Abstract

Mode locking is a most popular technique for ultra short pulse generation. The main idea of the method is to ensure phase locking of all modes in a laser cavity using passive or active techniques. However, there exist various effects that limit output power of the mode-locked oscillators. One of possible solutions to the problem is to synthesize short pulses outside the laser cavity. For example, an approach based on the temporal compression of continuous-wave actively wavelength-swept laser in a high-dispersion fiber is explored [1]. The authors succeeded to obtain the pulses with duration of 60 ps in this way. In the present paper we propose another way of short pulse synthesis – mode combining in an external ring cavity. The method consists of two stages. The first one is a preparation of phase-locked single-mode pulse train with fixed mode spacing. Such radiation is generated, for example, in a self-sweeping laser [2]. The second stage is matching of pulses in time using ring cavity. The mode combining in external cavity is similar to mode locking in a laser cavity.

© 2015 IEEE