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We report second-harmonic and sum-frequency generation in Al0.4Ga0.6As-on-insulator microdisk resonators at ~775 nm wavelengths. Our experiments reveal clear polygonal-shaped whispering-gallery mode profiles.

Beyond various application-specific photonic integrated circuits (PICs), a programmable PIC comprising identically designed generic building blocks with multiple active functionalities under different operational conditions is an attractive design option. Here, we propose and demonstrate proof-of-concept experiments of a heterogeneously integrated III–V-on-Si microring resonator (MRR) as such a versatile building block. The MRR can function as an electro-optical channel add-drop switch with signal amplification, a directly modulated injection laser, or a microcavity photodetector under different electrical bias conditions. We discuss the fabrication process for our heterogeneous integration platform based on an atomic layer deposition-assisted molecular bonding technique.

Beyond various application-specific photonic integrated circuits (PICs), a programmable PIC comprising identically designed generic building blocks with multiple active functionalities under different operational conditions is an attractive design option. Here, we propose and demonstrate proof-of-concept experiments of a heterogeneously integrated III–V-on-Si microring resonator (MRR) as such a versatile building block. The MRR can function as an electro-optical channel add-drop switch with signal amplification, a directly modulated injection laser, or a microcavity photodetector under different electrical bias conditions. We discuss the fabrication process for our heterogeneous integration platform based on an atomic layer deposition-assisted molecular bonding technique.

Beyond various application-specific photonic integrated circuits (PICs), a programmable PIC comprising identically designed generic building blocks with multiple active functionalities under different operational conditions is an attractive design option. Here, we propose and demonstrate proof-of-concept experiments of a heterogeneously integrated III–V-on-Si microring resonator (MRR) as such a versatile building block. The MRR can function as an electro-optical channel add-drop switch with signal amplification, a directly modulated injection laser, or a microcavity photodetector under different electrical bias conditions. We discuss the fabrication process for our heterogeneous integration platform based on an atomic layer deposition-assisted molecular bonding technique.

The AlGaAs-on-insulator material platform offers compact, integrated nonlinear devices. The 43 - mm point-group symmetry of AlGaAs enables a natural quasi-phase-matching. In this talk, we will present our work on 4-bar quasi-phase-matching in square microcavities.

The AlGaAs-on-insulator material platform offers compact, integrated nonlinear devices. The 43 - mm point-group symmetry of AlGaAs enables a natural quasi-phase-matching. In this talk, we will present our work on 4-bar quasi-phase-matching in square microcavities.

The AlGaAs-on-insulator material platform offers compact, integrated nonlinear devices. The 43 - mm point-group symmetry of AlGaAs enables a natural quasi-phase-matching. In this talk, we will present our work on 4-bar quasi-phase-matching in square microcavities.

We unfold the design principles for heterogeneously integrated III-V-on-silicon microdisk unidirectional singlemode lasers. Our simulations suggest hybrid modes between the vertically coupled III-V and silicon microdisks of different radii. Our experiments reveal unidirectional singlemode lasing. © 2018 OSA.

We unfold the design principles for heterogeneously integrated III-V-on-silicon microdisk unidirectional singlemode lasers. Our simulations suggest hybrid modes between the vertically coupled III-V and silicon microdisks of different radii. Our experiments reveal unidirectional singlemode lasing. © 2018 OSA.

Heterogeneously integrated lasers comprising an active layer (e.g., III-V semiconductor multiple quantum wells) bonded on top of a passive silicon photonic layer on the silicon-on-insulator substrate have been proposed and studied as one of the light sources for optical interconnects. However, the buried oxide layer and the bonding layer inhibit heat dissipation and compromise the laser's performance. In this paper, we adopt a thermal shunt design that provides a direct path for the heat generated in the gain layer to reach the silicon substrate. Using finite element modeling, we illustrate the effectiveness of our thermal shunt designs. We improve the thermal resistance from 1241 K/W without an integrated thermal shunt to 296 K/W with an integrated p-electrode thermal shunt. We have also identified the parameters that give the optimal thermal performance.

Electrically pumped and directly modulated microlasers comprising a III-V semiconductor multi-quantum well (MQW) heterogeneously integrated on a silicon photonic chip are potentially a key building block for datacenter optical interconnects. We adopt a microspiral disk cavity in the silicon photonic layer, with a seamlessly coupled silicon waveguide at the microspiral notch, for unidirectional laser output-coupling characteristics. We integrate a ring-shaped electrode on top of the III-V gain layer in order to preferentially inject into a group of whispering-gallery-like modes for improved energy efficiency and mode selection. In this paper, we report multi-mode lasing under both pulsed and continuous injection at room temperature. The threshold current density is typically a few kA/cm(2).

