LioniX (Netherlands)

This paper presents the procedure and the results of multi-beam beamforming and steering experiments on SPACEBEAM hybrid photonic integrated module, which is the first photonics-assisted scan on receive synthetic aperture radar (SCORE-SAR) receiver module intended for earth observation from space. The hybrid module combines a silicon nitride chip with indium phosphide chips to achieve up to 12x3 reconfigurable beamforming as well as frequency down-conversion functions. In the experimental demonstrations in this paper, we use four RF inputs to form two beams. Further, we demonstrate beam steering by changing the direction of the beams to different pointing angles. To our knowledge, this is the biggest-size multi-beam demonstration of a fully integrated optical beamforming network (OBFN).

In this work, we present and experimentally demonstrate for the first time a fully packaged 16×16 Benes switch prototype based on 3D photonic integration, operating in the O-band. The optical switch has been fabricated on a multi-layer 3D polymer-based photonic integration platform (PolyBoard) enabling a waveguide crossing-free architecture. The switch consists of horizontal in-plane Mach-Zehnder Interferometers (MZIs) serving as its fundamental crossbar switching units, as well as of vertical multi-mode interference (MMI) couplers, enabling the transition between the two parallel waveguiding layers and thus achieving crossing-free waveguides within the whole switching network. The performance of the 3D optical switch prototype was evaluated in terms of the pertinent switching metrics including insertion loss, crosstalk, polarization-dependent loss, power consumption, and high-speed signal transmission. The experimental results successfully validated the 3D photonic integration’s ability to restrict the overall crosstalk of the switch to that of its fundamental MZI switching unit.

A small laser engine for AR glasses is demonstrated based on a Silicon Nitride PIC using a flip-chip assembly process. By etching recesses in the silicon nitride PIC, and flip-chipping of bare Red, Green and Blue laser diodes, a passive alignment method is provided. The improved design of this device has a footprint of only 4×4.5×1.5mm. The optical output is optimized in performance for use in AR systems: Circular output modes (1:1) and low dispersion (NA~0.06) over wavelength. Optical output powers of >10mW are measured and depend on the laser diodes used. The devices are sealed with a top cap of silicon providing, next to wafer level laser integration, wafer level hermetic packaging for scalable volume manufacturing. In this paper we describe the flip-chip assembly process used to create the laser engine with small footprint of 4×4.5mm. As the alignment of the laser diodes to the photonic IC platform is critical for highly efficient systems, the process we propose is a passive flip-chip approach, were two directions are controlled by state-of-the art vision systems for submicron alignment. For the 3rd and most critical direction, a passive alignment is used based on accurately controlled landing pads (<100nm accuracy). Fixation and the electrical bottom contact are achieved using laser-assisted reflow of solder. The results show that this is a viable way to produce laser engines for AR on waferscale into large volumes.

This paper presents an integrated tunable hybrid multi-laser module designed to simultaneously generate multiple radiofrequency (RF) local oscillator (LO) signals through optical heterodyning. The device consists of five hybrid InP/Si3N4 integrated lasers, each incorporating an intracavity wavelength-selective optical filter formed by two micro-ring resonators. Through beating the wavelengths generated from three of these lasers, we demonstrate the simultaneous generation of two LO signals within bands crucial for satellite communications (SatCom): one in the Ka-band and the other in the V-band. The device provides an extensive wavelength tuning range across the entire C-band and exhibits exceptionally narrow optical linewidths, below 40 kHz in free-running mode. This results in ultra-wideband tunable RF signals with narrow electrical linewidths below 100 kHz. The system is compact and highly scalable, with the potential to generate up to 10 simultaneous LO signals, being a promising solution for advanced RF signal generation in high throughput satellite payloads.

This work presents an integrated tunable multi-laser module for the generation of multiple microwave signal carriers. The module consists of five InP-Si3N4 hybrid integrated lasers, where each laser is formed by an intracavity wavelength-selective optical filter based on two ring resonators. The single gain lasers characterized in this work exhibit optical linewidths below 40 kHz. By means of heterodyne mixing of optical frequencies, we have successfully demonstrated the simultaneous generation of two local oscillator (LO) signals for satellite communications in the Ka and V bands at 29 GHz and 41 GHz, respectively. This system has the potential to be scaled for the simultaneous generation of up to 10 LO signals.

This paper describes our hybrid integrated microwave photonic chip platform where ultra-low-loss $\mathrm{Si}_{3} \mathrm{~N}_{4}$-based-TriPleX<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> and active InP integrated circuits are combined to enable broadband and high frequency radio signal processing in the optical domain. The platform consists of a high-power laser, high-speed modulators and detectors. Using this platform, we demonstrated reconfigurable microwave filters, multiplexers and demultiplexers, local oscillator (LO) generation, frequency converters, and repeaters.

We report an experimental characterization of the long-term stability of a local oscillator (LO) signal generation module for satellite communications based on the optical heterodyning of two InP/Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> hybrid integrated lasers. Specifically, we analyze simultaneously the wavelength drift of both lasers in the optical domain and the electrical drift of the generated radiofrequency (RF) beat between the lasers. We identify the main factors that contribute to the overall drift such as the electrical noise coming from the supply sources, the thermal noise coming from the temperature control unit, and the thermal crosstalk between lasers. This investigation compares the stability of an RF signal generated by two approaches. Using two integrated lasers and using a combination of one integrated laser with one external laser. This work also analyzes the difference when lasers are mounted over a standard breadboard with a thermally-controlled. The results show that the best approach is to use both integrated lasers on the same chip. We report a 25 GHz RF signal with long-term stability of 30 MHz measured over 10 hours under free-running operation mode. Moreover, we experimentally demonstrate that integrated lasers can be stabilized by using injection locking. We experimentally demonstrate the optical injection locking of two hybrid InP/Si3N4 lasers when the leader laser and the follower laser are both hybrid integrated lasers of same system on chip. When the laser is locked, we report a locking range of 1.86 GHz.

This paper presents the design, fabrication, and characterization of the first photonic-assisted receiver module for a Scan-on-Receive synthetic aperture radar (SCORE-SAR) intended for Earth observation from space. The module is a hybrid photonic integrated circuit (PIC) that is designed to do precise and continuous beamforming-on-receive of wideband signals from a 12 antenna elements array, synthesizing up to three simultaneous beams. The PIC also implements frequency-agnostic photonic down-conversion so that the synthesized beams can be directly digitized. The PIC is realized by the hybrid integration of active chips on indium phosphide and a passive chip on silicon nitride. The design steps of the photonic module are discussed in this paper, including: the functional designs, the optical mask designs, the filters designs, the printed circuit boards (PCB) design, and the control electronics that drive the PIC. Characterization and tuning of the different building blocks of the PIC is also presented, and frequency down-conversion functionality is experimentally demonstrated.