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The life-design group (LDG) comprises an intervention designed to aid career specialists in helping groups of individuals work through career problems, transitions, and traumas. In this article, the authors describe the LDG and present case study results for 3 undergraduate students who were struggling with gaining movement in their career trajectories. Results indicated decreases in career uncertainty and indecision and increases in readiness for making academic major and career decisions. Although the LDG originated in a higher education setting, the LDG has application possibilities across the spectrum of career counseling clients.

Providing cost efficient, yet effective, student services, including career services, is a critical component in higher education. Career services must include the perspectives of the 21st-century work place. We advocate for the delivery of career development services in a group format using a narrative approach to career counseling with college students. Using career construction theory, we provide a framework for the Life Design Group and illustrate its use through a case vignette.

The “Gigabit access passive optical network using wavelength division multiplexing” project aims to implement 64-Gb/s data transmission over 20-km single-mode fiber. Per-user symmetric data rates of 1-Gb/s will be achieved using wavelength division multiplexing passive optical network (WDM-PON) architecture with a 1:64 user split per PON segment. Enabling technologies being developed within the scope of the project include tunable transceivers and athermal 50-GHz array waveguide grating multiplexer devices. The future-proof WDM architecture will enable convergence triple-play (telephony, TV, and broadband internet) service over existing optical infrastructure, and also facilitate cost-effective dense wavelength division multiplexing for metro aggregation and mobile backhaul networks.

Components of a 100 Gb/s transmitter with electrical time-division multiplexing are presented as following: electrical multiplexer, driver amplifier, and large-bandwidth distributed feedback-traveling-wave electro-absorption modulator module. The performance of the parts of the transmitter, as well as the complete chain, is investigated for data operation and transmission in future 100 Gb/s Ethernet (100GbE). Clearly open eye diagrams at 100 Gb/s are demonstrated together with data transmission over 300 m long standard single mode fiber link.

A monolithically integrated distributed feedback (DFB) laser and traveling-wave electro-absorption modulator (TWEAM) with ges 100 GHz -3 dBe bandwidth suitable for Non-return-to-zero (NRZ) operation with on-off keying (OOK) is presented. The steady-state, small-signal modulation response, microwave reflection, chirp characteristic, and both data operation and transmission were investigated. The DFB-TWEAM was found to be an attractive candidate for future short distance communication in high bitrates systems.

Strain compensated 1.3 μm InAsP/InGaAsP laser structures have been grown by using gas source MBE and the ridge waveguide laser diodes have been fabricated. The temperature characteristics of those laser chips have been investigated in detail. The ridge type laser chips show threshold current about 10 mA at room temperature, with slope efficiency greater than 0.35 W/A/un-coated facet. The characteristic temperature of the threshold current were greater than 90 K from 25°C to 90°C. The spectral and far field characteristics of those laser chips also have been investigated.

The formation of dark-area defects (DADs) along the active stripe in InGaAsP/InP-based buried-heterostructure multiquantum-well (BH-MQW) lasers, observed in electroluminescence and photoluminescence (PL) after degradation, is found to be related to dislocations along [011]. The fact that DADs only occurred in lasers showing an increase in threshold current of more than 30% indicates that the [011] dislocations are a consequence rather than the actual origin of the degradation. Observed jogs along a [011] dislocation imply the presence of point defects in the active stripe. The nature of these point defects is not clear, but a comparison of the results for lasers with p/n and semi-insulating current blocking singles out Zn as being a possible candidate. An observed direct proportionality between the increase in threshold current and the reduction in PL intensity is interpreted as being due to a reduction in carrier lifetime due to enhanced nonradiative recombination. A dependence of the distribution of threshold-current increase on current density during aging is explained in terms of a model, in which nonradiative defects are generated during current injection. A comparison of the degradation in MQW and in bulk lasers without an MQW structure shows the degradation characteristics to be different, although the BH structure is the same. The presence of a strained structure and/or a confinement of point defects within the MQW structure therefore seems to have a decisive influence on device reliability.

