-month survival rate of 84.9% (P =.037). CONCLUSION: These results confirm that, after an elective TIPS procedure, patients with risk scores of at least 1.8 have a significantly lower 3-month survival rate than patients with risk scores lower than 1.8.