We study the generation of correlated photon pairs via spontaneous four-wave mixing (SFWM) in a 15 cm long micro/nano-fiber (MNF). The MNF is properly fabricated to satisfy the phase-matching condition for generating the signal and idler photon pairs at wavelengths of about 1310 and 851 nm, respectively. Photon-counting measurements yield a coincidence-to-accidental ratio of 530 for a photon production rate of about 0.002 (0.0005) per pulse in the signal (idler) band. We also analyze the spectral information of the signal photons originating from SFWM and Raman scattering (RS). In addition to discovering some unique features of RS, we find the bandwidth of the individual signal photons is much greater than the calculated value for the MNF with homogeneous structure. Our investigations indicate the MNF is a promising candidate for developing the sources of nonclassical light and the spectral property of photon pairs can be used to noninvasively test the diameter and homogeneity of the MNF.
A series of systematic studies have been made on both optimum design and preparation technology of high efficiency a-Si/a-Si/a-SiGe triple-junction solar cells. It has been found that current matching is one of the key factors affecting the fill factor of two-terminal tandem solar cells, and excess carrier recombination at the p-n interface acting as an internal electrode is dominated by the density of the minority carriers, interfacial states, and geometrical factor match of the materials at the p-n interface. In this work, μc-Si:H with wide band gap and high conductivity, which was prepared at low substrate temperature, was used as an n layer of a-Si:H solar cells. In order to improve the n-i interface property, a novel approach involving the insertion of an n−a-Si:H buffer layer at the n-i interface was developed. The experimental results show that the buffer layer of appropriate thickness could enhance the fill factor and open circuit voltage of a-Si:H based solar cells. In addition, highly photosensitive a-SiGe:H(F) films used for a bottom cell in a-Si/a-Si/a-SiGe triple junction solar cells have been obtained by glow discharge of a gas mixture (SiH4—GeF4—H2) under conditions of high hydrogen dilution ratio and low deposition pressure. At present, the conversion efficiency of the a-Si/a-Si/a-SiGe triple-junction solar cell of 11.5% with Voc=2.48 V, Jsc=6.58 mA/cm2, and FF=70.4% has been obtained under AM1(100 mW/cm2) illumination by optimization of the solar cell structure and preparation technology.
We demonstrate a carrier-envelope phase (CEP) stabilized high temporal contrast generator at 1053 nm for the first time. The device relies on a collinear optical parametric amplifier (OPA) followed by a frequency-doubling crystal. It is driven by a femtosecond laser source centered at 800 nm and finally generates CEP passively stabilized pulses with an energy of 130 µJ and a FWHM for the spectrum of 40 nm with 46 fs pulse duration at 1053 nm. The temporal contrast reaches >10 11 at a few picoseconds before the main pulse.
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