Hong-Jin Kong

Ultraprecise microreproduction of a three-dimensional artistic sculpture by multipath scanning method in two-photon photopolymerization

Ultraprecise fabrication of three-dimensional (3D) microstructures comes up to be one of the most important issues in two-photon induced photopolymerization. To date, it has been difficult to fabricate 3D microstructures without any deformation due to the surface tension between a rinsing material and solidified microstructures during the developing process: In general, the surface tension significantly affects the precision of the resulting 3D microstructures. To overcome this problem, the authors propose a simple and effective laser scanning method to reinforce the strength of 3D microstructures without loss of precision. Overall, a complex 3D artistic sculpture such as “The Thinker” was reproduced in the controlled ultraprecise form, which shows that the proposed method enables the fabrication of 3D patterns with dramatically improved precision and stability.

Effective fabrication of three-dimensional nano/microstructures in a single step using multilayered stamp

A technique in ultraviolet nanoimprint lithography (UV-NIL) for the creation of three-dimensional (3D) nanopatterns in a single step is proposed. The single-step fabrication of 3D or multilevel structures has a multitude of benefits. Inherent in this is the elimination of a need for alignment for multilevel fabrications as well as being a cost effective and simple process. For 3D UV-NIL, a trial in the fabrication of multilayered stamps has been conducted employing two-photon polymerization and diamondlike carbon (DLC) coating technique. The DLC coating layer enables the polymer patterns to be used effectively as a stamp without the need for an antiadhesion material. Additionally, O2-plasma ashing has the potential for an epoch-making improvement of the precision of polymer patterns with a linewidth of 60nm. Overall, several fine patterns are imprinted using the multilayered stamp onto a UV-curable resist via a single-step process without any identifiable damage.

Proportional enlargement of movement by using an optically driven multi-link system with an elastic joint

Diverse movements using optical manipulation have been introduced. These are generally performed in the focal region of the laser beam. To achieve a wider range of movements based on precise motion transformation, an effective method for optical manipulation that overcomes the important obstacles such as small optical trapping forces, friction, and the viscosity of fluids is required. A multi-link system with an elastic joint is introduced that provides precise motion transformation and amplification. By considering the physical properties of the structure and the optical trapping force, an elastic micron-scale joint with the simple shape of a thin plate was designed. As a further example of a multi-link system with an elastic joint, a double 4-link system for motion enlargement was designed and fabricated. By performing experimental evaluations of the fabricated structures, it was confirmed that multi-link systems with an elastic joint were effective tools for precise motion transformation through optical manipulation.

Corrected Article: “Ultraprecise microreproduction of a three-dimensional artistic sculpture by multipath scanning method in two-photon photopolymerization” [Appl. Phys. Lett 90, 013113 (2007)]

Ultraprecise fabrication of three-dimensional (3D) microstructures comes up to be one of the most important issues in two-photon induced photopolymerization. To date, it has been difficult to fabricate 3D microstructures without any deformation due to the surface tension between a rinsing material and solidified microstructures during the developing process: In general, the surface tension significantly affects the precision of the resulting 3D microstructures. To overcome this problem, the authors propose a simple and effective laser scanning method to reinforce the strength of 3D microstructures without loss of precision. Overall, a complex 3D artistic sculpture such as “The Thinker” was reproduced in the controlled ultraprecise form, which shows that the proposed method enables the fabrication of 3D patterns with dramatically improved precision and stability.

Nd3+:ethylene glycol amplifier and its stimulated emission cross section

We demonstrate that Nd3+:ethylene glycol can be used as an amplifier gain medium for a Nd3+:YLF laser. It has been known that Nd3+:liquid is hard to use as a gain medium due to fluorescence quenching. However, we could use Nd3+:ethylene glycol as a gain medium by using a new amplification system, and we also measured the stimulated emission cross section of Nd3+:ethylene glycol. A maximum gain of ∼2 was obtained in our experimental setup, and the stimulated emission cross section of Nd3+:ethylene glycol was measured to be 1.5(±0.5) ×10−19 cm2.