High coupling efficiency and high responsivity 1.3 μm light emission and detection diodes with a butt-jointed spot-size converter

For bi-directional transmission in optical subscriber loops, the authors have fabricated light emission and detection (LEADs) diodes with spot-size converter region formed by butt-joint selective growth. With the spot-size converter region, this device has a low-loss coupling of 2.5 dB and high responsivity of 0.35 A/W. Using a bulk detection layer, uniform polarisation and wavelength dependence with wavelengths up to 40 nm longer than the lasing wavelength are achieved when the diodes are used as detectors. A low threshold current of 12 mA at 25°C and high temperature operation are also demonstrated when the diodes are operated as lasers