Chinese Academy of Sciences

Bincheng Li

Yanling Han

Qiang Wang

Zhechao Qu

Yuan Gong

The present invention discloses a dual beamsplitting element based excimer laser pulse stretching device comprising two beam splitting elements and one confocal resonator. The first beamsplitting element splits incident laser beam into two beams, one beam enters the confocal resonator, generates a certain time delay and then is incident on the second beamsplitting element, and the second beam is directly incident on the second beamsplitting element. The second beamsplitting element further splits each of the incident laser beams into two beams, one of the two beams enters the confocal resonator, generates a certain time delay and is returned back to the first beamsplitting element to be further split, and the other of the two beams is combined with other beams which are direct outputs after being split by the beamsplitting elements or being optically delayed by the confocal resonator to form a stretched output beam. The present invention may effectively enhance the efficiency of the pulse stretching, decrease the peak power of the stretched beam, and increase the lifetime of optical elements used in the excimer laser photolithography systems.

Dual beamsplitting element based excimer laser pulse stretching device

Apparatus and methods for measuring reflectance of optical laser components are disclosed. In one embodiment, when the reflectance of the test optical laser component is higher than 98%, a cavity ring-down (CRD) technique based configuration is employed to measure the reflectance of the test optical laser component. On the other hand, when the reflectance of the test optical laser component is lower than 98% or there is no measurable CRD signal, by removing the output cavity mirror in the CRD apparatus, a photometric configuration is formed to measure the reflectance. The switching between the two techniques can be achieved by removing or inserting the output cavity mirror of the ring-down cavity in the CRD apparatus.

Apparatus and method for measuring reflectance of optical laser components

A cavity ring-down apparatus and method is provided for measuring the reflectivity of highly reflective mirrors. The apparatus comprises an optical ring-down cavity including three highly-reflective mirrors whose frequency-selective optical transmission is retro-reflected into the oscillator cavity of a continuous-wave semiconductor laser, creating a change of output spectrum of said laser and enhancing the coupling coefficient of the laser power into the optical ring-down cavity. The drive current/voltage of the semiconductor laser is modulated by a square-wave function output by a function generation card. Thus the laser beam is suddenly switched off at the negative step of the square-wave signal periodically. Immediately after switching off the laser beam, an exponential decay signal of the ring-down cavity is measured by a photo detector and used to determine the decay time of the cavity and the reflectivity of highly reflective mirrors.

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Sichuan, China

Bincheng Li