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Selective area growth is used for the first time in the TU/e generic integration platform to modify independently the bandgap of active sections. A chip combining 4 tunable lasers with shifted wavelength ranges has been fabricated. A 96 nm wide tuning range is demonstrated.

The III-V semiconductor InGaAs is a key material for photonics because it provides optical emission and absorption in the 1.55 μm telecommunication wavelength window. However, InGaAs suffers from pronounced nonradiative effects associated with its surface states, which affect the performance of nanophotonic devices for optical interconnects, namely nanolasers and nanodetectors. This work reports the strong suppression of surface recombination of undoped InGaAs/InP nanostructured semiconductor pillars using a combination of ammonium sulfide, (NH4)2S, chemical treatment and silicon oxide, SiOx, coating. An 80-fold enhancement in the photoluminescence (PL) intensity of submicrometer pillars at a wavelength of 1550 nm is observed as compared with the unpassivated nanopillars. The PL decay time of ∼0.3 μm wide square nanopillars is dramatically increased from ∼100 ps to ∼25 ns after sulfur treatment and SiOx coating. The extremely long lifetimes reported here, to our knowledge the highest reported to date for undoped InGaAs nanostructures, are associated with a record-low surface recombination velocity of ∼260 cm/s. We also conclusively show that the SiOx capping layer plays an active role in the passivation. These results are crucial for the future development of high-performance nanoscale optoelectronic devices for applications in energy-efficient data optical links, single-photon sensing, and photovoltaics.

Summary form only given. In this work, we report a remarkable suppression of the surface recombination rates in passivated III-V undoped InGaAs nanopillars on InP (inset of Fig. 1a). The surface passivation comprises ammonium sulfide, (NH4)2S, chemical treatment followed by encapsulation with a 50 nm layer of SiOx by plasma-enhanced chemical vapor deposition performed at 300°C. Before passivation, fabricated nanopillars with -300 nm lateral width, d, show a very poor photoluminescence (PL) emission (blue curve in Fig. 1a). The corresponding carrier dynamics, measured by time-correlated single-photon counting, Fig 1b, reveal an extremely short lifetime of ~130 ps, related to the well-known strong surface recombination velocity at InGaAs surfaces [3]. After the sulfur treatment followed by SiOx, we observe a substantial increase by almost two orders of magnitude of the PL intensity (red curve in Fig. 1a), while the carrier lifetime increases by more than two orders of magnitude to a value ~23 ns, red curve in Fig 1b. The estimated surface recombination velocity, S, decreases from about 2×104 cm/s in the untreated nanopillars down to around 260 cm/s (inset of Fig. 1b). To our knowledge, this is a record low value in undoped InGaAs semiconductors. Most importantly, our passivation studies reveal that the SiOx capping layer not only protects the pillars' sidewalls against oxidation, as reported in [5], but actively takes part in the passivation process, a result never previously reported.

In this paper, measurements and analysis of the small-signal net modal gain of single-layer InAs/InP(100) quantum-dot (QD) optical amplifiers are presented. The amplifiers use only a single layer of InAs QDs on top of a thin InAs quantum well. The devices have been fabricated using a layer stack that is compatible with active–passive integration scheme, which makes further integration possible. The measurement results show sufficient optical gain in the amplifiers and can thus be used in applications such as lasers for long-wavelength optical coherence tomography and gas detection. The temperature dependence of the modal gain is also characterized. An existing rate-equation model was adapted and has been applied to analyze the measured gain spectra. The current injection efficiency has been introduced in the model to obtain a good fit with the measurement. It is found that only a small portion ($sim$1.7%) of the injected carriers is actually captured by the QDs. The temperature dependence of several parameters describing the QDs is also discovered. The mechanisms causing the blue shift of peak gain as the current density increases and the temperature changes are analyzed and discussed in detail.

