Optical phased arrays borrow concepts from radar phased array science and technology to provide non-mechanical beam steering of electromagnetic radiation in the far field. Like radar phased arrays, this is achieved through controlling the relative phases of individual emitters on the device. However, since the device size scales with the wavelength of the electromagnetic signal, moving from radar to optical signals involves a reduction in size by more than 4 orders of magnitude. As a result, optical phased arrays can be created on a compact, chip-scale platform. This is particularly of interest for inter-spacecraft communications where high bandwidth optical signals can be communicated in free-space from one location to another. Providing this functionality with a low SWaP, chip-scale device is crucial for space applications. Recently, many chip-scale optical phased arrays have been developed to provide non-mechanical beam steering of light at optical frequencies, including many demonstrations at the telecommunications wavelength of 1550 nm. Here we will discuss the existing demonstrations as well as highlight the tradeoffs between different designs. We will highlight the importance of spacing the emitters at a technologically challenging pitch that is half the operational wavelength in order to avoid the many negative effects of grating lobes, including power loss, steering range limitation, and the opportunities they provide for eavesdropping.
Optical beam spread and beam quality factor in the presence of both an initial quartic phase aberration and atmospheric turbulence are studied. We obtain the analytical expressions for both beam radius-squared and the beam quality factor using the moment method, and we compare these expressions with the results from Monte Carlo simulations, which allow us to mutually validate the theory and the Monte Carlo simulation codes. We then analyze the first- and second-order statistical moments of the fluctuating intensity of a propagating laser beam and the probability density function versus intensity as the beam propagates through a turbulent atmosphere with constant Cn2. At the end, we compare our analytical expression and our simulations with field test experimental results, and we find a good agreement.
We simulate the propagation of both a partially spatially coherent infra-red (IR) and a visible laser beam through a turbulent atmosphere, and we compare the intensity fluctuations produced in the simulation to the intensity fluctuations that are observed in both maritime and terrestrial environments at the US Naval Academy. We focus on the effect of the level of turbulence and the degree of the beam's spatial coherence on the receiver scintillations, and we compare the probability density function (PDF) of the intensity in our simulation to the experimental data. We also investigate the effect of optical beam spreading on the coherent and partially coherent laser beams along the propagation path.
KEYWORDS: Digital signal processing, Monte Carlo methods, Atmospheric turbulence, Turbulence, Atmospheric optics, Atmospheric propagation, Gaussian beams, Solids, Free space optical communications, Laser beam propagation
Optical beam spread and beam quality factor in the presence of both quartic phase aberrations and atmospheric turbulence is numerically analyzed. We obtain analytical expressions for both the mean-square beam radius and the beam quality factor using the moment method, and we compare these expressions to the results from Monte Carlo simulations, which allows us to mutually validate the theory and the Monte Carlo simulation codes. We also discuss the reason for the discrepancy between the classical approach for calculating the ensemble-averaged mean-square beam radius in a turbulent atmosphere that is described by Andrews and Phillips and by Fante versus using the moment method.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.