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Photonic integration in a micrometer-thick indium phosphide (InP) membrane on silicon (IMOS) offers intrinsic and high-performance optoelectronic functions together with high-index-contrast nanophotonic circuitries. Recently demonstrated devices have shown competitive performances, including high side-mode-suppression ratio (SMSR) lasers, ultrafast photodiodes, and significant improvement in critical dimensions. Applications of the IMOS devices and circuits in optical wireless, quantum photonics, and optical cross-connects have proven their performances and high potential.

Low-excess-loss arrayed waveguide gratings are enabled by unique application of deep UV lithography in InP integrated photonics through reduced feature sizes and, more specifically, well-resolved inter-waveguide gap dimensions. Submicrometer wafer-flatness is shown to be required to achieve the critical dimension uniformity better than 10 nm on 3-in substrates. Arrayed waveguide grating devices were fabricated and the effect of inter-waveguide gap scaling on the excess losses was measured and compared to simulations. Excess losses down to 0.15 dB were demonstrated to be lower than predicted with the 2-D simulations. The tapering of the etch depth inside the gaps due to the lag effect of the etch process may explain the improvements.

The standardization of photonic integration processes for InP has led to versatile and easily accessible generic integration platforms. The generic integration platforms enable the realization of a broad range of applications and lead to a dramatic cost reduction in the development costs of photonic integrated circuits (PICs). This paper addresses the SMART Photonics generic integration platform developments. The integration technology based on butt joint active-passive epitaxy is shown to achieve a platform without compromising the performance of the different components. The individual components or building blocks are described. A process design kit is established with a comprehensive dataset of simulation and layout information for the building blocks. Latest results on process development and optimization are demonstrated. A big step forward is achieved by applying high-resolution ArF lithography, which leads to increased performance for AWGs and a large increase in reproducibility and yield. The generic nature of the platform is demonstrated by analyzing a number of commercial multiproject wafer runs. It is clear that a large variety of applications is addressed with more than 200 designs from industry as well as academia. A number of examples of PICs are displayed to support this. Finally, the design flow is explained, with focus on layout-aware schematic-driven design flow that is required for complex circuits. It can be concluded that generic integration on InP is maturing fast and with the current developments and infrastructure it is the technology of choice for low cost, densely integrated PICs, ready for high-volume manufacturing.

For the first time we demonstrate the application of 193 nm optical lithography to InP-Membrane-on-Silicon (IMOS) passive nanophotonic integrated circuits. A record low propagation loss of $1. 3\pm 0.1\mathbf{dB}/\mathbf{cm}$ is demonstrated in a Mach-Zehnder interferometer (MZI) circuit and a microring resonator Q-factor up to $62 \cdot 10^{3}$ with 4 nm FSR is measured.

ArF deep UV (193 nm) lithography was successfully applied to fabricate Arrayed Waveguide Gratings in generic Indium Phosphide technology. The sub-dB transmission losses demonstrate the advantages of scaling down the minimum feature size to 100 nm.

We experimentally and numerically characterize the wavelength switching speed of a tunable semiconductor ring laser using filtered optical feedback. The feedback is realized employing two arrayed-waveguide gratings to split/recombine light into different wavelength channels. The wavelength tuning and switching is controlled by changing the currents injected in semiconductor optical amplifiers in the feedback section. A wavelength switching speed of a few nanoseconds is achieved. We investigate also the effect of the feedback parameters and noise strength on the wavelength switching speed.

All-optical regeneration has attracted growing interest due to the possibility to increase the all-optical reach. However, to be really competitive with optoelectronic regenerators, all-optical regenerators should process an entire wavelength division multiplexed (WDM) signal comb at once and significantly reduce the footprint and the power consumption, as possible, in principle, by exploiting photonic-integrated circuits (PICs). Moreover, since constant envelope modulation format signals have come into play in recent years, all-optical regenerators dealing with a multiplex of these signals are of particular interest. This paper presents a monolithically integrated indium-phosphide-based PIC acting as an all-optical regenerator for constant envelope WDM signals. The regeneration scheme is based on hard-limiting amplification in saturated semiconductor optical amplifiers (SOAs), which removes the signal intensity noise. The presented PIC, designed and fabricated within the JePPIX technology platform, can handle up to four WDM signals, which are demultiplexed and enter an array of SOAs to undergo regeneration before being multiplexed again. The channel-by-channel regeneration of both polarization shift keying and frequency shift keying signals at 10 Gb/s is experimentally demonstrated in terms of Q-factor improvement.

