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In this work, the thermo-optic coefficient (TOC) of the silicon-rich amorphous silicon carbide (a-SiC) thin film deposited by plasma-enhanced chemical vapor deposition (PECVD) was characterized. We found that the TOC of the film increases as its silicon content increases. A more than threefold improvement in the TOC was measured, reaching a TOC as high as 1.88×10−4∘C−1, which is comparable to that of crystalline silicon. An efficient thermo-optic phase shifter has also been demonstrated by integrating the silicon-rich a-SiC micro-ring structure with a NiCr heater. Tunability of 0.117 nm/mW was demonstrated, and a corresponding tuning efficiency P π as low as 4.2 mW has been measured at an optical wavelength of 1550 nm. These findings make silicon-rich a-SiC a good candidate material for thermo-optic applications in photonic integrated circuits.

在欧美国家左心室辅助装置（LVAD）已成为终末期心力衰竭非药物治疗的主要手段，国内亦有数十家医院正在临床开展应用。但LVAD术后患者面临的主要问题仍然是右心室功能衰竭，亦是引起LVAD术后死亡的主要原因。该文围绕LVAD植入术后右心功能障碍的发生机制、右心功能衰竭预测模型以及超声心动图在LVAD植入前后对右心功能的评估要点进行综述。.

Objectives The aim of this study is to quantify the mortality rate, direct healthcare costs, and cumulative life costs of pediatric patients with spinal muscular atrophy (SMA) type 1, type 2, and type 3 born in Hong Kong. Methods Data were collected from genetically confirmed SMA patients born in or after 2000 from the Hospital Authority medical database. Patients were followed up from birth until they died, left Hong Kong, reached 18 years, or initiated disease-modifying treatment. Study outcomes included incidence risks of mortality, cumulative direct medical costs—attendances of special outpatient clinics, emergency department, allied health services, and mean length of stay in hospitals over time. Total direct medical costs were calculated as unit costs multiplied by utilization frequencies of corresponding healthcare services at each age. Results Seventy-one patients with SMA were included. Over a median follow-up period of 6 years, the overall incidence rate of death was 5.422/100 person-years (95%CI 3.542–7.945/100 person-years). 67.7% and 11% of deaths occurred in SMA1 and SMA2 groups, respectively. The median age of death was 0.8 years in SMA1 and 10.9 years in SMA2. The mean cumulative direct medical costs in overall SMA, SMA1, SMA2 and SMA3 groups per patient were US$935,570, US$2,393,250, US$413,165, and US$40,735, respectively. Interpretation: Our results confirmed a significantly raised mortality and extremely high healthcare burden for patients with SMA especially SMA type 1 and 2 without disease-modifying treatment. Study evaluating health and economic impact of newborn screening and early treatment is needed.

An ultralow- $\text{V}_{\pi }\text{L}$ photonic switch device is demonstrated utilizing the high optical and electrical field confinement in silicon slot waveguides coupled with the strong electro-optic response of nematic liquid crystals. A silicon photonic directional coupler switch with a modulation efficiency of 0.0195 $\text{V}\cdot $ mm and a loss-efficiency product of 0.0624 $\text{V}\cdot $ dB is achieved. The 1.5 mm long device is based on two-mode interference within a single slot waveguide resulting in a $\text{V}_{\mathrm {\pi }}$ of 0.013 V and an extinction ratio of $\sim ~9$ dB at 1550 nm wavelength. The power consumption of the photonic switch is estimated to be below 0.6 nW and it possesses a response time of < 1.5 ms. A comparative performance study between the directional coupler switch and a Mach-Zehnder Interferometer (MZI) switch is performed. The directional coupler switch is projected to have a smaller footprint and lower optical loss compared to a similar design MZI switch making it a strong candidate for switch matrix designs and applications.

