Coherent beam combining of high power broad-area laser diode array with near diffraction limited beam quality and high power conversion efficiency

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.

Rear-side resonator architecture for the passive coherent combining of high-brightness laser diodes

“…Active correction of the lasers was demonstrated to allow phase-locked operation at high currents, but still with a low extracted power [10]. Efforts to improve the E-O efficiency of passively phase-locked arrays were also described in [13] in a V-shaped external cavity designed for broad area laser diodes, pointing out the importance of the cavity architecture to get both high power and efficiency.…”

A Linearly-Polarized Cesium Vapor Laser with Fundamental Mode Output and Low Threshold

“…For the diode pumped cesium vapor laser, three kinds of pumping sources are reported, which are an injection seeded diode laser, [7] a laser diode with an external cavity of volume Bragg grating (VBL) [8] and a laser diode with an external cavity of plane grating. [9] The third kind is often used due to the fact that their power is usually higher than the injection seeded diodes' and their linewidth is narrower than the VBLs. Anti-reflection coating to the laser diode bar's output facet will help to suppress the intrinsic emission spectra of the laser diode bar.…”

“…Anti-reflection coating to the laser diode bar's output facet will help to suppress the intrinsic emission spectra of the laser diode bar. [9] According to the equation given by Chann et al, [10] a laser diode bar's fast axial collimator (FAC) of large focal length will minimize the contribution of smile to the linewidth. For example, with an anti-reflection-coated front facet and an FAC of 9.7 mm focal length, Zhdanov et al obtained a laser diode bar with a linewidth of less than 11 GHz for cesium vapor laser pumping.…”

A Novel Technique for Designing High Power Semiconductor Optical Amplifier (SOA)-Based Tunable Fiber Compound-Ring Lasers Using Low Power Optical Components

“…High power laser sources with high beam quality have been demonstrated by using complex coherent and spectral beam-combining techniques in external cavities [28][29][30][31][32][33][34][35]. In addition, incoherent beam-combining method [36,37] has been used to scale up the optical power by combining individual laser elements as well.…”