A monolithic InGaAsP/InP 4 × 4 cross-connect is designed, fabricated and demonstrated. Each of the four inputs fan out to two stages of semiconductor optical amplifier-based gates to perform broadband-input-selection and wavelength-specific-selection. Stages of parallel cyclic arrayed waveguide grating routers and wavelength-agnostic fan-ins allow independent electronically controlled routing of four unique wavelength channels between the four inputs and outputs. The circuit is realized within a 15 mm area on a multi-project wafer. Circuit performance is evaluated by resolving optical power loss within the circuit to show component level performance at and close to design specification. Data routing experiments for wavelength multiplexed signals are performed and quantified in terms of optical power penalty. Multi-path routing is performed with both co- and counter-propagating data. Bi-directional and fast reconfigurable routing is similarly quantified. Low power penalty of less than 1 dB is measured for the simultaneous routing of data over multiple circuit paths.

We introduce a novel concept of discretely tunable semiconductor lasers with on-chip filtered optical feedback. The integrated device is based on a semiconductor ring laser that can sustain two counter-propagating modes. By means of a directional coupler, part of the light emitted by the laser is coupled out to a feedback section integrated on the same chip. The feedback section contains two arrayed waveguide gratings and a set of semiconductor optical amplifiers to provide filtering of particular longitudinal modes sustained by the ring cavity. By controlling the current injected into the semiconductor optical amplifiers, single mode operation in both directions is achieved. In this paper, the design, characterization, and modeling of the device is presented.

We report on an integrated approach to obtain multiwavelength emission from semiconductor ring lasers with filtered optical feedback. The filtered feedback is realized on-chip employing two arrayed-waveguide gratings to split/recombine light into different wavelength channels. Through experimental observations and numerical simulations, we find that the effective gain of the different modes is the key parameter which has to be balanced in order to achieve multiwavelength emission. This can be achieved by tuning the injection current in each amplifier.

We fabricated and experimentally tested a novel monolithically integrated Indium Phosphide optical circuit for differential phase-shift keying demodulation, which is robust to noise degradations of the received signal. The circuit consists of a one-bit-delay interferometer that demodulates the incoming signal and a semiconductor optical amplifier where the constructive and destructive demodulated outputs synchronously counter-propagate experiencing a reshaping effect. The novel optical circuit has been fabricated for 40 Gb/s signals, and the amplitude signal restoration is demonstrated by comparing the obtained output eye diagrams with those of a commercial fiber-based demodulator. We find a net improvement in the signal to noise ratio when the circuit is fed with a noisy input signal.

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.

Photonic integrated circuits (PICs) are considered as the way to make photonic systems or subsystems cheap and ubiquitous. PICs still are several orders of magnitude more expensive than their microelectronic counterparts, which has restricted their application to a few niche markets. Recently, a novel approach in photonic integration is emerging which will reduce the R&D and prototyping costs and the throughput time of PICs by more than an order of magnitude. It will bring the application of PICs 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. The paper explains the concept of generic photonic integration technology using the technology developed by the COBRA research institute of TU Eindhoven as an example, and it describes the current status and prospects of generic InP-based integration technology

We report on a novel integrated approach to obtain dual wavelength emission from a semiconductor laser based on on-chip filtered optical feedback. Using this approach, we show experiments and numerical simulations of dual wavelength emission of a semiconductor ring laser. The filtered optical feedback is realized on-chip by employing two arrayed waveguide gratings to split/recombine light into different wavelength channels. Semiconductor optical amplifiers are placed in the feedback loop in order to control the feedback strength of each wavelength channel independently. By tuning the current injected into each of the amplifiers, we can effectively cancel the gain difference between the wavelength channels due to fabrication and material dichroism, thus resulting in stable dual wavelength emission. We also explore the accuracy needed in the operational parameters to maintain this dual wavelength emission.

