Interferometric near-field imaging technique for phase and refractive index profiling in large-area planar-waveguide optoelectronic devices

Abstract

A versatile, interferometric optical technique is described for nondestructively imaging the near-field output phase uniformity and refractive index profile in broad-area optoelectronic waveguide devices or heterostructure materials. In active traveling-wave optical power amplifier devices, measurements are presented for thermal lensing, solder bond inhomogeneities, heatsink impedance, and carrier-lensing effects due to nonuniform gain saturation by the amplifier input beam, transverse amplified spontaneous emission, or intensity filaments. The thermal performance of diamond and copper heatsinks for high-power optical amplifiers is compared. In passive devices, the technique is used to observe heteroepitaxial material compositional uniformity, defects, photoelastic stress, and intentional structural waveguide index modifications. The technique has a phase and spatial resolution as low as /spl lambda//100 and 1 /spl mu/m. The corresponding refractive index and temperature resolutions (dependent on device length) are as low as /spl Delta/n=10/sup -5/ and /spl Delta/T=0.025/spl deg/C for 1000-/spl mu/m-long devices.