Measurement accuracy in silicon photonic ring resonator thermometers: identifying and mitigating intrinsic impairments.

Silicon photonic ring resonator thermometers have been shown to provide temperature measurements with a 10 mK accuracy. In this work we identify and quantify the intrinsic on-chip impairments that may limit further improvement in temperature measurement accuracy. The impairments arise from optically induced changes in the waveguide effective index, and from back-reflections and scattering at defects and interfaces inside the ring cavity and along the path between light source and detector. These impairments are characterized for 220 × 500 nm Si waveguide rings by experimental measurement in a calibrated temperature bath and by phenomenological models of ring response. At different optical power levels both positive and negative light induced resonance shifts are observed. For a ring with L = 100 µm cavity length, the self-heating induced resonance red shift can alter the temperature reading by 200 mK at 1 mW incident power, while a small blue shift is observed below 100 µW. The effect of self-heating is shown to be effectively suppressed by choosing longer ring cavities. Scattering and back-reflections often produce split and distorted resonance line shapes. Although these distortions can vary with resonance order, they are almost completely invariant with temperature for a given resonance and do not lead to measurement errors in themselves. The effect of line shape distortions can largely be mitigated by tracking only selected resonance orders with negligible shape distortion, and by measuring the resonance minimum wavelength directly, rather than attempting to fit the entire resonance line shape. The results demonstrate the temperature error due to these impairments can be limited to below the 3 mK level through appropriate design choices and measurement procedures.

Optical wavefront phase-tilt measurement using Si-photonic waveguide grating couplers.

Silicon photonic wavefront phase-tilt sensors for wavefront monitoring using surface coupling grating arrays are demonstrated. The first design employs the intrinsic angle dependence of the grating coupling efficiency to determine local wavefront tilt, with a measured sensitivity of 7 dB/°. The second design connects four gratings in an interferometric waveguide circuit to determine incident wavefront phase variation across the sensor area. In this device, one fringe spacing corresponds to 2° wavefront tilt change. These sensor elements sample a wavefront incident on the chip surface without the use of bulk optic elements, fiber arrays, or imaging arrays. Both sensor elements are less than 60 µm across and are potential unit cell sensor elements for large arrays that monitor wavefront shape across an image or pupil plane in adaptive optics systems for free-space optical communications, astronomy, and beam pointing applications.

[Current status and influencing factors for physicians in different departments prescribing novel hypoglycemic agent with cardiovascular benefits].

Objective: To investigate the knowledge, use and barriers when prescribing GLP-1RA and SGLT2i among cardiologists, endocrinologists and general practitioners, and explore the influencing factors that hinder the use of these medications. Methods: A questionnaire was conducted among physicians in the above departments in Peking University Third Hospital and health service institutions at all levels in its medical consortium. A total of 342 physicians were involved. Among them, 40.6% (139) were cardiologists, 28.9% (99) were endocrinologists and 30.4% (104) were general practitioners; 66.7% (270) came from Beijing while 33.3% (72) from other provinces. The survey included clinicians' knowledge and current use of GLP-1RA and SGLT2i, and the possible reasons that influenced the prescription of these medications. Medical therapies of physicians were investigated by simulating different clinical scenarios. The difference of measures among physicians in different departments was compared. Results: A total of 342 physicians were involved, with the average age of 40 (35, 46) years old and the average working time of 13 (7, 20) years. Among them, 40.6% (139) were male. 77.5% (265) physicians had comprehensive knowledge of SGLT2i and prescribed it, which was higher than that for GLP-1RA (70.5%, 241) (P<0.001). 21.1% (72) physicians prescribed SGLT2i more than 20 times per month, which was higher than that for GLP-1RA (8.2%, 28) (P<0.001). Endocrinologists had more knowledge and prescribed more GLP-1RA and SGLT2i compared with other physicians (both P values<0.001). 38.1% (53) cardiologists, 22.2% (22) endocrinologists, and 30.8% (32) general practitioners believed patients needed an endocrinologist to evaluate and adjust GLP-1RA, which was the primary barrier for the use of medications (P=0.042). 27.4% (38) cardiologists, 14.1% (14) endocrinologists, and 30.8% (32) general practitioners believed patients needed an endocrinologist to evaluate and adjust SGLT2i, which was the primary barrier for the use of medications (P=0.018). 21.6% (30) cardiologists, 45.5% (45) endocrinologists, and 31.7% (33) general practitioners believed side effects of SGLT2i was the primary barrier for the use of medications (P<0.001). For patients with unqualified glycemic control and cardiovascular complications, 65.4% (75) cardiologists, 69.7% (69) endocrinologists, and 43.3% (45) general practitioners chose the above medications (P<0.001). For patients with qualified glycemic control, combined with cardiovascular complications and diabetic organ damage, 35.3% (49) cardiologists, 52.5% (52) endocrinologists, and 25.0% (26) general practitioners chose the above medications (P<0.001). Conclusions: Physicians had more knowledge and prescription of SGLT2i than that of GLP-1RA. Endocrinologists had more knowledge and prescription of the above medications than other physicians. The side effect of medications was potential primary barrier for the use of the novel hypoglycemic agent with cardiovascular benefits. In clinical practice, most of physicians considered that high-risk patients with cardiovascular comorbidities need to be referred to cardiologist or endocrinologist to adjust clinical therapies.

