Micrometers, laser

Polyethylene cube (4x4x4 mm) being inserted into test chamber of swelling apparatus. The laser micrometer is visible. 

Woo, S.L-Y., Danto, M.I., Ohland, K.J., et al (1990) The use of a laser micrometer system to determine the cross-sectional shape and area of ligaments A comparative study with two existing methods. Journal of Biomechanical Engineering, 112, 426-431. 

Precision techniques are required to measure the finished products, including CNC coordinate measuring machine (CMM) capability with associated CAD/CAM features, laser micrometers, form-scan geometry gauge, optical comparators, and other digital gauges. 

Laser desorption to produce ions for mass spectrometric analysis is discussed in Chapter 2. As heating devices, lasers are convenient when much energy is needed in a very small space. A typical laser power is 10 ° W/cm. When applied to a solid, the power of a typical laser beam — a few tens of micrometers in diameter — can lead to very strong localized heating that is sufficient to vaporize the solid (ablation). Some of the factors controlling heating with lasers and laser ablation are covered in Figure 17.2. 

Deposition of Thin Films. Laser photochemical deposition has been extensively studied, especially with respect to fabrication of microelectronic stmctures (see Integrated circuits). This procedure could be used in integrated circuit fabrication for the direct generation of patterns. Laser-aided chemical vapor deposition, which can be used to deposit layers of semiconductors, metals, and insulators, could define the circuit features. The deposits can have dimensions in the micrometer regime and they can be produced in specific patterns. Laser chemical vapor deposition can use either of two approaches. 

Liquid crystal polymers are also used in electrooptic displays. Side-chain polymers are quite suitable for this purpose, but usually involve much larger elastic and viscous constants, which slow the response of the device (33). The chiral smectic C phase is perhaps best suited for a polymer field effect device. The abiHty to attach dichroic or fluorescent dyes as a proportion of the side groups opens the door to appHcations not easily achieved with low molecular weight Hquid crystals. Polymers with smectic phases have also been used to create laser writable devices (30). The laser can address areas a few micrometers wide, changing a clear state to a strong scattering state or vice versa. Future uses of Hquid crystal polymers may include data storage devices. Polymers with nonlinear optical properties may also become important for device appHcations. 

Hydrogen to uranium all isotopes Yes, on a scale of few micrometers depth Yes, depending on the laser irradiance... 

A carbon dioxide laser produces radiation of wavelength 106 micrometers (1 micrometer = 10-6 meter). If the laser produces about one joule of energy per pulse, how many photons are produced per pulse ... 

The random laser is a simple optical system in which the strong optical scattering in the random medium forms an optical recurrent path. Recent reports on random lasers have described the emission of laser light by metal-oxide polycrystalline and micrometer-sized particles [46]. Because of its structural simplicity and small size, the single random laser is a promising miniature light source for optical devices, such as waveguides and optical switches. 

Since the mass-transfer coefficient at a micropipette is inversely proportional to its radius, the smaller the pipette the faster heterogeneous rate constants can be measured. Micrometer-sized pipettes are too large to probe rapid CT reactions at the ITIES. Such measurements require smaller (nm-sized) pipettes. Nanopipettes are also potentially useful as SECM tips (see Section IV.D) because they can greatly improve spatial resolution of that technique. The fabrication of nanopipettes was made possible by the use of a micro-processor-controlled laser pipette puller capable of puling quartz capillaries [26]. Using this technique, Wei et al. produced nanopipettes as small as 20 nm tip radius and employed them in amperometric experiments [9]. 

In non-highly focussed laser desorption ionisation, employing spot sizes in the range of 50-200 pm in diameter, the surface is deformed by an ablation volume of about 1 pm3 per pixel per laser pulse. But this ablated volume is spread over a large desorption area leading to ablation depths of the order of a few nanometres. In laser microprobing, the same ablation volume leads to ablation crater depths in the micrometer range. 

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