Abstract
Optical feedback has an impact on the tunability of lasers. We created a model of a tunable distributed Bragg reflector (DBR) laser describing the effect of optical feedback from a constant reflector distance on the wavelength tuning. Theoretical and experimental results are in good agreement. A further discussion of the model sheds light on design rules to reduce the effect of optical feedback on the tuning behavior. We introduced a new parameter called mode loss difference (MLD) as a metric for the feedback tolerance of the tuning behavior. A large MLD indicates higher tolerance of the laser to cavity length variations.
Highlights
T HE reintroduction of a laser beam back into its laser cavity is called optical feedback [1]
Based on the model we extend the perspective on the feedback parameters, which are the power ratio and the distance to the external reflection, and include certain laser design parameters like the laser cavity length, the full width half maximum (FWHM), and the maximum reflectivity of the Bragg grating
This paper describes a model of a tunable laser with optical feedback from a constant distance reflection which can be handled as an external cavity
Summary
T HE reintroduction of a laser beam back into its laser cavity is called optical feedback [1]. A further discussion of the transition from short to long cavity regime can be found in [9] This does not tell us about the impact of optical feedback on the lasing mode stability during laser tuning. In order to describe the effect, we set up a laser model which allows the discussion of the wavelength tuning under optical feedback from a reflection at a constant short distance, which can be interpreted as an external cavity next to the laser cavity, on referred as feedback section. Certain design rules are suggested which reduce the negative effects on the tunability in the case of optical feedback from a reflection at a constant distance external to the laser cavity. We consider only one roundtrip of the back reflected beam which is on referred to as feedback beam
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