Abstract
We explored a path of achieving high quality phase-locking of broad-area laser diode (BALD) array that operates at high electrical to optical power conversion efficiency (PCE). We found that (a) improving single transverse mode control for each individual BALD, (b) employing global Talbot optical coupling among diodes, and (c) enhancing strength of optical coupling among diodes are key factors in achieving high quality phase-locking of high power BALD array. Subsequently, we redesigned and improved a V-shaped external Talbot cavity and employed low reflectivity anti-reflection (AR) coated, low-"smile" BALD array to meet these three important requirements. We demonstrated near-diffraction limit far-field coherent pattern with 19% PCE and 95% visibility. The far-field angle (full-width at half-maximum (FWHM)) of center lobe was measured as 1.5 diffraction angular limited with visibility of 99% for 5A injection current and 1.6 diffraction angular limited with visibility of 95% for 14A injection current. Power scaling of diode array is discussed.
Highlights
Laser beam combining provides a path to simultaneously scale up power, increase brightness and reduce thermal burden in laser arrays [1]
We explored a path of achieving high quality passive phase-locking of highpower broad-area laser diode (BALD) array with high power conversion efficiency (PCE)
We demonstrated 19% PCE at coherent beam combining with well-maintained coherence
Summary
Laser beam combining provides a path to simultaneously scale up power, increase brightness and reduce thermal burden in laser arrays [1]. We explored a path of achieving high quality passive phase-locking of highpower BALD array with near diffraction angular limit far-field and high PCE. We found that (a) improving single transverse mode control for each individual BALD on array, (b) implementing global Talbot optical coupling among diodes, and (c) enhancing strength of optical coupling among diodes are key factors in achieving high quality phase-lock high power BALD. To meet these three important requirements, we redesigned and improved a Vshaped external Talbot cavity and employed low reflectivity anti-reflection (AR) coated, low“smile” BALD array. The far-field angle (full-width at half-maximum (FWHM)) of center lobe was measured as 1.5 diffraction angular limited with visibility of 99% for 5 A injection current and 1.6 diffraction angular limited with visibility of 95% for 14 A injection current
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