Kai-Chung Hou

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Diffraction-limited nanosecond pulse generation with MW-peak powers and multi-mJ-energies has been explored using 80-mum core Yb-doped fibers, demonstrating 1-MW peak power pulses with 85-W of average power at 100-kHz and 1.56-MW peak at 50-Hz.
High peak power fiber lasers are important for a variety of applications ranging from material processing and remote sensing to laser-plasma produced extreme ultraviolet lithography (EUV) generation. These applications require high peak powers in the megawatt range, < 1-10-ns pulse durations and high average powers in preferably diffraction-limited(More)
In this paper, a fast motion estimation algorithm for variable block-size by using a motion vector merging procedure is proposed for H.264. The motion vectors of adjacent small blocks are merged to predict the motion vectors of larger blocks for reducing the computation. Experimental results show that our proposed method has lower computational complexity(More)
In this paper we report the development of nanosecond-pulsed fiber laser technology for the next generation EUV lithography sources. The demonstrated fiber laser system incorporates large core fibers and arbitrary optical waveform generation, which enables achieving optimum intensities and other critical beam characteristics on a laser-plasma target.(More)
Pulsed fiber laser spectral beam combining is demonstrated using spatial-dispersion-free approach based on 1nm-sharp spectral-edge filters. Three beams separated spectrally by ~2nm are combined with Gt90% efficiency yielding 52-W combined power and 1.9-mJ combined energy.
We present a detailed experimental investigation of a fiber-to-fiber coupling process by characterizing the mode content at the output of the system. In our experiment a single-mode fiber is transversally scanned with respect to a multimode fiber, revealing position-dependent higher-order mode excitation. The outlined measurement system can be used for(More)
Efficient generation of extreme UV (EUV) light at lambda = 13.5 nm from a bulk Sn target has been demonstrated by using a fiber laser. The conversion efficiency from the 1064 nm IR to the EUV was measured to be around 0.9% into 2pi steradians within a 2% bandwidth. To the best of our knowledge, this is the first time an all-fiber system was used to generate(More)
A comprehensive study of the spectral and Mo-Si mirror inband EUV emission from tin-doped droplet laser plasma targets irradiated with a single 1064 nm beam from an Yb:doped fiber laser is reported.With pre-pulse enhancement, in-band conversion efficiency of approximately 2.1% is measured for laser irradiance intensities near 8 x 10(10) W/cm(2). This is the(More)
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