In this letter, a symmetric double-feedback configuration, to improve the beam quality of broad-area diode lasers is demonstrated. With this configuration, a symmetric double-lobed far field can be obtained, and this configuration leads to good beam quality. The beam quality factor M-2 of a diode laser with the emitting area 1 mumx200 mum is improved by using both the asymmetric single feedback and the symmetric double feedback. M-2 values of 4.3 for the asymmetric single-feedback laser system and 3.3 for the symmetric double-feedback laser system are obtained, whereas the M-2 value of the freely running laser is 42. The far and the near fields are also measured and compared for the three conditions. (C) 2004 American Institute of Physics.
Applied Physics Letters, 2004, Vol 85, Issue 7, p. 1107-1109