Search

We present two different photonic integrated circuits aimed to generate electrical signals within the microwave and millimeter wave range with two different techniques. The first approach uses the heterodyne technique, implementing a monolithic dual wavelength source by integrating on a single chip two distributed feedback (DFB) lasers together with the high speed photodiode. The second approach, using mode locked lasers, describes a novel device structure based on multimode interference reflectors (MIR).

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 an integrated approach to obtain two color emission from a semiconductor ring laser with filtered optical feedback. This feedback is realized on-chip by employing two arrayed waveguide gratings to split/recombine light into different wavelength channels. Semiconductor optical amplifiers are used in the feedback loop to control the feedback strength of each wavelength channel independently. Results show that the effective gain of the different modes is the key parameter which has to be balanced to obtain two color emission. This can be achieved by tuning the injection current in each amplifier.

We report on an integrated approach to obtain two color emission from a semiconductor ring laser with filtered optical feedback. This feedback is realized on-chip by employing two arrayed waveguide gratings to split/recombine light into different wavelength chan nels. Semiconductor optical amplifiers are used in the feedback loop to control the feed back strength of each wavelength channel independently. Results show that the effective gain of the d(tferent anodes is the key parameter which has to be balanced to obtain two color emission. This can be aclueved by tuning the injection current in each amplifier

In this work we describe the fabrication and characterization of couplers realized with a wet etching process that is compatible with the standard COBRA active-passive process. The implementation of this broadband structure allows for wafer-scale waveguide loss and absolute-wavelength measurements.

By implementing SOAs that guide two waveguides through a single contact active section, we can reduce dimensions ofphotonic integrated circuits (Tics.) and decrea,ce the number of electrical contacts of current injection. In this paper we demonstrate linear 4-channel and 8-channel A WG-based lasers that take advantage of such SOAs. This resulted in a reduction of the required number of active regions and contacts by a factor Iwo. Measurements showed that these sources operate with an output power of I in W per A WG-channel and side-mode suppression ratio better than 40 dB. The lasers were fabricated in a multi-project wafer run on an indium phosphide (InP,) based generic photonic integration platform.

We present a monolithically integrated ring dual-wavelength semiconductor laser in which both wavelengths (¿1 and ¿2) are generated and amplified by the same semiconductor optical amplifier (SOA). An arrayed waveguide grating (AWG) is used as intra-cavity filter to combine the two wavelengths. The use of a Mach-Zehnder construction allows equalizing actively the power of ¿1 and ¿2 and tuning their frequencies. An analytical model is exploited to investigate the influence of crosstalk on the functioning of the device and to identify a calibration strategy. The device has been fabricated using active/passive integration technology on a standardized photonic integration platform.

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.

Electro-optical modulato,cc are considered to be a key devices for optical interconnects. In order to implement this device in the new InP membrane On Silicon platform (IMOS), a slot—waveguide configuration with a high nonlinear polymer is studied. Simulations and electrical calculations show good peiformance and fabrication tolerance using n-doped InP as the slot-waveguide material. The small dimensions of the structure and the high electro-optical coefficient of the polymer allow devices with a smnallfootprint (hundreds ofp2), high bandwidth (> 100GHz) and low Va x L value (~-~ 0.7Vmmn). This solution is suitable or integration with passive devices already developedfor this platform, and with active devices that are under development.

Particle detectors in High Energy Physics experiments provide huge amounts of data which needs to be transported to the data center. Fiber-optic links provide a highcapacity low-mass solution. Howevem~ the petformance of semiconductor lasers used in such links is shown to degrade by the amount of radiation that is generated when particles with high energy collide. We investigate a wavelength-division multiplexing (WDM,) scheme in which only the semiconductor modulators are in the high radiation environment; and test the modulators for radiation hardness. The InP-based WDM modulator circuits are designed .for fabrication on generic integration platforms. The samples will be irradiated with a 23 Me V proton beam at Karlsruhe Institute of Technology (KIT) up to various doses. Here we discuss the system concept and preliminary measurements of non-irradiated samples that will later be compared with the irradiated samples.

In this paper we numerically investigate the thermal crosstalk reduction that can be obtained by etching deep trenches in Indium Phosphide based photonic integrated circuits. We show how deep trenches between adjacent components inod(j5.’ the heat transfer path. The current injected in active components and the geometly of the trenches are the parameters considered in our analysis. We demonstrate how the geometry of the trenches play a role in the reduction of the thermal crosstalk. The nwnerical results show a reduction of the distance between components up to 50%.

A remotely reconfigurable wavelength selective switch is proposed which implements label detection and signal gating in the same SOA array. A proof of principle monolithic circuit is presented showing dynamic nanosecond label-controlled switching.

We report our recent results on utilization and optimization of the focused ion beam technique for the fabrication of grating structures for potential integrated photonic devices in crystalline KY(WO4)2:Yb3+. The FIB milling procedure for the realization of grating structures in KYW channel waveguides was optimized. Grating structures more than 4 µm in depth with an improved total sidewall angle of 4.3 were achieved by varying dwell time and pixel resolution distribution. Currently optical characterization of the resonator structures for achieving on-chip waveguide lasers is ongoing.

