Micro-lens on polarization maintaining fibre for coupling with 1.55 μm quantum dot devices

We propose a simple micro-lens scheme on polarization maintaining single mode fibre for characterization of 1.55 μm wavelength quantum dot devices such as lasers or amplifiers. The proposed micro-lens offers quite long working distance (45 μm), very small mode field diameter (<2 μm), low back reflections (around 45 dB) and easy fabrication process for high coupling efficiency. The coupling scheme principle and fabrication process are described. Characterization results of mode field diameter, working distance and polarization extinction ratio (around 22 dB) of this micro-lens are presented. The use of this micro-lens for characterizing polarization sensitivity of InAs/InP on 311B quantum dot wave-guides is also discussed.