Backward wave optical parametric oscillators (BWOPO) represent a class of nonlinear optical devices where the signal and idler photons are generated in strictly opposite directions [1]. Realizing such an oscillation requires a quasi-phase-matching (QPM) approach with sub-µm-periodicity structures [2]. Theoretically and experimentally, the temporal phases of the forward and backward waves generated in BWOPO have been shown to be well determined [3]. In particular, the forward-generated wave inherits the temporal phase modulation of the pump [4]. In contrast, the temporal phase of the backward-generated wave remains fixed as required by the general phase relations in the parametric interaction. Spatially structured beams have been receiving increasing interest due to substantial advantages offered for many applications, including optical communications [5]. The synthesis of parametric beams with spatially and temporally designed phases at any wavelength allowed by the transparency of the QPM material would be of great interest. So far, there has been no theoretical or experimental investigation on generating spatially structured beams in BWOPO.

As demand for customized specialty fibers grows, standardized production methods face challenges. This article reviews industry standards and discusses potentially disruptive techniques that enable rapid prototyping and fabrication of optical fiber devices. Furthermore, we showcase laser powder deposition's (LPD) potential for additive manufacturing (AM) of customized glass structures. In the case of, for example, fiber preforms, although the feasible size is smaller than the industry standard, utilizing laser-based manufacturing techniques for a small batch production presents an attractive avenue for rapid prototyping and expedites material and design optimization. In the realm of AM of glass, LPD offers numerous benefits, including minimal shrinkage, high densification, and the ability to tailor glass composition to achieve desired optical properties. The article reviews the latest achievements and highlights future directions in this technology.

In this study, quenching dynamics in RE-doped silica glass were investigated through the measurement of excited-state lifetimes of heavily doped silica micro-hemispheres fabricated directly on the end face of a multimode fiber (MMF).