We demonstrate all-optical wavelength routing of 80 Gb/s data packets without using electronic control. The system consists of an optical wavelength converter and a monolithically integrated optical flip-flop memory. The integrated optical flip-flop is based on two coupled lasers, exhibiting single-mode operation, having a 35 dB contrast ratio between the states, and switching its state in about 2 ns. The wavelength converter is optically controlled by the optical flip-flop. We show that the optical set and reset pulses can force the optical flip-flop to switch its continuous-wave output light between two specific wavelength positions. The output light feeds the wavelength converter, which, in turn, converts the data packet into the flip-flop's output wavelength, causing the data packet to be routed into a specific port.

We report the growth, device fabrication, and performance of stacked InAs/InGaAsP/InP (1 0 0) quantum dots (QDs) in telecom lasers. Wavelength tuning of the QDs grown by metalorganic vapor-phase epitaxy (MOVPE) over the 1.55-μm region at room temperature (RT) is achieved using ultrathin GaAs interlayers underneath the QDs, which suppress As/P exchange to reduce the QD height in a controlled way. Unpolarized photoluminescence from the cleaved side, important for realization of polarization-insensitive semiconductor optical amplifiers, is obtained for closely stacked QDs due to vertical electronic coupling. The wavelength shift due to group-V-atom intermixing in the QDs during growth at higher temperatures of device structures is compensated by adjusting the GaAs interlayer thickness and V/III flow ratio during QD growth. Device quality of the QDs is highlighted by continuous-wave ground-state lasing at RT of narrow ridge-waveguide QD lasers.

We report on a passively mode-locked InP/InGaAsP multiple quantum well semiconductor ring laser that operates at a 20 GHz repetition rate and around 1575 nm wavelength. The device has been realized using the active-passive integration technology in a standardized photonic integration platform. We demonstrate experimentally for the first time to our knowledge that the relative positioning of the amplifier and absorber in a monolithically integrated ring laser can be used to control the balance of power between counterpropagating fields in the mode-locked state. The directional power balance is verified to be in agreement with a model previously reported.

We present a method to prepare a mixed resist material composed of a positive electron-beam resist (ZEP520A) and C 60 fullerene. The method is modified from previous methods in literatures to achieve an optimized mixing. An improvement of the mixed material on the thermal resistance respect to the same structures fabricated with normal ZEP resist has been demonstrated by fabricating multimode interference couplers and coupling regions of micro-ring resonators. An improvement on the propagation loss of the InP membrane waveguides from 6.6 to 3.3 dB/cm using this mixed material is also shown.

We present a method to prepare a mixed resist material composed of a positive electron-beam resist (ZEP520A) and C60 fullerene. The method is modified from previous methods in literatures to achieve an optimized mixing. An improvement of the mixed material on the thermal resistance respect to the same structures fabricated with normal ZEP resist has been demonstrated by fabricating multimode interference couplers and coupling regions of micro-ring resonators. An improvement on the propagation loss of the InP membrane waveguides from 6.6 to 3.3 dB/cm using this mixed material is also shown.

The static and dynamic characteristics of a monolithically integrated InP 1 × 16 optical phased-array switch are presented. The device demonstrates static switching with an average extinction ratio of 18.6 dB, on-chip loss below 7 dB, and wavelength dependence of less than 0.8 dB in the entire C-band. A 40-Gb/s nonreturn-to-zero signal is transmitted through the switch with a power penalty below 0.4 dB. Using a programmable electronic circuit, dynamic switching to all 16 outputs is achieved with response times less than 11 ns.

Controlled anodic oxidation for achieving a better control of etch depth in AlGaAs semiconductor structures is studied. The rates of material consumption and oxide thickness growth for p ++ -GaAs and p-Al 0.38 Ga 0.89 As are given for the citric acid/glycol/water electrolyte. The etch profiles for GaAs/Al 0.45 Ga 0.55 As and GaAs/Al 0.50 Ga 0.40 As layer sequences in laser diode structures are presented. The underetch is rather high and depends on oxidation conditions (constant voltage or constant current). The profile obtained is very rough for constant voltage oxidation and much better when using constant current conditions. The latter also improves the uniformity of oxide growth. The etch rate of the anodic oxide in diluted HCl is much larger for GaAs than for AlGaAs.

