Gravitational collapse structures are commonly observed in shelf-margin deltas underlain by mobile shales. However, these structures are rarely accompanied by mud diapirs. This paper presents an updated study of the gravity-driven system in the West Luconia Deltas, a shelf-margin delta system, in the Kangxi Depression, southern South China Sea. Compared to the classical shale-detachment model, the syn-collapse deformation in the contractional domain in this study is accommodated mainly by thrust faults combined with mud diapirs rather than simply imbricated thrusts. Based on seismic interpretation and structural analysis, this gravity-driven system is divided into three domains, the extensional domain, the contractional domain and the transitional domain. All of these domains are intruded by mud diapirs. The quantitative analysis of the amounts of extension and contraction suggests that these structures mainly resulted from gravitational collapse rather than the tectonic compression. Quantification of the relative contributions of gravity spreading and gliding indicates that the gravitational collapse was mainly driven by gravity spreading. Two episodes of collapse are suggested by the analysis of the progradation of the West Luconia Deltas and the features of the syn-collapse structures. The first episode was minor and not accompanied by diapirism, whereas the second episode was major and accompanied by diapirism. The entire evolution of the GDS is divided into five stages: (1) the first episode of the gravitational collapse, lasted from the earliest Middle Miocene to the earliest Pliocene; (2) the deposition of an interval between the syn-collapse strata and the mobile shale, occurred in the Early Pliocene.; (3) the initiation of the second episode of the gravitational collapse, lasted from the Early Pliocene to the Late Pliocene; (4) the attenuation and basinward migration of the gravity-driven deformation, lasted from the Late Pliocene to the Early Pleistocene; and (5) the ending of the gravitational collapse, lasted from the Early Pleistocene to the present. The last four stages were accompanied by intensive diapirs which pierced the overlying strata and became targets for the hydrocarbon exploration.

We report a novel passively mode-locked quantum-well laser, which have an asymmetric colliding pulse mode-locked structure. The saturable absorber (SA) multi-quantum wells (MQWs) of the laser have bandgap, which is gradually varied along the ridge direction realized by selective area growth technique, forming a broadband absorber. As a result, light pulses are obtained at a repetition frequency of 226 GHz with a minimum pulse width of 605 fs under an appropriate current bias. Because of the continuous variation of the SA MQW bandgap, the SA absorption peak covers a wide range of wavelength, which makes the device more immune to SA bandgap change resulted from SA reverse bias or light absorption-induced heating of the SA, compared with traditional MQW mode-locked lasers.

A novel passively mode-locked quantum-well laser, which saturable absorber (SA) has gradually varied bandgap, is fabricated. Light pulses are obtained at a repetition frequency of 226 GHz with a minimum pulse width of 605 fs under an appropriate mono current bias.

We report the fabrication of a ten channel electroabsorption modulated DFB laser (EML) array. Different emission wavelengths of the laser array are obtained by selective area growth (SAG) technique, which is also used for the integration of electroabsorption modulators (EAM) with the lasers. An arrayed waveguide grating (AWG) combiner is integrated monolithically with the laser array by butt-joint regrowth (BJR) technique. A buried ridge waveguide structure is adopted for the AWG combiner. A self aligned fabrication procedure is adopted for the fabrication of the waveguide structure of the device to eliminate the misalignment between the laser active waveguide and the passive waveguide. A Ti thin film heater is integrated for each laser in the array. With the help of the heaters, ten laser emissions with 1.8nm channel spacing are obtained. The integrated EAM has a larger than 11dB static extinction ratios and larger than 8GHz small signal modulation bandwidths. The light power collected in the output waveguide of the AWG is larger than −13dBm for each wavelength.

The design and fabrication of an evanescently coupled waveguide InGaAs unitraveling-carrier photodiode (PD) are presented. Through doping the InGaAs absorption layer gradedly, a large built-in electric field can be obtained. As a result, a 4-mu m-wide 15-mu m-long PD has a bandwidth larger than 21 GHz at zero bias. Passive input waveguide is integrated monolithically with the PD by a simple process, which eases the integration of PD with other optical components.