[Effect of "one-stop" outpatient management on the control rate of multiple metabolic disorders patients].

Objective: To explore the effect of "one-stop" outpatient management on the therapeutic schedule and control rate of patients with metabolic disorders. Methods: A total of 332 patients who met the inclusion criteria were enrolled and treated regularly in the "one-stop" outpatient department of the Department of Cardiology of the Third Hospital of Peking University from November 1, 2020 to April 30, 2022. The general information, personal history, family history, drug treatment plan, blood pressure, height, weight, waist circumference, and hip circumference of patients were collected through the outpatient electronic medical record system, and patients were followed up through conducting "one-stop" comprehensive management. The baseline clinical characteristics were analyzed, and the changes of metabolic indexes, treatment conditions and control rate of patients with different metabolic disorders before and after the "one-stop" outpatient management were compared. Results: The time interval between the first visit and the last visit was 44 (26, 60) weeks in 332 patients, whose age was (57.2±13.2) years, including 219 males (66.0%). After the "one-stop" outpatient management, fasting blood glucose (FBG) [ 6.6 (5.6, 7.9) mmol/L vs 6.3 (5.6, 6.9) mmol/L], glycosylated hemoglobin A1c (HbA1c) [ (7.2±1.5) % vs (6.6±0.8) %], low density lipoprotein cholesterol (LDL-C) [ 2.70 (1.97, 3.55) mmol/L vs 2.04 (1.66, 2.63) mmol/L] and blood uric acid (UA) [ (383.7±107.1) µmol/L vs (341.2±90.6) µmol/L] all decreased significantly (all P values<0.05). The control rates of hypertension (19.8% vs 28.2%), diabetes (45.2% vs 66.5%), hyperlipidemia (54.9% vs 87.6%) and hyperuricemia (16.7% vs 49.0%) were significantly improved after the "one-stop" outpatient management (all P values<0.05). Conclusion: The "one-stop" outpatient management of cardiovascular department can significantly improve the metabolic condition and the control rate of patients with multiple metabolic disorders.

[Sepsis and acute kidney injury].

Sepsis is a life-threatening multiple organ dysfunction syndrome caused by infection, and kidney is one of the most organs susceptible to injury in sepsis. Critical ill patients with sepsis often suffer from acute kidney injury (AKI) of varying degrees with a high mortality. There are more and more researches on the early identification, pathogenesis, diagnosis and treatment of acute kidney injury in sepsis. In order to improve the understanding and reduce the mortality of acute kidney injury, this review briefly discussed the early identification, physio-pathologic mechanism, treatment, prognosis and follow up.

Fiber-chip grating coupler based on interleaved trenches with directionality exceeding 95.

We propose a fiber-chip grating coupler that interleaves the standard full and shallow etch trenches in a 220 nm thick silicon layer to provide a directionality upward exceeding 95%. By adjusting the separation between the two sets of trenches, constructive interference is achieved in the upward direction independent of the bottom oxide thickness and without any bottom reflectors, overlays, or customized etch depths. We implement a transverse subwavelength structure in the first two grating periods to minimize back-reflections. The grating coupler has a calculated coupling efficiency of CE~-1.05 dB with a 1 dB bandwidth of 30 nm and minimum feature size of 100 nm, compatible with deep-UV lithography.

Photonic wire biosensor microarray chip and instrumentation with application to serotyping of Escherichia coli isolates.

