Wavelength converter/amplifier with fine tunability
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The results of the study of a novel monolithic wavelength converter/amplifier which can be tuned, with the application of an external field are presented. The tuning range is Dl=300 angstrom about the operation wavelength, l=8400. The proposed device is a modified version of the HELLISH-1 (Hot Electron Light Emitting and Lasing Semiconductor Heterojunction) device. It consists of a graded Ga1-xAlxAs quantum well (0< x <0.15) placed on the n side of the depletion region, of a Ga0.7Al0.3As p-n junction, as shown in figure 1. As a result of the built-in field coupled with the grading the quantum well looks as if it were an isolated square well in zero field. Forward biasing the junction reduces the built-in field, thus the field associated with the grading becomes effective as shown in figure 2. The tuning of the operation wavelength is based on the Quantum Confined Stark Effect and is achieved during the forward biasing of the device. The wavelength as a function of the forward bias is shown in figure 3. Forward biasing the junction (electrical pumping) results in an enhanced conversion efficiency.