We report the design and fabrication of high speed evanescently coupled InCaAs/InP uni-traveling-car rier-photodiodes (UTC-PDs). A self-aligned passive waveguide is integrated with the PDs by a simple fabrication procedure. Open eye diagrams at 32 Gb/s under zero bias are demonstrated for the first time, to the best of our knowledge, from evanescently or edge coupled InP based PDs, which are easier to be integrated with other optical components than surface illuminated PDs. When used for photonic integrated circuits (PICs) applications, our POs help to lower the electrical cross talk and power consumption of PICs chips. (C) 2017 Elsevier Ltd. All rights reserved.

Monolithically integrated 4 channel electroabsorption modulated DBR lasers array is fabricated. The DBR lasers have over 11 nm wavelength turning range. The small signal modulation bandwidth of the integrated EAM is around 10 GHz.

An optoelectronic synthesizer based on photonic integrated circuits is reported for use in THz communication systems. The source has widely selectable channels, a broad range of continuous tuning (0.254-2.723 THz), and excellent resilience against failure.

We report a widely tunable distributed Bragg reflector (DBR) laser, in which InGaAsP with 1.4 μm wavelength emission wavelength is butt-jointed as the DBR material. A Ti thin film heater is integrated in the DBR section of the device. With the help of the tuning effect of the heater, an over 20nm wavelength tuning range is obtained.

We report side-wall sampled grating and quantum well intermixing techniques to fabricate a full function 4-channel DWDM source with excellent wavelength precision (residuals <0.13 nm) and high yield. Output power was >10 mW.

A novel dual-wavelength DFB laser integrated with a SOA is demonstrated. The two-mode emission can be obtained over a wide range of currents. Our device has advantages of simple structure, compact size and fabrication cost.

We report a monolithic photonic integrated circuit (PIC) for THz communication applications. The PIC generates up to 4 optical frequency lines which can be mixed in a separate device to generate THz radiation, and each of the optical lines can be modulated individually to encode data. Physically, the PIC comprises an array of wavelength tunable distributed feedback lasers each with its own electroabsorption modulator. The lasers are designed with a long cavity to operate with a narrow linewidth, typically < 4 MHz. The light from the lasers is coupled via an multimode interference (MMI) coupler into a semiconductor optical amplifier (SOA). By appropriate selection and biasing of pairs of lasers, the optical beat signal can be tuned continuously over the range from 0.254 THz to 2.723 THz. The EAM of each channel enables signal leveling balanced between the lasers and realizing data encoding, currently at data rates up to 6.5 Gb/s. The PIC is fabricated using regrowth-free techniques, making it economic for volume applications, such for use in data centers. The PIC also has a degree of redundancy, making it suitable for applications, such as inter-satellite communications, where high reliability is mandatory.

We present designs of wavelength-division-multiplexing (WDM) and mode-division- multiplexing (MDM) optical links using mode de/multiplexers (DE/MUXs) based on multimode interference (MMI) couplers with a tilt joint as a phase shifter. The properties of WDM-MDM links with three wavelengths and two optical modes are numerically studied by using 3-D beam propagation method. In the first design, the wavelength combiner is also an MMI coupler type. The insertion loss of the design is around 6 dB because of the inherent loss of the MMI combiner. The size of the main passive optical parts (mode DE/MUXs and wavelength combiner) of the design is only 10: 4 x 114: 2 mu m(2), making the design promising for future compact and high-capacity optical interconnection applications. In another design, arrayed waveguide gratings are used for wavelength multiplexing, leading to a lower insertion loss of the optical connections. For both designs, the mode crosstalk between the two different modes for the same wavelength are below -22 dB.

We report a dual-mode semiconductor laser that has two gratings with different periods below and above the active layer. A semiconductor optical amplifier (SOA), which is integrated with the dual-mode laser, plays an important role in balancing the optical power and reducing the linewidths of the emission modes. A stable two mode emission with the 13.92-nm spacing can be obtained over a wide range of distributed feedback and SOA injection currents. Compared with other types of dual-mode lasers, our device has the advantages of simple structure, compact size, and low fabrication cost.