The design of a traveling-wave electroabsorption modulator (TWEAM) has been improved to decrease the drive voltage. The absorption layer was optimized and together with a novel segmentation of microwave design was introduced to increase the active modulator length. The resulting - 3-dBe bandwidth of fabricated devices was estimated to be 99 GHz. Extinction ratios of 10 dB back-to-back and 6.7 dB after transmission over 2.2-km long fiber were measured with an incident drive voltage of only 2 V peak to peak. This TWEAM performance is believed to constitute a new state of the art for modulators suitable for 100-Gb/s Ethernet with on-off keying.

We have used cross‐sectional atomic force microscopy in combination with dopant‐selective etching to study structural details in InGaAsP/InP‐based laser diodes. The different etch rates of p‐type, n‐type, and semi‐insulating InP allowed us to relate topographic features in atomic force images of etched lasers to changes in the electrical characteristics of the semiconducting material. This allowed us to follow, e.g., the interdiffusion of Fe and Zn across the interface between p‐InP:Zn and semi‐insulating InP:Fe. A non‐linearity in the light‐output power response suggests that this interdiffusion has given rise to leakage currents in the structure. In addition, electron‐beam induced‐current images imply a widening of the depletion layer at this interface. Effects due to Zn diffusion across the interface between p‐InP:Zn and n‐InP:Si could also be observed. Unexpected traces of an unavoidable contamination at surfaces exposed to the atmosphere before regrowth was found in both atomic force microscopy images and cross‐sectional transmission electron microscopy images of the same laser type. The results illustrate how the atomic force microscopy in combination with selective etching can serve as a simple and convenient tool for detailed structural studies of InGaAsP/InP‐based lasers. © 1999 The Electrochemical Society. All rights reserved.

Degradation of InGaAsP-InP-based buried-heterostructure bulk (BH-bulk) lasers has been studied by means of electroluminescence (EL), photoluminescence (PL), electron-beam-induced current (EBIC) and transmission electron microscopy (TEM). Lasers with p/n as well as semi-insulating (SI) current-blocking layers were studied. The results show that moderate increases in the threshold current correlate well with formation of dark defects (DD's) (i.e., dark-line defects (DLD's) or dark-spot defects (DSD's), which cannot be distinguished in our case due to the narrowness of the laser stripe.) The DD's were found to be caused by dislocation loops. The dependence of threshold current increase on the number of DD's is explained in terms of a model which includes effects due to the DD's, as well as changes in the regions outside the DD's. The latter is found to be responsible for the major part of the threshold current increase. Values for the ratio between the carrier lifetimes inside and outside the DD's are presented, for the first time. In our lasers, strong degradation differs from moderate degradation in that DD's do not form during aging. The presence of dislocation loops only at the sidewalls of the active stripe in lasers with p/n current-blocking layers points to the sidewalls as being critical. The near absence of dislocation loops and the smaller increase in threshold current in SI lasers which have degraded strongly, compared to the strongly degrading p/n lasers, suggest that strong degradation is a synergistic combination of damage in the sidewalls and Zn indiffusion from the current-blocking layers.

We prepared In 0.53 Ga 0.47 As/InP electron waveguides with in-plane side gates by deep etching through a two-dimensional electron gas. In these structures we investigated the conductance dependent on the voltages applied at both gates. Our experiments show a remarkable asymmetry in the gate efficiency: negative gate voltages seem to be more efficient than positive ones, and the pinch-off voltage of the waveguide depends mainly on the more negative of the two gate voltages. A model is given which takes the etched surfaces into account. The conductance in the waveguide is essentially determined by the potentials at the etched surfaces, which are via Schottky-diode transitions coupled with the gates and the channel. With the help of this model we are able to explain the behavior of the electron waveguides.