We propose and demonstrate a passively biased 2 × 2 thermo-optic switch with high power efficiency and fast response time. The device benefits from the highly concentrated optical field of a slot waveguide mode and the strong thermo-optic effect of a nematic liquid crystal (NLC) cladding. The NLC fills the nano-slot region and is aligned by the subwavelength grating inside. The measured power consumption and thermal time constant are 0.58 mW and 11.8 µs, respectively, corresponding to a figure-of-merit of 6.8 mW µs. The proposed silicon-organic hybrid device provides a new solution to design thermo-optic actuators having low power consumption and fast operation speed.

The design and performance of optical switches are crucial for switch-based beam steering devices to be competitive among existing beam steering technologies for light detection and ranging (LIDAR) applications. An efficient liquid crystal (LC) filled directional coupler (DC) optical switch is proposed. Device performance as a function of geometric design is analyzed through numerical simulations. The analysis reveals that the DC is a promising candidate to replace more popular Mach-Zehnder Interferometer (MZI) configurations for optical switches when ultra-low $\mathrm{V}_{\pi}\mathrm{L}$ performance is important.

We demonstrate low loss ultra-compact bends in PECVD silicon rich silicon nitride and utilize them towards realizing efficient thermo-optic MMI switches with Pπ = 23 mW and a footprint of 68 x 68 µm2.

The design, fabrication, and characterization of low loss ultra-compact bends in high index (n = 3.1 at {\lambda} = 1550 nm) PECVD silicon rich silicon nitride (SRN) is demonstrated and utilized to realize efficient, small footprint thermo-optic phase shifter. Compact bends are structured into a folded waveguide geometry to form a rectangular spiral within an area of 65 x 65 \mum2 possessing a total active waveguide length of 1.2 mm. The device features a phase shifting efficiency of 8 mW/{\pi} and a 3 dB switching bandwidth of 15 KHz. We propose SRN as a promising thermo-optic platform combining the properties of silicon and silicon stoichiometric nitride, Comment: 4 page, 3 figures, 1 table

We propose a new technique to achieve low power consumption in silicon thermo-optic switches without sacrificing speed. By incorporating subwavelength gratings and nematic liquid crystals, a switching power of 3.7 mW is achieved.

A highly sensitive silicon photonic temperature sensor based on silicon-on-insulator (SOI) platform has been proposed and demonstrated. A two-mode nano-slot waveguide device structure cladded with a nematic liquid crystal (LC), E7, was adopted to facilitate strong light-matter interaction and achieve high sensitivity. The fabricated sensor was characterized by measuring the optical transmission spectra at different ambient temperatures. The extracted temperature sensitivities of the E7-filled device are 0.810 nm/°C around room temperature and 1.619 nm/°C near 50°C, which match well with simulation results based on a theoretical analysis. The results obtained represent the highest experimentally demonstrated temperature sensitivity for a silicon-waveguide temperature sensor on SOI platform. The slot waveguide directional coupler device configuration provides submicron one-dimensional spatial resolution and flexible selection in LC materials for designing temperature sensitivity and operational temperature range required by specific applications.

We characterize the thermo-optic coefficient of silicon nitride films with varying silicon contents using plasma-enhanced chemical vapor deposition (PECVD). A clear relation between the silicon content and the exhibited thermo-optic coefficient has been demonstrated along with a coefficient as high as (1.65±0.08) ×10-4 K-1.

