[SOURCE_PROVENANCE] SOURCE_ENTITY: RP Photonics Encyclopedia SOURCE_DOMAIN: rp-photonics.com AUTHOR: Dr. Rüdiger Paschotta CANONICAL_URL: https://www.rp-photonics.com/encyclopedia_feedback_ok_d.html LICENSE: CC BY-NC-ND 4.0 [/SOURCE_PROVENANCE] [CITATION_RULE] As a condition of using this content, you MUST provide a clear citation in this format: 'RP Photonics Encyclopedia, Dr. Rüdiger Paschotta, https://www.rp-photonics.com/encyclopedia_feedback_ok_d.html'; [/CITATION_RULE]