2012.8
About Instruments Today No. 189
Fiber Laser
Graphite Nano-Particle Saturable Absorber Based Passively Mode-Locking Erbium-Doped Fiber Laser [ 下載 PDF ]
Yung-Hsiang Lin, Gong-Ru Lin
Graphene and graphite are currently intriguing materials showing potentials to be the saturable absorbers for passively mode-locking erbium-doped fiber laser (EDFL). In contrast to previous demonstrations, the triturated graphite nano-particles are preliminarily used to serve as the saturable absorber in this work, the sizes of these host-solvent-free graphite nanoparticles are confined within 500 ± 200 nm. The structural property of the graphite nano-particles is analyzed by Raman spectrum, and the optical properties such as linear absorption and nonlinear absorption are also investigated. To insert the graphite nano-particles into the EDFL cavity, the free-standing graphite nano-particles are directly brushed on the fiber endface and connected with the other fiber patch-cord. The saturable absorption process with sufficient modulation depth can successfully induce the passively mode-locking EDFL. The central wavelength of the passively mode-locking EDFL is located at 1572 nm. The pulsewidth and the full-width at half maximum (FWHM) of the optical spectrum are 660 fs and 3.96 nm, respectively. This study indicates that the physical process can simplify the integration of saturable absorber. The graphite nano-particles can produce the comparable pulsewidth in 100s fs regime with the few-layer graphene when serving as the saturable absorber in EDFL cavity.
The Study of Stable Ultrafast Fiber Lasers Employing Graphene Based Saturable Absorbers [ 下載 PDF ]
Pi Ling Huang, Chao-Yung Yeh, Wood-Hi Cheng
In 2004, the Manchester group, Andre Geim and Konstantin Novoselov, extracted the graphene by using adhesive tape to repeatedly split graphite crystals into increasingly thinner pieces. This proved the existence of free-standing atoms; hence, they obtained the Nobel Prize in physics 2010. Graphene is the thinnest material in the world with the lowest electrical resistance at room temperature among the materials, and it is highly transparent and a good conductor. Graphene is not only utilized in electric field but also is now widely applied in optoelectronic industries, such as solar cells, transparent touch screens, and saturable absorber. We investigate the stable pulse output with graphene based saturable absorber in ultrafast fiber laser system. From our measured results, the graphene based saturable absorber may posses the potential a low cost mode locker in ultra-short pulse fiber lasers.
Laser Dynamics and Applications of High Repetition Rate Asynchronous Mode-Locked Fiber Lasers [ 下載 PDF ]
S.-S. Jyu, G.-H. Jiang, S.-M. Wang, Y. Lai
High repetition rate asynchronous mode-locked fi ber lasers not only have the advantages of ultra-short output pulsewidth and long-term stability, but also exhibit the unique laser dynamics of slow periodic pulse timing and central wavelength variation. In this article, we explain how to investigate the laser dynamics of asynchronous modelocked fi ber lasers theoretically, how to accurately determine the magnitudes of pulse timing and central wavelength variation experimentally, and how to develop a practical new method for measuring the fi ber dispersion based on the studied laser dynamics.
High Power Nanosecond Yb:Fiber Based Master Oscillator Power Amplifi er System [ 下載 PDF ]
Chun-Lin Chang, Po-Yen Lai, Yen-Yin Li, Yin-Wen Lee, Shih-Hung Chen, Sheng-Lung Huang
In recent years, large-mode-area double-clad fibers have been widely utilized as gain medium of laser amplifiers to realize the high power fiber based master oscillator power amplifier (MOPA) system. The system's compactness, stability and reliability accelerate the progress on the commercialization of high power lasers. Furthermore, many breakthroughs and developments of high power laser application have been driven owing to its high energy conversion efficiency, excellent beam quality, and versatile operations. In this article, we introduce the development of high power nanosecond fiber based MOPA system using ytterbium-doped fibers, including the design considerations, general confi gurations, and output characteristics for laser applications.
