High speed (≥1Ghz) and long distance (≥100km) data communication among CubeSats and NanoSats can accelerate the technology advancement and paves the way for critical applications such as formation flying and remote sensing. Design of a simple, lightweight optical transceiver with full duplex capability, fast-tracking speed and 360° field of regard for CubeSat is crucial due to extreme SWaP-C limitations. In this paper, we describe the design tradeoff between the field of view and collection efficiency in receiver design using Commercial off the Shelf (COTS) optics and detectors. We also briefly discussed the design tradeoffs in transmitter design for optimum performance. We show that to achieve maximum SNR at long distance(≥100km), the laser beam diameter needs to be 80%-90% of the scanning mirror diameter. In addition to that, we show that the intrinsic Field of View (FOV) of high speed(≥600MHz) Avalanche Photodiodes (APD) can be increased to ≥3° by incorporating optimized optics considering form factor of the CubeSat system. In addition, we present a scalable detector array design method using COTS components to achieve a wide full FOV(≥12°) with a uniform collection efficiency around 30%-60%. Furthermore, we demonstrated a multi-wavelength full duplex communication system based on dichroic filters as duplexer that shows significantly low crosstalk. The system also exhibits low transmission power loss(≤4%) as opposed to around 40% that of the conventional beam splitter based system.
We are developing an inter-satellite omnidirectional optical communicator (ISOC) that will enable gigabit per second data rates over distances up to 1000 km in free space. Key features of the ISOC include its high data rates and its ability to maintain multiple simultaneous links with other spacecraft. In this paper we present design considerations for the ISOC, including selection of the mission-appropriate geometry, telescope design, receiver design, as well as beam pointing considerations. We also present experimental results obtained with the ISOC prototype. In addition, we present design considerations for a low-Earth-Orbit mission where four ISOC-furnished CubeSats form a swarm suitable for remote sensing. We believe the ISOC could be a technology enabler for future constellation and formation flying CubeSat missions for Remote Sensing.
We propose a plasmo-thermomechanical mid-infrared detector operating at 4.3 μm wavelength. The design utilizes an array of the bimetallic fishbone nanowires that are suspended 50 nm above a 1.5 μm × 0.3 μm silicon nitride waveguide to create a leaky wave radiation. Moreover, the thermo-mechanically actuated nanowire will induce evanescent wave modulation that can be detected by the leaky wave or transmitted power of the waveguide. The antenna has a strip length of 1.77 μm and can yield an absorption coefficient of 42.4% with a period of 3.1 μm. Six unit cells are connected by a nanowire, and the fishbone-like nanowires are clamped at the two ends, leaving the center free to bend. The mid-infrared energy is absorbed by the resonant metallic antennas, resulting in a temperature increment. The mismatch of the thermal expansion coefficients of the bimetallic materials, gold and nickel, actuates the nanowire, and thus changes the gap between the nanowire and the waveguide. The deformation of the nanowire modulates the waveguide evanescent field, and hence alternates the transmitted power as well as the leak wave power. With a normal incident power of 4 μW/μm<sup>2</sup> , the temperature in the center of the nanobridge can be increased over 135 K above the ambient temperature, leading to an elevation of 23.5 nm in the center and thus weakening the evanescent modulation strength. The difference of S<sub>21</sub> caused by the gap change is 0.106. This methodology can be applied in other spectrums and the fabrication progress will be reported later.