A complete photonic wire molecular biosensor microarray chip architecture and supporting instrumentation is described. Chip layouts with 16 and 128 independent sensors have been fabricated and tested, where each sensor can provide an independent molecular binding curve. Each sensor is 50 µm in diameter, and consists of a millimeter long silicon photonic wire waveguide folded into a spiral ring resonator. An array of 128 sensors occupies a 2 × 2 mm2 area on a 6 × 9 mm2 chip. Microfluidic sample delivery channels are fabricated monolithically on the chip. The size and layout of the sensor array is fully compatible with commercial spotting tools designed to independently functionalize fluorescence based biochips. The sensor chips are interrogated using an instrument that delivers sample fluid to the chip and is capable of acquiring up to 128 optical sensor outputs simultaneously and in real time. Coupling light from the sensor chip is accomplished through arrays of sub-wavelength surface grating couplers, and the signals are collected by a fixed two-dimensional detector array. The chip and instrument are designed so that connection of the fluid delivery system and optical alignment are automated, and can be completed in a few seconds with no active user input. This microarray system is used to demonstrate a multiplexed assay for serotyping E. coli bacteria using serospecific polyclonal antibody probe molecules.

Cloning and expression analysis of Wnt6 and Hox6 during intestinal regeneration in the sea cucumber Apostichopus japonicus.

Many developmental genes play important roles in regeneration. Here, we cloned the two developmental genes, Wnt6 and Hox6, from Apostichopus japonicus by rapid amplification of cDNA ends (RACE) polymerase chain reaction (PCR). The Wnt6 full-length cDNA is 1140 bp long with a 1029-bp open reading frame encoding 342 amino acids. The deduced Wnt6 protein contained a 22-amino acid signal peptide and a 274-amino acid mature peptide. The Hox6 (AjHBOX6) full-length cDNA contained 1312 bp with a 966-bp open reading frame encoding 321 amino acids. Its deduced amino acid sequence included one homeodomain (60 amino acids) and three domains with low compositional complexity. Comparison and phylogenetic analysis revealed that Wnt6 and Hox6 in A. japonicus had the nearest relationship to those in sea urchins. Further expression analysis by real-time PCR showed that Wnt6 and Hox6 were apparently upregulated during intestine regeneration, which suggested that they were involved in the intestinal regeneration of sea cucumbers.

Colorless directional coupler with dispersion engineered sub-wavelength structure.

Directional couplers are extensively used devices in integrated optics, but suffer from limited operational wavelength range. Here we use, for the first time, the dispersive properties of sub-wavelength gratings to achieve a fivefold enhancement in the operation bandwidth of a silicon-on-insulator directional coupler. This approach does not compromise the size or the phase response of the device. The sub-wavelength grating based directional coupler we propose covers a 100 nm bandwidth with an imbalance of ≤ 0.6 dB between its outputs, as supported by full 3D FDTD simulations.

Highly tolerant tunable waveguide polarization rotator scheme.

Integrated polarization rotators are known to exhibit stringent fabrication tolerances, which severely handicap their practical application. Here we present a general polarization rotator scheme that enables both the compensation of fabrication errors and wavelength tunability. The scheme is described analytically, and a condition for perfect polarization conversion is established. Simulations of a silicon-on-insulator polarization rotator show polarization extinction ratios in excess of 40 dB even in the presence of large fabrication errors that in a conventional rotator configuration degrade the extinction ratio to below 5 dB. Additionally, wavelength tuning over ±30 nm is shown.

All-optical wavelength conversion for 10 Gb/s DPSK signals in a silicon ring resonator.

We demonstrate all-optical wavelength conversion at 10 Gb/s for differential phase-shift keyed (DPSK) data signals in the C-band, based on four-wave mixing (FWM) in a silicon ring resonator. Error-free operation with a system penalty of ~4.1 dB at 10⁻9 BER is achieved.

All-optical XOR logic gate for 40Gb/s DPSK signals via FWM in a silicon nanowire.

We demonstrate an all-optical XOR logic function for 40Gb/s differential phase-shift keyed (DPSK) data signals in the C-band, based on four-wave mixing (FWM) in a silicon nanowire. Error-free operation with a system penalty of ~3.0dB and ~4.3dB at 10⁻9 BER is achieved.

Single-etch grating coupler for micrometric silicon rib waveguides.

