We report optical tweezers with the assistance of a strong instantaneous force generated by a focused pulse laser beam of sub-microsecond duration. A strong instantaneous force is required in biological applications. A suitable pulse duration for pulse assistance in water is derived on the order of 100 to 1000 ns from motion analysis of a micrometer-sized particle. We performed optical tweezers experiments with a focused pulse beam of 160 ns duration coaxially incident with a CW laser beam. From the experiments on particle extraction from a glass surface, the required energy for extraction is smaller than the case of 150 µs duration by a factor of 60.

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Optical tweezers which enables to trap micron to nanometer sized objects by radiation pressure force is utilized for manipulation of particles under a microscope and for measurement of forces between biomolecules. Weak force of optical tweezers causes some limitations such as particle adhesion or steric barrier like lipid membrane in a cell prevent further movement of objects. For biomedical applications we need to overcome these difficulties. We have developed a technique to exert strong instantaneous force by use of a pulse laser beam and to assist conventional optical tweezers. A pulse laser beam has huge instantaneous laser power of more than 1000 times as strong as a conventional continuous-wave laser beam so that the instantaneous force is strong enough to break chemical bonding and molecular force between objects and obstacles. We derive suitable pulse duration for pulse assist of optical tweezers and demonstrate particle manipulation in difficult situations through an experiment of particle removal from sticky surface of glass substrate.

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We have developed a Laser Backlight LCD TV that uses red laser diodes and cyan LEDs. The laser diode is smaller divergence angle than the LED. Therefore in the backlight we have developed an optical system suitable to the characteristics of the laser light with a simple configuration.