X.J.M. Leijtens

Technische Universiteit Eindhoven, Eindhoven, North Brabant, Netherlands

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Publications (193)184.44 Total impact

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    ABSTRACT: This study presents the recently developed monolithic photonic-integrated circuits that provide efficient amplitude modulation for wavelength division multiplexed optical channels. The circuits were designed for application as a read-out unit in a high-energy physics experiment, and are sufficiently general to be applied in various types of high-speed photonic transmitters. They were constructed using basic building blocks provided in an indium phosphide-based generic integration technology process and fabricated in a multi-project wafer run. Two variants of the circuits, utilizing modulators in Mach–Zehnder and Michelson interferometer configuration, are discussed. A modulation bandwidth of 18.6 GHz was measured and error-free transmission of a 10-Gb/s signal through 85 km of optical fiber was achieved.
    Journal of Lightwave Technology 12/2014; 32(23). · 2.56 Impact Factor
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    ABSTRACT: 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.
    International Conference on Transparent Optical Networks (ICTON), GRAZ; 07/2014
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    ABSTRACT: Laser diodes that emit multiple wavelengths simultaneously are needed in a range of applications including wavelength division multiplexing, high speed optical networks, optical instruments testing, optical sensing and tera-hertz generation. In this work we report on an integrated approach to obtain multi-wavelength emission from a semiconductor ring laser based on on-chip filtered optical feedback. Semiconductor ring laser have the advantage that they can be easily integrated with other optical components as they do not require mirrors to form the cavity. Moreover, no thermal control of the wavelength emission is needed and therefore the device can be in principle fast. Ring lasers can be used for switching as they support lasing in two directions (clockwise and counterclockwise). The device consists of a semiconductor ring laser, two arrayed waveguide gratings and four semiconductor optical amplifiers. The different components are connected by passive waveguides. Light at the semiconductor ring laser's output is coupled to the arrayed waveguide gratings by a directional coupler. The filtered optical feedback is realized by employing the 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. Experimental observations have shown that the effective gain is the key parameter that has to be balanced using the feedback in order to achieve multi-wavelength emission. This can be achieved by tuning the injection current in each amplifier which will change the feedback phase and strength. We can select the number of emitted wavelengths by changing the number of gates being pumped. We can tune the emitted wavelengths by changing the currents injected in each of the gates. Numerical simulations using rate equation reproduce the experimental results and show the effects of feedback phase and strength on the multi-wavelength emission.
    SPIE Photonics Europe, Brussels; 04/2014
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    ABSTRACT: Semiconductor ring lasers are promising sources in photonic integrated circuits because they do not require cleaved facets or mirrors to form a laser cavity. In this work, we characterize the wavelength switching speed of a tunable semiconductor ring lasers using filtered optical feedback. The filtered optical feedback is realized 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 of each wavelength channel independently. The wavelength switching is achieved by changing the currents injected in the semiconductor optical amplifier gates. Experimentally, we observe a wavelength transition time of 5 ns. However, we also noticed a non-negligible delay in the switching process. [ Khoder et al, IEEE Photon. Technol. Lett. 26, 520{523, 2014]. We numerically reproduce the experimental results using rate equations taking into account the effect of spontaneous emission. The simulations further elaborate on the effect of the noise strength on the wavelength transition time and the delay time. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
    SPIE PHOTONICS EUROPE Silicon Photonics and Photonic Integrated Circuits IV, Brussels; 04/2014
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    ABSTRACT: We report a novel narrow-linewidth WDM transmitter operating at 10Gbps per transmission channel with 275kHz optical linewidth. The device was fabricated in generic InP-based foundry process and integrates AWG-laser with selective DBR-mirrors and Mach-Zehnder modulators.
    Optical Fiber Communication Conference; 03/2014
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    ABSTRACT: A ring mode-locked laser fabricated as a monolithic photonic integrated circuit using a InP based integration technology is presented. It generates an optical coherent comb around 1546 nm with a record 11.5 nm 3 dB bandwidth.
    Optical Fiber Communication Conference; 03/2014
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    ABSTRACT: 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 ns is achieved.We investigate also the effect of the feedback parameters and noise strength on the wavelength switching speed
    IEEE Photonics Technology Letters 03/2014; 26(5):520-523. · 2.04 Impact Factor
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    ABSTRACT: Parasitic reflections can deteriorate the performance of a photonic integrated circuit. This is especially true in circuits containing amplifiers, but even in passive circuits, small reflections can already have a strong influence on circuit performance. It is known that strong reflections can be present when using a 2$,times,$1 multimode interference coupler (MMI) as a combiner. We investigate methods for reducing these spurious reflections in a generic integration technology. We present a novel MMI shape whose measurements show reduced reflections by 17.5 dB.
