Thermal dissipation enhancement in flip-chip bonded uni-traveling carrier photodiodes.

The thermal properties of modified uni-traveling carrier (MUTC) photodiode flip-chip bonded to AlN and diamond are simulated. The thermal impedance of InGaAs is the primary source of internal heating. An n-down epitaxial structure is designed to improve thermal dissipation. Compared to the conventional p-down configuration, the n-down MUTCs bonded to diamond, or AlN submounts achieved 145% and 110% improvement in dissipated power density at thermal failure, respectively. The improved thermal characteristics presage higher RF output power before thermal failure.

Thin LiNbO3 on insulator electro-optic modulator.

This Letter presents a method for the fabrication and integration of a thin LiNbO3 substrate with a Si handle wafer. An inverted ridge structure guides a single optical mode in an electro-optic modulator fabricated on a mechanically thinned substrate. To define an optical waveguide, a ridge structure is first patterned on a 500 µm thick X-cut LiNbO3 wafer; then a low dielectric constant adhesive layer is used to bond the etched LiNbO3 to Si. The LiNbO3 is mechanically thinned to 4 µm, and planar electrodes are patterned. Experimental results demonstrating modulation with a V(π)L of 7.1 V-cm were shown, optical loss was low enough, and film quality high enough, to enable an interaction length of 0.8 cm.