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Summary he paper focuses on the relationship among the karst collapse sinkholes, extensional fault trends, and associated offset talus debris observed on several Miocene carbonate platforms of Central Luconia, Sarawak. The Central Luconia province is divided into several tectonic highs i.e. Mega Platform, G Fields High, Bunga Pelaga High, and Southern Field High. The carbonate platforms studied for the analysis are carbonate platforms located on the Bunga Pelaga High. As of now, there have been no in-depth studies concentrating on establishing the first Central Luconia’s Carbonate Karst Island Model. Each of these carbonate platforms actually creates the ideal background platform to further analyse the aforesaid carbonate island karst model. Sea-level changes are a critical factor that influences the distribution and the density of the karst formation. The type of karst features formed on a carbonate platform is also influenced by the rise and fall of the sea-level because these changes of sea-level will influence the period of exposure which in turn, will determine the duration of Stillstands that is needed to create the karst features. Therefore, to further analyse these carbonate platforms, results of this analysis will help construct the carbonate karst island model for the Bunga Pelaga High carbonate platforms.

We have developed a novel three-contact vertical-cavity surface-emitting laser (VCSEL) with an intracavity absorber for use in high-speed data communications. We demonstrate two distinct designs for our VCSEL and discuss the device physics underlying the behaviors of the two designs. Furthermore, we demonstrate a wide range of applications for these VCSELs, including optical intensity modulation, phase and amplitude modulation of a microwave optical subcarrier, optical bistability, self-pulsation, and optical disk readout.

We demonstrate the first intracavity quantum-well photodetector within an InGaAs DBR QW VCSEL for top- and bottom-emitting structures. Minimal spontaneous emission is detected by the internal detector. Dark current is on the order of picoamperes, limited by our instrument noise floor. The internal detector demonstrates high insensitivity to external ambient light as compared to an external detector. Combining various measurement techniques, we gain an understanding of such an integration and discuss the various ramifications of the issues surrounding the design, fabrication, and performance of these integrated VCSEL-detectors. This configuration facilitates flexible tailoring of the laser efficiency and the integrated detector responsivity.

The analog performance of a vertical-cavity surface-emitting laser is compared for gain and cavity loss modulation. Direct gain modulation consistently results in a larger spur free dynamic range (SFDR) than does cavity loss modulation; the maximum SFDR achieved is 96.5 dB Hz2/3. Analysis of the physical origins of variations in the measured SFDR with applied electrical bias indicates potential strategies for improving the analog response of these lasers.

We demonstrate a compact integrated method for phase and magnitude control of an optically carried microwave signal with no external high-frequency circuitry. Our device consists of a novel three contact VCSEL, which permits external control of both the cavity loss and gain. Independent control of the phase and magnitude of the optically carried signal is demonstrated. With reference to the small-signal rate equations, we show that such independent control is only possible given the extra degree of freedom offered by the three contact design.

We demonstrate a novel integrated optical disk readout head using a vertical-cavity surface-emitting laser (VCSEL) with an intracavity quantum-well absorber. Optical pickup detection is performed by measuring the change in the absorber voltage as optical feedback into the VCSEL cavity is varied. We obtain a 0.22-V peak-to-peak response with a RC time constant of 20 /spl mu/s, indicating a rolloff frequency of 50 kHz. The unique design flexibility of this device allows amplification of the detection signal by operating the device in a bistable regime.

We have constructed a vertical-cavity, surface-emitting laser with a voltage-controlled quantum well absorber in the upper mirror stack. If the lasing wavelength of this device is designed to be slightly longer than the absorber band edge, sharp negative differential resistance can be obtained in the absorber under lasing conditions. We present strong experimental evidence that this behavior arises from redshifting of the absorption excitonic peak due to the quantum confined Stark effect. Design criteria are proposed for applications including high speed modulation and self-pulsation.

We demonstrate a novel modulation technique with a vertical cavity surface-emitting laser (VCSEL) using an intracavity embedded voltage-biased quantum well absorber. We achieved a -3-dB small-signal bandwidth of 9 GHz and a response of 7 GHz//spl radic/(mA) by modulation of the absorber. Our calculations show that this technique introduces significantly less chirp at higher frequencies than direct current modulation.