Distributed feedback (DFB) laser parameters such as grating coupling coefficient, effective indices, facet reflectances, and the phases of facet reflectances have been determined using a method based on least-square fitting of theoretical spectra to measured, subthreshold DFB laser emission spectra. The only inputs needed are geometrical parameters such as length, grating period, and internal grating phase shifts. A larger number of devices have been successfully characterized, and consistent results have been obtained in both 1.3-/spl mu/m multi-quantum-well (MQW) DFB lasers with both facets as-cleaved, and in 1.55-/spl mu/m MQW DFB lasers with no, one, or two facets as-cleaved.

After a review of the design principles, we present new experimental and theoretical results about the multigrating filter (MGF), a tunable channel selection filter for wavelength division multiplexed (WDM) transmission systems. Bit error rates mere measured at 2.5 Gb/s for single- and multichannel operation of a packaged polarization independent four-channel MGF with integrated amplifiers. The single-channel results are compared with theory. A monolithic tunable channel dropping component has also been fabricated by integrating two MGF's, a splitter, and amplifiers. Bit error rates measurements are presented for optical (at 2.5 Gb/s) and electrical on-chip (at 622 Mb/s) channel dropping in single- and multichannel operation.

The modulation and chirp performance of an InGaAsP based monolithically integrated distributed feedback (DFB) laser and travelling wave electro-absorption modulator (TWEAM) designed for 100Gb/s operation is presented. Open eye-diagrams at 100Gb/s, and error free 50Gb/s BER (limited by measurement system) were achieved. The chirp factor varied between 1.5 and 0 for absorptions between 10% and 90%.

We demonstrate ges60 GHz Electro-Absorption-Transceiver (EAT) composed of monolithically integrated Distributed-Feedback laser (DFB) with low drive voltage Electro-Absorption-Modulator. Clear eye-openings at 50 Gb/s for modulation and detection are presented. The device can be used as efficient and compact size transmitter or as detector in direct 80 Gb/s links. Transmission over 7.2 km long fibre with dispersion compensation is achieved.

We report improved tuning regularity in a vertical grating assisted codirectional coupler laser with a super-structure grating distributed Bragg reflector (GCSR). Access to 20 wavelengths with SMSR better than 20 dB within a tuning range of 100 nn was obtained with a single current control in a GCSR laser. The total tuning behavior shows a potential of complete wavelength coverage over 100 nm by use of three tuning currents. >

―A vertical grating assisted codirectional coupler laser with a super structure grating distributed Bragg reflector is demonstrated. A record stepwise tuning range of 114 nm was measured with good side-mode suppression. The tuning behavior of the device is investigated showing a potential of a tuning range exceeding 100 nm with complete wavelength coverage.

A multi-grating filter with polarisation-independent channel positions and integrated with two amplifiers has been fabricated in InGaAsP/InP. The four tunable Bragg gratings allow the selection of one out of four channels in a WDM system at 1.55 µm. A packaged device with no fibre-to-fibre loss and worst case crosstalk below –16 dB has been fabricated.

Zn-Fe interdiffusion is an important issue in InP-based buried heterostructure lasers that utilise Zn for p doping and Fe for the semi-insulating layers. In this work, cross-sectional scanning capacitance microscopy (SCM) is used to characterise these laser structures. The capability of the SCM technique to analyse such complex devices is demonstrated. The SCM images (on as-cleaved samples) show that diffusion of Zn into the semi-insulating layer is significant and extends as far as 0.7 /spl mu/m. Similar values (about 0.5 /spl mu/m) were obtained by atomic force microscopy (AFM) investigations on samples etched with a dopant selective etchant. Further, the SCM images are shown to give additional useful information on the active doping levels in the different layers and the location of the (electrical) p-n junctions. Finally, the mechanisms for the contrast in the SCM images are discussed.

