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In addition, many practical factors, such as the uneven nature of the work material, processing and adjustment of optical cavity can lead to errors such as directional variation. Laser can achieve the minimum beam divergence is also subject to diffraction effects of the restrictions, it can not be less than the time of the laser through the output aperture diffraction angle θm. θm called diffraction limit. Set the output cavity aperture 2a, the diffraction limit θm as θm = λ/2a such as helium-neon gas laser, λ = 0.63m, take 2a = 3mm, then θm ≈ 2 × 10-4rad. The first chapter outlines the different types of lasers and laser lasers very different direction, it is the type of work and the uniformity of the material, the type of optical cavity and the cavity length, incentives, and the working status of the laser.The effect of pressing the page-turning button on green laster pointer is the same as that on the keyboard. Gas laser as a result of the material with good uniformity, and the cavity length is generally larger, so the best direction, up to θ ≈ 10-3rad, He-Ne laser or even up to 3 × 10-4rad, which has very close to its diffraction limit θm. Poor directional solid-state lasers, usually in the order of 10 -2 rad. The main reason is that there are many factors that cause the solid material of the optical non-uniformity, and general solid-state lasers use a shorter cavity length and the non-uniformity of excitation. Directional semiconductor lasers worst. May focus on the tremendous energy of the laser to a diameter of the order of the wavelength of laser and laser beam Chapter Overview Second, temporal coherence and monochromaticity τc = 1 / △ v color, the higher the longer the coherence time for a single transverse mode (TEM00) laser, the color depends on its longitudinal mode structure and pattern bandwidth.The green laster pointer could turn pages as the Page Up and Page Down keys do. If more than one longitudinal mode laser oscillation on the laser by a number separated by △ vq (longitudinal mode interval) composed of different frequencies of light, so the color is poor. Chapter I Overview of single-mode laser and the laser frequency stabilization of gas lasers of the best color, usually up to 106Hz ~ 103 Hz, the frequency stabilization measures to the most stringent conditions, the He-Ne laser has been observed of about 2Hz bandwidth of the monochromatic solid-state lasers is poor, mainly because of the work material gain curve is very wide, it is difficult to ensure that the work of a single longitudinal mode. Monochrome laser diode of the worst. Single-mode laser operation (selected mode technology) and frequency stabilization for improving the coherence is very important.With green laster pointer, you may finish the page-turning function in Word file. Frequency stabilization of a single longitudinal mode laser TEM00 laser emitted the best first chapter outlines three lasers and laser, laser, high-brightness (strong coherent light) to improve output power and efficiency an important issue is the development of lasers. Gas lasers (such as CO2) to produce the maximum continuous power, solid-state lasers can produce high pulse power, especially the use of cavity Q modulation and laser amplifier, the laser oscillation time compression to make a very small value (eg 10 - 9s order of magnitude), and the output energy amplification, resulting in high pulse power. Technology and the use of mode-locked pulse compression, the laser pulse width can be further compressed to 10-15s. Of particular importance is the laser power (energy) can be concentrated in a single (or few) mode, which has a very high photon degeneracy. You may turn pages as you like by green laster pointer in the Excel file.This is the difference between the laser light on an important common feature.