We present experimental studies of semiconductor optical amplifiers with a high integration density in an InP generic photonic integration platform. We study the active-passive butt-joint integration of dense arrays of active islands with widths ranging from 2 to 30 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> m, and pitches ranging from 4 to 270 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> m. We show that reducing the active island width from 20 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> m to 4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> m enables a decrease of pitch by almost 4 times while keeping a similar growth rate enhancement (GRE) in between the active islands. The impact of narrow active islands on amplifier performance is also studied with an array of Fabry-Pérot lasers fabricated in a commercial generic platform. We demonstrate the manufacturability of lasers with a pitch of 25 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> m and evaluate individual device performance. Threshold currents and slope efficiencies are not impaired with narrow active island down to 6 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> m, with values of 19-26 mA and 0.08-0.15 W/A respectively.