John Goldsmith

Hot isostatic pressing of transition metal ions into chalcogenide laser host crystals

This paper describes a technique using a hot isostatic pressing (HIP) for the diffusion of transition metal ions into chalcogenide laser host crystals. Thin layers of chromium metal are sputtered onto the surface of zinc selenide and zinc sulfide crystals before treatment in a HIP chamber. The transmissivities, excited state lifetimes, and diffusion rates are measured for various dopant concentrations. Efficiency, spectral output, and tuning data are also measured for a Cr:ZnSe laser. The diffusion rate of 5.48 × 10−8 cm2/s is two orders of magnitude faster than other techniques reported in the literature, and the sub 140 pm measured linewidth is more than 350 times smaller than what is typical of commercially available crystals. Preliminary results for Fe:ZnSe, Co:ZnSe, and Ni:ZnSe are presented as well.

Studies of the influence of deep subwavelength surface roughness on fields of plasmonic thin film based on Lippmann-Schwinger equation in the spectral domain

In this paper, we consider a line source over a plasmonic thin film with surface roughness. Using layered medium Green’s functions, we derive the Lippmann–Schwinger equation in the spectral domain with scattering potentials for the case of surface roughness over a layered medium. Because of deep subwavelength surface roughness, the scattering potentials are next approximated by the small potential approximation, so that the solutions of fields in the spectral domain can be readily computed. Numerical results are illustrated for the surface fields on the rough surface and the fields in the image plane. For periodic roughness, small periods, on the order of 0.1λ, and small heights, on the order of 0.01λ, are used. For the case of random roughness, we choose the correlation length to be much smaller than a wavelength, on the order of 0.1λ, and height on the order of 0.01λ. The results of the fields on the rough surface in the spectral domain show that subwavelength roughness creates fields with wave vector components that are many times larger than the free-space wavenumber (∼10k0 or larger). In the spatial domain, the imaging is enhanced by the deep subwavelength roughness. Results of the small roughness approximation are in good agreement with that of exact potential and that of the method of moments.

High throughput, large scale, broadband, plasmonic nanostructure fabrication for optical sensors

Plasmonics have the potential to enhance the performance of detectors. A thermal metal dewetting process was developed which can be easily scaled for high throughput production. Through this process, plasmonic nanostructures were fabricated providing broadband plasmon resonance tunable over a 1000 nm wavelength range. The plasmonic media and their integration into fluorescence-based sensors will be described.

Black Aluminum: a novel anti-reflective absorbing coating

Black absorbing and antireflective coatings have many optical sensing applications. A process to deposit Black Aluminum, a novel anti-reflective coating has been discovered. Black Aluminum films with controlled thickness were deposited on silicon and their reflection spectra were investigated. In addition, to test the effectiveness of this new material at the device level, pyroelectric devices were fabricated with Black Aluminum acting as the absorbing layer. Significant enhancement in the pyroelectric response is reported for devices coated with Black Aluminum as compared to devices without the Black Aluminum absorbing layer.

Influence of nitride buffer layers on superconducting properties of niobium nitride

Niobium nitride thin films were deposited using reactive magnetron sputtering simultaneously on sapphire substrates with TiN, VN, and AlN buffer layers. Deposition temperature was varied from 400 to 840 °C. It was found that the crystal structure, surface roughness, and transition temperatures of the resulting NbN films depend strongly on both the growth temperature and the type of the buffer layer. The use of VN and TiN buffer layers for growing NbN at 400 °C improved transition temperatures compared to NbN grown at 840 °C on sapphire. While increasing the temperature improved the superconducting performance of films grown directly on sapphire, it caused hexagonal δ′-NbN and e-NbN phases to emerge on the buffered films. A highly oriented hexagonal e-NbN film was achieved by using a TiN buffer and an 840 °C deposition temperature. The ability to deposit high performance NbN at a lower temperature will improve and simplify the fabrication of advanced superconducting devices such as superconducting single photon detectors.Niobium nitride thin films were deposited using reactive magnetron sputtering simultaneously on sapphire substrates with TiN, VN, and AlN buffer layers. Deposition temperature was varied from 400 to 840 °C. It was found that the crystal structure, surface roughness, and transition temperatures of the resulting NbN films depend strongly on both the growth temperature and the type of the buffer layer. The use of VN and TiN buffer layers for growing NbN at 400 °C improved transition temperatures compared to NbN grown at 840 °C on sapphire. While increasing the temperature improved the superconducting performance of films grown directly on sapphire, it caused hexagonal δ′-NbN and e-NbN phases to emerge on the buffered films. A highly oriented hexagonal e-NbN film was achieved by using a TiN buffer and an 840 °C deposition temperature. The ability to deposit high performance NbN at a lower temperature will improve and simplify the fabrication of advanced superconducting devices such as superconducting single p...

Doping transition metal ions into laser host crystals by hot isostatic pressing (HIP) (Conference Presentation)

This paper describes using a hot isostatic pressing (HIP) to improve II-VI crystal characteristics and diffuse metal ions into laser host crystals. Thin layers of metal are sputtered onto the surface of zinc selenide and zinc sulfide crystals prior to being HIP treated. The pre and post treatment optical properties for these materials are measured using various methods and at a variety of dopant concentrations.

Optical imaging over a plasmonic thin film with deep-subwavelength surface roughness

Subwavelength imaging has been reported for a layer of plasmonic thin film. In this paper, we investigate the enhancement of the sub-diffraction-limit imaging using subwavelength surface roughness. Full wave simulations are carried out based on Lippmann Schwinger equation with linearized scattering potentials. Progresses in experiment are also reported.

Surface plasmon enhanced rare earth fluorescence for increased imaging efficiency

Ions of rare earth metals are widely known for their versatile ultraviolet, visible, near infrared and middle infrared fluorescence; they can be excited by wavelengths ranging from the ultraviolet to near infrared. The preparation and optimization of infrared fluorescent ceramics will be discussed, as well as their thin film incorporation into plasmonic systems for fluorescent imaging with enhanced efficiency.