Thin films of SiO2 and TiO2 were used to fabricate one-dimensional photonic crystal devices using the sol-gel method: an omnidirectional reflector and microcavity resonator. The reflector consisted of six SiO2/TiO2 bilayers, designed with a stopband in the near infrared. Reflectivity over an incident angle range of 0°–80° showed an omnidirectional band of 70 nm, which agrees with theoretical predictions for this materials system. The microcavity resonator consisted of a TiO2 Fabry–Perot cavity sandwiched between two SiO2/TiO2 mirrors of three bilayers each. We have fabricated a microcavity with resonance at λ=1500 nm and achieved a quality factor of Q=35. We measured a resonance frequency modulation with a change in incident angle of light and defect layer thickness.

Abstract-We have micromachined a mechanical sensor that uses interferometry to detect the differential and absolute deflections of two adjacent cantilevers. The overall geometry of the device allows simple fluidic delivery to each cantilever to immobilize molecules for biological and chemical detection. We show that differential sensing is 50 times less affected by ambient temperature changes than the absolute, thus enabling a more reliable differentiation between specific cantilever bending and background effects. We describe the fabrication process and show results related to the dynamic characterization of the device as a differential sensor. The root-mean-squared (rms) sensor noise in water and air is 1 nm over the frequency range of 0.4-40 Hz. We also find that in air, the deflection resolution is limited only by the cantilever's thermomechanical noise level of 0.008 A Hz 1 2 over the frequency range of 40-1000 Hz.[781]

We introduce a general approach for inherently suppressing out-of-plane disturbances in scanning probe microscopy that enables higher-resolution imaging, particularly in noisy environments. In this approach, two distinct sensors simultaneously measure the probe–sample separation. One sensor measures a spatial average over a large sample area while the other responds locally to topography underneath the nanometer-scale probe. When the localized sensor is used to control the probe–sample separation in feedback, the spatially distributed sensor signal reveals only topography. We implemented this approach on a scanning tunneling microscope using a microcantilever with an integrated tunneling tip and interferometer. For disturbances applied normal to the sample, we measure −50dB of disturbance suppression at 1Hz, compared to 0dB with conventional imaging.

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Optical systems designed for some defense, environmental, and commercial remote-sensing applications must simultaneously have a high dynamic range, high sensitivity, and low noise-equivalent contrast. We have adapted James Janesick's photon transfer technique for characterizing the noise performance of an electron multiplication CCD (EMCCD), and we have developed methods for characterizing performance parameters in a lab environment. We have defined a new figure of merit to complement the traditionally used dynamic range that quantifies the usefulness of EMCCD imagers. We use the results for EMCCDs to predict their performance with hyperspectral and multispectral imaging systems.

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Scanning probe imaging is often limited by disturbances, or mechanical noise, from the environment that couple into the microscope. We demonstrate, on a modified commercial atomic force microscope, that adding an interferometer as a secondary sensor to measure the separation between the base of the cantilever and the sample during conventional feedback scanning can result in real-time images with inherently suppressed out-of-plane disturbances. The modified microscope has the ability to resolve nanometre-scale features in situations where out-of-plane disturbances are comparable to, or even several orders of magnitude greater than, the scale of the topography. We present images of DNA in air from this microscope in tapping mode without vibration isolation, and show improved clarity using the interferometer as the imaging signal. The inherent disturbance suppression approach is applicable to all scanning probe imaging techniques.

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