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Crossed gratings provide a functional effective period, shorter than the exposed grating periods. They can simultaneously provide feedback, outcoupling, and in-plane coupling c4 monolithic laser elements. Potential applications include OEIC architectures.Objective: The objectives of this work were to investigate 1) if a functional, effective gratin,; period could be obtained with a period shorter than that possible with conventional means; and 2) if crossed gratings could simultaneously provide feedback, outcoupling, and in-plane coupling of monolithic lasers.Background: Gratings that are not perpendicular to the direction of propagation of an optical mode in a waveguide deflect light off-axis [l].In addition, first order gratings for distributed feedback (DFB) and distributed Bragg reflector (DBR) semiconductor lasers are difficult to fabricate by holographic techniques for wavelengths shorter than 1 .O pm.Technique: The period Aexp of a grating fabricated by a simple holographic exposure is greater or equal to hexp / 2, where hexp is the exposing wavelength. If two sets of gratings with equal periods are fabricated at an angle to each other, as shown in Fig. 1, an effective grating period (A,& where a is the angle between between the two grating pairs as shown in Fig. 1. By using crossed gratings, periods approaching hexp / 4 can be simply fabricated. If a is 90' as in Fig. 2a and 2b, one set of gratings deflects upward (downward) propagating light to the left (right) and the other set deflects upward (downward) propagating light to the right (left). Fortuitously, the grating period for first-order Distributed Bragg Deflection (DBD) [ 11 at 90° is $times the grating period for secondorder DBR feedback and first order outcoupling. As a result, if opposing subarrays of semiconductor lasers surround a cross grating region, then each subarray could conceivably be coupled to each other by the gratings with the gratings also providing feedback and outcoupling (Fig. 2b). Figure 3a is a scanning electron micrograph (SEM) of a section of such an array with 8 evanescently-coupled riclgeguided elements in each subarray. Figure 3b is a higher magnification SEM showing the crossgrating in the center of Figure. 3a. These two dimensional cross-grating surface emitting lasers arrays were fabricated using a graded index separate confinement heterostructure single quantum well wafer with 0.2 pm thick linearly graded regions (graded from 60% AlAs to 20% AlAs) with a 100 8, thick GaAs quantum well. Each ridge in the subarray was 150 pm long and 2 pm wide on 5 pm centers. The passive cross-grating regions (Aexp = 3754 A, Aeff = 2655 8) were 55 pm x 55 pm.A lateral index step of approximately 8 x 10-3 in the gain region was achieved by removing the p-;lad material outside the ridges to within about 1000 8, of the graded region as described in [3]. Results:A probe tested near-field of a cross-grating array is shown in Fig. 4a and the corresponding far-field in Fig. 4b. The emission wavelength was -0.86 pm. A noticeable dot pattern in...

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