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.

Summary form only given. Single laser chips that emit multiple wavelengths simultaneously are interesting for a range of applications including wavelength division multiplexing, optical instrument testing and optical sensing. A number of approaches have been proposed to achieve multiple wavelength emission (MWE) by e.g. using multiple lasers, but they tend to be bulky and/or expensive. Some of these structures need thermal tuning of the emission wavelengths, which is relatively slow and requires precise control of the chip temperature. In this work we report on a novel integrated approach in order to obtain MWE from a single semiconductor laser based on on-chip filtered optical feedback. The layout of our device is shown in Fig.1(a). It consists of semiconductor ring laser (SRL), two arrayed waveguide gratings which are used to split/recombine light into 4 different wavelength channels, four semiconductor optical amplifier gates and passive and active waveguides to connect these different components.We can select either triple wavelength emission, dual wavelength emission (DWE) or single longitudinal mode emission (SME) by properly adjusting the currents in the semiconductor optical amplifier gates of the feedback loop. An advantage of our device is that we can select the lasing longitudinal modes, and thus the emitted wavelengths, in a simple manner by changing the current in the feedback amplifiers. Wavelength selection is done in a non-thermal fashion, which can in principle be done fast. MWE is achieved in a SRL, which has the additional advantage that it can easily be integrated with other photonic components on a chip.Experimentally the device output without feedback is multi-mode above the threshold current (64 mA). SME can be achieved by pumping one gate with a suitable current [1]. When current is applied to two gates at the same time while the SRL is biased above threshold current, SRL shows DWE for a range of currents on gate 4 and gate 2. This DWE can be observed in the optical spectrum shown in Fig.1(b), at the top of this figure we show a schematic plot of the filter passband of each of the gate channels. The selected longitudinal modes are spectrally positioned within the arrayed waveguide gratings filter passbands corresponding to gate 2 and gate 4 which are chosen to be pumped. The two peak wavelengths are λ1 = 1580.788 nm (gate 4 channel), λ2 = 1583.288 nm (gate 2 channel). This DWE can be explained by the fact that a suitable amount of feedback cancels the gain difference between the wavelength channels due to fabrication and material dichroism. By increasing or decreasing the current injected in one of the pumped gates, we notice switching from two modes in the output to one of them. By pumping three gates instead of two and by precise adjustment of the currents in the gates, triple wavelength emission was observed with similar switching behavior to DWE and then to SME just by changing one of the gate currents. In this contribution we will further discuss the precise behavior of the MWE from the device. We will also show results from numerical simulations based on two directional-mode model[2] extended with Lang-Kobayashi terms to take into account for optical feedback. Some of these numerical results are shown in Fig.1(c). We plot in this figure the maxima of the intensities of the three modes when the feedback phase is equal to 0.5π for each mode. The first modes feedback strength η1 is fixed while the feedback strength η2 and η3 of the second and third modes are kept equal η2 = η3 and are increased simultaneously. As can be seen from Fig1.(c), the device output is changing from SME when (η2 = η3) η1. The numerical results are in qualitative agreement with the experimental observations, showing that MWE is obtained when the effective gain (which includes the effects of material gain, losses and feedback) of the longitudinal modes is equal.

Here, we numerically and experimentally demonstrate that, by combining two post-processing methods (multi-bit extraction and bitwise OR-exclusive (XOR) operations). in a single chaotic semiconductor ring laser (SRL), it is possible to generate true random bits with a bit rate up to 40 Gb/s from a chaos bandwidth of ˜ 2 GHz, thanks to the device ability of lasing in two directional modes and the fact that the two mode signals have low correlations. In addition, SRLs can be easily implemented on chip.