The surface modification of bare Cu leadframe surfaces by heat treatment, or plasma cleaning, or the coupling of both treatments, either before die-attach, encapsulation, or before both processes, as a means to combat package reliability issue especially delamination of mode I & II were investigated. The effectiveness of these treatments were gauged with contact angle measurements: before, after and during post treatment ageing period of 24hrs. Prototype units were assembled and subjected to pre-condition of 85degC/85RH for 168hrs follow-up with 3 times reflow (peak temperature at 260degC for 20-40sec, MSLI). CSAM is used to interpret the performance of the epoxy adhesion on the pre-treated surfaces. The treatments were found to be effective in overcoming the delamination of mode I & II.

The choice of technology for today's mixed-signal/RF system-on-chip (SOC) designs has been driven by the performance enhancements and cost advantage derived from scaled CMOS technologies. This paper discusses the performance improvements of RF transistors resulting from technology downscaling. Comparisons between scaled RF CMOS and SiGe BiCMOS technologies to highlight the benefits of employing SiGe HBT devices in certain applications are made. Other technology enablements discussed include accurate, scalable models and statistical models to address the need for design flexibility and robust manufacturing. Thereafter the introduction of high Q inductors, high density capacitors and varactors as basic passive components for RF circuits are discussed. Analog requirements such as mismatch, temperature linearity and voltage linearity are also discussed.

We propose a generic vertical-cavity amplifier (VCA) using a coupled-cavity design to broaden the bandwidth. Calculations are made for cavities with GaAs-AlAs and GaAs-Al/sub x/O/sub 2/ distributed Bragg reflectors (DBR). We found that at reasonable pumping levels the VCA increased the bandwidth by 85% (GaAs-AlAs) to 500% (GaAs-Al/sub x/O/sub 2/) as compared to a simple two-mirror structure similar to vertical-cavity surface-emitting lasers. In particular, the GaAs-AlAs VCA shows a bandwidth of 2 nm at 6-dB signal gain, while the GaAs-Al/sub x/O/sub 2/ VCA demonstrates a 5-nm bandwidth at 6-dB signal gain with no ripple at required single-pass power gain of /spl sim/2-2.5%. Furthermore, as large as 30-nm bandwidth in a lossless bandpass filter can be obtained. >

A new integrated method of phase and magnitude control of a microwave optical subcarrier is demonstrated using a three-contact VCSEL. The entire first quadrant of 16-QAM signal space can be achieved.

We present the first detailed investigation of the sharp negative differential resistance (NDR) within a VCSEL intracavity quantum well absorber. The intensity dependent NDR is governed by the position of the Fabry-Perot wavelength relative to the absorber excitonic peak.

Summary form only given. Self-pulsating lasers are extremely useful in a variety of applications, including multimode fiber systems and optical disk readout. It is desirable to attain self-pulsating vertical-cavity surface-emitting lasers (VCSELs) because the surface-normal geometry facilitates two-dimensional array configurations and wafer-scale fabrication. We previously demonstrated on-off control of GHz-range self-pulsations in a VCSEL. In this work, we believe we demonstrate for the first time 700 MHz frequency tuning of self-pulsations in a VCSEL by using an active quantum well absorber integrated in the mirror stack. These pulsations have a 700 kHz relative frequency linewidth. We present theoretical and experimental demonstrations of a novel design criterion, whereby the absorber wavelength is slightly shorter than the lasing wavelength, leading to the negative differential resistance, which is essential to obtaining self-pulsation. By careful device design, the VCSEL can be made to self-pulsate at low absorber biases, GHz-range frequencies, and potentially at high output powers.

We show that the intracavity detector-VCSEL performance depends critically on the relative alignment of the Fabry-Perot wavelength and the quantum-well absorber band edge. By strategic design, we obtain well-matched behavior of the internal and external detectors-up to 5 times threshold. Comprehensive modeling agrees with experimental results.

We experimentally demonstrate the first self-pulsating VCSEL with a controllable quantum-well saturable absorber. Self-pulsation frequencies as high as 2 GHz were obtained. Self-pulsating lasers have proven extremely useful in applications where elimination of optical feedback and high-speed driving circuitry is needed. In this work, we present the first demonstrated InGaAs DBR QW VCSEL with self-pulsations occurring through a voltage-controlled saturable absorber.

In this paper, we propose a novel GaAs-AlAs DBR vertical coupled-cavity semiconductor laser amplifier (VCA) structure aimed at providing amplification with desirably broader transmission bandwidths and more square-like transmission spectra at acceptably low gain levels.

