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Indium Phosphide integrated photonics enables the combination of high-speed lasers and modulators with filters, detectors and multiplexers in one wafer-scale process flow. Low-voltage modulation at rates of 50Gigabit/second and above are feasible with combinations of semi-insulating substrates, optimised multi-quantum wells and high-speed electrical design. Advances in monolithic InP platform technologies have created a mechanism to rapidly introduce such high performance building blocks into sophisticated integration processes, enabling photonic integrated circuits with many tens of active components including distributed feedback lasers, tunable lasers and a range of passsive components. Our recent introduction of 192nm deep UV scanner lithography - believed to be a world first for InP integrated photonics - also enables a step change in the performance for the integrated filters and mode control. In this paper, we present recent innovations in the creation of high performance transceiver technologies for optical interconnects. We showcase circuits using InP integrated photonics to create high-speed, energy-efficient, optically-multiplexed circuits. Monolithic polarization multiplexing and wavelength domain multiplexing are reviewed where all components, inclusive of the lasers, are created in the same wafer. Line-rates of up to 320 Gb/s are demonstrated for optically multiplexed circuits using a variety of open access fabrication platforms. The challenges and approaches for Terabit/second class transceiver chips will be addressed, addressing crosstalk management, component miniaturisation, and intimate electronic integration.

The indium phosphide (InP) photonic integrated circuit (PIC) industry has been offering sensing solutions on a chip, with high precision and low cost. The major application is sensor signal read-out. Its next generation, where the InP PICs are much smaller and faster, enables new sensing opportunities. We review our recent developments in the next-generation InP PIC, and discuss their potential in optical sensing.

A tunable laser operating from 2011 – 2042 nm realized as a monolithic InP photonic integrated circuit and fabricated within a multi project wafer run is presented. The laser is tuned using an intracavity filter based on nested asymmetric Mach-Zehnder interferometers with electrorefractive modulators. The device is intended for a single line gas spectroscopy and was designed and realized using a generic integration technology.

InP generic processes allow monolithic integration of sources, passive elements and detectors on a common p-n doped layerstack. The passive loss can be greatly reduced by formation of local p-n junctions by means of Zn-Diffusion or regrowth. The attainable loss is experimentally derived from spiral ring resonators, coupled to a waveguide via multimode interference. By folding the ring into a spiral we obtain circumferences up to 73 mm, with a footprint of 2.4 mm x 3.6 mm. We measure a quality factor of 1.2 million and extinction ratio of 9.7 dB, implying a loss below 0.4 dB/cm

Au spiking is a long-standing problem for Ni/Ge/Au ohmic contacts on n-InP. This becomes more critical when the contacts are deposited on top of thin membrane devices. In order to reduce the spiking while maintaining a low resistance, we present a new approach which reduces the amount of Au in these contacts. A low specific contact resistance of 7×10-7 O cm2 is obtained after a 15 s annealing at 400 ºC. Afterwards the contacts can be thickened with an extra deposition of metals. Scanning electron microscope pictures show abrupt and uniform interfaces between metals and semiconductors.

Integrated spot size converters (SSCs) are key components for efficient coupling between Photonic Integrated Circuits (PICs) and fibre-arrays. We report a compact SSC which is suitable for integration into dense arrays with a pitch down to 25 µm and compatible with our generic InP-based platform technology, which supports integration of SOAs and Electro Optical Modulators with a range of passive components. The small pitch supports coupling tens of on-chip optical waveguide ports to fiber arrays via a low-loss dielectric interposer chip. The density allows the design of a customized optical bus between the InP PIC and the interposer chip. The dielectric chip may simply expand to the pitch of a fiber array but also contain low-loss passive circuitry like delay-lines, high Q-filters and multiplexers. The latter enables the formation of a hybrid integration platform with our InP-based technology. Efficient coupling is obtained by adiabatically transforming the sub-micron modes of the InP waveguides to the 3 µm diameter mode of the interposer. We tested our SSCs by coupling to a lensed fibre with a mode field diameter of 2.5 µm. Coupling losses were found to be as low as 0.6 dB per fiber chip coupling for device lengths of a few 100 µm. We also measured the crosstalk from one input port to output ports adjacent to the targeted output port. We present simple design rules for reducing the crosstalk to neighbouring output ports below -50 dB. The quality and uniformity of the SSCs is demonstrated by fabrication of an 8 x 8 AWG demultiplexer between two SSC arrays placed at input and output ports. We measured an insertion loss between fibres of 4 dB for the central channel of the AWG, which is record low for an InP-based device.

