Abstract
The optical-phased array (OPA) has gained special interest in recent years as a high-speed and compact imaging device. While large-scale OPAs have been demonstrated in single-pixel imaging, the complexity of the driver circuit is becoming a crucial problem as the number of phase shifters increases. Here, we investigate the phase shift requirement of OPA for single-pixel imaging and demonstrate, for the first time, that full 2π phase shifts are not mandatory to generate a set of illumination patterns with a sufficient degree of randomness required to reconstruct the image. Using a silicon photonic OPA chip with 128 carrier-depletion-based phase shifters, we experimentally confirm this property by successfully retrieving an image under a maximum phase shift of only ∼1.5π without affecting the quality of the image. Consequently, the input voltage can be reduced significantly. Since the carrier-depletion phase shifters generally require high driving voltages, this finding paves the way to high-speed OPA-based imaging with a minimum device requirement.
Highlights
S INGLE-PIXEL imaging has gained growing attention recently [1]–[10] and has been successfully implemented in numerous applications [9], including multi-spectral imaging [10], [11], light-detection-and-ranging (LiDAR) [12]–[14], ophthalmoscope [15], terahertz imaging [16], [17], threedimensional (3D) imaging [18]–[20], and flow cytometry [21]
From a singular-value decomposition (SVD) analysis, we show that these results can be explained by the general dependence of the condition number of the illumination pattern matrix on the applied phase shift
We have demonstrated numerically and experimentally that by using a silicon optical-phased array (OPA) with 128 carrier-depletion-based phase shifters, clear imaging with 90 resolvable points was possible at a maximum phase shift of only ∼1.5π
Summary
S INGLE-PIXEL imaging has gained growing attention recently [1]–[10] and has been successfully implemented in numerous applications [9], including multi-spectral imaging [10], [11], light-detection-and-ranging (LiDAR) [12]–[14], ophthalmoscope [15], terahertz imaging [16], [17], threedimensional (3D) imaging [18]–[20], and flow cytometry [21]. The pseudo-random illumination patterns constitute the key factor in determining the performance of single-pixel imaging. They have been commonly generated by using bulky spatial. Towards practical implementation of these systems, the authors have proposed and demonstrated the use of a compact and high-speed integrated optical phased array (OPA) in generating the illumination patterns [28], [29]. We investigate the phase shift requirement of OPA for single-pixel imaging and demonstrate, for the first time, that full 2π phase shifts are not mandatory to generate a set of illumination patterns with a sufficient degree of randomness required to reconstruct the image. From a singular-value decomposition (SVD) analysis, we show that these results can be explained by the general dependence of the condition number of the illumination pattern matrix on the applied phase shift
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