A versatile fabrication technique for GaAs-AlGaAs wet-etched mirror lasers is presented. This technique works independently of the Al concentration in the cladding layers up to a value of 70%, and it requires four photolithography steps. Ridge waveguide lasers have been successfully processed using a double heterostructure (DHS) as well as graded index separate confinement heterostructures (GRINSCH) having different quantum-well (QW) active layers. This technique is used to fabricate short-cavity lasers in GRINSCH structures having GaAs multiple-quantum-well (MQW) or bulk active layers. Laser operation was obtained in a 29-/spl mu/m-long device using a 5-QW structure. Short lasers with QW active layers show a complex spectral behavior. These lasers operate at higher current densities (/spl sim/20 kA/cm/sup 2/) and emit light at more than one wavelength. This implies that higher order transitions are involved which is not the case when using a bulk GaAs active layer. Besides the two peaks corresponding to the n=1 and n=2 transitions, we found an intermediate peak which corresponds presumably to the forbidden transition E1-HH2.

The authors report lasing of InAs/InGaAsP/InP (100) quantum dots (QDs) wavelength tuned into the 1.55 µm telecom region. Wavelength control of the InAs QDs in an InGaAsP/InP waveguide is based on the suppression of As/P exchange through ultrathin GaAs interlayers. The narrow ridge-waveguide QD lasers operate in continuous wave mode at room temperature on the QD ground state transition. The low threshold current density of 580 A/cm2 and low transparency current density of 6 A/cm2 per QD layer, measured in pulsed mode, are accompanied by low loss and high gain with an 80-nm-wide gain spectrum.

We have fabricated InP nanowire array solar cells with an axial p-n junction. Catalyst gold nanoparticles were first patterned into an array by nanoimprint lithography. The nanowire array was grown in 19 minutes by vapor-liquid-solid growth. The sidewalls were in-situ etched by HCl and ex-situ cleaned with a piranha etch. With this cleaning procedure, we could remove the sidewall extrusions and carbon contamination on the nanowire sidewall. We obtained a Voc of 0.68V, a fill factor of 71%, a diode rectification ratio of 107, an ideality factor of 2.12, a solar cell efficiency of 10.2% and a >90% device yield.

In this paper, we present mode-locked operation of a monolithic 20GHz integrated extended cavity ring laser. The 4mm-long laser ring cavity incorporates a 750µm-long optical amplifier section (SOA), a separate 40µm-long saturable absorber (SA) section, passive waveguide sections (shallow and deep etch) and a passive MMI-type 50% output coupler. The active sections contain a four quantum well active layer. The output waveguides are tilted under an angle of 7° to minimize back reflections into the device. Device fabrication has been carried out in the JePPIX technology platform [1]. A mask layout image of the device under test is shown in Fig.1.

We report the formation of site-controlled InAs quantum dots (QDs) on InP pyramids and their integration into planar structures by metalorganic vapor-phase epitaxy. The QD number is reduced by the shrinking pyramid size during growth. Finally the emission from a single QD is observed at 1.55 µm, after optimization of the growth parameters. Employing regrowth epitaxy, position-controlled InAs QDs are integrated into planar InP structures. A smooth surface morphology is obtained at 640 °C during regrowth.

We present experimental evidence that asymmetric current injection in intracavity contacted vertical-cavity surface-emitting lasers (VCSELs) stabilizes the polarization of the emitted light. Anisotropies in the gain and loss mechanisms introduced by asymmetric current injection are considered to explain this effect. The design scheme opens perspectives to obtain actual polarization control in VCSELs.

We developed an InP-based photodetector which was bonded on a CMOS wafer containing a Si 3 N 4 -wiring photonic circuit. The detector fabrication is compatible with wafer scale processing steps, guaranteeing compatibility towards future generation electronic IC processing. Integration technology and experimental results are presented in this paper.

