Rapid prototyping (also called generative manufacturing) is evolving from polymer-based prototyping to metal-based prototyping, thanks to the development of titanium, stainless, aluminum, and cobalt-chrome powders that can be melted or “sintered” one layer at a time using a laser. Research being conducted by SPI Lasers (Southampton, England) is now showing that rapid prototyping can be further improved by the better surface finish and increased fill density made possible by fiber lasers.
Compared to conventional carbon dioxide (CO2) lasers, fiber lasers have a beam waist up to four times smaller (or 16 times the power-density) at the focal point. Using power levels of 200 W at 1070 nm, fiber lasers can produce 100% dense parts that exhibit 10 times the tensile strength of parts manufactured using CO2 lasers. The temporal and spatial stability of fiber lasers contributes to an overall improvement in the layer uniformity as metal parts are being fabricated, while the energy-efficiency and compactness of fiber lasers make them attractive options for industrial-prototyp-ing environments. Contact Steve Norman at steve. norman@spilasers.com.
Researchers at the European Laboratory for Non-Linear Spectroscopy (Firenze, Italy), the University of Trento (Trento, Italy), and the University of Paderborn (Paderborn, Germany) have used precisely controlled microscopic quantities of liquid (on the order of a femtoliter) to locally modify refractive indices in 2-D photonic crystals—a potential method for fabricating the optical equivalent of integrated circuits. A solution of water and the organic dye Rhodamine 6G (with refractive index high enough to introduce permitted states into the photonic bandgap) was introduced into selected pores of photonic crystal via capillary action using a micropipette positioned with 0.1 µm precision with respect to the photonic-crystal surface. A custom-built confocal laser-scanning microscope was used to monitor the process, assisted by the photoluminescence of the Rhodamine dye.
Calculations confirmed that the researchers fabricated optical-resonator and waveguide structures as intended. Inserting liquids of specific refractive index and nonlinear constant, local light sources, and liquid crystals to tune the refractive index externally is expected to enable pixel-by-pixel fabrication of erasable and rewritable optical components, such as waveguides, active elements, and sources, as well the assembly of such optical components into integrated optical circuits. Contact Francesca Intonti at intonti@lens.unifi.it.
Pablo Artal and Juan Tabernero at the University of Murcia (Murcia, Spain) have built a prototype imaging system for recording reflections (called Purkinje images) from four ocular interfaces—air-cornea (PI), cornea-aqueous (PII), aque-ous-lens (PIII), and lens-vitreous (PIV)—in vivo. The prototype imaging system contains a chin and forehead rest for the subject; a semicircular array of infrared LEDs to illuminate the eye; a telecentric camera objective and CCD camera to collect and record the reflections; an array of LEDs for the subject to fixate on; and other optical components. When an illumination source is aligned with principle line of sight in a well-aligned human eye, the reflection images align around a common center. PI and PII usually overlap due to small corneal thickness. PIII appears largest, and PIV appears inverted. The outermost circle, in the large image on the left of well-aligned reflections, traces the circumference of the pupil. The relative positioning of the Purkinje images changes, however, with misalignments, either among ocular surfaces or between the illumination source and the line of sight. The new instrument is expected to prove useful in basic studies of the eye and in clinical ophthalmology. Contact Pablo Artal at pablo@um.es.
References:
http://www.laserfocusworld.com
Archives