Ruyi-Jinhuang Gao (RJG) is an ointment prepared from Ruyi-Jinhuang San (RJS), a traditional formula of powder-type Chinese medicine, usually used in anti-inflammatory analgesic care in China. The present study is aimed to detect the anti-inflammatory signaling of RJG exposed by an experimental model of lipopolysaccharides (LPS)-induced pro-inflammatory expression of inducible nitric oxide synthase (iNOS) and prostaglandin endoperoxide synthase (PGH synthase-2, COX-2). LPS-induced activation of iNOS and COX-2 has been recognized to increase cytokines and nitric oxide (NO), which play predominant roles in inflammation. In the culture of RAW264.7 cells, RJG concentration-dependently inhibited LPS-induced iNOS and COX-2 expression. However, the herbal components of RJG displayed different results, including increase and decrease of both protein expressions. Among them, inhibition by Curcuma Zedorarica Rhizoma (Cu), Atractylodis Lancea Rhizoma (At), and Glycyrrhizae Radix (Gl) are more potent than that by others. Inhibition by Cu and At are associated with their cytotoxicity. Glycyrrhizae Radix (Gl), with lower cytotoxicity in comparison with Cu and At, is the most potent component of RJG on inhibiting LPS-induced iNOS and COX-2 expression. In comparison with LPS-induced tumor necrosis factor-α (TNF-α), croton oil-induced formation of TNF-α and interleukin-4 (IL4), RJG did not increase the pro-inflammatory cytokines. These facts indicated that RJG could not significantly sensitize an immunologic response during the treatment of non-wounded inflammation on body surface. Ruyi-Jinhuang Patch (RJP), a pharmaceutical preparation of RJG, has proven to have significant relief of cutaneous inflammation-associated somatic pain in clinical use.

We demonstrate the thermo-optic properties of silicon-rich silicon nitride (SRN) films deposited using plasma-enhanced chemical vapor deposition (PECVD). Shifts in the spectral response of Mach-Zehnder Interferometers (MZIs) as a function of temperature were used to characterize the thermo-optic coefficients of silicon nitride films with varying silicon contents. A clear relation is demonstrated between the silicon content and the exhibited thermo-optic coefficient in silicon nitride films, with the highest achievable coefficient being as high as (1.65+/-0.08) x 10-4 K-1. Furthermore, we realize an SRN Multi-Mode Interferometer (MMI) based thermo-optic switch with over 20 dB extinction ratio and total power consumption for two-port switching of 50 mW., 10 pages, 7 figures, submitted to a journal

To evaluate the changes in marginal bone levels (MBL) and soft tissue dimension around platform-switched implants with the implant-abutment junction (IAJ) placed at the crest or 1.5-2 mm subcrestally.In all, 96 platform-switched implants were placed in either the posterior maxilla or mandible in 48 partially edentulous patients in a split-mouth study. All implants were provisionally restored after 4-5 months and definitively after 6 months (T6). Radiographic assessment of MBL was assessed at implant placement (T0), T6, 12 months (T12), and 18 months (T18) after placement. Mid-buccal soft tissue and papilla measurements were performed at T6, T12, and T18.In all, 43 patients with 86 implants completed the study. The T18 examination showed an implant survival rate of 100% in both groups. Analysis showed that MBL varied as a function of IAJ location, which indicated more coronal bone levels with subcrestal (2.39 ± 0.08 mm) than with epicrestal placements (0.88 ± 0.08 mm) (p .05). Greater average marginal bone loss was found in the subcrestal group (0.40 ± 0.07 mm) compared to the epicrestal group (0.13 ± 0.08 mm) although no statistically significant difference was found at T18 (p .05). Levels of mid-buccal soft tissue had no significant changes over time, regardless of group (p .05). There was a significant difference in increase in papilla between T6 and T12 and T18 (p = .005 and .001), but not between T12 and T18 (p = .61). These papilla levels and changes were similar between groups (p .05).The MBL changes around platform-switched implants with same geometry were not affected by the epicrestal or subcrestal location of the IAJ. Furthermore, the location of the IAJ did not affect the implant survival and soft tissue dimensions. However, no bone loss was located apical to the IAJ when the implants were placed subcrestally.

