Laser forming

Other potential applications of photonic crystals include crystals with rows of holes to guide radiation around sharp bends (something that cannot be attained with conventional optical fibres), nanoscopic lasers formed from thin films, ultrawhite pigment formed from a regular array of submicron titanium dioxide particles, radio frequency reflectors for magnetic resonance imaging (MRI) and LEDs. 

This Synchroscan [68] streak camera system has been used to study the time resolved fluorescence of trans-stilbene in the picosecond time regime. The experimental arrangement [69] is shown in Fig. 20. An acousto-optically mode-locked argon ion laser (Spectra Physics 164), modulated at 69.55 MHz was used to pump a dye laser. The fundamental of this dye laser, formed by mirrors M, M2, M3 and M4, was tunable from 565 to 630 nm using Rhodamine 6G and second harmonic output was available by doubling in an ADP crystal placed intracavity at the focal point of mirrors M5 and M6. The peak output power of this laser in the ultraviolet was 0.35W for a 2ps pulse which, when focused into the quartz sample cell of lens L, produced a typical power density of 10 KW cm-2. Fluorescence was collected at 90° to the incident beam and focused onto the streak camera photocathode with lens L3. The fluorescence was also passed through a polarizer and a bandpass filter whose maximum transmission corresponded to the peak of the trans-stilbene fluorescence. 

Fig. 20. Schematic diagram of the Synchroscan streak camera system. A Spectra Physics model 164 acousto-optically mode-locked argon ion laser modulated at 69.44MHz pumps the Rhodamine 6G dye laser formed by mirrors Mi, M2, M3 and M4. This dye laser typically produces pulses of 2 ps duration with an energy content of 0.6 nJ. The second harmonic is generated intracavity in an ADP crystal. The UV radiation is then coupled out through mirror Ms and a filter F2 is used to eliminate any transmitted visible light before focusing into the sample cell with lens Lt. The fluorescence is detected at 90 to the incident beam. A lens L2 collects the fluorescence which passes through a polarizer and a bandpass filter and then onto the slit of the streak camera. (After ref. 69.)...

Lasers form the basis of precision-measuring tools called interferometers that can measure distances less than 1/100th the thickness of a human hair, and are as useful on construction sites as in laboratories. Such instruments can be scanned over objects to create images, and are used on highways to identify vehicles automatically, or on NASA spacecraft to map the surface of the... 

The spectrum of lattice-trapped atoms is recorded using a heterodyne technique. Light fluoresced by the trapped atoms is combined with light (frequency shifted by a modulator) from the laser forming the lattice. When the beams mix on a photodiode they create a beat signal at the difference frequency between the fluorescence and the frequency-shifted laser. The power spectrum of the photocurrent is identical to the fluorescence power spectrum, but centered at radio frequency. This heterodyne technique is not sensitive to the frequency jitter of the laser because the jitter is common between the fluorescence and the laser, which acts as a local oscillator. 

The photobehaviour of methyl iodide clusters is dependent on the mode of excitation. Thus, in a supersonic jet iodine molecules are formed, while a visible laser forms ions. Pulsed photolysis has been used to generate iodine atoms from trifluoromethyl iodide. 

The rotational structure of a molecular gas provides a suitable frequency ladder. The very high spectral quality of some of the molecular gas lasers forms an excellent source for spectroscopy with very high sensitivity. Therefore two molecular gas lasers, the CO2-laser and the CO-laser will also be outlined in this survey in sections... 

A new technique, not yet commercialized for karat gold, is laser forming where the laser beam is rastered over the sheet surface in a controlled pattern, inducing thermal stresses that cause it to self-deform in a controlled way [94,95]. This technique also presents unique design opportunities. Another newer use of lasers is in DMLS, a method of SFF or RM, mentioned previously and described in the later section, Powder Metallurgy Processes. 

S. Silve and H. Zhao, 2004. Laser forming as a method of producing designed objects. In Proceedings of the Santa Fe Symposium on Jewelry Manufacturing Technology, ed. E. Bell, 401 34. Albuquerque, NM Met-Chem Research. 

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