We report on integrated optics Ti:LiNbO/sub 3/-based 8/spl times/8 switch matrices. The matrix design uses a tree structure with 112 digital optical switches as switch elements. The matrix, which has been pigtailed and packaged in an open package for convenient system demonstrator use, exhibits a worst case insertion loss of less than 15 dB. >

A new tunable optical notch filter for use in wavelength division multiplexing (WDM) transmission system has been fabricated in the InGaAsP/InP material system for use at 1.55 /spl mu/m. The device uses tunable reflection gratings in a waveguide to control the channels (4 in this case). Crosstalk levels between 9 dB and 20 dB have been measured, depending on the channel. System experiments at 150 Mb/s show less than 1 dB crosstalk penalty at 10/sup /spl minus/9/ bit-error rate. >

Summary form only given. Complete wavelength coverage over 67 nm was measured with SMSR better than 25 dB using a grating assisted codirectional coupler with WDM sampled rear reflector (GCSR) laser. Wavelength switching time for coupler current step was also measured.

A novel reconfigurable InP wavelength demultiplexer is reported and WDM experiments have been performed on a packaged device demonstrating tunability across the EDFA window. 4000 km in a recirculating loop was achieved at 2.5 Gbit/s.

The connections between gain, carrier concentration and internal losses were experimentally investigated for a 6 QW 1.55 /spl mu/m laser as a function of temperature. The material gain drops dramatically with increasing temperature.

The grating coupling coefficients for a large number of 1.3 μm and 1.55 μm MQW DFB lasers with no, one, or two facets as-cleaved have been successfully extracted from spontaneous emission spectra.

An important element in optical transmission networks based on Wavelength Division Multiplexing (WDM) is the Optical Add-Drop Multiplexer (OADM). It allows the selective dropping of one or several wavelength channels (fixed or selectable) and the addition of new signals at the same wavelengths. To reduce cost, an integrated optics solution would be preferable to discrete components. Several technologies can be used, including acousto-optic devices in LiNbO3 [1], planar diffraction gratings in InGaAsP/InP [2] or SiO2/Si [3], and arrayed-waveguides, also in InGaAsP/InP [4] or SiO2/Si. One of the most advanced examples to date is a 16 channels device in SiO2/Si [5] Using three arrayed-waveguide grating demultiplexers on the same chip (80 by 65 mm).

A four channel Multi-Grating Filter (at 1.55 microns) with polarization-independent channel positions and two integrated amplifiers has been fabricated in InGaAsP/InP. A packaged device has no fiber-to-fiber loss and worst case crosstalk below -18 dB.

A new type of tunable optical filter for use in Wavelength Division Multiplexing (WDM) transmission system has been fabricated in the InGaAsP/InP material system for use at 1.55 pm. The device uses tunable reflection gratings in a waveguide to control the channels (4 in this case). Crosstalk levels between 9 dB and 20 dB have been measured, depending on the channel.

Monolithically integrated 4×4 semiconductor laser amplifier gate switch arrays comprising twenty-four integrated laser amplifiers have been fabricated and evaluated. We report observation of net positive optical gain between fibres, high extinction ratio, and low crosstalk.

Transmission over 150 km of standard fibre at 5 Gbit/s, and over 75 km at 8 Gbit/s, is reported with a monolithically integrated DFB laser and Franz-Keldysh absorption modulator. The modulator facet reflectance is low. The device is stable over a range of operating parameters. The butt-joint, buried-heterostructure device is entirely grown by MOVPE.

We report on the first 4 × 4 switch matrix with digital optical switches as switch elements. The matrix is arranged in a tree structure, and comprises 24 switch elements and is pigtailed and packaged.

The authors report a 40 nm (1560 to 1520 nm) quasi-continuous tuning with a minimum output power of 3 mW, sidemode suppression >30 dB and high current tuning efficiency in a vertical grating assisted codirectional coupler laser with a sampled Bragg reflector (GCSR).

InGaAsP/InP butt-joint, buried-heterostructure DBR lasers, with 8 mA threshold current at T = 293 K. have been developed, using electron-beam lithography and a four-step MOVPE process with a semi-insulating Fe : InP current-blocking structure. Packaged devices give 5 mW fibre-coupled power. The maximum tuning range is 9.1 nm. The 3 dB modulation bandwidth is 9 GHz.

