Tesi etd-09292024-234845
Link copiato negli appunti
Tipo di tesi
Dottorato
Autore
CAMPONESCHI, FEDERICO
URN
etd-09292024-234845
Titolo
Hybrid and Heterogeneous Photonic Integrated Circuits for Radar and Remote Sensing Applications
Settore scientifico disciplinare
ING-INF/01
Corso di studi
Istituto di Tecnologie della Comunicazione, dell'Informazione e della Percezione - PHD IN EMERGING DIGITAL TECHNOLOGIES
Commissione
relatore BOGONI, ANTONELLA
Presidente Prof. ESPOSITO, FLAVIO
Membro Dott. PEDRO, JOAO
Presidente Prof. ESPOSITO, FLAVIO
Membro Dott. PEDRO, JOAO
Parole chiave
- microwave photonics
- photonic integrated circuits
- radar
- beamforming
- hybrid integration
- heterogeneous integration
Data inizio appello
06/11/2024;
Disponibilità
completa
Riassunto analitico
Microwave Photonics (MWP) is an interdisciplinary field that leverages photonic technologies
to address complex functions in microwave systems, offering advantages such as low-loss
signal distribution, wide bandwidth, and immunity to electromagnetic interference. MWP
finds applications in areas like photonic microwave generation, optically controlled phased
array antennas, and radio-over-fiber systems. Photonics-based radar systems, in particular,
greatly benefit from these advantages, enabling low phase noise, ultra-wide bandwidth, and
flexible signal generation. This dissertation explores the integration of photonic technologies
to enhance the performance of radar and remote sensing systems. Due to the inherent
complexity of MWP systems and the limitations of current monolithic platforms, this work
investigates innovative multi-platform integration techniques to develop fully integrated systems
with advanced functionalities. The first chapters holds the theory behind MWP systems
and the state-of-the-art of photonics for radar and remote sensing systems and of the main
Photonic Integrated Circuit (PIC) platforms and multi-platform integration techniques. Then,
the research activities are organized into several chapters, each focusing on systems that use
different integration methods.
Chapter 2 focuses on monolithic platforms and details the development of an RF receiver with
down-conversion capability for electronically scanned active array antenna systems using Silicon-
on-Insulator (SOI) technology. Two packaged architectures, both relying on an external Mode-
Locked Laser (MLL), are developed. The first architecture consists of a cascade of a Mach-
Zehnder Modulator (MZM) and a Balanced Photodetector (BPD), achieving 48 dB of RF-to-IF
conversion gain, in line with previous implementations in SOI, and an Spurious Free Dynamic
Range (SFDR) of 94 dB · Hz2/3. The second architecture employs two very narrow-band optical
filters to select the MLL lines, eliminating the need for electrical filtering after photodetection.
Its very limited conversion gain emphasizes the need for active materials to provide on-chip
amplification.
The subsequent chapter delves into the butt-coupling approach for hybrid integration of
distinct platforms. Indium Phosphide (InP) and Silicon Nitride (SiN) chips are die-attached
to realize a multibeam beamformer for a Synthetic Aperture Radar (SAR) receiver and an
RF scanner for Electronic Support Measurement (ESM) systems. The former leverages the
Scan-on-Receive (SCORE) method to achieve precise and continuous beamforming-on-receive
of wideband signals from a 12-element antenna array, synthesizing up to three simultaneous
receiving beams. The Optical Beamforming Network (OBFN) implemented in low-loss SiN is a
Blass matrix. Experimental results demonstrate successful frequency down-conversion from X-
band at 9.65 GHz to a low intermediate frequency at 1.35 GHz with a measured conversion loss
of 50 dB. Furthermore, multi-beam beamforming operations of the PIC receiver module are, for
the first time, experimentally demonstrated through radiation diagrams showing beam steering at different pointing angles. Two distinct architectures implement a 6-channel RF scanner that
work up to 40 GHz. In one, frequency scanning is achieved using an electrical oscillator up-
converted in the optical domain, while the other relies on a tunable laser. For both architectures,
system simulations and PIC designs are presented. Additionally, preliminary device-level testing,
enabled by the hybrid approach, is reported for both the SiN and InP chips. The core of both
architectures are optical filters implemented as SiN microring resonator-assisted Mach-Zehnder
Interferometer (MZI), which show transmission bandwidth as low as 2 GHz, and record values
of Free Spectral Range (FSR) and out-of-band rejection of 36 GHz and 57 dB, respectively.
