Abstract:Quantum entanglement of two photons created by spontaneous parametric downconversion (SPDC) can be used to probe quantum optical phenomena during a single cycle of light. Harris [Phys. Rev. Lett. 98, 063602 (2007)] suggested using ultrabroad parametric fluorescence generated from a quasi-phase-matched (QPM) device whose poling period is chirped. In the Harris's original proposal, it is assumed that the photons are collinearly generated and then spatially separated by frequency filtering. Here, we alternatively propose using noncollinearly generated SPDC. In our numerical calculation, to achieve 1.2 cycle temporal correlation for a 532 nm pump laser, only 10% -chirped device is sufficient when noncollinear condition is applied, while a largely chirped (50%) device is required in collinear condition. We also experimentally demonstrate an octave-spanning (790-1610 nm) noncollinear parametric fluorescence from a 10 % chirped MgSLT crystal using both a superconducting nanowire single-photon detector and photomultiplier tube as photon detectors. The observed SPDC bandwidth is 194 THz, which is the largest width achieved to date for a chirped QPM device. From this experimental result, our numerical analysis predicts that the bi-photon can be compressed to 1.2 cycles with appropriate phase compensation.

Bismuth based perovskites are emerging as a candidate for photovoltaic application due to their low-toxicity, high structural stability and suitable application in photovoltaic applications. Here in this work, bismuth halide...

Lead (Pb)‐free bismuth (Bi) halide perovskites are promising alternatives to Pb‐based ones for the fabrication of perovskite solar cells (PSCs). However, the energy‐level mismatch at the interface between Bi perovskite (CsBi3I10;CBI) and the charge carrier transport layer limits the performance of the PSCs. Here, spray pyrolysis processed nickel oxide (sp‐NiOx) is reported as a hole transport layer (HTL) for CBI‐based inverted planar PSCs. Influence of inorganic NiOx HTL is systematically studied on the structural and morphological properties of the CBI perovskite layer growth. The CBI perovskite deposited on top of the sp‐NiOx exhibits improved crystallinity. The fabricated sp‐NiOx layer also exhibits favorable optical and electrical properties. The deep valence band (−5.4 eV) of the sp‐NiOx HTL is able to reduce the energy‐level mismatch up to 0.3 eV at the interface with the CBI layer. The PSCs fabricated with sp‐NiOx as HTL also exhibits a power conversion efficiency (PCE) of 0.72%, with a short‐circuit current density of 2.89 mA cm−2. The sp‐NiOx HTL based device maintains 85% of its initial PCE value even after 100 h of light soaking. This work highlights the importance of having a suitable HTL along with appropriate interface engineering for the Bi halide photovoltaic devices.

Abstract:We propose a novel method for generating broadband spontaneous parametric fluorescence by using a set of bulk nonlinear crystals (NLCs). We also demonstrate this scheme experimentally. Our method employs a superposition of spontaneous parametric fluorescence spectra generated using multiple bulk NLCs. A typical bandwidth of 160 nm (73 THz) with a degenerate wavelength of 808 nm was achieved using two β -barium-borate (BBO) crystals, whereas a typical bandwidth of 75 nm (34 THz) was realized using a single BBO crystal. We also observed coincidence counts of generated photon pairs in a non-collinear configuration. The bandwidth could be further broadened by increasing the number of NLCs. Our demonstration suggests that a set of four BBO crystals could realize a bandwidth of approximately 215 nm (100 THz). We also discuss the stability of Hong-Ou-Mandel two-photon interference between the parametric fluorescence generated by this scheme. Our simple scheme is easy to implement with conventional NLCs and does not require special devices. power levels using tapered optical fibers in rubidium vapor," Phys.

We report on the solution processed bismuth triiodide (BiI3) solar cells and their optoelectronic properties under different fabrication approach. We report on solar cells device using solution processed bismuth triiodide...