LIDARs are considered a key enabling technology for an array of applications in space, including celestial body approach, landing, rendezvous and docking, space debris identification and CubeSat constellations. Reliability, low cost and low size, weight and power (SWaP) are critical factors for these applications. Current spaceborne LIDAR systems are based on discrete optical components. These systems consume a lot of power and are bulky. In this work, a hybrid integrated (FMCW) LIDAR system operating at 1550 nm and based on an indium phosphide (InP) and silicon nitride (Si3N4) platform along with an external erbium-doped fiber amplifier (EDFA) compact module is proposed. By using a telecom-wavelength laser with an ultra-narrow linewidth of 1 kHz, and a 1D optical phased array (OPA) using lead zirconate titanate (PZT) phase shifters, the proposed PIC microlidar can operate up to 100 km. In order to realize small beam divergence, a 1x100 linear array consisting of 4 mm Si3N4 dual-layer grating antennas with a coupling efficiency of up to 80% of the incident power is utilized.
To match the growing demand for data transmission capacities, silicon photonic tunable multichannel filters with architectures like ring resonators or Bragg gratings are the leading technology. However, their performance, especially the channel count, is often limited by the free spectral range or fabrication difficulties due to small size grating teeth (~ 150 nm). The long-period waveguide gratings (LPWGs) with periodicity ~ μm can be a promising alternative to overcome these limitations. In this context, we propose a four-channel wavelength division (de) multiplexer (WDM) based on cascaded LPWG geometry, operating in the C-band of telecommunication. The proposed structure consists of four cascaded LPWGs in which each LPWG comprises two parallel waveguides made of silicon and titanium dioxide (TiO2) with apodized gratings placed in between having a length of 720 μm. The 3-dB bandwidth of each channel is found to be 1.59 nm with a small insertion loss of -0.1 to -0.6 dB owing to the unique spectral property of LPWG. The channel spacing is decided through the efficient tuning with the metallic heaters placed on top of each grating due to the high and opposite thermo-optic coefficient of silicon and TiO2. A minimum spacing of 268 GHz between two consecutive channels is achieved with a power consumption of 30 mW. The cross-talk between the channels is found to be < -20 dB even with ± 10 nm random errors in the waveguide’s width along the propagation direction. The proposed structure possesses great potential towards dense WDM application.
Nanophotonic structures optimise the strength of optical forces, enabling trapping at the nanoscale. To improve the impact of nanotweezers in biological studies, it is necessary to move from individual traps to large multiplexed arrays. Here, we discuss the state-of-the-art of nanotweezers for multiplexed trapping, describing advantages and drawbacks of the configurations that have demonstrated the strongest impact in this field. Finally, we focus on our latest results with a dielectric metasurface that supports strong resonances with thousands of trapping sites. We demonstrate near-field enhancement and simulate trapping performance for 100 nm particles, verifying the possibility to trap > 1000 particles with a low total power of P < 30 mW. The multiplexed trapping with dielectric metasurfaces can open up new biological studies on viruses and vesicles.
Photonic generation and transmission of Linearly Chirped Microwave Waveform (LCMW) with a high Time-BandWidth Product (TBWP), of the order of 102 or more, is a widely used approach in Synthetic Aperture Radar (SAR) payloads to realize high range resolution, improving the distinction between two or more targets on the same bearing. In standard payload systems, an electronic approach based on voltage-controlled oscillator or digital signal processing, is used as LCMW generator, with both limited TBWP and operating frequency. In this context, a photonic approach plays a crucial role, ensuring low phase noise, high TBWP and operation frequency of the order of GHz, with a significant reduction of mass and size with respect to the electronic counterparts. Here, we propose the design of a Ka-band photonic LCMW generator, based on a frequency-tuneable Opto-Electronic Oscillator (OEO) and a Recirculating Phase Modulation Loop (RPML), with high spectral purity and high chirp rate in a small footprint. The OEO heart is a one-dimensional photonic crystal ring resonator with an ultra-high Q factor value and an optical delay < 10 μs. A low-frequency optical signal, with a high chirp rate and TBWP values of the order of 102-103, is generated in the RPML section.