Electrically pumped and directly modulated microlasers comprising a III-V semiconductor multi-quantum well (MQW) heterogeneously integrated on a silicon photonic chip are potentially a key building block for datacenter optical interconnects. We adopt a microspiral disk cavity in the silicon photonic layer, with a seamlessly coupled silicon waveguide at the microspiral notch, for unidirectional laser output-coupling characteristics. We integrate a ring-shaped electrode on top of the III-V gain layer in order to preferentially inject into a group of whispering-gallery-like modes for improved energy efficiency and mode selection. In this paper, we report multi-mode lasing under both pulsed and continuous injection at room temperature. The threshold current density is typically a few kA/cm(2).

Heterogeneously integrated lasers comprising an active layer (e.g., III-V semiconductor multiple quantum wells) bonded on top of a passive silicon photonic layer on the silicon-on-insulator substrate have been proposed and studied as one of the light sources for optical interconnects. However, the buried oxide layer and the bonding layer inhibit heat dissipation and compromise the laser's performance. In this paper, we adopt a thermal shunt design that provides a direct path for the heat generated in the gain layer to reach the silicon substrate. Using finite element modeling, we illustrate the effectiveness of our thermal shunt designs. We improve the thermal resistance from 1241 K/W without an integrated thermal shunt to 296 K/W with an integrated p-electrode thermal shunt. We have also identified the parameters that give the optimal thermal performance.

Heterogeneously integrated lasers comprising an active layer (e.g., III-V semiconductor multiple quantum wells) bonded on top of a passive silicon photonic layer on the silicon-on-insulator substrate have been proposed and studied as one of the light sources for optical interconnects. However, the buried oxide layer and the bonding layer inhibit heat dissipation and compromise the laser's performance. In this paper, we adopt a thermal shunt design that provides a direct path for the heat generated in the gain layer to reach the silicon substrate. Using finite element modeling, we illustrate the effectiveness of our thermal shunt designs. We improve the thermal resistance from 1241 K/W without an integrated thermal shunt to 296 K/W with an integrated p-electrode thermal shunt. We have also identified the parameters that give the optimal thermal performance.

Electrically pumped and directly modulated microlasers comprising a III-V semiconductor multi-quantum well (MQW) heterogeneously integrated on a silicon photonic chip are potentially a key building block for datacenter optical interconnects. We adopt a microspiral disk cavity in the silicon photonic layer, with a seamlessly coupled silicon waveguide at the microspiral notch, for unidirectional laser output-coupling characteristics. We integrate a ring-shaped electrode on top of the III-V gain layer in order to preferentially inject into a group of whispering-gallery-like modes for improved energy efficiency and mode selection. In this paper, we report multi-mode lasing under both pulsed and continuous injection at room temperature. The threshold current density is typically a few kA/cm(2).

Terpenoids are a large structurally diverse group of natural products with an array of functions in their hosts. The large amount of genomic information from recent sequencing efforts provides opportunities and challenges for the functional assignment of terpene synthases that construct the carbon skeletons of these compounds. Inferring function from the sequence and/or structure of these enzymes is not trivial because of the large number of possible reaction channels and products. We tackle this problem by developing an algorithm to enumerate possible carbocations derived from the farnesyl cation, the first reactive intermediate of the substrate, and evaluating their steric and electrostatic compatibility with the active site. The homology model of a putative pentalenene synthase (Uniprot: B5GLM7) from Streptomyces clavuligerus was used in an automated computational workflow for product prediction. Surprisingly, the workflow predicted a linear triquinane scaffold as the top product skeleton for B5GLM7. Biochemical characterization of B5GLM7 reveals the major product as (5S,7S,10R,11S)-cucumene, a sesquiterpene with a linear triquinane scaffold. To our knowledge, this is the first documentation of a terpene synthase involved in the synthesis of a linear triquinane. The success of our prediction for B5GLM7 suggests that this approach can be used to facilitate the functional assignment of novel terpene synthases.

Porphobilinogen synthase (PBGS) catalyzes the asymmetric condensation and cyclization of two 5-aminolevulinic acid (5-ALA) substrate molecules to give porphobilinogen (PBG). The chemical step of PBGS is herein revisited using QM/MM (ONIOM) calculations. Two different protonation states and several different mechanisms are considered. Previous mechanisms based on DFT-only calculations are shown unlikely to occur. According to these new calculations, the deprotonation step rather than ring closure is rate-limiting. Both the C–C bond formation first mechanism and the C–N bond formation first mechanism are possible, depending on how the A-site ALA binds to the enzyme. We furthermore propose that future work should focus on the substrate binding step rather than the enzymatic mechanism.

