Lasing Modes in a Monolithic Talbot Cavity

Sixty-one lasing fiber channels are passively combined in a monolithic optical resonator array to produce an output power above 200 W at two-micrometer wavelength with the central intensity enhanced by a factor of 8 compared to incoherent beam combination. The 61-channel lasing mode corresponds to a transitional state with 75-degree phase shift between neighboring cores and has a far-field peak intensity 4.6 times below theoretical prediction for a fully coherent array. A 7-channel mode corresponds to the anti-phase supermode of the Talbot cavity, which has no central lobe in the far field. The monolithic laser cavity is formed by a fiber array, which is drawn and fusion-spliced to an endcap serving as a Talbot cavity mirror without air gaps. The central intensity enhancement, which is achieved without spectral or polarization selectivity, improves as the number of channels increases. This is an important step towards a passively combined multichannel all-solid-state laser system.