Monolithic and Heterogeneous Integration

Our first objective relates to the development of GaN based UV (330 nm) light sources that can be used to excite natural fluorophores, especially during catheter delivered investigations. This requires engineering the coupling of the generated light to fibre waveguides. Our second objective is the development of photonic integrated circuits (PICs) in the 1 – 2 micron wavelength range, used in advanced data communication and sensor applications. Our team of PhD students and investigators are experts in these topics, covering from the atomic scale to integrated devices, with particular noteworthy achievements noted below.

Materials: Boron-Gallium Nitride – from atomic simulations to devices
Boron-Gallium Nitride is a new material with interesting properties for extending the performance of conventional AlGaInN alloy system. We have established multi-scale models as an ideal starting point for studying the properties of boron containing III-N alloys for LEDs. We performed the first atomistic ab-inito study on the impact of boron atom clustering in GaN, revealing significant impact (strong bandgap variations) with alloy configuration. This effect has been widely neglected in the theoretical literature to date while experimental studies indicate boron atom clustering. This work provides an ideal starting point for future studies of other boron-containing III-N alloys for emission in the red, (B,In,Ga)N alloys, and the deep UV, (B,Al,Ga)N alloys. In addition, we have established a multi-scale simulation framework to investigate the impact of alloy disorder on carrier transport and recombination processes (both radiative and nonradiative) in UV light emitters based on (Al,Ga)N materials. While our calculations reveal that radiative recombination rates increase with alloy disorder, when compared to a simulation that neglects these effects, non-radiative Auger-Meitner recombination may be even more strongly be enhanced by alloy disorder induced carrier localisation effect. The high energy Auger-Meitner carriers may also play an important role for degradation of UV light emitters, as these hot carriers may cause defects in the system.

We have realised the first LED with boron-containing quantum wells. The LED showed improved performance compared to a boron-free reference device. This demonstrates proof-of-concept potential for future work, targeting longer (red) and shorter emission (deep UV) wavelength in comparison to this proof-of-concept system.

Materials: Epitaxial understanding of InP and GaAs materials
Despite Metalorganic Vapour Phase Epitaxy’s (MOVPE) widespread technological popularity and usage, a considerable number of fundamental issues about epitaxial processes remain unresolved. The main reason being that a comprehensive insight into the complex physical processes at the atomistic level responsible for the material incorporation is still lacking, forcing the epitaxial community to a ‘recipe’ approach, lacking a fundamental understanding of the complex surface dynamics influencing the material growth. In IPIC we have been focusing (rather uniquely in the III-V community) over many years on developing a stronger understanding of planar and patterned surface dynamics and processes, acquiring a prominent standing in the community, clarifying many issues such as MOVPE step organization and its influencing of material optical properties, surfactant induced processes and, in general, the interplay between MOVPE precursors and adatom diffusion and incorporation. All considered, our work allowed for unique material and device quality over the years.

Monolithic integrated optical combs using InP materials
The IPG group within IPIC has led research worldwide into coupled lasers within a photonic integrated circuit (PIC). These mutually coupled laser systems are of great academic interest for studies in laser dynamics, and of practical interest in the creation and demultiplexing of coherent optical combs. Multiple first demonstrations have resulted, such the first PIC generating a coherent comb through the gain switching of one of the lasers on chip, and the first demonstration of how to filter out individual comb lines on a chip using an injection locked laser as an active filter.

Integrated optical sensors
We are demonstrating a new family of photonic crystal hybrid external cavity lasers (HECL). The laser comprises of an III-V gain chip and a silicon nitride based one-dimensional photonic crystal (PhC) which acts as a resonant mirror that sets the operating wavelength. Much of the mode supported by the 1D PhC exists in the top cladding material (in this case, the air or water of the sample) meaning the lasing wavelength is affected by the sample’s refractive index giving a sensitivity of approx. 140nm/RIU (Refractive index unit). Due to the narrow linewidth of the lasing more, we measure a 16x improvement in the detection limit with respect to the traditional refractive index sensing using integrated photonics. We are also working on new applications that use integrated refractive index sensors as a transducer for Photothermal Spectroscopy (PTS). Very recently, we have demonstrated gas phase PTS with a chip based transducer for the first time.

Photonic Integrated Circuits using heterogeneous integration of InP and GaAs devices
Photonic Integrated Circuits provide the backbone signaling in datacenters and are set to reach widespread use in sensing, medical and consumer applications. These circuits, based on Si and SiN waveguides, need active laser, modulator and detector functionality. At IPIC, we have pioneered the transfer printing technique, which seamlessly integrates components providing these properties. We have successfully integrated GaN, GaN, InP, GaSb, Si, Lithium Niobate and other devices to these waveguide circuits enabling highly efficient use of these valuable materials. The base materials and devices are produced within IPIC and the advanced PICs are being packaged and demonstrated within the corresponding Themes.