Setting: Mzuzu Central Hospital (MZCH), Mzuzu, and Chitipa District Hospital (CDH), Chitipa, Malawi. Objective: To compare management and outcomes of human immunodeficiency virus (HIV) exposed infants in early infant diagnosis (EID) programmes at MZCH, where DNA polymerase chain reaction (PCR) testing is performed on site, and CDH, where samples are sent to MZCH, between 2013 and 2014. Design: Retrospective cohort study. Results: Of infants enrolled at MZCH (n = 409) and CDH (n = 176), DNA PCR results were communicated to the children's guardians in respectively 56% and 51% of cases. The median time from sample collection to guardians receiving results was 34 days for MZCH and 56 days for CDH. In both hospitals, only half of the dried blood spot (DBS) samples were collected between 6 and 8 weeks. More guardians from MZCH than CDH received test results within 1 month of sample collection (25% vs. 10%). Among the HIV-positive infants, a higher proportion at MZCH (92%) started antiretroviral therapy than at CDH (46%). The relative risk (RR) of death was higher among infants with late DBS collection (RR 1.3, 95%CI 1.0-1.7) or no collection (RR 5.8, 95%CI 4.6-7.2), and when guardians did not receive test results (RR 8.3, 95%CI 5.7-11.9). Conclusion: EID programmes performed equally poorly at both hospitals, and might be helped by point-of-care DNA PCR testing. Better programme implementation and active follow-up might improve infant outcome and retention in care.

The aim of this report is to present a case with a 10-year follow-up of a single anterior tooth dental implant replacement with a xenogenous bone graft in a patient with a large bone defect associated with a cleft lip and palate. At 10 years postloading, the implant was healthy and well-integrated. Although the implant restoration appeared slightly intruded due to growth and development at that time, the patient was happy with the esthetic result and refused corrections of the uneven occlusal plane.

A major challenge in gallium nitride (GaN) vertical power devices and other large bandgap materials is the high defect density that compromises the performance, reliability, and yield. Defects are typically nucleated at the heterointerface where there are both lattice and thermal mismatches. Here, we report the selective area growth (SAG) of thick GaN on Si and on the newly available Qromis Substrate Technology™ (QST) substrates that lead to a significant reduction of the defect densities to a level that is nearly comparable to that on native substrates by defect annihilation. We performed a parametric study of the electrical properties of the SAG GaN layers by fabricating and characterizing Schottky barrier diodes for SAG GaN layer thicknesses of 5, 10, 15, and 20 μm for GaN-on-Si, GaN-on-QST, and GaN-on-GaN diodes. While thicker layers led to a significant reduction in defect densities and improvement in the diode forward current characteristics, the GaN-on-QST diodes exhibited nearly similar characteristics to the GaN-on-GaN diodes. Further improvement in the device structure and/or SAG growth for GaN-on-Si is needed to achieve a comparable performance as the defect densities in the GaN-on-Si are comparable to that of GaN-on-QST substrates.

No abstract provided.

We describe a new class of electric motor/generator technology with specific power more than 10kW/kg for a variety of applications including terrestrial, airborne hybrid and all electric propulsion. The technology utilizes a new type of turn-less electro-mechanics configuration intimately integrated with dedicated inverters which utilize high current, low voltage GaN MOSFET switches.

In this paper, we review the key performance of optical modulators operating in the wavelength range of 1.3–1.5 μm for fiber-optic link applications and compare the design of two nanoscale modulators which are based upon (a) second-harmonic generation (SHG) from GaN nanopillars and (b) electrooptic polymer in nanoslot waveguides, respectively.

Second-harmonic generation (SHG) from single GaN nanpoillar is reported. A model for the SHG processes in the GaN nanopillar as a function of diameter is presented; the analysis showed quantitatively that the SHG is dominated by its surface area. The effective second order nonlinear optical susceptibility increases as the diameter of the GaN nanopillar decreases, reaching a value of 136 pm/V at 150nm diameter, making them attractive for modulator applications.

Thermal resistances of AlGaN/GaN high electron mobility transistors (HEMTs) on polycrystalline diamond (with thermal conductivity >1500 W/m K) and on Si substrates are respectively extracted and compared. GaN HEMTs on diamond and on Si with the same device dimensions were fabricated and their direct-current (DC) characteristics were compared. Thermally-induced negative differential output resistance in the saturation region at DC was observed for GaN-on-Si HEMT but was negligible for the GaN-on-diamond device at comparable power densities, which is consistent with reduced thermal resistance. Thermal resistances of the HEMTs on Si and diamond substrates determined experimentally from analysis of I–V characteristics agree with estimates based on simulation.