Monolithically integrated 2*2 semiconductor laser amplifier gate switch arrays have been fabricated and evaluated. Net positive chip gain, high extinction ratio, and high electrical isolation between the integrated laser amplifiers are reported.

Monolithically integrated 4×4 semiconductor laser amplifier gate switch arrays comprising 24 integrated laser amplifiers have been fabricated and evaluated. Net positive optical gain between fibres, high extinction ratio, and low crosstalk are reported.

The use of a small ultrafast electrical signal differentiator is described. Its application in conjunction with photoconductive elements in the measurement of mode-locked laser pulses with picosecond resolution has been investigated.

Stimulated Raman scattering of Q -switched and mode-locked Nd:YAG laser pulses at 1.06 μm in a 120-m-long single-mode fiber has been investigated experimentally. A Photochron IIA Synchrosan streak camera with picosecond resolution was used to give time resolved detection of the first four order Stokes-Raman pulses at 1.12, 1.18, 1.24, and 1.31 μm. It has been shown that in traversing the fiber the fundamental and the first two order Stokes were substantially shortened and that the Stokes pulses were asymmetrical with sharper leading edges.

The performance of LiNb03 waveguide devices, e.g. switches and modulators, is impaired by drift in the output light characteristics when they are subject to temperature changes or DC voltages are applied to the electrodes 1,2,3,4,5. The latter phenomenon, known as DC drift, arises from free charge carriers present in the crystal, which move in the applied field and change the "effective" electric field experienced by the light. Since the "effective" field will change in time due to charge carrier motion, the light output of the device will be time dependent. The magnitude and time constants of the described behaviour depends on several parameters. Some of them are: the crystal quality and cut, the buffer layer material, the electrode configuration and in general the processing of the chip. As the DC drift will impair the crosstalk of a switch, it is desirable to minimize its magni-tude. Depending on the application, it can also be an advantage to adjust the time constants for the drift to suitable values. All this can be done through careful design and manufacturing of the switch. However, it is difficult to get rid of the DC and temperature drift problems completely that way, and if the application requires extremely low crosstalk values it might be necessary to stabilize the switch with some kind of feed-back control system. A LiNb03 chip that is subject to temperature changes will to some extent alter its characteristics. That is due to electric fields set up through the pyro-electric effect. The described phenomenon will affect the transfer function of a switch, and appear as a temperature drift in the crosstalk characteristic. The parameters that determine the drift magnitude, are related to those of the DC drift. Another important factor is the packaging of the chip, so careful design of the package is required in order to get a small temperature dependence for the packaged switch. The most interesting parameter, when characterizing a LiNb03 switch under various conditions, is the extinction ratio or crosstalk between the output ports. It is shown here how the crosstalk deteriorates due to drift problems (DC and temperature drift), and how to overcome those problems through stabilization by means of feed-back control signals.

Methode numerique basee sur l'integration directe de l'equation d'onde scalaire pour l'etude du retard de mode differentiel dans les fibres optiques multimodes. En meme temps etude de la validite de la simple methode d'optique geometrique due a Peterman pour determiner le profil d'indice de refraction a partir des vitesses de groupe en presence d'un fort couplage de mode induit par l'ellipticite

We use an all-optical method to characterize the modulation bandwidth of a DFB-EA designed for 100 Gb/s Ethernet. In a large-signal wavelength conversion set-up, we show the device has an all-optical bandwidth of 83 GHz.

We report on a strictly nonlocking 8×8 integrated optics switch matrix in Ti: LiNbO3. The matrix comprises 64 directional couplers on one chip. Insertion losses less than 7 dB have been measured. The extinction ratio has an average value of 30.5 dB for the directional couplers.

We report a novel type of polarisation independent directional coupler switch on X-cut, Y-propagating Ti: LiNbO3, with modest fabrication tolerances. The device can also be used as a polarisation splitter. The principle of operation and experimental results are given.

We report on the performance of a 4×4 polarisation independent LiNbO3switch matrix with a ‘tree-structure’, permitting strictly nonblocking communicative as well as distributive switching.