Fundamental Limits on Subwavelength Range Resolution

We establish fundamental bounds on subwavelength resolution for the radar ranging problem, ``super radar''. Information theoretical metrics are applied to probe the resolution limits for the case of both direct electric field measurement and photon-counting measurements. To establish fundamental limits, we begin with the simplest case of range resolution of two point targets from a metrology perspective. These information-based metrics establish fundamental bounds on both the minimal discrimination distance of two targets as well as the precision on the separation of two subwavelength resolved targets. For the minimal separation distance, both the direct field method and photon counting method show that the discriminability vanishes quadratically as the target separation goes to zero, and is proportional to the variance of the second derivative of the electromagnetic field profile. Nevertheless, robust subwavelength estimation is possible. Several different band-limited function classes are introduced to optimize discrimination. We discuss the application of maximum likelihood estimation to improve the range precision with optimal performance. The general theory of multi-parameter estimation is analyzed, and a simple example of estimating both the separation and relative strength of the two point reflectors is presented

Visualization 3: Digital integral cloaking

The actual input scan used for generating our cloaked image, but sped up by 500%, reduced frame rate (30 fps (frames per second) versus 60 fps), with reduced bitrate (5 Mbps from 26 Mbps). Originally published in Optica on 20 May 2016 (optica-3-5-536

Visualization 1: Digital integral cloaking

Cloak observed from changing horizontal positions, compared to without cloak. Camera was 260 cm from display screen. Movie sped up by 200% from original. 13.4 deg total viewing range. Centers of cloak and camera aligned (0 deg , x = 0) at 13 s (of 20 s clip). Originally published in Optica on 20 May 2016 (optica-3-5-536

Visualization 2: Digital integral cloaking

Example scan of background objects by input camera on a horizontal slider. A shorter scan distance than Visualization 1 sufficed for the setup we demonstrated. Originally published in Optica on 20 May 2016 (optica-3-5-536

Media 2: Paraxial ray optics cloaking

Originally published in Optics Express on 01 December 2014 (oe-22-24-29465

Supplement 1: Digital integral cloaking

Supplemental document Originally published in Optica on 20 May 2016 (optica-3-5-536

Media 3: Paraxial ray optics cloaking

Originally published in Optics Express on 01 December 2014 (oe-22-24-29465

Media 1: Paraxial ray optics cloaking

Originally published in Optics Express on 01 December 2014 (oe-22-24-29465

Media 4: Paraxial ray optics cloaking

Originally published in Optics Express on 01 December 2014 (oe-22-24-29465

Frequency-modulated continuous-wave LiDAR compressive depth-mapping

We present an inexpensive architecture for converting a frequency-modulated continuous-wave LiDAR system into a compressive-sensing based depth-mapping camera. Instead of raster scanning to obtain depth-maps, compressive sensing is used to significantly reduce the number of measurements. Ideally, our approach requires two difference detectors. % but can operate with only one at the cost of doubling the number of measurments. Due to the large flux entering the detectors, the signal amplification from heterodyne detection, and the effects of background subtraction from compressive sensing, the system can obtain higher signal-to-noise ratios over detector-array based schemes while scanning a scene faster than is possible through raster-scanning. %Moreover, we show how a single total-variation minimization and two fast least-squares minimizations, instead of a single complex nonlinear minimization, can efficiently recover high-resolution depth-maps with minimal computational overhead. Moreover, by efficiently storing only $2m$ data points from $