A multi-section technique for the electroabsorption measurements in waveguide semiconductor electroabsorption modulators

A technique for measuring the optical absorption spectra of waveguides, semiconductors and electroabsorption modulators is described. The technique uses a multi-sectioned optical waveguide that has electrically isolated longitudinal sections and has a p-i-n cross-section structure. Light generated in forward biased sections is used to probe the optical absorption in sections that can be reverse biased. The technique is applied to a p-i-n electroabsorption device that was designed to operate over a broadband of optical communication wavelengths. It has an active region consisting of multiple-width InGaAs-InAlGaAs quantum wells. For this device, a band edge shift of 40 meV is obtained at an applied field of 105 kV cm^-1, and figures of merit Deltaalpha, Deltaalpha/F and Deltaalpha/alpha₀ were also determined as a function of wavelength and applied field, where alpha₀ is the absorption coefficient change due to electroabsorption, Deltaalpha static absorption coefficient of the wells at zero bias field and F the applied reverse bias field.