OPOs

OPOs denote two distinct concepts in different fields. In optics, Optical Parametric Oscillators are nonlinear devices that generate tunable coherent light. An OPO uses a nonlinear crystal inside a resonator and is pumped by a laser. The pump photon splits into two lower-energy photons, called signal and idler, via parametric down-conversion. Phase matching ensures energy and momentum conservation. By adjusting temperature, angle, or pump wavelength, OPOs offer continuous tunability across broad spectral ranges, often from near- to mid-infrared. They may be singly or doubly resonant, with designs chosen for efficiency, stability, and linewidth. Applications include spectroscopy, metrology, imaging, and laser science.

In healthcare, OPOs stand for Organ Procurement Organizations. These nonprofit entities coordinate recovery and distribution of organs from deceased and some living donors. They work with hospitals, transplant centers, organ registries, and regulators to evaluate donors, obtain consent, preserve and recover organs, and arrange transport. They operate within a national network that coordinates allocation based on urgency, compatibility, and waiting time. OPOs also educate the public to encourage donation and maintain performance data. In the United States, OPOs are federally designated and collaborate with UNOS/OPTN. Key challenges include donor shortages, geographic disparities, and the need for ethical, transparent allocation.