title: Comparison of efficiency and feedback characteristics of techniques of coupling semiconductor lasers into single-mode fiber.
abstract: The coupling of CSP lasers to single-mode fibers with different coupling structures made on the fiber face is investigated. In this case easy to make coupling arrangements such as tapers and microlenses, result in a high launching efficiency (approximately 2-dB loss), in contrast to launching from gain-guided lasers with strong astigmatism and a broader far-field pattern. Index-guiding lasers exhibit, however, a higher sensitivity to optical feedback. Laser output power and wavelength are changed due to reflections from the fiber tip. Critical distances exist which lead to a highly unstable laser spectrum. A comparison of the influence of various fiber faces on laser power and wavelength stability is presented. It is concluded that a tapered fiber end with a large working distance reduces the influence on the laser's performance.
authors.affiliation: Heinrich-Hertz-Institut fur Nachrichtentechnik Berlin GmbH; Einsteinufer 37, 1000 Berlin 10, West Germany.
authors.forename: G
authors.initials: G
authors.lastname: Wenke
authors.forename: Y
authors.initials: Y
authors.lastname: Zhu