    IEEE Photonics Technology Letters 01/2014; 26(4):408-410. · 2.04 Impact Factor
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    ABSTRACT: In this letter, we demonstrate a novel monolithically integrated photonic multiwavelength transmitter that was realized by integrating an arrayed waveguide grating-based laser with selective distributed Bragg reflector mirrors and Mach-Zehnder modulators. The integrated circuit was designed according to a generic integration model, by utilizing standardized photonic building blocks, and was fabricated on an InP-based platform in a multiproject wafer run. The device delivers above 1 mW of optical power into the fiber with a side mode suppression ratio better than 40 dB. The linewidth of the generated signals is 275 kHz. We achieved error free 50-km transmission at the modulation data rate of 10 Gb/s per channel, for a received power of ${-}{26.5}~{rm dBm}$ .
    IEEE Photonics Technology Letters 01/2014; 26(7):710-713. · 2.04 Impact Factor
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    ABSTRACT: 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.
    18th Annual Symposium of the IEEE Photonics Benelux Chapter, Eindhoven, The Netherlands; 11/2013
  • Emil Kleijn, Meint K. Smit, Xaveer J. M. Leijtens
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    ABSTRACT: An analytical model of star couplers in arrayed waveguide gratings (AWG) is derived. By retaining the real 1-D mode shapes, the model is able to calculate the star coupler response to fundamental modes, as well as higher order modes. This is desirable for modeling passband flattened AWGs. The model can calculate the response of an AWG very fast, because no numerical root finding or integral calculation is involved. This allows it to be used in circuit level simulations.
    Journal of Lightwave Technology 10/2013; 31(20). · 2.56 Impact Factor
  • Emil Kleijn, M.K. Smit, X.J.M. Leijtens
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    ABSTRACT: An analytical model of star couplers in arrayed waveguide gratings (AWG) is derived. By retaining the real 1-D mode shapes, the model is able to calculate the star coupler response to fundamental modes, as well as higher order modes. This is desirable for modeling passband flattened AWGs. The model can calculate the response of an AWG very fast, because no numerical root finding or integral calculation is involved. This allows it to be used in circuit level simulations.
    Journal of Lightwave Technology 10/2013; 31(20):3309-3314. · 2.56 Impact Factor
  • E. Kleijn, M.K. Smit, X.J.M. Leijtens
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    ABSTRACT: Multimode interference devices are very versatile components that are often used as components for power splitting or combining in larger circuits. In this paper, we present a new class of multimode interference couplers that are designed to reflect all or part of the light. The components can act as on-chip mirrors with partial out-coupling, or they can act as compact mirrors with full reflection. We present an overview of such devices, the basic theory and practical design guidelines. Their simple layout makes these devices easy to fabricate and tolerant to fabrication errors. We fabricated devices of several types and present the experimental results.
    Journal of Lightwave Technology 09/2013; 31(18):3055-3063. · 2.56 Impact Factor
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    ABSTRACT: 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.
    Optics Letters 07/2013; · 3.39 Impact Factor
  • Emil Kleijn, Meint K. Smit, Xaveer Leijtens
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    ABSTRACT: We present a novel monolithically integrated semiconductor laser based on a Reflective Arrayed Waveguide Grating and Multimode Interference Reflectors. The laser emits at seven distinct wavelengths using only four optical amplifiers.
    Integrated Photonics Research, Silicon and Nanophotonics; 07/2013
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    ABSTRACT: On-wafer probing of optical signals offers powerful means for assessing the fabrication process quality of photonic integrated circuits. We describe the fabrication and characterization of a vertical optical coupler that enables on-wafer probing.
    Optical Sensors; 07/2013
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    ABSTRACT: A new widely and continuously tunable ring laser contains an integrated series filter with a Vernier pair of Ring Resonators (RR) and a pair of identical Delayed Interferometers (DI). Tuning currents of only a few mA yield tuning ranges of 2000 GHz.
    CLEO: Science and Innovations; 06/2013
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    ABSTRACT: Spectral phase control of optical pulses is often required to generate short pulses, and an important application of a pulse shaper is spectral chirp/dispersion (pre-) compensation. In this paper, we present the pulse shaping/compression capability of a monolithically integrated optical pulse shaper. Chip fabrication has been carried out in a standardized generic photonic integration platform which is available in the framework of European FP7 project EuroPIC. A key capability of this platform is the active-passive integration scheme which allows direct integration of active components such as semiconductor optical amplifiers (SOAs) with passive elements such as arrayed waveguide gratings (AWGs) and phase modulators (PMs) on a single photonic chip.
    The European Conference on Lasers and Electro-Optics; 05/2013
  • The European Conference on Lasers and Electro-Optics; 05/2013
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    ABSTRACT: 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 b- 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 to triple wavelength emission when η1 = η2 = η3, then the output changes to DWE when (η2 = η3) > η1. The numerical results are in qualitative agreement with the e
    The European Conference on Lasers and Electro-Optics; 05/2013