2024

60 nm Widely Tunable Three Section Slot Laser J Mulcahy, J McCarthy, FH Peters, X Dai, IEEE Journal of Quantum Electronics 59, no. 6, pp. 1-6Art no. 2000706, https://doi.org/10.1109/JQE.2023.3318588

Integration of High-Performance InGaAs/GaN Photodetectors by Direct Bonding via Micro-transfer Printing Y Liu, Z Li, FB Atar, H Muthuganesan, B Corbett, L Wang
ACS Applied Materials & Interfaces 16, 8, 10996–11002 https://doi.org/10.1021/acsami.3c17663

On the multifaceted journey for the invention of epitaxial quantum dots E Pelucchi, Progress in Crystal Growth and Characterization of Materials 69 (2-4), 100603 https://doi.org/10.1016/j.pcrysgrow.2023.100603

Photothermal spectroscopy on-chip sensor for the measurement of a PMMA film using a silicon nitride micro-ring resonator and an external cavity quantum cascade laser G Ricchiuti, A Walsh, JH Mendoza-Castro, A S Vorobev, M Kotlyar, G VB Lukasievicz, S Iadanza, M Grande, B Lendl, L O’Faolain

Perspective: Theory and simulation of highly mismatched semiconductor alloys using the tight-binding method CA Broderick, EP O’Reilly, S Schulz, Journal of Applied Physics 135 (10) https://doi.org/10.1063/5.0192047

Impact of random alloy fluctuations on the carrier distribution in multicolor (,)/ quantum well systems M O’Donovan, P Farrell, J Moatti, T Streckenbach, T Koprucki, S Schulz, Physical Review Applied 21 (2), 024052 https://doi.org/10.1103/PhysRevApplied.21.024052

Surface Morphology Evolution of AlGaN Microhoneycomb Structures during Epitaxial Overgrowth SM Singh, VZ Zubialevich, PJ Parbrook physica status solidi (b), 2300471 (2024) https://doi.org/10.1002/pssb.202300471

Micro-transfer printing of thick optical components using a tether-free UV-curable approach, S Wakeel, PE Morrisey, M Genc, P Ramaswamy, R Bernson, K Gradkowski, B Corbett, P O’Brien, Journal of Optical Microsystems 4 (1), 011003-011003 (2024) https://doi.org/10.1117/1.JOM.4.1.011003

Compact angled multimode interference duplexers for multi-gas sensing applications, A Thottoli, AS Vorobev, G Biagi, S Iadanza, M Giglio, G Magno, M Grande, L O’Faolain, Optics Express 32 (3), 3451-3460 (2024) https://doi.org/10.1364/OE.503483

2023
Carrier density dependent Auger recombination in c-plane (In, Ga) N/GaN quantum wells: insights from atomistic calculations JM McMahon, E Kioupakis, S Schulz Journal of Physics D: Applied Physics, 57 (12), 125102 (2023) https://doi.org/10.1088/1361-6463/ad1146

Electronic and optical properties of boron-containing GaN alloys: The role of boron atom clustering, CL Nies, TP Sheerin, S Schulz APL Materials, 11 (9) 1 (2023) https://doi.org/10.1063/5.0171932

Disentangling the impact of point defect density and carrier localization-enhanced Auger recombination on efficiency droop in (In, Ga) N/GaN quantum wells, RM Barrett, JM McMahon, R Ahumada-Lazo, JA Alanis, P Parkinson, S Schulz, M J Kappers, R A Oliver, D Binks, ACS photonics 10 (8), 2632-2640 (2023) https://doi.org/10.1021/acsphotonics.3c00355

Theoretical study of the impact of alloy disorder on carrier transport and recombination processes in deep UV (Al, Ga) N light emitters, R Finn, M O’Donovan, P Farrell, J Moatti, T Streckenbach, T Koprucki, S Schulz, Applied Physics Letters 122 (24) 4 (2023) https://doi.org/10.1063/5.0148168

Imaging threading dislocations and surface steps in nitride thin films using electron backscatter diffraction KP Hiller, A Winkelmann, B Hourahine, B Starosta, A Alasmari, P Feng, Tao Wang, Peter J Parbrook, Vitaly Z Zubialevich, Sylvia Hagedorn, Sebastian Walde, Markus Weyers, Pierre-Marie Coulon, Philip A Shields, Jochen Bruckbauer, Carol Trager-Cowan, Microscopy and Microanalysis, ozad118 (2023) https://doi.org/10.1093/micmic/ozad118

