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Comparison of efficiency and feedback characteristics of techniques for coupling semiconductor lasers to single-mode fiber

: Wenke, G.; Zhu, Y.

Applied optics 22 (1983), No.23, pp.3837-44
ISSN: 0003-6935
ISSN: 1539-4522
ISSN: 1559-128X
Journal Article
Fraunhofer HHI ()
feedback; laser beam applications; light reflection; optical fibres; semiconductor laser coupling to single mode fibres; index guiding lasers; laser output power; critical distances; efficiency; feedback characteristics; csp lasers; coupling structures; fiber face; tapers; microlenses; launching efficiency; gain-guided lasers; astigmatism; far-field pattern; optical feedback; reflections; unstable laser spectrum; laser power; wavelength stability; tapered fiber; working distance

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.