Shi-Chun Tsai

Diode-pumped Q-switched Nd:YVO4 yellow laser with intracavity sum-frequency mixing

A compact high-power yellow pulsed laser has been demonstrated by use of intracavity sum-frequency mixing in a diode-end-pumped Q -switched Nd:YVO(4) dual-wavelength laser. A three-mirror configuration forming two separate laser cavities is used to optimize the gain match for simultaneous dual-wavelength emission in Q -switched operation. Under the optimum cavity-length condition, the highest yellow average power is 340 mW and the peak power is 2 kW, obtained at 12.5 W of pump power.

High-power diode-pumped Q-switched and mode-locked Nd:YVO 4 laser with a Cr 4+ :YAG saturable absorber

We demonstrate a high-power passively Q -switched and mode-locked Nd:YVO(4) laser with a Cr(4+):YAG saturable absorber. 2.7 W of average power with an 18-kHz Q -switched repetition rate was generated at a 12.5-W pump power. The peak power of a single pulse near the maximum of the Q -switched envelope was greater than 100 kW.

Compiler optimization on instruction scheduling for low power

In this paper, we investigate the compiler transformation techniques to the problem of scheduling VLIW instructions aimed to reduce the power consumption on the instruction bus. It can be categorized into two types: horizontal and vertical scheduling. For the horizontal case, we propose a bipartite-matching scheme. We prove that our greedy algorithm always gives the optimal switching activities of the instruction bus. In the vertical case, we prove that the problem is NP-hard, and propose a heuristic algorithm. Experimental results show average 13% improvements with 4-way issue architecture and average 20% improvement with 8-way issue architecture for power consumptions of instruction bus as compared with conventional list scheduling for an extensive set of benchmarks.

Permutation Arrays Under the Chebyshev Distance

An (n,d) permutation array (PA) is a subset of Sn with the property that the distance (under some metric) between any two permutations in the array is at least d. They became popular recently for communication over power lines. Motivated by an application to flash memories, in this paper, the metric used is the Chebyshev metric. A number of different constructions are given, as well as bounds on the size of such PA.

Efficient generation of continuous-wave yellow light by single-pass sum-frequency mixing of a diode-pumped Nd : YVO4 dual-wavelength laser with periodically poled lithium niobate

We report efficient generation of cw yellow light by use of single-pass sum-frequency mixing from a diode-pumped Nd:YVO(4) dual-wavelength laser with periodically poled lithium niobate. A diode-pumped Nd:YVO(4) dual-wavelength laser is implemented with a three-mirror cavity, and the optimum oscillation condition is obtained from theoretical analysis. We extracted 78 mW of power at 593 nm from 1.2 W at 1064 nm and from 1.0 W at 1342 nm in a beam with excellent quality. The output power could probably be increased to ~92 mW by antireflection coating of the crystal.

Distance-preserving mappings from binary vectors to permutations

Mappings of the set of binary vectors of a fixed length to the set of permutations of the same length are useful for the construction of permutation codes. In this article, several explicit constructions of such mappings preserving or increasing the Hamming distance are given. Some applications are given to illustrate the usefulness of the construction. In particular, a new lower bound on the maximal size of permutation arrays (PAs) is given.

Diode-end-pumped passively mode-locked high-power Nd : YVO4 laser with a relaxed saturable Bragg reflector

We demonstrate a high-power passively mode-locked Nd:YVO (4) laser that uses a saturable Bragg reflector (SBR) with strain relaxation. 23.5 W of average power with ~21.5-ps cw mode-locked pulse trains was generated at a 50-W pump power. Experimental results show that appropriate strain relaxation in the SBR makes the mode-locking operation less sensitive to temperature variation.

Compiler optimization on VLIW instruction scheduling for low power

In this article, we investigate compiler transformation techniques regarding the problem of scheduling VLIW instructions aimed at reducing power consumption of VLIW architectures in the instruction bus. The problem can be categorized into two types: horizontal scheduling and vertical scheduling. For the case of horizontal scheduling, we propose a bipartite-matching scheme for instruction scheduling. We prove that our greedy bipartite-matching scheme always gives the optimal switching activities of the instruction bus for given VLIW instruction scheduling policies. For the case of vertical scheduling, we prove that the problem is NP-hard, and we further propose a heuristic algorithm to solve the problem. Our experiment is performed on Alpha-based VLIW architectures and an ATOM simulator, and the compiler incorporated in our proposed schemes is implemented based on SUIF and MachSUIF. Experimental results of horizontal scheduling optimization show an average 13.30% reduction with four-way issue architecture and an average 20.15% reduction with eight-way issue architecture for transitional activities of the instruction bus as compared with conventional list scheduling for an extensive set of benchmarks. The additional reduction for transitional activities of the instruction bus from horizontal to vertical scheduling with window size four is around 4.57 to 10.42%, and the average is 7.66%. Similarly, the additional reduction with window size eight is from 6.99 to 15.25%, and the average is 10.55%.

Decoding Frequency Permutation Arrays Under Chebyshev Distance

A frequency permutation array (FPA) of length n = mλ and distance d is a set of permutations on a multiset over m symbols, where each symbol appears exactly λ times and the distance between any two elements in the array is at least d. FPA generalizes the notion of permutation array. In this paper, under the Chebyshev distance, we first prove lower and upper bounds on the size of FPA. Then we give several constructions of FPAs, and some of them come with efficient encoding and decoding capabilities. Moreover, we show one of our designs is locally decodable, i.e., we can decode a message bit by reading at most λ+1 symbols, which has an interesting application to private information retrieval.

An Optimal Data Hiding Scheme With Tree-Based Parity Check

Reducing distortion between the cover object and the stego object is an important issue for steganography. The tree-based parity check method is very efficient for hiding a message on image data due to its simplicity. Based on this approach, we propose a majority vote strategy that results in least distortion for finding a stego object. The lower embedding efficiency of our method is better than that of previous works when the hidden message length is relatively large.