BAlGaN light‐emitting diode emitting at 350 nm, P Milner, VZ Zubialevich, T O’Connor, SM Singh, D Singh, B Corbett, P Parbrook, Electronics Letters 59 (19), e12976 (2023) https://doi.org/10.1049/ell2.12976

InGaN/AlInN interface with enhanced holes to improve photoelectrochemical etching and GaN device release, Z Shaban, VZ Zubialevich, EA Amargianitakis, FB Atar, PJ Parbrook, Z Li, B Corbett, Semiconductor Science and Technology 38 (5), 055015 (2023) https://doi.org/10.1088/1361-6641/acc681

Continuous‐Wave Operation of 457 nm InGaN Laser Diodes with Etched Facet Mirrors for On‐Chip Photonics, M Genc, VZ Zubialevich, A Hazarika, PJ Parbrook, B Corbett, Z Li
Advanced Photonics Research, 4, 2300208 (2023) https://doi.org/10.1002/adpr.202300208

Dislocation and strain mapping in metamorphic parabolic-graded InGaAs buffers on GaAs, N. Stephen, P. Kumar, A. Gocalinska, E. Mura, D. Kepaptsoglou, Q. Ramasse, E. Pelucchi, and M. Arredondo J. Mater. Sci. 58, pages9547–9561 (2023) https://doi.org/10.1002/adpr.20230020810.1007/s10853-023-08597-y

On the multifaceted journey for the invention of epitaxial quantum dots E. Pelucchi, Progress in Crystal Growth and Characterization of Materials, 69, (2–4), 100603 (2023) https://doi.org/10.1016/j.pcrysgrow.2023.100603

60 nm Widely Tunable Three Section Slot Laser J. Mulcahy, J. McCarthy, F. H. Peters, and X. Dai, IEEE Journal of Quantum Electronics, 59 (6), pp. 1-6, Dec. 2023, https://doi.org/10.1109/JQE.2023.3318588

Gain Switched Frequency Comb Enhancement using Monolithically Integrated Mutually Coupled Lasers, J. McCarthy, Z. Jia, B. Kelleher and F. H. Peters, IEEE Photonics Technology Letters, 35 (22), 1195-1198, 2023 https://doi.org/10.1109/LPT.2023.3307725

Minimisation of Parasitic Capacitance in Lumped-Element Electro-Absorption Modulators for High-Speed Optical Components, Jack Mulcahy, Shengtai Shi, Frank H. Peters, and Xing Dai. Photonics 10 (8): 885 (2023) https://doi.org/10.3390/photonics10080885

On-chip gain switched frequency comb generation using a two sectioned single cavity laser without additional optical injection, John McCarthy and Frank H. Peters, Opt. Express 31, 29619-29626, (2023) https://doi.org/10.1364/OE.500300

Tunable, coherent optical comb source via on-chip bidirectional coupling, John McCarthy, Diarmuid O’Sullivan, Maryam Shayesteh, Mohamad Dernaika, Frank H. Peters, and Bryan Kelleher, Opt. Lett. 48, 4137-4140, (2023) https://doi.org/10.1364/OL.492230

Highly efficient and selective integrated directional couplers for multigas sensing applications, A Thottoli, G Biagi, AS Vorobev, M Giglio, G Magno, L O’Faolain, Marco Grande
Scientific Reports 13 (1), 22720 (2023) https://doi.org/10.1038/s41598-023-49889-2

Unlocking the monolithic integration scenario: optical coupling between GaSb diode lasers epitaxially grown on patterned Si substrates and passive SiN waveguides, A Remis, L Monge-Bartolome, M Paparella, A Gilbert, G Boissier, Marco Grande, Alan Blake, Liam O’Faolain, Laurent Cerutti, Jean-Baptiste Rodriguez, Eric Tournié Light: Science & Applications 12 (1), 150 (2023) https://doi.org/10.1038/s41377-023-01185-4

100 Gbps PAM4 ultra-thin photodetectors integrated on SOI platform by micro transfer printing, H Muthuganesan, E Mura, S Chugh, C Antony, E Pelucchi, P Townsend, X Yan, M Banakar, Y Tran, C Littlejohns, and B Corbett Optics Express 31 (22), 36273-36280 (2023) https://doi.org/10.1364/OE.502285

