J. Eur. Opt. Society-Rapid Publ. 21, 25( 2025) 249
Funding
Funding has been provided by the Swedish Foundation for Strategic Research grant no. STP19-0081 and the Swedish Research Council grants 2019-04330 and 2024-05529.
Conflicts of interest The authors have no conflict of interest.
Data availability statement This article has no associated data generated.
Author contribution statement Both authors have contributed to and reviewed the manuscript.
Fig. 7. BWOPO scan measuring ambient air in the laboratory where the two dips in the spectrum comes from absorption of CO 2 and H 2 O [ 44 ].
absorption lidar( DIAL) systems. The system stability and narrow linewidth provides means for improves detection sensitivity for CO 2 or other trace gases, even for lowconcentration scenarios.
5 Summary and future outlook
BWOPOs are highly efficient, energy-scalable devices with a simple architecture that eliminates the need for mirrors or external feedback. The unique distributed feedback mechanism and stability ensures robust operation, even in demanding environments. This feature is particularly valuable for applications where external feedback systems may introduce complexity or alignment challenges.
Moreover, their spectral properties, particularly the narrow linewidth and tunability make them ideal for precision tasks, as the backward wave at the same time is both highly stable and resistant to environmental fluctuations. These advantages underscore the growing interest in BWOPOs across various scientific disciplines and will make them indispensable in applications ranging from biomedical research and quantum optics to different types of spectroscopies like Raman, OCT, or DIAL. Fundamental research will benefit from their use in atomic and molecular physics, cold atom experiments, and nonlinear optics, while industrial applications include precise manufacturing, advanced sensing, and semiconductor inspection. These versatile light sources will help to transform industries, providing unparalleled accuracy and reliability for cutting-edge innovations.
Looking ahead, the integration of BWOPOs with emerging technologies, such as machine learning and adaptive optics, holds promise for unlocking new functionalities and applications. These advancements could pave the way for breakthroughs in fields as diverse as healthcare, environmental monitoring, and fundamental physics. Future research aims to demonstrate continuous wave devices and further enhance their energy efficiency, extend wavelength coverage, and explore new material systems for broader applicability.
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