OBJECTIVES: To describe oral health behaviour, illness behaviour, oral health knowledge and attitudes among 35-44 and 65-74-year-old Chinese; to analyse the oral health behaviour profile of the two age groups in relation to province and urbanisation, and to assess the relative effect of socio-behavioural risk factors on dental caries experience.METHODS: A total number of 4,398 35-44-year-olds and 4,399 65-74-year-olds were selected by multistage stratified cluster random sampling which involved 11 provinces in China. Data were collected by self-administered structured questionnaires and clinical examinations (WHO criteria).RESULTS: 32% of the 35-44-year-olds and 23% of the 65-74-year-olds brushed at least twice a day but only 5% used fluoridated toothpaste; 30% and 17% respectively performed 'Love-Teeth-Day' recommended methods of tooth brushing. A dental visit within the previous 12 months was reported by 25% of all participants and 6% had a dental check-up during the past two years. Nearly 15% of the subjects would visit a dentist if they experienced bleeding from gums; about 60% of the subjects paid no attention to signs of caries if there was no pain. Two thirds of the urban residents and one fifth of the rural participants had economic support for their dental treatment from a third party, either totally or partially. Significant variations in oral health practices were found according to urbanisation and province. At age 35-44 years 43% of participants had daily consumption of sweets against 28% at age 65-74 years. Dental caries experience was affected by urbanisation, gender, frequency, time spent on and method of tooth brushing. Knowledge of causes and prevention of dental diseases was low with somewhat negative attitudes to prevention observed.CONCLUSION: Systematic community-based oral health promotion should be strengthened and preventive-oriented oral health care systems are needed, including promotion of further self-care practic

OBJECTIVES: To describe oral health behaviour, illness behaviour, oral health knowledge and attitudes among 35-44 and 65-74-year-old Chinese; to analyse the oral health behaviour profile of the two age groups in relation to province and urbanisation, and to assess the relative effect of socio-behavioural risk factors on dental caries experience.METHODS: A total number of 4,398 35-44-year-olds and 4,399 65-74-year-olds were selected by multistage stratified cluster random sampling which involved 11 provinces in China. Data were collected by self-administered structured questionnaires and clinical examinations (WHO criteria).RESULTS: 32% of the 35-44-year-olds and 23% of the 65-74-year-olds brushed at least twice a day but only 5% used fluoridated toothpaste; 30% and 17% respectively performed 'Love-Teeth-Day' recommended methods of tooth brushing. A dental visit within the previous 12 months was reported by 25% of all participants and 6% had a dental check-up during the past two years. Nearly 15% of the subjects would visit a dentist if they experienced bleeding from gums; about 60% of the subjects paid no attention to signs of caries if there was no pain. Two thirds of the urban residents and one fifth of the rural participants had economic support for their dental treatment from a third party, either totally or partially. Significant variations in oral health practices were found according to urbanisation and province. At age 35-44 years 43% of participants had daily consumption of sweets against 28% at age 65-74 years. Dental caries experience was affected by urbanisation, gender, frequency, time spent on and method of tooth brushing. Knowledge of causes and prevention of dental diseases was low with somewhat negative attitudes to prevention observed.CONCLUSION: Systematic community-based oral health promotion should be strengthened and preventive-oriented oral health care systems are needed, including promotion of further self-care practic

OBJECTIVES: A national representative study to describe oral health behaviour, illness behaviour, oral health knowledge and attitudes among 12-year-old and 18-year-old Chinese, to analyse the oral health behaviour profile of the two age groups in relation to province and urbanisation, and to assess the relative effect of socio-behavioural risk factors on dental caries experience.METHODS: The total number of 4,400 of each age group were selected and data were collected by clinical examinations (WHO criteria) and self-administered structured questionnaires.RESULTS: 44.4% of the respondents brushed their teeth at least twice a day but only 17% used fluoridated toothpaste. Subjects who saw a dentist during the previous 12 months or two years were 31.3% and 35.3% for 12-year-olds and 22.5% and 20.2% for 18-year-olds, respectively. Nearly one third (29%) of 12 year-olds and 40.5% of 18-year-olds would visit a dentist in case of signs of caries but only when in pain. Nearly half of the participants (47.2%) had never received any oral health care instruction. Significant variations in oral health practices were found according to province and regular dental care habits were more frequent in urban than in rural areas. The risk of dental caries was high in the case of frequent consumption of sweets and dental caries risk was low for participants with use of fluoridated toothpaste.CONCLUSION: Systematic community-oriented oral health promotion programmes are needed to target lifestyles and the needs of children, particularly for those living in rural areas. A prevention-oriented oral health care policy would seem more advantageous than the present curative approach.

