Fundamental Transverse Mode Selection (TMS#0) of Broad Area Semiconductor Lasers with Integrated Twice-Retracted 4f Set-Up and Film-Waveguide Lens

Abstract

Previously we focused on fundamental transverse mode selection (TMS#0) of broad area semiconductor lasers (BALs) with two-arm folded integrated resonators for Fourier-optical spatial frequency filtering. The resonator had a round-trip length of 4f, where f is the focal length of the Fourier-transform element (FTE), that is, a cylindrical mirror in-between the orthogonal resonator branches. This 4f set-up can be called "retracted once" due to the reflective filter after 2f ; that is, the 2f path was used forwards and backwards. Now the branches are retracted once more resulting in a compact 1f long linear resonator (called "retracted twice") with a roundtrip length of 2f. One facet accommodates the filter, while the other houses the FTE, now incorporating a film-waveguide lens. The BAL facet with the filter represents both the Fourier-transform plane (after 2f, i.e., one round-trip) as well as the image plane (after 4f, two round-trips). Thus filtering is performed even after 4f, not just after 2f. Experimental results reveal good fundamental TMS for pump currents up to 20% above threshold and a one-dimensional beam quality parameter 2 1D = 1.47. The BALs are made from AlGaInAsSb, but the concept can equally well be employed for BALs of any material system.

1D Confocal Broad Area Semiconductor Lasers (Confocal BALs) for Fundamental Transverse Mode Selection (TMS#0)

“…Previously in this journal we have also reported on a concept for TMS#0, which has employed a twice-retracted integrated 4f set-up with an actual length of 1f forming the laser resonator [26]. One facet has incorporated the spatial frequency filter, while the other one has housed a film-waveguide lens as the 1D Fourier-transform element.…”

Chirped photonic crystal for spatially filtered optical feedback to a broad-area laser

“…In contrast to single lateral (transverse) mode lasers, a substantial width (x-coordinate) of the broad-area (BA) DLs leads to emission on multiple lateral optical modes, therefore the proper modeling of the spatiotemporal dynamics in these DLs should be performed by at least 1 (time) + 2 (space)-dimensional partial differential equations [3,4]. Hence, the detailed experimental and theoretical study of BA-ECDLs and high-power (HP) BA-ECDLs, in particular, becomes much more complex [4][5][6][7][8][9][10][11][12][13][14][15]. Due to potential applications of BA-HPDLs as HP optical sources, the majority of works on BA-HPECDL systems are discussing methods for tailoring the emitted beam and improving the beam quality by optical feedback from a properly designed EC [8][9][10][11][12], study the damages implied by unwanted reinjection of the optical fields [13], or analyze the optical modes governed by the reduced-dimension PDE models [14][15][16].…”

“…Hence, the detailed experimental and theoretical study of BA-ECDLs and high-power (HP) BA-ECDLs, in particular, becomes much more complex [4][5][6][7][8][9][10][11][12][13][14][15]. Due to potential applications of BA-HPDLs as HP optical sources, the majority of works on BA-HPECDL systems are discussing methods for tailoring the emitted beam and improving the beam quality by optical feedback from a properly designed EC [8][9][10][11][12], study the damages implied by unwanted reinjection of the optical fields [13], or analyze the optical modes governed by the reduced-dimension PDE models [14][15][16]. In the present paper, we consider theoretical modelling and numerical studies of a BA-HPDL subjected to optical feedback from a particular type of EC, see figure 1(a), containing an anti-reflection (AR) coated photonic crystal (PhC) as spatial filtering element, see figure 1(b).…”