This paper provides an extensive survey of nonlinear parametric upconversion infrared (IR) imaging, from its origin to date. Upconversion imaging is a successful innovative technique for IR imaging in terms of sensitivity, speed, and noise performance. In this approach, the IR image is frequency upconverted to form a visible/near-IR image through parametric three-wave mixing followed by detection using a silicon-based detector or camera. In 1968, Midwinter first demonstrated upconversion imaging from short-wave-IR (1.6 μm) to visible (484 nm) wavelength using a bulk lithium niobate crystal. This technique quickly gained interest, and several other groups demonstrated upconversion imaging further into the mid- and far-IR with significantly improved quantum efficiency. Although a few excellent reviews on upconversion imaging were published in the early 1970s, the rapid progress in recent years merits an updated comprehensive review. The topic includes linear imaging, nonlinear optics, and laser science and has shown diverse applications. The scope of this article is to provide in-depth knowledge of upconversion imaging theory. An overview of different phase matching conditions for the parametric process and the sensitivity of the upconversion detection system are discussed. Furthermore, different design considerations and optimization schemes are outlined for application-specific upconversion imaging. The article comprises a historical perspective of the technique, its most recent technological advances, specific outstanding issues, and some cutting-edge applications of upconversion in IR imaging.

Helico-conical optical beams, different from higher-order Bessel beams, are generated with a parallel-aligned nematic liquid crystal spatial light modulator (SLM) by multiplying helical and conical phase functions leading to a nonseparable radial and azimuthal phase dependence. The intensity distributions of the focused beams are explored in two- and three-dimensions. In contrast to the ring shape formed by a focused optical vortex, a helico-conical beam produces a spiral intensity distribution at the focal plane. Simple scaling relationships are found between observed spiral geometry and initial phase distributions. Observations near the focal plane further reveal a cork-screw intensity distribution around the propagation axis. These light distributions, and variations upon them, may find use for optical trapping and manipulation of mesoscopic particles.

We transform a ${\mathrm{TEM}}_{00}$ laser mode into multiple counterpropagating optical traps to achieve four-dimensional simultaneous manipulation of multiple particles. Efficient synthesis and dynamic control of the counterpropagating-beam traps is carried out via the generalized phase contrast method, and a spatial polarization-encoding scheme. Our experiments genuinely demonstrate real-time, interactive particle-position control for forming arbitrary volumetric constellations and complex three-dimensional trajectories of multiple particles. This opens up doors for cross-disciplinary cutting-edge research in various fields.

Counterpropagating light fields provide a stationary optical potential well for a Brownian particle. Introducing variability in the relative strengths of the counterpropagating beams allows us to create a more general configuration—the optical elevator. An optical elevator dynamically controls the axial location of the potential minimum where the particle finds a stable equilibrium position. We describe the implementation of multiple real-time reconfigurable optical elevators with the generalized phase contrast method for dynamic manipulation of polystyrene spheres and yeast cells S. cerevisiae in three dimensions.

Cellular development is highly influenced by the surrounding microenvironment. We propose user-reconfigurable microenvironments and bio-compatible scaffolds as an approach for understanding cellular development processes. We demonstrate a model platform for constructing versatile microenvironments by fabricating morphologically complex microstructures by two-photon polymerization (2PP) and then assembling these archetypal building blocks into various configurations using multiple, real-time configurable counterpropagating-beam (CB) traps. The demonstrated capacity for handling feature-rich microcomponents may be further developed into a generalized microassembly platform.

Applying a newly developed user-interactive optical trapping system, we controllably surrounded individual cells of one yeast species, Hanseniaspora uvarum, with viable cells of another yeast species, Saccharomyces cerevisiae, thus creating a confinement of the former. Growth of surrounded and non-surrounded H. uvarum cells was followed under a microscope by determining their generation time. The average generation time of surrounded H. uvarum cells was 15% higher than that of non-surrounded cells, thereby showing that the confinement imposed by viable S. cerevisiae cells on H. uvarum inhibits growth of the latter. This study is the first to demonstrate that confinement is a determinant of growth in a microbial ecosystem.