# Non-Mechanical Beam Steering with Polarization Gratings: A Review
## 4 Conclusions  
When used for non-mechanical beam steering, PGs provide a unique combination of wide angle, large aperture, and manufacturability that makes them attractive for a wide range of optical systems. In this review, we have attempted to summarize the defining characteristics of this steering architecture and highlight several applications that can benefit from PG steering in different ways. In general, the technology is best suited to narrowband applications that require a modest number of steering angles or in SWaP-constrained applications requiring large clear apertures. Conversely, the technology is often a poor choice to replace conventional raster  
Figure 16: Diagram of the telescope assembly incorporating the shutter array and relay optics integrated with the InSb infrared FPA. Figure 17: Imaging tests with hot targets at a range of \(\sim\)50 m. The testing verified the effective shutter extinction of hot, bright targets. The targets were separated by 5.8\({}^{\circ}\) to verify the switching of the field-of-regard. scanning devices where dense, high-resolution point clouds are to be acquired one angle at a time at high speed. For example, a 512 \(\times\) 512 resolution image would require an 18-stage PG steering assembly. At an approximate per stage transmission of 96%, such a device would offer a maximum of 48% efficiency and the millisecond-scale switching speeds can push acquisition times into minutes. At this time, these continuous steering applications pose a challenge to PG steering approaches. As previously noted, in these cases PG steering can be paired with small-angle continuous steering modalities, or perhaps with emerging tunable PG approaches [30]. Nevertheless, there is a growing demand for rugged, inexpensive, non-mechanical steering solutions to meet the needs of emerging markets, such as automotive lidar, ground- and satellite-based laser communications, and turbine-mounted wind sensing. In such applications, PG steering has the potential to play a significant role. [PERSON], [PERSON], and [PERSON] ([PERSON]), wrote the manuscript. [PERSON]. ([PERSON]), [PERSON], and [PERSON] revised the manuscript. [PERSON] led the development of the PG-steered ToF camera and MWIR imager. [PERSON] led the development of the coherent Doppler lidar work. All authors have read and agreed to the published version of the manuscript. Section 3.1 was supported under NASA Phase I SBIR contract 80 NSSC18P2206. Section 3.2 was supported under NASA Phase I SBIR contract NNX15 CL44F. Section 3.3 was supported under Air Force Phase II SBIR contract FA8650-08-C-1311. * (12) [PERSON]; [PERSON]; [PERSON]; [PERSON] Wide-angle, nonmechanical beam steering with high throughput utilizing polarization gratings. _Appl. Opt._**2011**, _50_, 2636-2639. [CrossRef]
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