The paper describes the quantum effects to be considered in the model of new integrated optical angular velocity sensors. Integrated optics provides a promising approach to low-cost, light weight, and high performance devices. Some preliminary results are also reported.
A fiber optic digital link for on-board data handling is modeled, designed and optimized in this paper. Design requirements and constraints relevant to the link, which is in the frame of novel on-board processing architectures, are discussed. Two possible link configurations are investigated, showing their advantages and disadvantages. An accurate mathematical model of each link component and the entire system is reported and results of link simulation based on those models are presented. Finally, some details on the optimized design are provided.
Recent results obtained on integrated optical gyroscopes are presented in this paper. The sensors configuration, based on high-Q resonators both in silica-onsilicon and InP technologies, is discussed and the estimation of the resonators performance through an accurate optical characterization is reported. On the basis of the numerical and experimental achievements, we demonstrate that resonant micro optical gyros can potentially exhibit resolution values in the range 1-10 °/h, which is demanded by several emerging space applications.
The experimental results of the system test of an optical resonant passive gyroscope based on a high Q-factor ring resonator in InP technology are reported. The open loop configuration based on the phase modulation was preferred among the analyzed configuration options, especially because it is potentially suitable for the monolithic integration of the entire sensor on a single chip. The setup components are described with a special emphasis on a custom digital readout board based on a field-programmable gate array. The board processes the input signals according to the proportional-integral algorithm which has been implemented through an optimized firmware. For the system test, the sensor rotation has been simulated using two properly driven acousto-optic modulators. The results reported here prove the gyro functionality and are a good starting point for the full development of the sensor.
Guidelines for the design and fabrication of polymer photonic crystal channel drop filters for coarse wavelength division multiplexing are provided. A Fabry-Perot cavity consisting of a membrane-type slab photonic crystal, where a hole row perpendicular to the propagation direction is removed, is considered. We selected nanoimprinting as the manufacturing technique. The influence on the cavity performance of several key parameters, i.e., polymer core material, lattice geometry, defect length, and holes’ radius, has been investigated in a device compliant with the requirement of the ITU-T G.694.2 standard. A detailed analysis of the fabrication tolerances has been carried out at 1551 nm. The maximum acceptable drift of the geometrical parameters has been accurately evaluated by using the finite element method to prove that the fabrication tolerances do not significantly affect the performance of polymer filters for coarse wavelength division multiplexing, when manufactured by thermal nanoimprinting lithography.
Here, we report the guidelines to be followed to optimize the design of a new angular velocity sensor based on an indium phosphide (InP) ring resonator. Optical properties of InP ring resonators have been investigated together with some significant physical effects for improving the sensor sensitivity. Three-dimensional algorithms have been utilized for the theoretical estimation of the waveguide loss. An optimized waveguide with propagation loss <0.3 dB/cm and a ring resonator with a quality factor of 1.5×10 6 have been designed. Performance of angular velocity sensors based on InP low-loss ring resonators has been estimated and discussed. Resolution of 10 deg/h and bias drift in the range of 0.1 to 0.3 deg/h have been evaluated for a fully integrated optical gyro including an InGaAsP/InP optical cavity having a footprint less than 24 cm 2 .
In this paper report on the design of a 2D PBG filter in polymeric material. The filter is a Fabry-Perot cavity having a
self-sustained membrane configuration. A deep parametric analysis has been carried out for improving the performance,
taking also into account the fabrication tolerances Best performance in terms of lateral confinement have been obtained
in case of square lattice. As for materials, polystyrene shown best in terms of refractive index value, length of the
photonic crystal structure and attenuation value in the band gap. The filter can be used either in sensing applications or in
telecommunication field.
