Optical trap

Figure C 1.4.8. (a) An energy level diagram showing the shift of Zeeman levels as the atom moves away from the z = 0 axis. The atom encounters a restoring force in either direction from counteriDropagating light beams, (b) A typical optical arrangement for implementation of a magneto-optical trap.

Early experiments witli MOT-trapped atoms were carried out by initially slowing an atomic beam to load tire trap [20, 21]. Later, a continuous uncooled source was used for tliat purjDose, suggesting tliat tire trap could be loaded witli tire slow atoms of a room-temperature vapour [22]. The next advance in tire development of magneto-optical trapping was tire introduction of tire vapour-cell magneto-optical trap (VCMOT). This variation captures cold atoms directly from the low-velocity edge of tire Maxwell-Boltzmann distribution always present in a cell... 

Walker T, Sesko D and Wieman C 1990 Collective behavior of optically trapped neutral atoms Phys.Rev.Lett. 64 408-11... 

Chiu D T and Zare R N 1996 Biased diffusion, optical trapping and manipulation of single molecules in solution J. Am. Chem. Soc. 118 6512-13... 

Optical storage disks Optical storage media Optical switches Optical trapping Optical tweezers Optical wave guides... 

Optical trapping can also be used as a hthographic tool (90). For example, a combination of optical molasses and an optical standing wave have been used to focus a beam of neutral sodium atoms and deposit them in the desired pattern on a suitable substrate (eg, siUcon). Pattern resolutions of the order of 40 nm with good contrast (up to 10 1 between the intended features and the surrounding unpattemed areas) and deposition rates of about 20 nm /min were obtained (90). 

Movements of single myosin molecules along an actin filament can be measured by means of an optical trap consisting of laser beams focused on polystyrene beads attached to die ends of actin molecules. (Adapted from Finer et at., 1994. Nature 368 113- 119. See also Block, 1995. Nature 378 132 133.)... 

Coppin, C. M., Finer, J. T, Spndicli, J. A., and Vale, R. D., 1996. Detection of. snb-8-nm movements of kine.sin by liigli-re.solntion optical-trap microscopy. Proceedings of the National Academy of Sciences 93 1913—1917. 

Figure 7.3 shows the two-beam photon-force measurement system using a coaxial illumination photon force measurement system. Two microparticles dispersed in a liquid are optically trapped by two focused near-infrared beams ( 1 pm spot size) of a CW Nd YAG laser under an optical microscope (1064 nm, 1.2 MWcm , lOOX oil-immersion objective, NA = 1.4). The particles are positioned sufficiently far from the surface of a glass slide in order to neglect the interaction between the particles and the substrate. Green and red beams from a green LD laser (532 nm, 21 kWcm ) and a He-Ne laser (632.8 nm, 21 kW cm ) are introduced coaxially into the microscope and slightly focused onto each microparticle as an illumination light (the irradiated area was about 3 pm in diameter). The sizes of the illumination areas for the green and red beams are almost the same as the diameter of the microparticles (see Figure 7.4). The back scattered light from the surface of each microparticle is...

J. E. and Chu, S. (1986) Observation of a single-beam gradient force optical trap for dielectric particles. Opt. Lett., 11, 288-290. 

Eujiwara, H., Takasaki, H., Hotta, J. and Sasaki, K. (2004) Observation of the discrete transition of optically trapped particle position in the vicinity of an interface. Appl. Phys. Lett., 84, 13-15. 

We have also developed a method of measurement for local temperature in microspace with a fluorescence correlation technique. Using this method, the temperature elevation at the optical trapping point due to absorption of the NIR trapping beam by solvent was quantitatively evaluated the temperature at the trapping point increased linearly with increase in the incident NIR light, and the temperature elevation coefficient was mainly dependent on two physical parameters of the solvent the absorption coefficient at 1064 nm and the thermal conductivity. 

Application of fluorescence correlation spectroscopy to the measurement of local temperature in solutions under optical trapping condition./. Phys. Chem. B, 111, 2365-2371. 

Optical Trapping of CdTe QDs Probed by Nonlinear Optical Properties... 

Ashkrn, A. (2000) History of optical trapping and manipulation of small-neutral particle, atoms, and molecules. IEEE J. Select. Topics Quantum Electron., 6, 841-856. 

Hosokawa, C., Yoshikawa, H. and Masuhara, H. (2004) Optical assembling dynamics of individual polymer nanospheres investigated by singleparticle fluorescence detection. Phys. Rev. E, 70, 061410-1-061410-7 (2005) Cluster formation of nanoparticles in an optical trap studied by fluorescence correlation spectroscopy. Phys. Rev. E, 72, 021408-1-021408-7. 

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