Mid-infrared (MIR) microscopy provides rich chemical and structural information about biological samples, without staining. Conventionally, the long MIR wavelength severely limits the lateral resolution owing to optical diffraction; moreover, the strong MIR absorption of water ubiquitous in fresh biological samples results in high background and low contrast. To overcome these limitations, we propose a method that employs photoacoustic detection highly localized with a pulsed ultraviolet (UV) laser on the basis of the Grüneisen relaxation effect. For cultured cells, our method achieves water-background suppressed MIR imaging of lipids and proteins at UV resolution, at least an order of magnitude finer than the MIR diffraction limits. Label-free histology using this method is also demonstrated in thick brain slices. Our approach provides convenient high-resolution and high-contrast MIR imaging, which can benefit diagnosis of fresh biological samples.

We present a measurement of phonon propagation in a silicon wafer utilizing an array of frequency-multiplexed superconducting resonators coupled to a single transmission line. The electronic readout permits fully synchronous array sampling with a per-resonator bandwidth of 1.2 MHz, allowing submicrosecond array imaging. This technological achievement is potentially vital in a variety of low-temperature applications, including single-photon counting, quantum-computing, and dark-matter searches. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3459142

We experimentally demonstrate the high bandwidth readout of a thermometer based on a superconductor-insulator-normal metal ͑SIN͒ tunnel junction, embedded in a rf resonant circuit. Our implementation enables basic studies of the thermodynamics of mesoscopic nanostructures. It can also be applied to the development of fast calorimeters, as well as ultrasensitive bolometers for the detection of far-infrared radiation. We discuss the operational details of this device, and estimate the ultimate temperature sensitivity and measurement bandwidth.

We have fabricated and characterized the principal thermal properties of a mechanically suspended nanostructure, consisting of a micron-scale suspended GaAs island, upon which we have defined superconductor-insulator-normal metal tunnel junctions. The tunnel junctions allow for sensitive thermometry and heating of the electrons in a thermally isolated normal metal element, permitting the determination of the low-temperature thermal conductance of the legs that support the GaAs island, as well as the low-temperature electron-phonon coupling. This device forms the basis of a nanoscale bolometric detector, whose optical performance can be estimated from these measurements.

Coatings comprised of carbon nanotubes are very black; that is, characterized by low reflectance over a broad wavelength range from the visible to far infrared. Arguably there is no other material that is comparable. This is attributable to the intrinsic properties of graphene as well as the morphology (density, thickness, disorder, tube size) of the coating. The need for black coatings is persistent for a variety of applications such as baffles and traps for space instruments. Because of the thermal properties, nanotube coatings are also well suited for thermal detectors, blackbodies and other applications where light is trapped and converted to heat. We briefly describe a history of other coatings such as nickel phosphorous, gold black and carbon-based paints and the comparable structural morphology that we associate with very black coatings. In many cases, it is a significant challenge to put the blackest coating on something useful. We describe the growth of carbon nanotube forests on substrates such as metals and silicon along with the catalyst requirements and temperature limitations. We also describe coatings derived from carbon nanotubes and applied like paint. Another significant challenge is that of building the measurement apparatus and determining the optical properties of something having negligible reflectance. There exists information in the literature for effective media approximations to model the dielectric function of vertically aligned arrays.We summarize this as well as other approaches that are useful for predicting the coating behavior along with the refractive index of graphite from the literature that is necessary for the models we know of. In our experience, the scientific questions can be overshadowed by practical matters, so we provide an appendix of our best recipes for making as-grown, sprayed or other coatings for the blackest and most robust coating for a chosen substrate and a description of reflectance measurements.