A modal analysis is conducted for analyzing the absorption profile of high power waveguide photodiodes designed for analog optical link. The excitation of guided modes with large filling factor in the absorber is identified as a limiting factor for the performance of waveguide photodiodes at high optical power, including power handling capability, and bandwidth-efficiency product. A waveguide photodiode design, which spatially separates the input waveguide from the absorber in the lateral direction, is analyzed and experimentally demonstrated to suppress the excitation of mode with large filling factor. Photocurrent>60 mA under − 4 V bias is measured, with 0.80 A/W responsivity. This design illustrates that high power handling capability can be achieved without compromising the bandwidth-efficiency product.

Present research in widebandgap semiconductors is concentrated predominantly in continuous-wave applications. While their applicability for pulsed power is recognized, little work has been done in taking advantage of the individual characteristics, such as the large drift velocities, of the candidate materials. Analysis of the relative merits of the key semiconductor technologies—Si, GaAs, SiC, and GaN—in the pulsed-power regime is presented, including limitations associated with majority carrier operation and thermal transients. We will also discuss a GaN photoconductor with a vertical topology, which is particularly well suited to higher current applications and also is geometrically more applicable for integration to transmission lines without degrading the high blocking field (2 MV/cm) now available. The relation between the blocking voltage and conduction current typical of majority carrier operation is analyzed and we will show how optical carrier generation provides the much higher switching power associated with bipolar operation.

We describe the technology and experimental work done at Polarix Corporation on photoconductive switch-based high-power microwaves systems for airborne counter-improvised explosive device (IED) applications. We address the fluence requirement for nanosecond pulse range for coupling to IED harnesses both theoretically and experimentally. We describe some of the key elements of the technology and the system being developed. They include silicon backed biased junction switch technology, low inductance–high current switch integration with thin film Blumlein type circuits, multiswitch multicycle generation, and radiation concepts using asymmetric Wheeler–Chu apertures for side firing small diameter but long unmanned aerial vehicles platforms. We will also present the experimental results showing switch source and radiator performance.

High-power and high-linearity photodiodes (PDs) are of critical importance to achieve high-efficiency analogue fibre links. A small-signal analysis is utilised on the nonlinear responsivity of the modified uni-travelling-carrier PDs to understand the theoretical limitation on the third-order output intercept point (OIP3) of the link. It is theoretically shown that a nonlinear responsivity depending on both the voltage and the current can give rise to an enhanced OIP3 at certain bias and current values.

We studied the impact of optical pulse coding techniques on Brillouin optical time-domain analysis (BOTDA) systems experimentally. The results show that complementary-coding-based schemes can provide significant enhanced signal-to-noise ratio (SNR) to the BOTDA system. Using complementary coding, the average time can be reduced significantly and so does the measurement time. The complementary-coded pulses with individual pulse duration of 0.1 ns allowed us to realize temperature sensing over 50 m of single-mode fiber with 1-cm spatial resolution.

A study of the reverse-leakage-current mechanisms in metal-organic-chemical-vapor-deposition (MOCVD)-grown GaN Schottky-barrier diodes is presented. An analysis is carried out of the characteristics of GaN Schottky diodes as well as of diodes with an InGaN surface layer to suppress the reverse leakage current and increase the breakdown voltage. The experimental results of the diodes with InGaN surface layers showed a ~ 40-V breakdown voltage increase and a significant leakage-current reduction under high reverse bias, in comparison with the design with GaN only. Such improvements are attributed to the reduced surface electric field and the increased electron tunneling distance induced by the polarization charges at the InGaN/GaN interface. We also report the effect of a high-pressure (near atmospheric pressure) MOCVD growth technique of the GaN buffer layer to further improve the leakage current and breakdown voltage.

