Wafer bonded 1.55 mum vertical cavity laser arrays for wavelength division multiplexing

Vertical cavity lasers in the 1.55 μm wavelength band are attractive sources for optical networks. Previous devices have been limited by low output power and poor thermal performance. In this work, novel wafer bonding techniques were developed to create high-performance 1.55 μm vertical cavity lasers and a new class of multiple wavelength vertical cavity laser arrays. Wafer bonding enables the integration of thermally conductive GaAs/AlGaAs mirrors and traditional InP/InGaAsP active regions. A superlattice barrier was used as a buffer layer during bonding to reduce the number of non-radiative recombination centers in the active region. The surface of these superlattice layers was patterned prior to bonding to define multiple wavelength cavities. Continuous-wave operation was achieved at temperatures up to 105°C. This is the highest reported lasing temperature for a 1.55 μm vertical cavity laser. Threshold currents of 0.8 mA were measured. The peak output power at 20°C was 0.7 mW. The peak output power at 80°C was 0.2 mW. Single-mode operation with a side-mode suppression ration in excess of 40 dB was observed for a 5 μm aperture device. Four-channel arrays were also fabricated. The wavelength span was 1509.1–1524.4 nm with channel spacing of approximately 5 nm. This is the first demonstration of an independently addressable, multiple-wavelength vertical cavity laser array at 1.55 μm. Threshold currents of 1.0 mA and peak output powers of 0.5 mW were measured for array elements. Thermal and optical crosstalk between array elements are negligible, due to the high thermal conductivity of the bottom mirror and large device pitch.