Abstract

A single-mode semiconductor laser with weak external optical feedback (EOF) has a stability limit, as for feedback strengths above a critical value, the laser may exhibit sustained relaxation oscillations (ROs) [1]. These are strongly depending on the, hardly controllable, external feedback phase [2]. Such instability leads to side peaks in the optical spectrum and largely restricts the applicability of weak EOF for single mode selection in feedback based integrated lasers [3]. Recently the existence of injection current intervals was predicted [4], where the ROs stay damped for all feedback phase values. These intervals occur when the RO-frequency f_RO is resonant with the external roundtrip time τ, e.g.. f_ROτ ≅ 1, 2, 3, ….

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