Semiconductor quantum well (QW) light-emitting diodes (LEDs) have limited temporal modulation bandwidth of a few hundred MHz due to the long carrier recombination lifetime. Material doping and structure engineering typically leads to incremental change in the carrier recombination rate, whereas the plasmonic-based Purcell effect enables dramatic improvement for modulation frequency beyond the GHz limit. By stacking Ag-Si multilayers, the resulting hyperbolic metamaterials (HMMs) have shown tunability in the plasmonic density of states for enhancing light emission at various wavelengths. Here, nanopatterned Ag-Si multilayer HMMs are utilized for enhancing spontaneous carrier recombination rates in InGaN/GaN QWs. An enhancement of close to 160-fold is achieved in the spontaneous recombination rate across a broadband of working wavelengths accompanied by over tenfold enhancement in the QW peak emission intensity, thanks to the outcoupling of dominating HMM modes. The integration of nanopatterned HMMs with InGaN QWs will lead to ultrafast and bright QW LEDs with a 3 dB modulation bandwidth beyond 100 GHz for applications in high-speed optoelectronic devices, optical wireless communications, and light-fidelity networks.

Locomotion is a complex behavior affected by many different brain- and spinal cord systems, as well as by variations in the peripheral nervous system. Recently, we found increased gene expression for EphA4, a gene intricately involved in motor neuron development, between high-active parental strain C57BL/6J and the low-active chromosome substitution strain 1 (CSS1). CSS1 mice carry chromosome 1 from A/J mice in a C57BL/6J genetic background, allowing localization of quantitative trait loci (QTL) on chromosome 1. To find out whether differences in motor neuron anatomy, possibly related to the changes in EphA4 expression, are involved in the motor activity differences observed in these strains, motor performance in various behavioral paradigms and anatomical differences in the ventral roots were investigated. To correlate the behavioral profiles to the spinal motor neuron morphology, not only CSS1 and its parental strains C57BL/6J (host) and A/J (donor) were examined, but also a set of other mouse inbred strains (AKR/J, 129x1/SvJ and DBA/2J). Significant differences were found between inbred strains on home cage motor activity levels, the beam balance test, grip test performance, and on alternating versus synchronous hind limb movement (hind limb hopping). Also, considerable differences were found in spinal motor neuron morphology, with A/J and CSS1 showing smaller, possibly less developed, motor neuron axons compared to all other inbred strains. For CSS1 and C57BL/6J, only genetically different for chromosome 1, a correlation was found between motor activity levels, synchronous hind limb movement and neuro-anatomical differences in spinal motor neurons. Inclusion of the other inbred strains, however, did not show this direct correlation. These data verifies the complex nature of the mammalian motor system that may be further dissected using genetic mapping populations derived from these inbred strains.

A novel fabrication procedure is developed that allows for the direct measurement of the linear electrooptic coefficient of semiconducting nanowires to determine their viability for use in electrooptic devices. Vertically aligned InP nanowires are transferred from their growth substrate to a glass substrate using a host polymer, while still retaining the alignment of the nanowires. The linear electrooptic coefficient of the InP nanowires exhibited a 1-2 orders of magnitude enhancement over bulk InP and ranged from 31 to 147 pm/V. The figure of merit, n3r, exhibited a factor of 20 enhancement over lithium niobate and ranged from 1010 to 4817 pm/V.

A novel design is presented for a nanowire/polymer hybrid photodiode. n-InP nanowires are grown directly onto an indium tin oxide (ITO) electrode to increase carrier collection efficiency and to eliminate the need for an expensive substrate. Experiments show that an ohmic contact is achieved between the nanowires and the ITO electrode. The nanowires are then enveloped by a high hole mobility conjugated polymer, poly(3-hexylthiophene). Compared to the control polymer-only device, the inclusion of InP nanowires increases the forward bias current conduction by 6-7 orders of magnitude. A high rectification ratio of 155 is achieved in these photodiodes along with a low ideality factor of 1.31. The hybrid device produces a photoresponse with a fill factor of 0.44, thus showing promise as an alternative to current polymer solar cell designs.