Integrated InP/InGaAsP phased-array 1×16 optical switch is fabricated and characterized for broadband WDM optical packet switching. Wavelength-insensitive operation covering the C-band and penalty-free transmission of 40-Gbps signal are demonstrated.

Scalable quantum dot based optical switches offer energy-efficient low-latency data routing. Low power penalty routing over multiple stages are feasible with with the prospect of larger scale photonic integration.

A compact cascaded crossbar element with low power penalty, high distortion threshold and low crosstalk penalty is presented. Dual-stage monolithic switch integration is facilitated using a quantum dot epitaxy at 1550nm wavelength.

A versatile sealing process for AlAs layers is presented. This sealing prevents the AlAs layers of AlAs/GaAs top distributed Bragg reflectors from further undesired oxidation during the wet oxidation of the AlAs current constriction layers in vertical cavity surface emitting lasers. This method has been successfully applied to protect the etched pillars in top mirrors although those pillars were plasma dry etched. © 1999 The Electrochemical Society. S1099-0062(98)07-019-9. All rights reserved.

In this paper, we present a low cost and polarization independent photoreceiver which is part of the optical network unit (ONU) for the fiber access network. It consists of one InP-photodetector and a low cost SiGe amplifier. It operates error free with 223 - 1 PRBS word length at 1.25 Gbit/s with -13 dBm input optical power before the fiber chip coupling whose loss is about 5 dB. From the rise and fall time shown in measured eye diagram, it is estimated that it will also operate up to 2.5 Gbit/s.

A waveguide photodetector (PD) based on semi-insulating (SI) indium phosphide (InP) was simulated, designed, and fabricated. The layer stack for this PD was optimized for use as an optical amplifier or laser and it can be combined with the passive components. By using an SI substrate and deep etching, a small, efficient, and high-speed PD was made, which allows for easy integration of source, detector, and passive optical components on a single chip. A 3-dB bandwidth of 35 GHz and 0.25 A/W external radio-frequency reponsivity is measured at 1.55-mum wavelength for a 1.5-mum-wide and 30-mum-long waveguide PD at -4-V bias voltage. The polarization dependence in the responsivity is less than 0.27 dB.

All-optical packet switching at high bit-rates is discussed. We focus on the utilizing monolithically integrated devices to achieve high-bit-rate operation.

All-optical packet switching is discussed. In particular, we focus on the utilisation of monolithically integrated building to achieve high-bit-rate operation.

We report the first time ever fabrication and characterisation of a Cross Waveguide Grating (XWG) device.

The novel hot electron injection laser (HEL), a three-terminal vertically integrated transistor-laser structure, is designed to investigate and possibly utilize the effects of carrier-heating on the optical gain and wavelength chirp. Simulations show the potential of carrier heating assisted gain switching to directly modulate the optical field intensity at frequencies up to 100 GHz while maintaining control over the wavelength chirp. The HEL is designed to demonstrate these results through independent but complementary control over the concentration and the energy of the electrons injected into the active layer. Previous research has shown though that proper LIV behavior and a strong carrier heating efficiency requires a trade-off between electron heating and hole leakage current. Furthermore, stringent control over the epitaxial growth is crucial for these devices. Recent devices now show proper LIV behavior and strongly reduced threshold current densities around 2 kA/cm2 at room temperature. They also show the external `heating' voltage modulating the intensity of the lasing mode. The possible link between this modulation and carrier heating is further explored

This article reviews the recent progress in the growth and device applications of InAs/InP quantum dots (QDs) for telecom applications. Wavelength tuning of the metalorganic vapor-phase epitaxy grown single layer and stacked InAs QDs embedded in InGaAsP/InP (100) over the [email protected] region at room temperature (RT) is achieved using ultra-thin GaAs interlayers underneath the QDs. The GaAs interlayers, together with reduced growth temperature and V/III ratio, and extended growth interruption suppress As/P exchange to reduce the QD height in a controlled way. Device quality of the QDs is demonstrated by temperature-dependent photoluminescence (PL) measurements, revealing zero-dimensional carrier confinement and defect-free InAs QDs, and is highlighted by continuous-wave ground-state lasing at RT of narrow ridge-waveguide QD lasers, exhibiting a broad gain spectrum. Unpolarized PL from the cleaved side, important for realization of polarization insensitive semiconductor optical amplifiers, is obtained from closely stacked QDs due to vertical electronic coupling.

