Laser-based satellite communication systems stabilized by non-mechanical electro-optic scanners

Abstract

Laser communications systems provide numerous advantages for establishing satellite-to-ground data links. As a carrier for information, lasers are characterized by high bandwidth and directionality, allowing for fast and secure transfer of data. These systems are also highly resistant to RF influences since they operate in the infrared portion of the electromagnetic spectrum, far from radio bands. In this paper we will discuss an entirely non-mechanical electro-optic (EO) laser beam steering technology, with no moving parts, which we have used to form robust 400 Mbps optical data connections through air. This technology will enable low cost, compact, and rugged free space optical (FSO) communication modules for small satellite applications. The EO beam-steerer at the heart of this system is used to maintain beam pointing as the satellite orbits. It is characterized by extremely low values for size, weight and power consumption (SWaP) -approximately 300 cm 3 , 300 g, and 5 W respectively, which represents a marked improvement compared to heavy, and power-consuming gimbal mechanisms. It is capable of steering a 500 mW, 1 mm short wave infrared (SWIR) beam over a field of view (FOV) of up to 50º x 15º, a range which can be increased by adding polarization gratings, which provide a coarse adjust stage at the EO beam scanner output. We have integrated this device into a communication system and demonstrated the capability to lock on and transmit a high quality data stream by modulation of SWIR power.

Validation of a spatial light modulator for space applications

“…Because of this work, polarization modulators based on liquid crystal variable retarders are used in remote sensing instruments on board the Solar Orbiter mission, from the European Space Agency [5]. Alternatively, in communication systems, this technology allows developing of non-mechanical laser beam steering technology, which provides advantages for stablishing satellite-to-ground data links [6].…”

Propagating transverse electric and transverse magnetic modes in liquid crystal-clad planar waveguides

“…An elegant alternative to these approaches exploits refraction, where beam deflection occurs when light passes through a tunable LC-based prism. This approach is laser-agnostic and can be combined with other discrete steering devices, like PGs, to greatly expand the field of regard [12]. The operating principle has been demonstrated by bulk transmission through a LC phase prism [13,14] and by utilising tunable LC prisms patterned in waveguides [15][16][17].…”

“…The operating principle has been demonstrated by bulk transmission through a LC phase prism [13,14] and by utilising tunable LC prisms patterned in waveguides [15][16][17]. The latter method has demonstrated low SWaP (size, weight and power), high throughput ( > 85%), rapid beam redirection (60 kHz) and continuous large-angle 2D steering (50°× 15°) [12].…”

“…Scattering losses are dominant at shorter wavelengths [26] and absorption losses oppress longer wavelengths [27]. Using the LC as a cladding layer and targeting wavelength regimes with low scattering and absorption helps mitigate these losses, which has led to the commercial development of tunable LC waveguides in the short-wave IR (SWIR) [12,16]. Prototype devices have been developed in the near IR (NIR) [28] and mid-wave IR (MWIR) [17], but LC losses in these regimes can already be prohibitive.…”

Large angle nonmechanical laser beam steering at 4.6 μm using a digital micromirror device

“…Over the past few years, the development of smaller, lighter beam steering devices with low power requirements has come to the forefront in response to applications such as remote LIDAR systems for chemical sensing as well as for reconnaissance, surveillance, and navigational systems for robots, drones, autonomous vehicles, and autonomous ships. [1][2][3][4][5][6] Other applications include communications systems, laser designators, and countermeasure systems against missile attacks. Several nonmechanical beam steering technologies have been demonstrated in the visible, near-infrared (NIR), and short wave IR (SWIR) spectral regions including systems based on diffraction [such as spatial light modulators (SLM), 7 optical phased arrays, 8 and polarization gratings 9 ] and refraction (for example, the SEEOR technology 10 or tunable liquid lenses 1 ).…”