Photonic devices that exploit photonic crystal (PhC) principles in a planar environment continue to provide a fertile field of research. 2D PhC based channel waveguides can provide both strong confinement and controlled dispersion behaviour. In conjunction with, for instance, various electro-optic, thermo-optic and other effects, a range of device functionality is accessible in very compact PhC channel-guide devices that offer the potential for high-density integration. Low enough propagation losses are now being obtained with photonic crystal channel-guide structures that their use in real applications has become plausible. Photonic wires (PhWs) can also provide strong confinement and low propagation losses. Bragg-gratings imposed on photonic wires can provide dispersion and frequency selection in device structures that are intrinsically simpler than 2D PhC channel guides--and can compete with them under realistic conditions.
Production of high- performance and low-cost new devices to be used in space applications is strongly required due to the remarkable development of innovative technologies in the last few years. Guided-wave optoelectronics technologies, including integrated optics, acousto-optics and electro-optics can provide some significant benefits to the space applications. In particular, they can overcome the intrinsic limits of the conventional technologies improving also the cost/performance figures, and enabling new services. Earth observation, telecommunications, radar surveillance and navigation control are the main space areas where guided-wave devices can contribute significantly. In this paper, after some general considerations on the potential of optoelectronics for space, on the use of acousto-optic guided-wave devices, a brief description of the acousto-optic interaction is given. Some functional devices reported in literature having significant potential impact in space applications are described with the aim of highlighting the main features of the acousto-optic technology. The performance limits of guided-wave devices for space applications are also shortly discussed.
Photonic crystal devices are now being produced for a variety of functions-and the need to provide thermal control of the behaviour suggests the use of thermo-optic effects. It has emerged that thermo-optic effects can provide useful modulation, switching and tuning capability. Future trends indicate fast, low-power, thermo-optically operated photonic crystal and photonic wire devices-and the possibility of simultaneous athermal characteristics.
Very compact and low-cost rotation sensors are strongly required for any moving systems in several applications. Integrated optical angular velocity sensors seem to be very promising in terms of low cost, compactness, light weight and high-performance.
In the paper a new integrated optical angular velocity sensor having a passive resonant configuration is proposed. Preliminary results are really encouraging and demonstrate the possibility of using the sensor in gyro systems for satellite applications.
In this paper a detailed analysis and design of guided-wave 2D photonic bandgap filters are presented by using the Floquet-Bloch approach. Significant performance has been obtained in one and three cavity PBG structures.
Widely tunable lasers are promising sources for future high-capacity dense wavelength divison multiplexing and photonic switching systems. These devices can be used for sparing in the cold standby mode, restoring in hot standby restoring, rerouting wavelength rerouting or conversion, or fast switching in all-optical networks. Tunable lasers need to demonstrate some featuers such as wide tunability range, optical output power of 10 dBm or more, cost and structure similar to those of commercial DFB lasers. High performance devices would require low laser chirp, high modulation speed, small size and very high reliability. For system applications, requirements on the tunable laser reliability are very stringent. Reliability studies and appropriate related testing procedures are necessary to define stability of tunable lasers and their expected lifetime. In this paper we propose some reliabilty test 'strategies' useful for qualification of tunable lasers with reference to some critical issues of the main technologies used to achieve the tunability feature.
In this paper system applications, geometry, physical effects and materials of optical switching devices are reviewed. Main system scenarios are presented and some key features such as size, loss, speed, scalability and granularity are highlighted. Two principal categories of optical switches are considered, i.e. guided-wave switches and free-space switches. In the first category some sub- classes have been identified according to their geometrical configuration, principle of operation and, then physical mechanism and materials. As for the geometry, the most frequently used configurations are briefly described together with their advantages and disadvantages. Different physical effects suitable to obtain the index change, which the switching function is based on, are also described with reference to the material substrates. Switches based on semiconductor optical amplifier gate are also analyzed. In the free-space category the main sub-classes are represented by the opto-mechanical devices and micro-opto-electro- mechanical systems switches. The last technology combines the free-space interconnecting with the integration capability on a single silica chip. The main advantages such as the ability to scaling up to large switch fabric and some issues such as packaging and reliability are analyzed. Finally, devices based on polarization change, acousto- optics interaction, total internal reflection and holography are illustrated.
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