Reduction in Roughness of Waveguides Leads to Ultralow Transmission Loss
- PDF / 682,466 Bytes
- 2 Pages / 612 x 792 pts (letter) Page_size
- 19 Downloads / 171 Views
of soft scanning force microscope cantilevers. These cantilevers have oscillations perpendicular to the surface of the order of 10-10 m, while a particle in an optical trap can fluctuate as much as several hundred nanometers in any direction. In this manner, the particle is able to scan over an area becoming a “natural 3-D mechanism”. Scientists from the European Molecular Biology Laboratory in Germany obtained 3-D images of an agar gel by means of this technique, as they describe in the November 26, 2001, issue of Applied Physics Letters. An agar gel is a transparent substrate used for biological cultures and chromatography. In this case, liquid agar was mixed with latex beads with a nominal diameter of 216 ± 8 nm. The beads were added at a concentration of 1/20 µm3. A photonic force microscope, which is a scanning force microscope based on optical tweezers, was used to conduct the experiments. It included a 1064-nm laser beam and a three-dimensional detector. This detector consists of a quadrant photodiode where the scattered laser light from the particle produces an interference pattern. The position of the optical trap is measured with < 1 nm error; the position of the center of the particle is measured with nanometer resolution. A position histogram was calculated after recording the position of a particle for 0.8 s. The thermally induced particle fluctuations allowed it to scan a volume of 300 × 120 × 120 nm3. It was also possible for the particle to scan areas around an object. When the optical trap was moved along the agar network in 80-nm steps, the variations on the position of the particle showed indications of the presence of the network filaments. The same effect was observed when the optical trap was moved along the xand y-axes of the agar network in 80-nm steps and along the z-axis in 160 nm steps. After scanning a volume of 600 × 600 × 300 nm3, three filaments of the agar network were detected: two of them located inside this volume and one at the edge. The size of the particle affects the resolution which, in these experiments, is ~20 nm. SIARI S. SOSA
Micro-Optical Devices Dry Etched into Diamond Diamond has the widest optical transparency window and highest thermal conductivity of all known substances. Consequently, it is a very versatile material for use in optics. Diffractive optical elements (DOEs) are interesting for many applications, including the shaping of CO 2 lasers and Nd:YAG lasers. As 6
reported in the November 15, 2001, issue of Optics Letters, M. Karlsson, K. Hjort, and F. Nikolajeff fabricated continuousrelief blazed gratings and diffractive Fresnel lenses in diamond of optical quality at the Angstrom Laboratory in Sweden. The DOE pattern was first written in an electron-sensitive resist by direct-write electron-beam lithography, then transferred from the resist into the diamond by dry-etching in an inductively coupled plasma. The researchers used electronic-grade O2 and Ar gases for etching of the diamond substrate, and the surfaces were polished to a root-meansquare (rms) roug
Data Loading...
