‘Printed photonics on anything’
The Monolithic and Heterogeneous Integration theme will develop a range of essential semiconductor material, device and integration technologies, with a key objective being to find new ways to combine photonics and electronics together on multiple substrates (silicon, ceramic, polymer etc.) with unprecedented simplicity and cost-effectiveness, using transfer printing. We refer to this colloquially as "printed photonics on anything".
Enrica E. Mura*, Agnieszka M. Gocalinska, Megan O’Brien, Ruggero Loi, Gediminas Juska, Stefano T. Moroni, James O’Callaghan, Miryam Arredondo, Brian Corbett, and Emanuele Pelucchi
Abstract: We investigated and demonstrated a 1.3 μm band laser grown by metalorganic vapor-phase epitaxy (MOVPE) on a specially engineered metamorphic parabolic-graded InxGa1–xAs buffer and epitaxial structure on a GaAs substrate. Bottom and upper cladding layers were built as a combination of AlInGaAs and InGaP alloys in a superlattice sequence. This was implemented to overcome (previously unreported) detrimental surface epitaxial dynamics and instabilities: when single alloys are utilized to achieve thick layers on metamorphic structures, surface instabilities induce defect generation. This has represented a historically limiting factor for metamorphic lasers by MOVPE. We describe a number of alternative strategies to achieve smooth surface morphology to obtain efficient compressively strained In0.4Ga0.6As quantum wells in the active layer. The resulting lasers exhibited low lasing threshold with a total slope efficiency of 0.34 W/A for a 500 μm long-ridge waveguide device. The emission wavelength is extended as far as 1360 nm.
Full artical here.
Peter J. Parbrook, Brian Corbett, Jung Han, Tae‐Yeon Seong, Hiroshi Amano
Abstract: Typical light‐emitting diodes (LEDs) have a form factor >(300 × 300) µm2. Such LEDs are commercially mature in illumination and ultralarge displays. However, recent LED research includes shrinking individual LED sizes from side lengths >300 µm to values <100 µm, leading to devices called micro‐LEDs. Their advent creates a number of exciting new application spaces. Here, a review of the principles and applications of micro‐LED technology is presented. In particular, the implications of reduced LED size in necessitating mitigation strategies for nonradiative device edge damage as well as the potential for higher drive current densities are discussed. The opportunities to integrate micro‐LEDs with electronics, and into large‐scale arrays, allow pixel addressable scalable integrated displays, while the small micro‐LED size is ideal for high‐speed modulation for visible light communication, and for integration into biological systems as part of optogenetic therapies.
Full article here.
Phys. Rev. B 102, 245404 – Published 3 December 2020
The wavelength scale confinement of light offered by photonic crystal (PhC) cavities is one of the fundamental features on which many important on-chip photonic components are based, opening silicon photonics to a wide range of applications from telecommunications to sensing. This trapping of light in a small space also greatly enhances optical nonlinearities and many potential applications build on these enhanced light-matter interactions. In order to use PhCs effectively for this purpose it is necessary to fully understand the nonlinear dynamics underlying PhC resonators. In this work, we derive a first principles thermal model outlining the nonlinear dynamics of optically pumped silicon two-dimensional (2D) PhC cavities by calculating the temperature distribution in the system in both time and space. We demonstrate that our model matches experimental results well and use it to describe the behavior of different types of PhC cavity designs. Thus, we demonstrate the model’s capability to predict thermal nonlinearities of arbitrary 2D PhC microcavities in any material, only by substituting the appropriate physical constants. This renders the model critical for the development of nonlinear optical devices prior to fabrication and characterization.
Full article here.
R. Loi, S. Iadanza, B. Roycroft, J. O’Callaghan, L. Liu, K. Thomas, A. Gocalinska, E. Pelucchi, A. Farrell, S. Kelleher, R. F. Gul, A. J. Trindade, D. Gomez, L. O’Faolain & B. Corbett, IEEE Journal of Quantum Electronics 56 (1), 6400108 (2020).