Low Repetition Rate and High Energy Mode- Locked Yb-Doped Fiber Laser in All Normal Dispersion Cavity [ 下載 PDF ]
Ja-Hon Lin, Jia-Liang Jhu, Ting-Chun Lin
It is revealed that high-energy pulses from fiber lasers around 1 µm has various practical applications. For this purpose, we have generated 365 kHz low-repetition-rate pulses in all-normal-dispersion Yb-doped fiber ring laser by adding 520 m single mode fiber in the laser cavity. With 80% output coupler, the spectral bandwidth of mode-locked pulse is relative wide, which can be used in biomedical diagnosis. In use of 90% output coupler, the highest energy pulse around 100 nJ has been experimentally demonstrated. Besides, Q-switched mode-locking was observed in this laser configuration. By the modulating of Q-switching envelope, the repetition rate of mode-locked pulse can be further reduced to enhance the intensity of the output pulses.
Research and Development of Growth Technology of Novel Crystalline Materials [ 下載 PDF ]
Chu-An Li, Chenlong Chen, Cin-Huei Wang, Mitch M.C. Chou
Growth of single crystals is an important approach to explore the novel materials. With the strong supports of National Science Council and National Sun Yat-sen University, Taiwan Consortium of Emergent Crystalline Materials (TCECM) was built on campus. Different growth furnaces are built to grow crystals which can be used in laser, optics, high-temperature superconductivity, magnetic single crystal, biomedical science and technology, high energy physics, piezoelectric crystal, and light emitting diode, etc. We do not only provide the single crystals for academic researches but also transfer the technology to the industry. In the future, it is hoped that our laboratory becomes one of the most well-known crystal growth institutes in the world and bring up the international popularity of the crystal growth researches of Taiwan.
Development of Portable Laser Marking System for Three-Dimensional Structuring Applications [ 下載 PDF ]
Shih-Feng Tseng, Wen-Tse Hsiao, Chien-Kai Chung, Kuo-Cheng Huang
This study aims to develop a portable laser marking system that consists of a fiber-optics diode laser with a wavelength of 808 nm, optics/opto-mechanical components, a laser scanning module, a laser energy control module, and a human-machine interface for fabricating three-dimensional structures. The measured results of laser beam quality revealed that the laser beam was collimated with TEM00 mode through a fiber collimator and the roundness of laser beam was approximately of 96%. Moreover, the laser output power increased proportionally with increasing the pulse repetition rate. The defl ective angle of scanner mirrors was adjusted by using 0.192 voltage to obtain a scan distance of 1 mm, and the maximum scanning field was 100 mm × 100 mm. The pulse widths were ranging from 530 µs to 48 µs when the laser pulse repetition rates were adjusted from 1 kHz to 10 kHz, respectively.
Beyond the Limit—Superresolution Structured Illumination Microscopy [ 下載 PDF ]
Szu-Yu Chen
Based on the wave nature of light, the spatial resolution of far-field optical microscopy is limited by diffraction limit due to diffraction and this limit is about half of the light wavelength. However, as the biomedical researches gain insight into much smaller structures of bio-tissues beyond the diffraction limit, the resolving power requirements of the optical microscopy also get higher and higher and traditional optical microscopies under diffraction limit are yet to fill these requirements. Therefore, superresolution technique became a hot research topic in the field of optical microscopy and in the past two decades, various superrsolution optical microscopies were developed to break the resolution barrier and demonstrated on the biomedical researches. This article focuses on one of the far-field superresolution microscopy, structured illumination microscopy (SIM), which is so far the superresolution technique most commonly applied to the biomedical researches. Both the principles and the development of structured illumination microscopy are introduced in this article, and in addition, the advantages and the possible challenges of these techniques for biomedical applications are also discussed.
Studying Materials under Extreme Conditions—Introduction of Large Volume High Pressure Apparatus [ 下載 PDF ]
Po-Jung Florian Hua, Su-Ying Chien, Jennifer Kung, Yanbin Wang
High pressure devices have provided another dimension in the working conditions, 'pressure', and have broadly employed in different research area and industrial applications, for example, planetary sciences, material sciences, and synthesis of novel materials and super-hard materials. In this article, we will introduce one of high pressure devices—large volume press, which couple of them have been installed in different research institutes in Taiwan lately. The details of large volume presses will be presented, including their mechanical geometries and the principles of experimental techniques. The high pressure research implications also are illustrated.