We demonstrate that 80 Gb/s data-packets can be all-optically switched into two different ports employing an optical wavelength converter controlled by a monolithically integrated optical flip-flop memory. The optical wavelength converter consists of a semiconductor optical amplifier and an optical filter. The integrated optical flip-flop exhibits single-mode operation, has 35 dB contrast ratio between the states and switches state in about 2 ns. We show that the integrated flip-flop is capable to control an optical wavelength conversion up to 160 Gb/s. The system is capable of routing 80 Gb/s data packets with duration of 35 ns, separated by 15 ns of guard time.

An integrated InP-InGaAsP two-state coupled-laser device for use in optical packet switching and signal processing is presented. The two states are identified by distinct lasing wavelengths. Single-mode lasing occurs in both states and the contrast ratio between the two states is 35 dB. Switching between states with optical pulses is demonstrated. The use of an arrayed waveguide grating (AWG) and ring laser configuration permits monolithic integration without the need for cleaved facets. How the AWG can be used to obtain partial isolation between multiple interconnected devices is also discussed.

We have developed a scanning tunneling microscope using an optoelectronic switch which gates the tunneling tip current. The switch is fabricated within several tens of microns from the tip by photolithography and an accurate cleavage method. We demonstrate this approach by detecting picosecond electrical transients on a coplanar stripline. We have investigated the signal dependence on contact resistance and found significant differences when the tip is brought from low-ohmic contact into the tunneling regime.

An InP-based integrated beamformer for beamsteering of a four-element Phased-Array Antenna has been designed, fabricated and characterized. This beamformer consists of an AWG, 14 high-speed MZI switches, and 9delaylines integrated on a single compact chip.

We have investigated the potential of asymmetric current injection for polarization switching in GaAs-based intracavity contacted vertical-cavity surface-emitting lasers using two sets of p- and n-type contacts per device. When using the contacts aligned along the [11~0] crystal direction, the observed laser polarization is parallel to [110], whereas, using the contacts along the [110] crystal direction, the polarization of the laser emission switches to a direction making an angle of 25/spl deg/-90/spl deg/ towards [110]. To overcome this peculiar result, a careful design of the contact layers in the intracavity structure is required.

Etched mirror lasers offer the possibility of being integrable in Opto-Electronic Integrated Circuits (OEIC). A versatile processing technique of GaAs/AlGaAs Wet Chemically Etched Mirror Lasers (WCEML) has been developed previously. It is applicable to all laser structures in the InGaAs/AlGaAs/GaAs system. A special set of masks allowed us to vary the cavity lengths of ridge waveguide type devices from 750 /spl mu/m down to 11 /spl mu/m and ridge widths of 4, 6 and 10 /spl mu/m. The processing requires four photolithography steps. In this paper we report on the results obtained from four different GRINSCH laser structures: one having a bulk GaAs active layer (50 nm thick) while the others have 2, 3 and 5 QWs of 7 nm GaAs as an active layer respectively.

Dynamical microroughening of the etch front of InP[100] due to Electron Cyclotron Resonance plasma etching was investigated. A quantitative study of the etch front morphology shows that the scaling law holds and the observed structure is self-affine. The low value of the growth exponent (/spl beta/=0.37) indicates that neither plasma reemission nor geometrical shadowing controls the Electron Cyclotron Resonance etching of InP.