InP lasers operating in the O- and C- optical bands are required to be integrated onto silicon photonics for high bandwidth telecom and data-communication applications. The first O-band Fabry Perot InP laser was edge coupled to a polymer waveguide by integration into a tailored recess on a silicon photonics chip by using micro transfer printing, which provides accurate planar alignment and scalability. Highly accurate vertical alignment of the laser waveguide and thermal sink are achieved by bonding the devices on an intermediate metal layer of calibrated thickness deposited at the bottom of the recess and connected to the Si substrate. The work presents a roadmap for delivering light to polymer interconnects and potentially enable hybrid polymer-SOI based photonic integrated circuits.
Full article here.
Sharon M. Butler, Praveen K. J. Singaravelu, Liam O’Faolain, and Stephen P. Hegarty
A novel configuration of a Fourier domain mode locked (FDML) laser based on silicon photonics platform is presented in this work that exploits the narrowband reflection spectrum of a photonic crystal (PhC) cavity resonator. Configured as a linear Fabry-Perot laser, forward biasing of a p-n junction on the PhC cavity allowed for thermal tuning of the spectrum. The modulation frequency applied to the reflector equalled the inverse roundtrip time of the long cavity resulting in stable FDML operation over the swept wavelength range. An interferometric phase measurement measured the sweeping instantaneous frequency of the laser. The silicon photonics platform has potential for very compact implementation, and the electro-optic modulation method opens the possibility of modulation speeds far beyond those of mechanical filters.
Full article here.
Marco Passoni, Dario Gerace, Liam O’Faolain, and Lucio Claudio Andreani
Reducing power dissipation in electro-optic modulators is a key step for widespread application of silicon photonics to optical communication. In this work, we design Mach–Zehnder modulators in the silicon-on-insulator platform, which make use of slow light in a waveguide grating and of a reverse-biased p-n junction with interleaved contacts along the waveguide axis. After optimizing the junction parameters, we discuss the full simulation of the modulator in order to find a proper trade-off among various figures of merit, such as modulation efficiency, insertion loss, cutoff frequency, optical modulation amplitude, and dissipated energy per bit. Comparison with conventional structures (with lateral p-n junction and/or in rib waveguides without slow light) highlights the importance of combining slow light with the interleaved p-n junction, thanks to the increased overlap between the travelling optical wave and the depletion regions. As a surprising result, the modulator performance is improved over an optical bandwidth that is much wider than the slow-light bandwidth.
Full article here.
Researchers at the Tyndall National Institute in Cork have demonstrated highly efficient power conversion on silicon substrates under laser light at 808-nm using GaAs based photovoltaic (PV) power convertersAn open circuit voltage of 1.235 V and conversion efficiency of 49 percent was obtained under an equivalent power density of 700 suns.
Full article here.
Justin K. Alexander, Ludovic Caro, Mohamad Dernaika, Shane P. Duggan, Hua Yang, Satheesh Chandran, Eamonn P. Martin, Albert A. Ruth, Prince M. Anandarajah, and Frank H. Peters
The first demonstration of a dual optical frequency comb source with all light sources monolithically integrated in a photonic integrated circuit (PIC) was shown.
Agnieszka M. Gocalinska, Enrica E. Mura, Marina Manganaro, Gediminas Juska, Valeria Dimastrodonato, Kevin Thomas, Andrew Zangwill, Dimitri D. Vvedensky, and Emanuele Pelucchi
Phys. Rev. B 101, 165310 – Published 27 April 2020
We present a systematic study of the morphology of InP films grown on macroscopically lattice-matched AlxIn1−xAs during low-pressure MOVPE.
