MULTIPLE WAVELENGTH TUNABLE SURFACE-EMITTING LASER ARRAYS

Wavelength multiplexing and tuning capabilities are highly important for applications in optical communications and optical interconnects. In this paper, we describe novel techniques and experimental results to achieve these operations in vertical-cavity surface-emitting lasers (VCSEL) for the first time. We achieve 140 unique, uniformly separated, single-mode wavelength emissions from a 7 x 20 VCSEL array. Large total wavelength span (approximately 430 angstrom) and small wavelength separation (approximately 3 angstrom) are obtained simultaneously with uncompromised laser performance. All 140 lasers have nearly the same threshold currents, voltages, and resistances. Wavelength tuning is obtained by using a novel three-mirror coupled-cavity configuration. The three-mirror laser is a two-terminal device and requires only one top contact, which is advantageous for a highly packed two-dimensional array. Discrete tuning with a range as large as 61-angstrom, corresponding to 1830 GHz, is achieved with a small change in drive current of only 10.5 mA. The VCSEL output power variation is within 5 dB throughout the entire tuning range. In addition, a unique on-off-on-off-type light versus current characteristics is obtained for this laser structure. Such characteristics may be used to make optical memory or logic devices when combined with a suitable feedback mechanism.