A low-confinement asymmetric GaAs-AlGaAs double-quantum-well molecular-beam-epitaxy grown laser diode structure with optical trap layer is characterized, The value of the internal absorption coefficient is as low as 1.4 cm/sup -1/, while keeping the series resistance at values comparable cm with symmetrical quantum-well gradient index structures in the same material system. Uncoated devices show COD values of 35 mW//spl mu/m. If coated, this should scale to about 90 mW//spl mu/m. The threshold current density is about 1000 A/cm/sup 2/ for 2-mm-long devices and a considerable part of it is probably due to recombination in the optical trap layer. Fundamental mode operation is limited to 120-180 mW for 6.5-/spl mu/m-wide ridge waveguide uncoated devices and to 200-300 mW for 13.5-/spl mu/m-wide ones, because of thermal waveguiding effects. These values are measured under pulsed conditions, 10 /spl mu/s/l ms.

An experimental equivalent of the lumped circuit model of a photoconductively gated scanning tunneling microscope (PG-STM) is studied. This model can be used as long as the distance between the tunnel-junction and the pc-switch is small. For suitable parameters it implies a response-time below the carrier lifetime in the pc-switch.

This paper reports on low confinement (Γ= 7.5 x 10-3/well), DQW 2 x 8 nm asymmetric laser diode structure designed for high power operation [1]. The low value of Γ is achieved by adding an optical trap layer at one side of the QW’s. A significant part of the optical field is trapped in the n-type Al0.20Ga0.80As optical trap layer with a thickness cf about 0.2 μm, as shown in fig. 1.

Three terminal (3T) Double Barrier Resonant Tunneling (DBRT) devices having the base contact to the quantum well have been fabricated from GaAs/AlAs material system. The technological solution is based on high selective etching processes to reach the plane of the very thin quantum well on which, subsequently, a Schottky base contact is obtained using a nonalloyed Ti/Pt/Au metallization scheme. DC and AC electrical measurements demonstrate that the base contact lies on the quantum well of the DBRT structure and the base voltage modulates the collector current. It is shown that the electrical characteristics of these devices enlarge the possibilities of investigations on DBRT structures and suggest important applications in high-speed electronics.

We have developed a scanning tunneling microscope using an optoelectronic switch that gates the tunneling tip current. The switch is fabricated within 30 mm from the tip by photolithography and an accurate cleavage method. We demonstrate this approach by detecting picosecond electrical transients on a coplanar stripline. We have investigated the signal dependence on contact resistance and found significant differences when the tip is brought from low-ohmic contact into the tunneling regime. In this regime, the THz signal amplitude was found to depend linearly on the tunnel conductance, and disappeared when the tip was retracted.

It was recently proposed,1,2 that the power density related to the window width (in W/μm) of a laser diode can be substantially improved using a low confinement epitaxial structure. Keeping a reasonable high value of the intrinsic gain in the active region, a low confinement structure shall work also with a low modal gain value. The power optimization process is essentially connected to the attenuation coefficient of the laser waveguide α. When operating with an α value around 1 cm−1 and pursuing a high differential efficiency, the modal gain should have a value around 5 cm−1 and the laser length should be increased accordingly.2 A beneficial consequence of the low modal gain value is the possibility to increase the stripe width while preserving well the operation in the fundamental lateral mode above the threshold.

A highly compact quantum dot semiconductor optical amplifier based crossbar switch is proposed, fabricated and demonstrated at a wavelength of 1550 nm. Power penalty measurements at 10 Gbit/s show minimal path dependence with values of 0.15 to 0.25 dB and an extinction ratio of 24 dB.

The linear polarization of the optical gain of closely stacked InAs∕InP (100) quantum dots (QDs) grown by metal-organic vapor-phase epitaxy with emission wavelength tuned into the 1.55μm region is controlled by the number of stacked QD layers and the injection current. Increasing the number of stacked QD layers to five rotates the linear polarization of the cleaved-side photoluminescence and QD ground state (GS) gain, determined from the amplified spontaneous emission (ASE) of a Fabry–Perot ridge-waveguide laser, from transverse electric (TE) to transverse magnetic due to vertical electronic coupling. When the QD GS ASE and gain saturate with an increase of the injection current and the excited state ASE and gain become dominant, the linear polarization of ASE and gain changes back to TE. This limits the polarization insensitive operation of QD-based semiconductor optical amplifiers, however, opening routes to novel functionalities.