Single-crystal InAs nanowires (NWs) are synthesized using metal-organic chemical vapor deposition (MOCVD) and fabricated into NW field-effect transistors (NWFETs) on a SiO(2)/n(+)-Si substrate with a global n(+)-Si back-gate and sputtered SiO(x)/Au underlap top-gate. For top-gate NWFETs, we have developed a model that allows accurate estimation of characteristic NW parameters, including carrier field-effect mobility and carrier concentration by taking into account series and leakage resistances, interface state capacitance, and top-gate geometry. Both the back-gate and the top-gate NWFETs exhibit room-temperature field-effect mobility as high as 6580 cm(2) V(-1) s(-1), which is the lower-bound value without interface-capacitance correction, and is the highest mobility reported to date in any semiconductor NW.

The construction of a prototype Schwarzschild-Couder telescope (pSCT) started in early June 2015 at the Fred Lawrence Whipple Observatory in Southern Arizona, as a candidate medium-sized telescope for the Cherenkov Telescope Array (CTA). Compared to current Davies-Cotton telescopes, this novel instrument with an aplanatic two-mirror optical system will offer a wider field-of-view and improved angular resolution. In addition, the reduced plate scale of the camera allows the use of highly-integrated photon detectors such as silicon photo multipliers. As part of CTA, this design has the potential to greatly improve the performance of the next generation ground-based observatory for very high-energy (E>60 GeV) gamma-ray astronomy. In this contribution we present the design and performance of both optical and alignment systems of the pSCT.

We study nanopatterned multilayer hyperbolic metamaterials with tunable plasmonic properties for enhancing fluorescent molecules and LEDs at different working wavelengths. About two order of magnitude of spontaneous emission rate enhancement was demonstrated.

High power photodiodes were proposed in prior works for conversion of broadband modulated optical signals to electrical signals for transmission at high frequencies. At moderate to high optical powers, the linearity of the photodiode becomes a main concern for achieving high linearity transmission in fiber link. In this invited talk the mode analysis for understanding the absorption profile of high power coupled waveguide photodiodes is presented. which also illuminated the design parameters pertinent for high saturation power and linear detection.

This paper presents results of normally-off AlGaN/GaN MOS-HEMTs fabricated with a two-step gate recess technique which includes a chloride based Inductively Coupled Plasma (ICP) etch followed by HCI and NH 4 OH surface treatment. The latter can effectively smoothen evenly the ICP etched surface. The two-step gate recessed device with atomic layer deposited (ALD) Al 2 O 3 as gate dielectric delivers a threshold voltage (V th ) of +1V and a maximum current density per gate width (I max ) of up to 0.583 A/mm which is 90% that of an un-recessed gate depletion-mode AlGaN/GaN HEMT device (V th of −3.5V) fabricated from the same epitaxial wafer.

A simple and comprehensive modeling approach is developed for analyzing the frequency response of segmented traveling-wave optical modulators. The approach is based on the microwave transmission (ABCD) matrix theory. The case study for a GaAs traveling-wave Mach-Zehnder modulator (MZM) verifies this analysis approach with excellent agreement to the reported experimental results; the analyses for the quantum-well-based MZMs and electroabsorption modulators indicate that the segmented traveling-wave design can provide much better bandwidth than the lumped-element or the continuous-traveling-wave counterparts, with a few decibels penalty in the electrical-to-optical (E/O) conversion gain if low-loss optical waveguides are available. Meandered transmission line design, which provides more design freedom, is also analyzed using this modeling approach.

This tutorial describes the basic principles and performance analysis of optical intensity modulators using electrooptic and electroabsorption effects, for use in analog and digital communication systems. These include lithium niobate modulators, semiconductor electroabsorption modulators, semiconductor Mach-Zehnder modulators, and polymer modulators.