Abstract
In this study, high-order distributed-feedback (DFB) polymer lasers were comparatively investigated. Their performance relies on multiple lasing directions and their advantages include their high manufacturing tolerances due to the large grating periods. Nine laser cavities were fabricated by spin-coating the gain polymer films onto a grating structure, which was manufactured via interference lithography that operated at the 2nd, 3rd, and 4th DFB orders. Low threshold lasing and high slope efficiency were achieved in high-order DFB polymer lasers due to the large grating groove depth and the large gain layer thickness. A high-order DFB configuration shows possible advantages, including the ability to control the lasing direction and to achieve multiple-wavelength lasers. Furthermore, our investigation demonstrates that the increase in threshold and decrease in slope efficiency with an increase in the feedback order can be limited by controlling the structural parameters.
Highlights
Fluorene-based polymers, which have large stimulated emission cross-sections and wide gain spectra ranges, are ideal active materials for creating distributed feedback (DFB) lasers [1,2,3]
In the realm of DFB configurations, the 1st and 2nd order laser cavities have already been comprehensively studied [9,10,11,12], especially 2nd order DFB lasers, which has a feedback mechanism that was found to be provided by 2nd order diffraction
We focus on improving the performance of high-order DFB polymer lasers, and the gain layer thickness
Summary
Fluorene-based polymers, which have large stimulated emission cross-sections and wide gain spectra ranges, are ideal active materials for creating distributed feedback (DFB) lasers [1,2,3]. The above Bragg condition states that one may 2continue operating at a given wavelength by increasing the period Λ and by resorting to selecting a feedback grating period, m is the Bragg order, and λ is the free-space lasing wavelength), the optical grating mechanism associated a higher order m. DFB polymer adjusting structural parameters, which are mainly the grating groove depth of the grating structure lasers In this present study, we focus on improving the performance of high-order DFB polymer lasers, and the gain layer thickness. By spin-coating the gain polymer onto the grating structures, the total cavity heights are aiming to improve the lasing threshold and the slope efficiency. Bragg orders and various structural parameter combinations in the DFB and a larger grating groove depth and larger gain layer thickness will decrease the lasing threshold polymer lasers.
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