Charting a course to efficient difference frequency generation in molecular-engineered liquid-core fiber.

Although χ(2) nonlinear optical processes, such as difference frequency generation (DFG), are often used in conjunction with fiber lasers for wavelength conversion and photon-pair generation, the monolithic fiber architecture is broken by the use of bulk crystals to access χ(2). We propose a novel solution by employing quasi-phase matching (QPM) in molecular-engineered hydrogen-free, polar-liquid core fiber (LCF). Hydrogen-free molecules offer attractive transmission in certain NIR-MIR regions and polar molecules tend to align with an externally applied electrostatic field creating a macroscopic χ e f f(2). To further increase χ e f f(2) we investigate charge transfer (CT) molecules in solution. Using numerical modeling we investigate two bromotrichloromethane based mixtures and show that the LCF has reasonably high NIR-MIR transmission and large QPM DFG electrode period. The inclusion of CT molecules has the potential to yield χ e f f(2) at least as large as has been measured in silica fiber core. Numerical modeling for the degenerate DFG case indicates that signal amplification and generation through QPM DFG can achieve nearly 90% efficiency.

Modeling quasi-phase-matched electric-field-induced optical parametric amplification in hollow-core photonic crystal fibers.

Laser sources in the short- and mid-wave infrared spectral regions are desirable for many applications. The favorable spectral guidance and power handling properties of an inhibited coupling hollow-core photonic crystal fiber (HC-PCF) enable nonlinear optical routes to these wavelengths. We introduce a quasi-phase-matched, electric-field-induced, pressurized xenon-filled HC-PCF-based optical parametric amplifier. A spatially varying electrostatic field can be applied to the fiber via patterned electrodes with modulated voltages. We incorporate numerically modeled electrostatic field amplitudes and fringing, modeled fiber dispersion and transmission, and calculated voltage thresholds to determine fiber lengths of tens of meters for efficient signal conversion for several xenon pressures and electrode configurations.

Volumetric imaging efficiency: the fundamental limit to compactness of imaging systems.

A new metric for imaging systems, the volumetric imaging efficiency (VIE), is introduced. It compares the compactness and capacity of an imager against fundamental limits imposed by diffraction. Two models are proposed for this fundamental limit based on an idealized thin-lens and the optical volume required to form diffraction-limited images. The VIE is computed for 2,871 lens designs and plotted as a function of FOV; this quantifies the challenge of creating compact, wide FOV lenses. We identify an empirical limit to the VIE given by VIE < 0.920 × 10-0.582×FOV when using conventional bulk optics imaging onto a flat sensor. We evaluate VIE for lenses employing curved image surfaces and planar, monochromatic metasurfaces to show that these new optical technologies can surpass the limit of conventional lenses and yield >100x increase in VIE.