Application Specific Photonic Integrated Circuits (ASPICs) are considered key elements to make photonic systems or subsystems cheap and ubiquitous. ASPICs still are several orders of magnitude more expensive than their microelectronic counterpart: ASICS, which has restricted their application to a few niche markets. A novel approach in photonic integration is emerging that will reduce the R&D costs of ASPICs by more than an order of magnitude. It will bring the application of ASPICs that integrate complex and advanced photonic functionality on a single chip within reach for a large number of small and larger companies and initiate a breakthrough in the application of Photonic ICs. In this paper the process is explained. A significant number of designs has been realized the last 4 years, for a variety of applications in telecoms, datacoms, medical and sensing, from parties all over the world.

Electrically pumped metal-cavity nanolasers in III-V semiconductors are promising for their application in optical interconnects, where high integration density and low optical powers are required. They offer a low threshold current and excellent cooling properties due to the metal encapsulation. In this contribution, an overview about the technology required for the fabrication of a nanolaser coupled to an InP-membrane waveguide on silicon is presented. A variety of techniques are used including electron-beam lithography, dry and wet etching, as well as deposition of dielectrics and metals. The technological challenges to fabricate such a complex nanostructure are also discussed.

The InP Membrane on Silicon (IMOS) generic technology promises high index contrast photonic integrated circuits. To make this a reality fabrication of an electrically pumped twin-guide laser is pursued. In this paper, one of the bottle-necks for the processing is discussed, the planarization step and subsequent etch-back. Benzocyclobutene (BCB) is used to planarize SOA structures before contacting. Complete curing of BCB at 280oC creates uniformity issues during etch-back. To mitigate this, a partial cure at 180oC before the etch-back and a complete cure afterwards is performed. Experiments show repeatability and reproducibility. Good uniformity after etch-back is found.

We are developing a generic integration platform for Fhoto,iic Integrated Circuits with a target wavelength of2 pm. The platform is based on the platform process .for 1.55 pm which supports monolithic integration of a wide range of passive and active components as anipl~fiers, modulators and detectors. In this paper we discuss the extension to longer wavelengths and its impact on the performance of the passive components. supported by initial characterization results of the waveguide loss and an Arrayed Waveguide Grating in a wavelength windowfrom 1.88 to 2 pm.

Highly integrated photonic InP circuits raise the demand for an augmented number of optical ports. Therefore, we present the integration of an optical bus in our generic platform consisting of a compact Spot-Size Converter (SSC) array, and we demonstrate it by connecting it to an 8 x 8 AWG. The SSCs have a 25 µm pitch and expand the mode from 0.5 µm in the AWG waveguide layer to 3 µm after the SSC. The adiabatic conversion is based on a vertical taper with two linear sections. We measured 0.7 dB loss per fiber-chip coupling for a 700 µm long SSC device.

Europe is making significant investments in development of generic photonic foundry platform infrastructures for InP-based and Silicon Photonic ICs. Here we present the present status for the InP-based JePPIX platform.

In this paper we present the design and characterization of a monolithically integrated tunable laser for optical coherence tomography in medicine. This laser is the first monolithic photonic integrated circuit containing quantum-dot amplifiers, phase modulators and passive components. We demonstrate electro-optical tuning capabilities over 60nm between 1685 and 1745nm, which is the largest tuning range demonstrated for an arrayed waveguide grating controlled tunable laser. Furthermore, it demonstrates that the activepassive integration technology designed for the 1550nm telecom wavelength region can also be used in the 1600-1800nm region. The tunable laser has a 0.11nm effective linewidth and an approximately 0.1mW output power. Scanning capabilities of the laser are demonstrated in a free space Michelson interferometer setup where the laser is scanned over the 60nm in 4000 steps with a 500Hz scan frequency. Switching between two wavelengths within this 60nm range is demonstrated to be possible within 500ns.

An ultra-short (

In recent years, the Photonics industry has evidenced a great interest for going toward Photonic Integrated Circuits (PICs) operating at wavelengths beyond 1.55 µm. The COBRA research group at the University of Eindhoven has initiated development of a generic integration platform functioning at wavelengths up to 2.1 µm. At present, our research is focused on Semiconductor Optical Amplifiers (SOAs), reversely biased phase shifters, passive waveguides and dense Spot-Size Convertor (SSC) arrays as building blocks for such a platform. Here we present results about several active materials tested in a Fabry-Pérot structure and lasing at wavelengths as long as 2.06 µm. In addition, some investigations are performed for lowering the loss level in passive waveguides via local Zinc diffusion restricted to the active areas.