Summary form only given.Analog applications of VCSELs require highly linear wideband operation, minimal intermodulation distortion, and high dynamic range. The maximum spur-free dynamic range (SFDR) obtained for a VCSEL is 104.3 dB Hz/sup 2/3/ at 102 MHz; error-free analog transmission over 3 km of fiber has been demonstrated at 1 GHz. This work suggests that, with future design improvements, VCSELs may be able to compete with DFB lasers for analog applications. The device used in this study is a VCSEL with an independently biased, voltage-controlled, intracavity absorber.

We have developed a commercially manufacturable oxide VCSEL process. Good uniformity control in epitaxial thickness and oxide aperture is found to be important in achieving high yield. The manufactured VCSELs have superior performance with operating voltage less than 2 V. Preliminary results show that oxide VCSEL reliability is similar to that of proton-implanted VCSELs.

The high reflectivity of VCSEL mirrors renders the device very sensitive to small changes int he reflectivity or absorption within the laser cavity. Therefore, the integration of a quantum-well absorber within the VCSEL enables compact, monolithic devices with multiple functions. As a result, the VCSEL exhibits a variety of useful characteristics under different configurations. In this work, we demonstrate the use of a quantum-well absorber within one of the VCSEL mirror stacks. With strategic design and simple biasing circuitry, we have shown experimentally (1) a VCSEL with an integrated quantum-well photodetector, (2) a self-pulsating VCSEL with a controllable quantum-well saturable absorber, and (3) a novel technique for VCSEL modulation where the quantum-well absorption is modulated, thereby modulating the laser light output. The theory, design criteria, experimental results, and potential applications for these devices are discussed.

Summary form only given. We use a novel bistable vertical cavity surface-emitting laser (VCSEL) with an intracavity quantum-well absorber to create a compact, integrated optical pickup head. By careful design of the relative wavelengths of the quantum-well absorption edge and the Fabry Perot peak, we achieve significant negative differential resistance (NDR) in the absorber, which under proper bias conditions leads to a large signal amplification of the integrated monitor.

We have constructed a novel VCSEL structure in which a voltage biased quantum well absorber is embedded in the mirror stack. Several applications for these devices are demonstrated. The devices exhibit regimes of negative differential resistance in the absorber under varying laser bias conditions. By choosing the absorber bias conditions such that the operating load line intersects the absorber IV trace three times, the laser can be made to exhibit optical bistability. The magnitude of the bistability and consequent hysteresis loop can be controlled by adjusting the absorber bias. If the bias conditions are adjusted so that the load line is tangential to the portion of the absorber IV exhibiting negative differential resistance, then the device can be made to self-pulsate. Self-pulsations at frequencies as high as 2 GHz with 700 kHz rf linewidth FWHM (full-width at half-maximum) have been obtained using these devices. Furthermore, the self-pulsation frequency can be tuned over 700 MHz by adjusting the bias conditions, representing a substantial advance over existing self- pulsating VCSELs. We have also demonstrated a novel modulation scheme using these devices, in which the drive signal is applied to the bias voltage across the absorber. Theoretical analysis of the chirping mechanism leads us to expect that this technique will minimize the chirp at high modulation frequencies, while still providing substantial modulation depth and high speeds. We achieved a minus 3 dB bandwidth of 9 GHz; the bandwidth increases with the laser bias current at a rate of 7 GHz/(root)mA.

Polarisation and modal behaviour are compared for very low threshold oxide confined and airgap confined vertical cavity lasers. Although both structures have nearly identical optical models leading to the same stable fundamental mode emission up to many times threshold, they show very different polarisation behaviours. Predetermined polarisation up to 18 times threshold is achieved for the oxide confined vertical cavity lasers.

The authors demonstrate the first intracavity quantum-well photodetector within a VCSEL. Minimal spontaneous emission is detected by the internal detector. The effective responsivity is as high as 9 A/W; the dark current is

The authors report the first demonstration of a VCSEL with GHz-range self-pulsations using a quantum-well saturable absorber. Negative differential resistance in the saturable absorber was observed, which can lead to bistable operation or self-pulsations under a range of user-controlled conditions. Self-pulsation frequencies up to 2 GHz with an RF linewidth

We have confirmed that most of third trimester amniotic fluid alkaline phosphatase is macromolecular. This is not, however, as has been previously suggested, due to complexing with lamellar body phospholipid. Amniotic fluid high-Mr ALP and serum high-Mr ALP are similar with regard to p-nitrophenylphosphate hydrolysis, thermostability, and activation energy but experiments with uncompetitive inhibitors indicate differences in isoenzyme composition.