RF crosstalk in multiple-wavelength vertical-cavity surface-emitting laserarrays

We present the crosstalk measured in multiple-wavelength vertical-cavity su rface-emitting laser (VCSEL) arrays under RF modulation. The array consists of eight bottom-emitting VCSEL's arranged with a "pie"-like configuration within a 60-mu m-diameter circle with a 3-mu m spacing for coupling into a multimode fiber. The crosstalk is investigated by measuring a cross-modulat ion response of two VCSEL's in the array using a monochromator in an optica l spectrum analyzer as a receiver. Excess crosstalk is minimized by flip-ch ip mounting the array and introducing a proper bias condition. The crosstal k observed in the adjacent VCSEL's is less than -40 dB at the modulation fr equency below 700 MHz and it increases at 20 dB/decade above this frequency when both VCSEL's are biased at 5.0 mA.