Rahbek Bagge (lunchfowl1)

We describe a microscopic setup implementing phase imaging by digital holographic microscopy (DHM) and transport of intensity equation (TIE) methods, which allows the results of both measurements to be quantitatively compared for either live cell or static samples. Digital holographic microscopy is a well-established method that provides robust phase reconstructions, but requires a sophisticated interferometric imaging system. TIE, on the other hand, is directly compatible with bright-field microscopy, but is more susceptible to noise artifacts. We present results comparing DHM and TIE on a custom-built microscope system that allows both techniques to be used on the same cells in rapid succession, thus permitting the comparison of the accuracy of both methods.A high-sensitivity ultralow-frequency fiber optic interferometric seismometer using phase feedback control is proposed and demonstrated. The principle of sensitivity improvement using feedback is described, and the characteristics of the seismometer, including the ultralow-frequency vibration sensing with Michelson interferometer with and without feedback control, are analyzed in terms of the amplitude response and phase response. The phase feedback control loop is designed and implemented, and higher sensitivity for very low frequency vibration is achieved. The efficacy of the new approach is demonstrated experimentally, showing that the weak vibration signal originally buried in noise can be observed unambiguously.We propose an ultraviolet perfect ultranarrow band absorber by coating a dielectric grating on the monolayer graphene-dielectric-metal structure. The absorber presents an ultranarrow Fano lineshape with quality (Q) factor of 70 and a nearly perfect absorption of over 99.9% in the ultraviolet region, which is ascribed to the near field coupling of the optical dissipation of graphene and guide mode resonance of the dielectric grating. Structure parameters to the influence of the performance are investigated. The structure exhibits the high optical sensitivity (S = 150 nm/RIU, S* = 48/RIU) and figure of merit (FOM = 50, FOM* = 25374) and can also be used to detect the nanoscale analyte layer of sub-nanometer thickness, suggesting great potential applications in ultra-compact efficient biosensors for a much more sensitive detection of small refractive index changes.A tungsten disulfide (WS2) coated surface plasmon resonance (SPR) sensor based on gradient pitch Mach-Zehnder interferometer (GP-MZI) for measuring ethanol vapor concentration is proposed and verified by experiments. Under continuous CO2 laser heating, a MZI based on GP helix structure is fabricated by twisting single mode fiber (SMF), which can excites multi-order cladding modes. A gold film is deposited on the surface of the GP helix structure by a magnetic sputtering coating machine. WS2 film is coated on the gold film of the GP helix structure, which increases the evanescent field strength of the twisted structure surface and enhances the interaction between SPR wave and ethanol molecules. Since the absorption of ethanol molecules by WS2 sheets will cause the change of effective refractive index (RI) of WS2 film, the intensity of transmission signal can be adjusted accordingly. For multi-order cladding modes, the effective RI and the effective thermo-optic coefficient vary with the modal order, so the RI and temperature sensitivity of different modal orders are also different. So, the ethanol vapor concentration, relative humidity (RH), and temperature can be simultaneously measured by monitoring the intensity of those dips with the resolution of ± 0.030 mg/L, ±0.035%RH, and ± 0.010 ℃, respectively. This sensor structure provides a promising platform for multi-parameter sensing applications.In this paper, a localized surface-plasmon resonance (LSPR) biosensor, which uses a U-shaped multi-mode fiber (U-MMF), is introduced and investigated. It is modified with a complex of three-dimensional (3D) gol