OBJECTIVES: A national representative study to describe oral health behaviour, illness behaviour, oral health knowledge and attitudes among 12-year-old and 18-year-old Chinese, to analyse the oral health behaviour profile of the two age groups in relation to province and urbanisation, and to assess the relative effect of socio-behavioural risk factors on dental caries experience.METHODS: The total number of 4,400 of each age group were selected and data were collected by clinical examinations (WHO criteria) and self-administered structured questionnaires.RESULTS: 44.4% of the respondents brushed their teeth at least twice a day but only 17% used fluoridated toothpaste. Subjects who saw a dentist during the previous 12 months or two years were 31.3% and 35.3% for 12-year-olds and 22.5% and 20.2% for 18-year-olds, respectively. Nearly one third (29%) of 12 year-olds and 40.5% of 18-year-olds would visit a dentist in case of signs of caries but only when in pain. Nearly half of the participants (47.2%) had never received any oral health care instruction. Significant variations in oral health practices were found according to province and regular dental care habits were more frequent in urban than in rural areas. The risk of dental caries was high in the case of frequent consumption of sweets and dental caries risk was low for participants with use of fluoridated toothpaste.CONCLUSION: Systematic community-oriented oral health promotion programmes are needed to target lifestyles and the needs of children, particularly for those living in rural areas. A prevention-oriented oral health care policy would seem more advantageous than the present curative approach.

OBJECTIVES: To describe the oral health status of Chinese children and adults at national level in relation to location and province and to highlight changes in dental caries experience.DESIGN: Cross-sectional study, oral epidemiological survey based on WHO methodology, clinical examinations.SETTING: National survey by National Committee for Oral Health.SUBJECTS: Representative samples of provinces, districts, townships; cluster sampling including subjects aged 5,12,15,18, 35-44 and 65-74. Each age group consisted of 23,452 participants, i.e. total of 140,712 individuals.RESULTS: At age 5, 76.6% were affected by dental caries and mean dmft was 4.5. Mean DMFT varied from 1.0 in 12-year-olds, 1.4 in 15-year-olds, 1.6 in 18-year-olds, 2.1 in 35-44-year-olds to 12.4 in 65-74-year-olds. In adults, caries experience was higher in females than in males. The effect of urbanisation on caries prevalence in children varied by province and age. Among adolescents and young adults caries levels were high in urban areas while caries experience was high for old-age people of rural areas. At national level, changes in dental caries prevalence of 12- and 15-year-olds were small. However, some provinces with extensive oral health programmes (e.g. Love Teeth Day) showed declining caries experience whereas provinces with limited preventive activities had increasing levels of caries. For all age groups, gingival bleeding and calculus were most frequent. Severe periodontal conditions were relatively rare.CONCLUSION: The systematic implementation of preventive oral care and community-oriented health programmes are needed for the continuous promotion of oral health in China.

OBJECTIVES: To describe the oral health status of Chinese children and adults at national level in relation to location and province and to highlight changes in dental caries experience.DESIGN: Cross-sectional study, oral epidemiological survey based on WHO methodology, clinical examinations.SETTING: National survey by National Committee for Oral Health.SUBJECTS: Representative samples of provinces, districts, townships; cluster sampling including subjects aged 5,12,15,18, 35-44 and 65-74. Each age group consisted of 23,452 participants, i.e. total of 140,712 individuals.RESULTS: At age 5, 76.6% were affected by dental caries and mean dmft was 4.5. Mean DMFT varied from 1.0 in 12-year-olds, 1.4 in 15-year-olds, 1.6 in 18-year-olds, 2.1 in 35-44-year-olds to 12.4 in 65-74-year-olds. In adults, caries experience was higher in females than in males. The effect of urbanisation on caries prevalence in children varied by province and age. Among adolescents and young adults caries levels were high in urban areas while caries experience was high for old-age people of rural areas. At national level, changes in dental caries prevalence of 12- and 15-year-olds were small. However, some provinces with extensive oral health programmes (e.g. Love Teeth Day) showed declining caries experience whereas provinces with limited preventive activities had increasing levels of caries. For all age groups, gingival bleeding and calculus were most frequent. Severe periodontal conditions were relatively rare.CONCLUSION: The systematic implementation of preventive oral care and community-oriented health programmes are needed for the continuous promotion of oral health in China.