We demonstrate experimentally the application of a phase error detection method in the coherent beam combination (CBC) of a laser array. The method is based on the Hartmann micro-lens array. Both the piston and tilt errors can be detected and corrected simultaneously by combining this method with adaptive optics-correcting technology. The far-field intensity pattern of the combined beam has high energy concentration and good beam quality. The power encircled in the main lobe of the far-field pattern is 41.3%, and the contrast of the pattern reaches 81.8%. Experimental results show the great potential of the Hartmann phasing method for use in the CBC of a large number of laser beams.OCIS codes: 140.3298, 110.1080, 120.5050. doi: 10.3788/COL201210.081402.The coherent beam combination (CBC) of single mode lasers is a reliable method to acquire high-power or high-brightness beams with good beam qualities. Compared with the single high-power lasers, combining several low-power laser beams coherently has advantages in terms of thermal loading distribution and reduction of the diffraction angle. The coherent combining approaches can be classified mainly into active phasing [1−5] and passive phasing [6−9] . The active phasing is mostly based on the master oscillator power amplifier (MOPA) configuration [2−4] , in most of which the fiber phase modulators are inserted before the fiber amplifiers to compensate for the piston aberrations. In some other configurations, the adaptive optics (AO) technologies, such as active segmented mirror (ASM) [5,10] and adaptive photonics phase-locked elements (APPLE) [11] , are employed to perform this task. In addition, the steering mirrors and deformable mirrors can be used to correct tiptilt and higher-order aberrations, respectively [2] . Some of the active phasing methods, such as heterodyne [2,12] and zero-order interference (ZOI) detections, need an external reference beam, while others do not, such as SelfSynchronous and Self-Reference [3] and SPGD algorithm control [4,11] . Most of these techniques extract the phase errors from the signals coming from the photo-detectors with a pinhole. Another type of phasing method [13−16] is applied in phasing large segmented telescopes in order to detect the piston errors between two neighboring apertures or segmented mirrors. These methods measure the piston errors by processing the interference images of the two apertures. Some of these methods have been used to detect the piston errors in two-beam CBC [15,17] . For a multi-aperture case, the Hartmann sensor is first applied to phase the 36 primary mirror segments in Keck telescopes [16] . A simulation work [18] demonstrates the application of a Hartmann sensor in multi-beam CBC. In these applications, Hartmann sensors are employed to acquire the interference images of two neighboring apertures or beams. Apart from piston error detection, the Hartmann sensor can also perform tilt error detection simultaneously.In this letter, we demonstrate experimentally the method of piston and ti...