Trap beams

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. 

FIGURE 6.8 TH power generated from a 200-nm-diameter polystyrene particle trapped by a CW laser beam as a fnnction of the incident power of the trapping beam. Dashed line shows a third-power dependence on the incident power. 

The temperature rise due to power absorbed from a laser beam is shown as a function of particle size. The trapping beams have a power of 1 mW and a width of 2 pm where the particle is trapped. Small particles absorb little energy from the beam while very large particles lose significantly more heat through conduction due to their large surface area. 

We calculated the dynamic behavior modeling of a micro-particle in laser-trapping beams, we pulsed a 20mW laser with a cycle period of 1, 10, 100, 250, 500, 1000 and 1500msec. The beam cycling process started at the laser irradiation from the optical fiber A. The micro-particle is first pushed towards the beam axis A by the attracting force. After a few seconds the micro-particle was circulated between the beam axis A and beam axis B. 

Figure 1 Illustration (Monat et al., 2008) of a multifunctional optofluidic chip. The chip includes (i) a photonic chip (bottom) that is coupled to optical fibers, (ii) a microfluidic circuit (on top) that is connected to fluid sources with different refractive indexes, and (iii) optical trapping beams to manipulate micro-mechanical components. The schematic diagram on the top right-hand side shows a close-up image of the chip, where the optical signal intersects with a fluidic channel on the micrometer scale.

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