An Ultrasonically-Powered System for 1.06mm3 Implantable Optogenetics and Drug Delivery Dust, K Laursen, M Zamani, Y Rezaeiyan, S Hosseini, T Mondal, B Corbett, A M Ouagazzal, M Amalric, F Moradi, IEEE Transactions on Circuits and Systems II: Express Briefs 1 (2023) https://doi.org/10.1109/TCSII.2023.3289028

III-V-on-Si DFB Laser With Co-Integrated Power Amplifier Realized Using Micro-Transfer Printing, J Zhang, L Bogaert, B Haq, R Wang, B Matuskova, J Rimböck, S Ertl, A Gocalinska, E Pelucchi, B Corbett, J Van Campenhout, G Lepage, P Verheyen, G Morthier, and G Roelkens, IEEE Photonics Technology Letters 35 (11), 593-596 (2023) https://doi.org/10.1109/LPT.2023.3263279

Robust single frequency index-patterned laser design using a Fourier design method, ND Boohan, B Corbett, EP O’Reilly Optics Express 31 (7), 11536-11546 (2023) https://doi.org/10.1364/OE.485879

Tunable dual optical frequency comb at 2 μm for CO2 sensing, E Russell, AA Ruth, B Corbett, FCG Gunning, Optics Express 31 (4), 6304-6313 (2023) https://doi.org/10.1364/OE.477295

Integration of Edge-Emitting Quantum Dot Lasers with Different Waveguide Platforms using Micro-Transfer Printing, A Uzun, FB Atar, S Iadanza, R Loi, J Zhang, G Roelkens, I Krestnikov, J Rimböck, L O’Faolain, B Corbett, IEEE Journal of Selected Topics in Quantum Electronics 29 (2023) https://doi.org/10.1109/JSTQE.2023.3243943

A System‐Level Feasibility Study of a Lead‐Free Ultrasonically Powered Light Delivery Implant for Optogenetics, S Baghaee Ivriq, K Laursen, AM Jørgensen, T Mondal, M Zamani, Y Rezaeiyan, B Corbett, B Brummerstedt Iversen, F Moradi, Advanced Intelligent Systems, 2300527 https://doi.org/10.1002/aisy.202300527

2022
Impact of random alloy fluctuations on the electronic and optical properties of (Al, Ga) N quantum wells: Insights from tight-binding calculations, R Finn, S Schulz, The Journal of Chemical Physics 157 (24) (2022) https://doi.org/10.1063/5.0132490

High-Q asymmetrically cladded silicon nitride 1D photonic crystals cavities and hybrid external cavity lasers for sensing in air and liquids, S. Iadanza, J. H. Mendoza-Castro, T. Oliveira, S. M. Butler, A. Tedesco, G. Giannino, B. Lendl, M. Grande, and L. O’Faolain, Nanophotonics 11, 4183–4196 (2022) https://doi.org/10.1515/nanoph-2022-0245

Analysis of the optical coupling between GaSb diode lasers and passive waveguides: a step toward monolithic integration on Si platforms, M Paparella, LM Bartolome, JB Rodriguez, L Cerutti, M Grande, Liam O’Faolain, Eric Tournié, IEEE Photonics Journal 14 (5), 1-6 (2022) https://doi.org/10.1109/JPHOT.2022.3203593

Spectral translation unlocks 2-μm window, F Gunning, B Corbett, Nature Photonics 16 (11), 744-745 (2022) https://doi.org/10.1038/s41566-022-01090-z

Transfer printing of roughened GaN‐based light‐emitting diodes into reflective trenches for visible light communication, Z Shaban, Z Li, B Roycroft, M Saei, T Mondal, B Corbett
Advanced Photonics Research 3 (8), 2100312 (2022) https://doi.org/10.1002/adpr.202100312

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.

S. Iadanza, M. Clementi, C. Hu, S. A. Schulz, D. Gerace, M. Galli, and L. O’Faolain

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.

Here comes the last session of our workshop, LASER demo competition! Check details on our YouTube Channel and score them!

We held a 9 sessions LASER workshop for the IPIC summer interns in 2021, who were 2nd/3rd undergraduate students from universities across Ireland. We inluded 4 technical talks, 1 simulation, 2 interactive video session and 1 Ph.D. experience sharing session. Due to the restrictions, they were all done online. Many thanks to Brian Corbett, Sandeep Madhusudan Singh,John McCarthy,Niall Boohan,Megan O’Brien,Hemalatha Muthuganesan, Shengtai Shi, Adarsh Ananthachar, Simone Iadanza!
Check some of the videos on our YouTube channel.

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.

Details of the talk on our theme YouTube channel.

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 [001]-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.