|a Scanning electron microscope image of three adjacent laser ridges. Each laser consists of a roughly 3 mm long gain section and a shorter (320–480 μm) modulation section.
b Simulated gain and loss spectrum in a standard active region design depending on the applied bias. Upon decreasing the bias, the structure becomes almost transparent at the lasing wavelength λL, limiting the maximally achievable modulation depth.
c Simulated gain and loss spectrum in a bi-functional active region design, allowing to tune the gain at 10V continuously to absorption (shown as negative gain) at 0 V.|