Grating couplers are widely used as an efficient and versatile fiber-chip coupling structure in nanometric silicon wire waveguides. The implementation of efficient grating couplers in micrometric silicon-on-insulator (SOI) rib waveguides is, however, challenging, since the coupler waveguide region is multimode. Here we experimentally demonstrate grating couplers in 1.5 µm-thick SOI rib waveguides with a coupling efficiency of -2.2 dB and a 3 dB bandwidth of 40 nm. An inverse taper is used to adiabatically transform the interconnection waveguide mode to the optimum grating coupler excitation field with negligible higher order Bloch mode excitation. Couplers are fabricated in the same etch step as the waveguides using i-line stepper lithography. The benefits of wafer-scale testing and device characterization without facet preparation are thus attained at no additional cost.

Temperature-independent silicon subwavelength grating waveguides.

We demonstrate, by experiment and numerical calculations, temperature-independent subwavelength grating waveguides with a periodic composite core composed of alternating regions of silicon and SU-8 polymer. The polymer has a negative thermo-optic (TO) material coefficient that cancels the large positive TO effect of the silicon. Measurements and Bloch mode calculations were carried out over a range of silicon-polymer duty ratios. The lowest measured TO coefficient at a wavelength of 1550 nm is 1.8×10(-6) K(-1); 2 orders of magnitude smaller than a conventional silicon photonic wire waveguide. Calculations predict the possibility of complete cancellation of the silicon waveguide temperature dependence.

Error-free all-optical demultiplexing at 160Gb/s via FWM in a silicon nanowire.

We demonstrate all-optical time division demultiplexing from 160Gb/s to 10Gb/s in the C-band, based on four-wave mixing (FWM) in a silicon nanowire. We achieve error-free operation with a system penalty of approximately 3.9dB at 10(-9) BER.

Real-time cancellation of temperature induced resonance shifts in SOI wire waveguide ring resonator label-free biosensor arrays.

A comprehensive investigation of real-time temperature-induced resonance shift cancellation for silicon wire based biosensor arrays is reported for the first time. A reference resonator, protected by either a SU8 or SiO(2) cladding layer, is used to track temperature changes. The temperature dependence of resonators in aqueous solutions, pertinent to biosensing applications, is measured under steady-state conditions and the operating parameters influencing these properties are discussed. Real-time measurements show that the reference resonator resonances reflect the temperature changes without noticeable time delay, enabling effective cancellation of temperature-induced shifts. Binding between complementary IgG protein pairs is monitored over 4 orders of magnitude dynamic range down to a concentration of 20 pM, demonstrating a resolvable mass of 40 attograms. Reactions are measured over time periods as long as 3 hours with high stability, showing a scatter corresponding to a fluid refractive index fluctuation of ± 4 × 10(-6) in the baseline data. Sensor arrays with a SU8 protective cladding are easy to fabricate, while oxide cladding is found to provide superior stability for measurements involving long time scales.

Continuously apodized fiber-to-chip surface grating coupler with refractive index engineered subwavelength structure.

We demonstrate a fully etched, continuously apodized fiber-to-chip surface grating coupler for the first time (to our knowledge). The device is fabricated in a single-etch step and operates with TM-polarized light, achieving a coupling efficiency of 3.7 dB and a 3 dB bandwidth of 60 nm. A subwavelength microstructure is employed to generate an effective medium engineered to vary the strength of the grating and thereby maximize coupling efficiency, while mitigating backreflections at the same time. Minimum feature size is 100 nm for compatibility with deep-UV 193 nm lithography.

Label-free biosensor array based on silicon-on-insulator ring resonators addressed using a WDM approach.

We report a silicon-on-insulator ring resonator biosensor array with one output port, using wavelength division multiplexing as the addressing scheme. With the use of on-chip referencing for environmental drift cancellation, simultaneous monitoring of multiplexed molecular bindings is demonstrated, with a resolution of 0.3 pg/mm(2) (40 ag of total mass) for protein concentrations over 4 orders of magnitude down to 20 pM. Reactions are measured over time periods as long as 3 h with high stability.

Extracting coupling and loss coefficients from a ring resonator.

A method is developed for extracting the coupling and loss coefficients of ring resonators from the peak widths, depths, and spacings of the resonances of a single resonator. Although the formulas used do not distinguish which coefficient is coupling and which is loss, it is shown how these coefficients can be disentangled based on how they vary with wavelength or device parameters.

Low power four wave mixing in an integrated, micro-ring resonator with Q = 1.2 million.

We demonstrate efficient, low power, continuous-wave four-wave mixing in the C-band, using a high index doped silica glass micro ring resonator having a Q-factor of 1.2 million. A record high conversion efficiency for this kind of device is achieved over a bandwidth of 20 nm. We show theoretically that the characteristic low dispersion enables phase-matching over a tuning range > 160 nm.