This paper describes a Generic InP-based Photonic Integration Technology that enables fabrication of a large variety of active- as well as passive circuits. In the COBRA clean room in Eindhoven a robust modular process flow is developed which consists of more than 10 depositions (including epitaxial growth), about 10 lithography steps (depending on the design) and more than 20 dry and wet etching steps. This process can be used to fabricate different circuits on one wafer in so-called multi-project wafer runs which allows a drastic reduction of the fabrication costs making even small-volume production economically feasible.

We report on design and measurement of a series of spot-size converters (SSCs) for adapting the optical mode size in an InP-based photonic integrated circuit. SSCs are designed to transfer the mode of a 0.6mm-thick high-contrast waveguide to that of a 3mm-thick low-contrast waveguide below the core layer using a vertical taper. Fabrication of the taper is compatible with the standard processing and coupling loss values below 1dB have been achieved. Based on the experimental results we have designed an improved structure which enables adiabatic vertical coupling for taper lengths below 1mm. The simulation results predict losses below 0.5dB

only.

In this paper, we present the design, fabrication, and characterization of two monolithically InP-based integrated electro-optically tunable filters. The combination of these filters can be used to achieve a filter with a narrow passband and a large free spectral range. These filters are designed to be used in an integrated tunable laser source in the 1600-1800 nm wavelength region using active-passive integration technology. The fact that these filters worked successfully shows that this integration technology, originally designed to be used around 1550 nm wavelength, can also be used successfully in the 1600-1800 nm wavelength region without a large penalty in performance. The two filters, a high-resolution arrayed waveguide grating-type filters and a low-resolution multimode interferometer-tree-type filter are made tunable using 5 mm long electro-optic phase modulators in the arms of the waveguide arrays. Measurements show that these filters can be tuned over a wavelength range of more than 100 nm with an accuracy of 0.1 nm (1% of the free spectral range) for the high-resolution filter and an accuracy of 9 nm (4% of the free spectral range) for the low-resolution filter.

Recently, an ultra-short polarization converter in Indium phosphide membrane was proposed with excellent simulated performance. In this paper, we present experimental results showing that this device can be fabricated using high-resolution lithography and dry/wet-etch steps.

We investigate a new class of integrated mirrors, so called MMI reflectors. In addition to one-port full reflectors, we introduce two-port MMI reflectors, capable of both reflection and transmission. The reflection to transmission ratio in these devices can be set freely by changing their geometry. This is deinonstrated through numerical simulations as well as through a set ofworking devices realized on an indium phosphide layer stack.

The fabrication ofInP-based Photonic Integrated Circuits (PICs) is a complex process. The process used in the COBRA cleanroom in Eindhoven consists of 13 deposition, 10 lithography, 14 dry- and 7 wet-etching steps. Together with the intermediate cleaning, preparation and inspection procedures, the total process flow consists of 243 steps. In this paper we show how we created a robust modular process flow that can be usedfor a large variety of active- and passive circuits. These circuits can be fabricated together in multi-project wafer runs, allowing a drastic reduction of the fabrication costs making even small-volume production economicallyfeasible.

The design of an ultra-small (4.1 µm length) polarization converter in Indium phosphide (InP) membrane is presented. The device is modelled using a vectorial 2D mode solver. Simulations show strong conversion (> 94%) and low-loss operation (

To make a direct electrically pumped photonic crystal membrane laser is a challenging task. One of the problems is how to avoid short circuiting between the p- and n-doped parts of the laser diode, when the membrane thickness is limited to 200-300nm.In COBRA, we want to use the oxide of AlInAs to realize the current blocking Junction. In this way, together with a subinicron selective area re-growth technique, we expect to make electrically injected Photonic crystal lasers with higher pumping efficiency and small threshold currents, as well as low power consumption. In this paper results are presented on the development of oxidation of AlInAs. The results show that it is practically feasible to use oxide of AlInAs for current blocking in a photonic crystal laser in a InP-based membrane system.

The high vertical index contrast and the small thickness of thin InP-based membrane structures bonded with BCB on Silicon allow the realization of very small devices. To make photonic integrated circuits with both passive and active components in these membranes, active-passive integration on a small scale is essential. In this paper we will present our results on sub-micrometer active areas for membrane applications.

The high vertical index contrast and the small thickness of InP-based membrane structures bonded with BCB on Silicon allow the realization of very small devices. Since photonic integrated circuits consist of both passive and active components, a successful active-passive integration with sub-micrometer active regions is an essential step. In this paper we will present our results on active-passive integration with sub-micrometer active areas. The interference of active and passive area shows a good quality in terms of morphology. Moreover we find that in the sub-micrometer size active area, the degradation of the material(InGaAsP QWs) due to clean room processing is limited.