Agnieszka Gocalinska1, Andrea Pescaglini1, Eleonora Secco1, Enrica E Mura1, Kevin Thomas1, Anya Curran1, Farzan Gity1, Roger Nagle1, Michael Schmidt1, Paweł P Michałowski2, Paul K Hurley1, Ian Povey1 and Emanuele Pelucchi
Abstract: We report on the growth and electronic properties of polycrystalline III–V semiconductors, which to date have not been discussed in depth in the literature. III–V polycrystalline semiconductor thin films were grown by metalorganic vapour phase epitaxy in the temperature range 410 °C–475 °C, which is compatible for integration into the Back-End-Of-Line (BEOL) silicon based integrated circuits. The thickness of the films in this study is in the range of tens to a few hundreds of nanometers, and deposited on amorphous substrates (either smart-phone-grade glass or Si/SiO2) and, also, on oxidised GaAs epi-ready wafers. Extensive AFM, SEM and TEM analyses show interlinked-to-continuous polycrystalline III–V films based on In(Al)As or GaSb. Hall-van der Pauw measurements return results of high mobility and controllable charge density for n- and p-type field effect transistors. In the GaAs/In(Al)As system, electron density ranging from 1 × 1016 to 1 × 1019 cm−3 (n) was achieved, with room temperature mobility values in the range of 100–150 cm2 V−1 s−1 and hole mobility values in the range of 1–10 cm2 V−1 s−1 have been measured in Zn doped samples. Polycrystalline GaSb films demonstrated p-type behaviour (1 × 1017 cm−3) with remarkably high room temperature hole mobility values up to 66 cm2 V−1 s−1 for the films grown on Si/SiO2 substrate (and 300 cm2 V−1 s−1 for the GaAs substrate where an epitaxial process is actually in place). Materials could be stacked into heterostructures, providing a promising platform for complex devices enabling compatible n- and p- hetero-layers for 3D integration formed at temperatures ≤480 °C.
Full article here.
We report on the growth and electronic properties of polycrystalline III–V semiconductors.
Chris Broderick from Eoin O’Reily’s team had a general article published in the IEEE Photonics Society newsletter, February 2020.
“Routes to Ideal Telecom Lasers?” It features on the cover with a picture of lasers made by James O’Callaghan.
Contributions were made by Brian Corbett and by Emanuele Pelucchi.
Conal Murphy completed my Bsc Physics degree at University College Cork (UCC) in 2020. I completed a number of summer internships during my undergraduate degree, including an IPIC summer studentship in the Photonics Theory Group under the supervision of Prof. Eoin O’Reilly and Dr.Chris Broderick. Later in 2020 I joined the Photonics Theory Group on an IRC funded PhD studentship, again under the supervision of Prof. O’Reilly and Dr. Broderick.
Summary: There exists significant demand for efficient mid-IR LEDs and lasers for applications in environmental monitoring, medical diagnostics and industrial process control. InAs/GaSb superlattices (SLs) possess type-III (“broken gap”) band offsets. Prototype inter-band cascade LEDs (IC-LEDs) based on -oriented InAs/GaSb SLs have demonstrated high output power and wallplug efficiency relative to competing technologies at wavelengths close to 4 μm. To elucidate the origin of the observed high output power of these IC-LEDs we undertake a quantitative theoretical analysis of their optoelectronic properties. We employ an 8-band k.p Hamiltonian in conjunction with a plane wave expansion method to compute SL optoelectronic properties. Using the calculated SL electronic properties we compute spontaneous emission spectra and estimate the radiative recombination coefficient B. Significant delocalisation of the lowest energy bound electron state (e1) in the SL – a result of a combination of narrow layer thicknesses and low InAs electron effective mass – leads to relatively large spatial overlap of bound electron and hole wave functions in hole-confining GaSb layers. The electron-hole spatial overlap in these structures results in increased inter-band optical matrix elements compared to conventional type-II structures, leading to B values which are comparable to those in several proposed type-I mid-IR quantum well systems.
Dr. Emanuele Peluchi gave a talk ‘What is Quantum Science’ to celebrate the Word Quantum Day, check the video here.
Check our recent theme talk, ‘Applications of UV light for biomedical applications‘. This time, we’re honored to have Stefan Andersson-Engels, the director of the Biophotonics theme in IPIC, Professor in Physics Department, UCC to give us this comprehensive talk.You could find how the 4 themes in IPIC are working together.
