Light controlled bending of a holographic transmission phase grating

We recorded a permanent phase transmission grating on a thin film made by using a recently developed holographic photomobile mixture. The recorded grating pitch falls in the visible range and can be optically manipulated by using an external coherent or incoherent low power light source. When the external light source illuminates the grating the entire structure bends and, as a consequence, the optical properties of the grating change. This peculiarity makes it possible to use the recorded periodic structure as an all-optically controlled free standing thin colour selector or light switch depending on the source used to illuminate the grating itself. Additionally, it could open up new possibilities for stretchable and reconfigurable holograms controlled by light as well as thin devices for optically reconfigurable dynamic communications and displays.

Probing the circumnuclear environment of NGC 1275 with High-Resolution X-ray spectroscopy

NGC 1275 is the Brightest Cluster Galaxy (BCG) in the Perseus cluster and hosts the active galactic nucleus (AGN) that is heating the central 100 kpc of the intracluster medium (ICM) atmosphere via a regulated feedback loop. Here we use a deep (490 ks) Cycle-19 Chandra High-Energy Transmission Grating (HETG) observation of NGC 1275 to study the anatomy of this AGN. The X-ray continuum is adequately described by an unabsorbed power-law with photon index Γ ≈ 1.9, creating strong tension with the detected column of molecular gas seen via HCN and HCO+ line absorption against the parsec-scale core/jet. This tension is resolved if we permit a composite X-ray source; allowing a column of $N_H\sim 8\times 10^{22}\hbox{${\rm \, cm}^{-2}\, $}$ to cover ∼15 per cent of the X-ray emitter does produce a significant improvement in the statistical quality of the spectral fit. We suggest that the dominant unabsorbed component corresponds to the accretion disk corona, and the sub-dominant X-ray component is the jet working surface and/or jet cocoon that is expanding into clumpy molecular gas. We suggest that this may be a common occurence in BCG-AGN. We conduct a search for photoionized absorbers/winds and fail to detect such a component, ruling out columns and ionization parameters often seen in many other Seyfert galaxies. We detect the 6.4 keV iron-Kα fluorescence line seen previously by XMM-Newton and Hitomi. We describe an analysis methodology which combines dispersive HETG spectra, non-dispersive microcalorimeter spectra, and sensitive XMM-Newton/EPIC spectra in order to constrain (sub)arcsec-scale extensions of the iron-Kα emission region.

Bend-Insensitive Discrimination of Strain and Temperature Based on Fiber Transmission Grating Inscribed on High Birefringence Photonic Crystal Fiber

In this paper, we propose a bend-insensitive optical fiber sensor capable of separately measuring strain and temperature by incorporating a fiber transmission grating (FTG) inscribed on high birefringence photonic crystal fiber (HBPCF) with a CO2 laser. The FTG was fabricated by exposing unjacketed HBPCF to CO2 laser pulses using the line-by-line technique. The FTG inscribed on HBPCF, referred to as the HBPC-FTG, has two resonance dips with different wavelengths depending on input polarization. These two resonance dips were utilized as sensor indicator dips denoted by a shorter wavelength dip (SD) and a longer wavelength dip (LD). The strain and temperature responses of the SD and LD were investigated in a strain range of 0 to 3105 μ and a temperature range of 30 to 85 °C, respectively. The measured strain sensitivities of the SD and LD at room temperature (25 °C) were approximately −0.46 and −0.58 pm/μ, respectively. Similarly, the measured temperature sensitivities of the SD and LD without applied strain (0 μ) were ˜5.99 and ˜9.89 pm/°C, respectively. Owing to their linear and independent responses to strain and temperature, strain and temperature changes applied to the HBPC-FTG can be simultaneously estimated from the measured wavelength shifts of the two indicator dips (i.e., SD and LD) using their predetermined strain and temperature sensitivities. Moreover, bend-induced spectral variations of the SD and LD were also examined in a curvature range of 0–4.705 m−1, and it was observed that both dips showed little wavelength shift due to applied bending. Thus, it is concluded from the experimental results that the fabricated HBPC-FTG can be employed as a cost-effective sensor head for bend-insensitive discrimination of strain and temperature.