In this paper we show that using a DVS-BCB adhesive bonding process compact heterogeneously integrated III-V/silicon single mode lasers can be realized. Two new designs were implemented: in a first design a multimode interferometer coupler (MMI) - ring resonator combination is used to provide a comb-like reflection spectrum, while in a second design a triplet-ring reflector design is used to obtain the same. A broadband silicon Bragg grating reflector is implemented on the other side of the cavity. The III-V optical amplifier is heterogeneously integrated on the 400nm thick silicon waveguide layer, which is compatible with high-performance modulator designs and allows for efficient coupling to a standard 220nm high index contrast silicon waveguide layer. In order to make the optical coupling efficient, both the III-V waveguide and the silicon waveguide are tapered, with a tip width of the III-V waveguide of around 500nm. The III-V thin film optical amplifier is implemented as a 3 mu m wide mesa etched through to the n-type InP contact layer. In this particular device implementation the amplifier section was 500 mu m long. mW-level waveguide coupled output power at 20 degrees C and a side mode suppression ratio of more than 40dB is obtained.

Compact multi-frequency lasers are realized by combining III-V based optical amplifiers with silicon waveguide optical demultiplexers using a heterogeneous integration process based on adhesive wafer bonding. Both devices using arrayed waveguide grating routers as well as devices using ring resonators as the demultiplexer showed lasing with threshold currents between 30 and 40 mA and output powers in the order of a few mW. Laser operation up to 60°C is demonstrated. The small bending radius allowable for the silicon waveguides results in a short cavity length, ensuring stable lasing in a single longitudinal mode, even with relaxed values for the intra-cavity filter bandwidths.

The use of the postprocessing method consisting of bitwise Exclusive-OR and least significant bits extraction to generate random bit sequences typically requires two distinct chaotic outputs. While the two signals are, in general, generated using two separated devices, e.g. two Fabry-Perot lasers, a single semiconductor ring laser can be used as an alternative due to its circular symmetry which facilitates lasing in two counterpropagating mode directions. We consider a chaotic semiconductor ring laser and investigate both numerically and experimentally its char- acteristics for fast random bit generation. In particular, we show that by sampling each directional mode's output signal using a 8-bit analog-digital converter and through Exclusive-OR operation applied to the two resulting signals (after throwing away 4 most significant bits), we can achieve fast random bit-streams with a bit rate 4 × 10 = 40 Gbit/s, passing the statisti- cal randomness tests. To optimize the system performance, we also study the dependence of randomness on the main system parameters and on noise.

A 4-channel multi-wavelength laser integrated on a silicon waveguide circuit is realized. Waveguide-coupled output powers of 2mW and a side mode suppression ratio of more than 45dB for all channels is realized.

We demonstrate for the first time the simultaneous routing of three 40GB/s input signals through an integrated 4x4 broadcast and select wavelength selective switch. Power penalty less than 0.2dB is measured for multiple routed channels.

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.

A monolithic 4x4 WDM cross-connect is presented comprising a broadcast select switch and four wavelength selective switches. Multi-path routing is demonstrated for both co-and counter-propagating data with under 1dB power penalty indicating negligible crosstalk.

Heterogeneously integrated III-V-on-silicon second-order distributed feedback lasers utilizing an ultra-thin DVS-BCB die-to-wafer bonding process are reported. A novel DFB laser design exploiting high confinement in the active waveguide is demonstrated. A 14 mW single-facet output power coupled to a silicon waveguide, 50 dB side-mode suppression ratio and continuous wave operation up to 60°C around 1550 nm is obtained.

A monolithically integrated InP optical circuit performing current-controlled DPSK demodulation is reported. The circuit consists of an interferometric structure with a 1-bit delay SOA-amplified loop. Operation at 8 Gb/s in C-band is reported.

We report on an integrated approach to achieve fast wavelength switching in a semiconductor ring lasers using on-chip filtered optical feedback. The feedback section consists of two arrayed waveguide gratings and four semiconductor optical amplifiers. The wavelength tuning and switching are controlled by changing the injected currents into the semiconductor optical amplifiers. Experimental observations and numerical simulations show a wavelength switching speed of few nano seconds. We also investigate the effect of the feedback parameters and the noise strength on the wavelength switching speed.