Biomedical subjects

Michael J Brett

Publications and source records attributed to Michael J Brett.

4 recordsLinked to original sources

PubMed2005

Functional pattern engineering in glancing angle deposition thin films.

We present a new method for making functional patterns in thin films consisting of highly ordered arrays of complex, submicrometer structures, deposited at oblique flux incidence angles using the glancing angle deposition technique. By performing physical vapor deposition on direct write seed layers with intentional point and line lattice defects, we are able to generate embedded air-filled linear and planar patterns in the films in a single-step transfer approach with no need for conventional postdeposition micromachining. The uniformity and porosity of the thin films is fully maintained, with minimal impact on the film morphology adjacent to the patterns. This ability to engineer air-filled patterns is crucial to several promising thin-film applications, including photonic band gap crystals and microfluidics.

Crystallization↗

PubMed2004

Gradient-index narrow-bandpass filter fabricated with glancing-angle deposition.

Glancing-angle deposition (GLAD) is a fabrication method capable of producing thin films with engineered nanoscale porosity variations. GLAD can be used to create optical thin-film interference filters from a single source material by modification of the film refractive index through control of film porosity. We present the effects of introducing a layer of constant low density into the center of a rugate thin-film filter fabricated with the GLAD technique. A rugate filter is characterized by a sinusoidal refractive-index profile. Embedding a layer of constant refractive index, with a thickness equal to one period of the rugate index variation, causes a narrow bandpass to appear within the filter's larger stop band. Transmittance measurements of such a gradient-index narrow-bandpass filter, formed with titanium dioxide, revealed an 83% transmittance peak at a vacuum wavelength of 522 nm, near the center of the stop band, with a FWHM bandwidth of 15 nm.

Journal Article↗

PubMed2004

Optical properties of porous helical thin films.

Porous dielectric thin films, composed of isolated helical columns, are fabricated by the glancing angle deposition technique. The selective reflection of circularly polarized light and the optical rotation of linearly polarized light are investigated as a function of film material and helical morphology. The strongest chiral optical response is observed for titanium-dioxide films because of its large refractive index. Optical rotatory powers as high as 4.5 degrees are observed in 830-nm-thick helical films. By tailoring the pitch of the helical columns, the wavelength dependence of the circular reflection band is tuned to preferentially reflect red, green, or blue light, a promising quality for display applications.

Journal Article↗

PubMed2003

Porous broadband antireflection coating by glancing angle deposition.

We deposited graded-index SiO2 films using glancing angle deposition to produce high-transmission antireflection coatings on glass. Because of the accurate control over the thin-film microstructure provided by this technique, we were able to create graded densities with a Gaussian profile resulting in transmission values greater than 99.9% for a single-layer interface with bandwidths up to 460 nm. The graded-index layer also provides low reflectance at nonnormal angles of incidence with transmission values degrading little for incidence angles up to 30 degrees.

Journal Article↗