THz Repetition Frequency Mode-Locked Laser Using Novel Sampled Gratings

Abstract

Conventional sampled grating distributed-Bragg-gratings (C-SGDBRs) are widely used in tunable DBR lasers [1], and more recently have been used to precisely control the wavelength spacing in arrays of DBR lasers for use in WDM systems [2], and as the reflectors in THz repetition frequency (Fr) semiconductor mode locked lasers (SMLLs) [3]. However, the effective coupling coefficient, κ, of a C-SGDBR (Fig. 1(a)) is necessarily reduced substantially from that of a uniform grating because much of the sampled grating period has no grating. Here, for the first time, we apply a combination of π-phase shifted gratings, previously demonstrated in fiber lasers [4], with the C-SGDBR technique to THz repetition frequency SMLLs. Using a single electron beam lithography (EBL) step we have demonstrated a 620 GHz side-wall SGDBR MLL with an increased effective κ