Linewidth reduced cascaded Raman fiber lasers and their harmonic conversion for visible laser sources.

Cascaded Raman Fiber Lasers (CRFLs) are wavelength versatile sources that can provide power at any wavelength in the Near-Infrared (NIR) region. Conventional CRFLs with broadband feedback are widely wavelength tunable but have broad line widths. A feedback mechanism must be used to reduce the broadening of the linewidth without compromising the wavelength tunability. Here, we propose to use a dual feedback mechanism that combines broadband feedback at all wavelengths, using a flat cleave, with filtered feedback at a desired wavelength due to a grating filter. This allows substantial linewidth reduction of CRFLs up to the 6th Raman shifts, from 1100 nm to 1500 nm, and can be extended further. Significantly reduced linewidth with multi-watt in-band output power is achieved with fine wavelength tuning within each Raman Stokes band using a fixed wavelength pump. As an application of linewidth narrowed output, we performed frequency doubling of CRFL output to generate over 100 mW of wavelength tunable yellow-green and yellow output with enhanced efficiency.

Food security and sustainability dimensions of organic farming in the context of India: a comprehensive scientometric review (2010-2023).

The study investigated the scientific output, collaboration, and impression of research on organic farming due to the increasing interest of commoners in food quality and sustainability. Efforts to enhance agroecological sustainability call for assessing the structural overview of the numerous research works done so far to understand the growth in diverse subject areas in organic farming. The scientometric method is considered for analyzing 639 documents extracted from the Scopus and WoS online database from 2010 till January, 2023. The pulled-out data is analyzed via VOSviewer and RStudio, revealing prominent contributing authors (Groot J. with eight documents and 186 citations under Wageningen University and Research), maximum cited references (R Core Team & R lang env. 2019), the significant collaboration between the countries (USA with Netherlands), and co-occurrence of author keywords ("organic farming" occurring 148 times) using analysis of co-authorship, co-occurrence, and citation count. Furthermore, as the existing literature suggests a substantial advancement in organic cultivation in India, thus, an immediate evaluation of its performance is necessitated. Hence, the current study performed the bibliographic coupling of documents, sources, authors, and global collaboration of India. The study found that a total of 241 Indian authors have contributed 102 documents in collaboration with 54 nations towards organic farming which are available in 39 different sources under the Scopus and WoS databases. This study helps to comprehend the recent growth trend of organic agricultural research and can enhance academic as well as research and development policies based on brainstorming to action formulation.

Cascaded Raman fiber lasers with ultrahigh spectral purity.

Random distributed feedback (RDFB) cascaded Raman fiber lasers (CRFLs) are simple, wavelength agile, and enable high-power fiber lasers outside emission bandwidths of rare-earth doped fiber lasers. However, the spectral purity, defined as the percentage of total output power in the desired Stokes wavelength band, and relative intensity noise (RIN) of these systems are limited due to the intensity noise of the pump source used for Raman conversion. RIN gets amplified and transferred to Raman Stokes orders which causes incomplete Raman conversion and hence limits the spectral purity. Here, we demonstrate a low-intensity noise (<-100 dBc/Hz from 9 kHz to 10 GHz) CRFL with a record spectral purity of ∼99%, tunable over six Stokes orders, using a very low-intensity noise, narrow linewidth Yb-fiber amplifier as a pump source.