https://www.selleckchem.com/products/ly3009120.html Gourd-shaped hole array germanium (Ge) vertical p-i-n photodiodes were designed and demonstrated on a germanium-on-insulator (GOI) substrate with the excellent responsivity of 0.74 A/W and specific detectivity of 3.1 × 1010 cm·Hz1/2/W. It is calculated that the gourd-shaped hole design provides a higher optical absorption compared to a cylinder-shaped hole design. As a result, the external quantum efficiency for the gourd-shaped hole array photodetector was enhanced by ∼2.5× at 1,550 nm, comparing with hole-free array photodetectors. In addition, the extracted specific detectivity is superior to that of commercial bulk Ge photodiodes. The 3-dB bandwidth for the hole array photodetectors is improved by ∼10% due to a lower device capacitance. This work paves the way for low-cost and high-performance CMOS compatible photodetectors for Si-based photonic-integrated circuits.We addressed the problem of a state of polarization (SOP) drift caused by heating under intense clad pumping in different types of active tapered double-clad fibers. We investigated experimentally the variations of the SOP and degree of polarization (DOP) under clad pumping in polarization-maintaining (PANDA type) and regular (non-PM) Yb-doped double-clad large mode area tapered fibers. We discovered that the birefringence of active fibers is highly dependent on the launched pump power. To solve the problem of the SOP drift in active large mode are fibers, we, for the first time to the best of our knowledge, presented an active double-clad fiber with low intrinsic birefringence as a gain medium. An Yb-doped spun tapered double-clad fiber (sT-DCF) with intrinsic birefringence as low as 1.45×10-8 was manufactured and experimentally studied. We have proved experimentally that the DOP and SOP remains more stable in sT-DCF with increasing pump power compared to PM PANDA-type and regular non-PM tapered double-clad fibers. In particular, the SOP drift in sT