Evaluation of optical amplification properties using dressed photons in a silicon waveguide

We fabricated an optical waveguide having a high optical confinement effect using a silicon-on-insulator substrate, and we eliminated the difficulty involved with optical alignment for making laser light pass through a p–n homojunction that is transparent to infrared light. Laser light was introduced via one of the cleaved edges of the optical waveguide and was guided to the transparent p–n homojunction, and the power of the light emitted from the other edge was measured. As a result, we successfully evaluated the optical amplification properties with high precision. For light with a wavelength of 1.31 µm, we obtained a differential gain coefficient of g = 2.6 × 10−2 cm/A, a transparency current density of J tr = 1 mA/cm2, and a saturation optical power density of P sat = 30 kW/cm2. The observation of gain saturation due to the incident optical power shows that this measurement method was suitable for evaluating the optical amplification properties.