Multiwavelength laser arrays with 25-GHz channel spacing have been fabricated by upper separate confinement heterostructure (SCH) layer selective area growth (SAG) technique. The reconstruction equivalent chirp (REC) technique is used to introduce an equivalent phase shift into the grating structure, so that a high single longitude mode yield of lasers can be ensured. Because different emission wavelengths are realized through thickness modulation of the upper SCH layer by SAG, the sampling period in the REC technique is the same for all the lasers in an array, which may alleviate the effects of the facet phase on the emission wavelength. The fabricated laser arrays have less than 0.051 nm standard deviation of wavelength deviations. Only conventional photolithography process is needed, helping to lower the fabrication cost of the laser arrays.

We present the fabrication of a low-cost multiwavelength laser array monolithically integrated with a passive optical combiner for optical line terminals (OLTs) in wavelength-division multiplexing (WDM) passive optical networks (PONs). By combining the upper separate confinement heterostructure layer selective area growth technique and the bundle integrated guide technique, both multiwavelength emission with highly uniform spacing and low-loss passive-waveguide material can be obtained in a single metal-organic chemical vapor deposition (MOCVD) growth step, which greatly simplifies the fabrication of the device. A prototype laser array, which has four distributed feedback (DFB) laser elements and a multimode interference coupler as combiner, is successfully fabricated. The shallow ridge structure of the DFB lasers and the deep ridge structure of the passive waveguides are obtained by a single dry etching step, which further eases the device fabrication. The properties of the device are measured and discussed. The results indicate that our method is promising for fabricating cost-effective OLT light sources for WDM-PONs.

We propose a transistor laser with a current confinement aperture (a-TL) formed in a reverse junction layer in the middle of emitter ridge. The a-TLs are studied numerically in comparison with the deep ridge TLs. Data show that in a-TLs, the effects of nonradiative recombination centers on the side walls of the emitter ridge can be reduced greatly due to the confinement of carrier flow in the center region of the emitter ridge. Furthermore, the reverse junction layer can be used as an etching stop layer for the emitter ridge formation, which facilitates both the design and the fabrication of the device. Together with the fact that in a-TLs, the effects of p-type material are alleviated effectively by placing the multi-quantum wells above the base layer, high performance can be expected, especially for long-wavelength devices.

Transistor lasers (TLs) with n-doped quantum wells (QWs), which own low threshold current, are reported in this paper. The exposed side walls of QWs introduce amounts of recombination centers, which damages the properties of deep ridge TLs greatly. It is found that the heavily doping in quantum wells can effectively alleviate this effect. Assuming that the surface recombination is 10 6 cm/s, the light output power and current gain of common emitter configurations as functions of varying doping concentration and ridge width are studied. With doping concentration of 10 18 cm -3 and ridge width of 2μm, the threshold current of TLs can be reduced from more than 100 mA to 31 mA and current gain can be increased from 0.1 to 2.4.

We present an InP-based distributed Bragg reflector (DBR) laser transmitter which has a wide wavelength tuning range and a high chip output power for wavelength division multiplexing passive optical network (WDM-PON) applications. By butt-jointing InGaAsP with 1.45μm emission wavelength as the material of the grating section, the laser wavelength can be tuned for over 13nm by the DBR current. Accompanied by varying the chip temperature, the tuning range can be further enlarged to 16 nm. With the help of the integrated semiconductor optical amplifier (SOA), the largest chip output power is over 30mW. The electroabsorption modulator (EAM) is integrated into the device by the selective-area growth (SAG) technique. The 3dB small signal modulation bandwidth of the EAM is over 13 GHz. The device has both a simple tuning scheme and a simple fabrication procedure, making it suitable for low cost massive production which is desirable for WDM-PON uses.

A novel design of a two-mode de/multiplexer (DE/MUX) based on multimode interference (MMI) couplers is presented. Instead of the phase shifter (PS) in the shape of a narrow strip waveguide, which needs tight design and fabrication requirements, a tilted joint is used as a PS in the proposed device, so that the effects of the fabrication errors of the PS on the performance of the device can be reduced greatly. Simulations show that while the size of the device is as small as 39.54 mu m, which is more compact than other MMI-based DE/MUX, the fabrication tolerance is larger than +/- 25 nm. Within the entire C-band wavelength range, the de-multiplexing crosstalk of the device is lower than -28 dB and the insertion loss is below 1.0 dB. (C) 2015 Optical Society of America