Summary: Within IPIC we are designing novel biomedical diagnostic equipment needing UV sources. The sources needed are not easily available, and research is ongoing at IPIC to fill this gap. In this context, I am presenting my understanding of the biomedical need for such light sources. The presentation aims at providing inputs to program for developing UV sources that best utilises our unique expertise and resources, and best fills the unmet needs.
For more talks, please find our theme YouTube channel.
John MaCarthy is currently a Ph.D. student in the Integrated Photonics group working on the development of a chip for frequency comb generation. Presentation abstract: Modern optical networks use hundreds of separate lasers which fill up the limited bandwidth. The channels in the spectral bandwidth are separated by empty regions called guard bands where the purpose is to prevent one channel from interfering with another. The problem is that these guard bands are spectrally inefficient and, due to the increased demand, the bandwidth has become more and more limited. Optical frequency comb sources can potentially reduce or eliminate these guard bands. Optical frequency combs are used to generate a number of precisely spaced spectral carriers with a stable frequency. Due to the fixed phase relation between the carriers in the comb, there is no interference between comb lines.
Details could be found here.
Sharon is a postdoctoral researcher in the CAPPA Nanophotonics group led by Dr. William Whelan-Curtain. She recently completed her Ph.D. degree as part of the CAPPA group in Cork Institute of Technology under the supervision of Dr. Stephen P. Hegarty with research focused on wavelength swept III-V/silicon hybrid photonic crystal lasers. Her current research interests include integration of hybrid lasers, photonic crystal lasers, frequency modulated and wavelength swept lasers, and laser dynamics for applications in data communications and sensing. Presentation abstract: A novel configuration of a Fourier Domain Mode Locked (FDML) laser based on silicon photonics platform is presented in this work that exploits the narrowband reflection spectrum of a photonic crystal (PhC) cavity resonator. Configured as a linear Fabry-Perot laser, forward biasing of a p-n junction on the PhC cavity allowed for thermal tuning of the spectrum. The modulation frequency applied to the reflector equalled the inverse roundtrip time of the long cavity resulting in stable FDML operation over the swept wavelength range. An interferometric phase measurement measured the sweeping instantaneous frequency of the laser. The silicon photonics platform has potential for very compact implementation, and the electro-optic modulation method opens the possibility of modulation speeds far beyond those of mechanical filters.
Dr. Hui Wang made a video about laser for the virtual Cork Discovers this year. This video aims at the general public, including kids. it contains information about different applications of laser, the concept of laser, and the research work happening in IPIC.
More information on Cork Discovers.
The video link is here.
Niall Boohan, a Ph.D. candidate in Photonics Theory Group, working on laser design and modeling, gave a presentation on our theme open talk series.
Low-cost laser devices are crucial to the development of the optoelectronics industry. Slotted Fabry-Pérot is a type of laser device with these qualities. An Initial proposal for design involved creating an ideal modal threshold function (sinc) and performing an inverse Fourier transform to develop a pattern in cavity space. This resulted in a less than ideal slot pattern as the effectiveness of a slot scales with cavity position. We propose a more effective slot pattern can be developed by choosing a mode selection function that provides a more even slot distribution along the cavity. From our analysis we have shown an improvement across all steady-state parameters i.e. 18% increase in nearest neighbor selectivity and 71% increase at the gain-band edge over the existing sinc selection function.
Niall’s LinkedIn profile.
Check our YouTube channel for more videos.
IPIC 2020 summer bursary has started, several researchers and students have provided technical talks to the students. Check available videos here:
“Single-Mode Laser Characterisation” by a 1st year Ph.D. candidate, John McCarthy,
“Monolithic and Heterogeneous Integration Theme Introduction” by the theme director, Brian Corbett,
Welcome to subscribe to our Youtube Channel for more talks.
Dr. Agnieszka Gocalinska did 2 online outreach meetings, on 29th and 30th of April, with primary school children (“Playing with the rainbow” adapted workshop for the younger group (6-10 year olds), and career talk with some added demos for older kids (10+).