Next, the design and device-level characterization of an integrated frequency converter, enabled
by butt-coupling of InP and Lithium Niobate-on-Insulator (LNOI) chips, is presented. The
LNOI platform is attractive for its potential to implement low half-wave voltage (Vπ) and high
bandwidth MZMs, which are crucial for MWP systems. Measurements conducted on the LNOI
MZM show a modulation efficiency of 10 V/cm and a bandwidth of 23 GHz, though performance
is expected to consistently improve with new fabrication processes.
Chapter 4 explores the Micro-Transfer Printing (MTP) technique for heterogeneously integrating
InP Semiconductor Optical Amplifiers (SOAs) onto an SOI platform, resulting in the design of
a frequency converter for radar transceivers and a coherent Multiple-In-Multiple-Out (MIMO)
radar constellation. Device-level characterization of the printed SOAs shows a maximum on-chip
gain of 9 dB, which is relatively low compared to InP SOAs on native substrates. System-level
testing of the fully packaged frequency converter revealed a limited conversion gain due to
damage in the pig-tailed fiber array. However, considering the damage, a higher SOA gain,
and the addition of a Trans-Impedance Amplifier (TIA) to electrically amplify the output
photocurrent, the system could achieve a gain comparable to standard electronics. System
simulation and design of PIC for coherent MIMO SAR constellation is then reported. For this
application photonics allows for the flexible generation of multi-band signals and centralized
generation in a primary satellite with coherent distribution to all the secondary satellites of the
SAR signals over Free Space Optical (FSO) links. Moreover, the use of integrated technologies
enables Size Weight and Power Consumption (SWaP) reduction. Numerical analysis shows the proposed
system has a Noise Equivalent Sigma Zero (NESZ) < -29.6 dB, satisfying the SAR system
requirements. MTP-SOAs on the consolidated SOI platform are intended to decrease the overall
conversion gain. Polarization multiplexing is used to consistently reduce system complexity.
Finally, measurements of heterogeneously integrated external cavity lasers, enabled by wafer
bonding of III-V materials onto SiN and LNOI platforms, are presented. The combination of
wafer bonding, which offers significantly low alignment tolerances and compatibility with high-
volume production, along with the low-loss properties of the SiN platform and the strong electro-
optic characteristics of the LNOI platform, makes these heterogeneous platforms extremely
promising for future MWP systems.
This research advances MWP systems for radar and remote sensing applications by utilizing
innovative integration methods. My primary contributions involved system simulations,
PIC design, and testing at both the device level (with bare PICs) and the system level
(with fully packaged PICs) to demonstrate system functionalities. Although the photonic
integrated platforms reported in this work exhibit specific limitations, multi-platform integration techniques, particularly heterogeneous ones, offer a promising direction for future developments
capable of meeting the demanding requirements of MWP systems.
to address complex functions in microwave systems, offering advantages such as low-loss
signal distribution, wide bandwidth, and immunity to electromagnetic interference. MWP
finds applications in areas like photonic microwave generation, optically controlled phased
array antennas, and radio-over-fiber systems. Photonics-based radar systems, in particular,
greatly benefit from these advantages, enabling low phase noise, ultra-wide bandwidth, and
flexible signal generation. This dissertation explores the integration of photonic technologies
to enhance the performance of radar and remote sensing systems. Due to the inherent
complexity of MWP systems and the limitations of current monolithic platforms, this work
investigates innovative multi-platform integration techniques to develop fully integrated systems
with advanced functionalities. The first chapters holds the theory behind MWP systems
and the state-of-the-art of photonics for radar and remote sensing systems and of the main
Photonic Integrated Circuit (PIC) platforms and multi-platform integration techniques. Then,
the research activities are organized into several chapters, each focusing on systems that use
different integration methods.
Chapter 2 focuses on monolithic platforms and details the development of an RF receiver with
down-conversion capability for electronically scanned active array antenna systems using Silicon-
on-Insulator (SOI) technology. Two packaged architectures, both relying on an external Mode-
Locked Laser (MLL), are developed. The first architecture consists of a cascade of a Mach-
Zehnder Modulator (MZM) and a Balanced Photodetector (BPD), achieving 48 dB of RF-to-IF
conversion gain, in line with previous implementations in SOI, and an Spurious Free Dynamic
Range (SFDR) of 94 dB · Hz2/3. The second architecture employs two very narrow-band optical
filters to select the MLL lines, eliminating the need for electrical filtering after photodetection.