We report on the fabrication and characterization of a distributed feedback channel waveguide laser in erbium-doped aluminium oxide on a standard thermally oxidized silicon substrate. Holographically-written surface-relief Bragg gratings have been integrated with the aluminium oxide waveguides via reactive ion etching of a silicon dioxide overlay film. The laser operates at a wavelength of 1545.2 nm and exhibits a threshold of 2.2 mW absorbed pump power, while it produces a maximum output power of 3 mW. The emission is TE polarized and has a Lorentzian linewidth of 1.70±0.58 kHz, which corresponds to a Q-factor of 1.14×E11.

Foundry services for PICs open the way to realize economically complex optical functionality. In the expanding field of fibre sensors Brillouin scattering is a powerful effect for determining strain and temperature distributions along fibres. However, the high cost of the optical circuitry has prevented wide use of this technique. Here a design study is reported for a foundry-based Brillouin Optical Time Domain Reflection (BOTDR) read-out unit with low-cost potential. The circuit contains narrow linewidth tuneable DBR-lasers, photodiodes with an optical mixer for coherent detection, a switchable delay line for frequency tuning and a switching fabric which allows three modes of operation.

Recently we presented a novel discretely tunable that consists of a Fabry-Perot laser which was forced to operate in single-mode condition by applying on-chip filtered feedback. The laser switches extremely fast and requires simple on/off control currents to switch the wavelength. In these first devices it was not possible to control the phase of the feedback light independently from the feedback intesity. In was solved by adding an extra electrode allowing us to control the phrase seperatly. In this paper we present the new device and study the effect of the control of the feedback phase in order to improve the performance of the original tunable laser concept.

Incoherent QAM is a differentially detected, multilevel modulation format that can improve spectral efficiency in optical communication systems. The effect of three receiver impairments on the performance of an incoherent QAM system is assessed in this paper for the first time. Specifically, the impairments studied are an unbalanced Mach-Zehnder Interferometer (MZI,), the phase detuning of the MZI and the amplitude imbalance of the Balanced Photodetectors (BPD). Extensive simulations were carried out and results indicate that incoherent QAM is quite robust in respect to the aforementioned impairments, with the phase detuning being the most critical parameter leading to peiformance degradation

We present experimental results of silicon-oxynitride (SiON) based arrayed waveguide grating (AWG) spectrometers operating around 800 nm and 1300 nm. A 100-channel AWG with 0.4 nm channel spacing centered at 1300 nm and a 125-channel AWG with 0.16 nm channel spacing centered at 800 nm have been fabricated and characterized. The measured crosstalk and insertion loss values near the central wavelengths were ranging between -22 and -32 dB and between 3.2 and 2 dB for 800-nm AWG and 1300-nm AWG, respectively. The highest wavelength resolution (0.16 nm) and the largest free spectral range value (38.8 nm) have been achieved in SiON technology so far.

We investigate methods for monolithically integrated multiwavelength transmitters in indium phosph ide-based materials. In particular, we focus our interest on two transmitter types. The first uses arrayed waveguide grating as wavelength selective element and the second one takes advantage ofDBR lasers that are integrated with electro-optical Mach-Zehnder modulators. In this paper we explain the operation principles and demonstrate the design process of the multiwavelength sources. We also present the mask layouts of the devices that will be fabricated in a multi-project wafer run within the EUNMPprogramme EuroPIC.

All-optical devices such as optical filters, (de)multiplexers, switches, modulators and optical buffers etc. have been demonstrated either on silicon or hybrid silicon platform. Power consumption, speed of operation, bandwidth and footprint etc. are important performance metrics for on-chip interconnects. Here we present the experimental and theoretical analysis of the performance of an all-optical gate, realized on III- V/SQl platform, for its applications in on-chip photonic interconnects.

InP membrane disc lasers have been considered as light sources for off chip data communication for logic microprocessors or for all optical logic devices such as gates and flip-flops. However, another family of CMOS devices can benefit greatly from integration of on chip light sources, mixed-signal and analog CMOS. In this paper we discuss recent results in the application of disc lasers for analog signal transmission such as radio over fiber. Large analog modulation bandwidth is demonstrated, and transmission of 64 and 256 QAM signals on a 5GHz RF carrier is successfully demonstrated with low EVM performance penalty

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.

Lateral arrangements of size and number controlled InAs quantum dots (QDs) on truncated InP (100) nanopyramids grown by selective area metalorganic vapor-phase epitaxy (MOVPE) are reported. The QDs nucleate on high-indexfacets on pyramids top allowing precise position and distribution control. The size and shape of QDs are related to As/P exchange determined by the growth temperature, as demonstrated for circular-based pyramids. The QD number is controlled by both the size of the highindex facets (governed by pyramids top area) and As/P exchange (governed by growth temperature). Sharp emission peaks from individual QDs are observed around 1.55 pm.

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.

Nanowire superconducting single photon detectors (SSPDs) are unique detectors for many applications in quantum information and communications technology, owing to their ultrafast photoresponse, low dark count rate and low timing jitter. However, they have limited detection efficiency due to small optical absorption in ultrathin wires. A promising approach to increase the photon absorption in SSPDs, is integrating them with advanced optical structures. We demonstrate the successful integration of SSPDs with optical microcavities based on GaAs/AlAs Bragg mirrors. Characterization of these devices reveals clear cavity enhancement of the detection efficiency, resulting in a peak value of18% at 2=l300nm and T=4.2K