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Study Of Q-switched Nd: YAG Laser On The Laser Trimming

Posted on:2004-03-11Degree:MasterType:Thesis
Country:ChinaCandidate:Z J HeFull Text:PDF
GTID:2168360092470533Subject:Optical Engineering
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At present, laser process technology develops fast, since a laser light can obtain many good characteristics such as good direction, high energy density to focus the beam at a micrometer level, small pulse width ranging from dozens of Nanoseconds to dozens of Picoseconds, heating material immediately, decreasing heat effect on materials and so on. These advantages of laser above can provide good conditions for laser process.From 1995 on, some papers have been published by some international scholars. They coat a a-Si (amorphous silicon) thin film on the Si-substrate of a waveguide and treat the film by a laser in order to control the birefregence and the dispersion of the waveguide precisely. It is thus enhances the stability of waveguide devices and reduces the transmission loss of them. They also show some examples, which apply the laser micro-process technology to the real waveguide devices.In this thesis, our purpose is mainly to reappear the process and the results shown by the international scholars. Some experimental conditions should be setup to do the experiment of laser process, we should firstly build a laser which has light beam of high quality and the ability of incision. Here are the needs for the laser: firstly, the stability is 2%; secondly, the start up and working of laser should not affect the work of other precise devices; thirdly, the laser has continuous, long pulse width, short pulse width, totally three output forms.The hot lenses effect leads to the instability of laser output, in order to compensate the effect of Nd:YAG stick. We mainly design a heat-stable resonancecavity according to the formula G, xG, = ?. The measurement we take is to adjustthe curve radius of the two reflected mirrors in the resonance cavity. After building the acoustic-optic Q-switched Nd:YAG laser, we test its characteristic. We obtain some results: repetition frequency can reach at the top of 3000 Hz, the peak power is 50 KW, the stability of pulse energy is 1%, the pulse width is 80-100nS, and the diameter of light spot is 60-90 urn. The characteristic of laser beam is good to the process on a a -Si thin film on the Si-substrate of waveguide device. However, wecannot achieve the perfect experimental results since the wave-guide device coated by a a-Si film cannot be provided at present.The laser-micro-engraving technology, which processes glass or crystal by a laser beam, develops fast recently. In order to achieve laser-micro-engraving, the pulse width of the laser beam should be at about several nanoseconds level and its peak power should also be at dozens of megawatt level. In addition, a ring-focused light beam which can keep the emission angle at a constant and has a large depth-to-radius, is needed.According to the special applications in laser-micro-engraving, we design a laser with special configuration resonance cavity, which is different from the reservoir cavity of the operating substance, the reservoir cavity of the resonance cavity. The key component of the special resonance cavity is a special output coupling device, which is set on the laser resonance cavity formed by two stage holophotes. According to the principle of laser, photons can escape from the cavity after a reflecting trip within a period because of the function of holophote with a 45-degree angle, whether the electric voltage of Q-switched is on or off. It is thus the output pulse width Arp cann r fbe kept at the theoretical value level: Ar =------, where L' is the distance betweencthe small hole and holophote.The aperture of small hole wafer of the special output coupling device is the key parameter. It's very difficult to make a hole on the wafer with a 45-degree angle exactly. We do much theoretic and experimental work about this. Finally we obtain the perfect value of the aperture of the small hole, which is between 0.6 mm to 2.5 mm, after many experiments and testings.The acoustic-optic Q-switched Nd:YAG laser with special resonance cavity we design holds some characteristics as f...
Keywords/Search Tags:Nd:YAG laser, laser trimming, acoustic-optic Q-switched, laser-micro-engraving, photoelectric Q-switched
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