Its very limited conversion gain emphasizes the need for active materials to provide on-chip
amplification.
The subsequent chapter delves into the butt-coupling approach for hybrid integration of
distinct platforms. Indium Phosphide (InP) and Silicon Nitride (SiN) chips are die-attached
to realize a multibeam beamformer for a Synthetic Aperture Radar (SAR) receiver and an
RF scanner for Electronic Support Measurement (ESM) systems. The former leverages the
Scan-on-Receive (SCORE) method to achieve precise and continuous beamforming-on-receive
of wideband signals from a 12-element antenna array, synthesizing up to three simultaneous
receiving beams. The Optical Beamforming Network (OBFN) implemented in low-loss SiN is a
Blass matrix. Experimental results demonstrate successful frequency down-conversion from X-
band at 9.65 GHz to a low intermediate frequency at 1.35 GHz with a measured conversion loss
of 50 dB. Furthermore, multi-beam beamforming operations of the PIC receiver module are, for
the first time, experimentally demonstrated through radiation diagrams showing beam steering at different pointing angles. Two distinct architectures implement a 6-channel RF scanner that
work up to 40 GHz. In one, frequency scanning is achieved using an electrical oscillator up-
converted in the optical domain, while the other relies on a tunable laser. For both architectures,
system simulations and PIC designs are presented. Additionally, preliminary device-level testing,
enabled by the hybrid approach, is reported for both the SiN and InP chips. The core of both
architectures are optical filters implemented as SiN microring resonator-assisted Mach-Zehnder
Interferometer (MZI), which show transmission bandwidth as low as 2 GHz, and record values
of Free Spectral Range (FSR) and out-of-band rejection of 36 GHz and 57 dB, respectively.
Next, the design and device-level characterization of an integrated frequency converter, enabled
by butt-coupling of InP and Lithium Niobate-on-Insulator (LNOI) chips, is presented. The
LNOI platform is attractive for its potential to implement low half-wave voltage (Vπ) and high
bandwidth MZMs, which are crucial for MWP systems. Measurements conducted on the LNOI
MZM show a modulation efficiency of 10 V/cm and a bandwidth of 23 GHz, though performance
is expected to consistently improve with new fabrication processes.
Chapter 4 explores the Micro-Transfer Printing (MTP) technique for heterogeneously integrating
InP Semiconductor Optical Amplifiers (SOAs) onto an SOI platform, resulting in the design of
a frequency converter for radar transceivers and a coherent Multiple-In-Multiple-Out (MIMO)
radar constellation. Device-level characterization of the printed SOAs shows a maximum on-chip
gain of 9 dB, which is relatively low compared to InP SOAs on native substrates. System-level
testing of the fully packaged frequency converter revealed a limited conversion gain due to
damage in the pig-tailed fiber array. However, considering the damage, a higher SOA gain,
and the addition of a Trans-Impedance Amplifier (TIA) to electrically amplify the output
photocurrent, the system could achieve a gain comparable to standard electronics. System
simulation and design of PIC for coherent MIMO SAR constellation is then reported. For this
application photonics allows for the flexible generation of multi-band signals and centralized
generation in a primary satellite with coherent distribution to all the secondary satellites of the
SAR signals over Free Space Optical (FSO) links. Moreover, the use of integrated technologies
enables Size Weight and Power Consumption (SWaP) reduction. Numerical analysis shows the proposed
system has a Noise Equivalent Sigma Zero (NESZ) < -29.6 dB, satisfying the SAR system
requirements. MTP-SOAs on the consolidated SOI platform are intended to decrease the overall
conversion gain. Polarization multiplexing is used to consistently reduce system complexity.
Finally, measurements of heterogeneously integrated external cavity lasers, enabled by wafer
bonding of III-V materials onto SiN and LNOI platforms, are presented. The combination of
wafer bonding, which offers significantly low alignment tolerances and compatibility with high-
volume production, along with the low-loss properties of the SiN platform and the strong electro-
optic characteristics of the LNOI platform, makes these heterogeneous platforms extremely
promising for future MWP systems.
This research advances MWP systems for radar and remote sensing applications by utilizing
innovative integration methods. My primary contributions involved system simulations,
PIC design, and testing at both the device level (with bare PICs) and the system level
(with fully packaged PICs) to demonstrate system functionalities. Although the photonic
integrated platforms reported in this work exhibit specific limitations, multi-platform integration techniques, particularly heterogeneous ones, offer a promising direction for future developments
capable of meeting the demanding requirements of MWP systems.
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