DISTRIBUTED-FEEDBACK GRATING USED AS AN ARRAY-MODE SELECTOR IN RESONANT ANTIGUIDED DIODE-LASER ARRAYS - EFFECTS OF THE MIRROR FACET POSITION WITH RESPECT TO THE GRATING

In resonant and nearly resonant antiguided arrays (ROW arrays), if the grating is located below the active region, a distributed-feedback (D FB) grating can function as a selector for the in-phase array mode in addition to its role as a frequency discriminator. Threshold current d ensities are calculated for competing (lateral) spatial modes in AR/HR coated 10- and 20-element arrays incorporating lower gratings (ROW-LD FB arrays), Calculations include the effects of random facet locations relative to the grating phase. The threshold current density, J(th), of the in-phase mode and its discrimination, Delta J(th), against othe r (array) spatial modes vary with facet location. For 20 (10) elements , J(th) approximate to 350-525 (400-550) A/cm(2) and Delta J(th) reach es a maximum of 55 (58) A/cm(2) for 0.01/0.95 AR/HR-coated 350 mu m-lo ng devices, For 10-element arrays, the probability of in-phase operati on is approximately 50%; for 20-element arrays, the probability is 100 %. Preliminary experimental results from 20-element nonresonant device s with uncoated facets are near diffraction-limited beams and nearly s ingle-frequency operation to 250 mW.