Meet the conditions R2 + R2 = L cavity called the total of the heart chamber. If R1> 0, R2> 0, and R1 + R2 = L, and public centers in the cavity, known as the real heart chamber. At this time, gl <0 and g2 <0, g1g2 = 1, which corresponds to the third quadrant in Figure g1g2 = 1, hyperbolic. In particular, R1 = R2 = R = L / 2, g1 = g2 = -1, the symmetric chambers of the heart, which corresponds to point B in the figure. If R1 and R2 are of different signs, and R2 + R2 = L, public centers in the cavity, known as virtual chambers of the heart. G1> 0, g2> 0, g1g2 = 1, which corresponds in the first quadrant g1g2 = 1, hyperbolic. Consists of a plane mirror and a concave mirror. Concave mirror radius R = L, and thus, g1 = 1 g2 = 0, which corresponds to point C, and D. The appearance color of this kind of   green laser pointer   is argent.
Implemented a total of intracardiac a beam convergence point will cause the destruction of the working substance; heart chamber beam convergence point on the plane mirror, it will cause the destruction of the mirror. Therefore, the actual value of the critical cavity only parallel plane cavity and the virtual total heart chamber. Corresponding to the shaded optical resonator are unstable resonator. Unstable resonator, because the geometric loss of light, not suitable for small and medium-power lasers. The gain coefficient G solid-state lasers can also be used unsteady cavity laser, its advantage is the continuous change of the output light power, in certain special circumstances make light collimation and uniformity. Distinguish between stable cavity unstable resonator in the manufacture and use of lasers have very important practical significance of any number of times without escaping the cavity and from the stable cavity near the axis of light propagation. The high output of   200mW green Laser Pointer    is due to the new production technology of   50mW blue violet laser pointer .
Therefore, the geometric loss of light in this chamber (due to reflection loss) is extremely small, generally small and medium-power gas lasers (due to the gain coefficient G) used stable cavity, its advantages are easy to produce laser. The following will be seen that the stable laser cavity mode theory is built on the basis of the symmetric confocal cavity, therefore, symmetric confocal cavity is the most important and representative of a stable cavity. With the stability diagram, select the radius of curvature of the optical resonator cavity length or mirror is much more convenient, the examples are as follows: To create a cavity length L, symmetric stable cavity, and how to determine the range of the mirror radius of curvature? In a stable figure, the symmetric cavity corresponding in region 1, 2 connection A, B, the two line segments AB, as shown in Figure (2-2). The size of    100mW green laser pointer   can be customized.
Range of coordinate values corresponding to the AB segment can immediately find the scope of the radius of curvature is: L / 2 R <, the maximum radius of curvature can take R1 = R2, which is parallel to the plane cavity, the minimum take R1 = R2 = L / 2, that is, the heart chamber. To a given stable cavity mirror, matching the radius of curvature of a mirror, how to determine its range?, According to the existing mirror, for example, R1 = 2L, find g1 = l-L/R1 = 0.5, in the stability diagram g1 axis to find the corresponding point C, as shown in (2-3a) than point C to make a straight line parallel to the g2 axis, this line falls within the stable region of the line CD is required another one his point by the corresponding value of R2 can already mirror dubbed stable cavity mirror radius of curvature range from CD, R2 can be used a concave mirror can also be used a convex mirror, using a concave mirror, the range : L, R2, <, with a convex mirror, the range – <R2-L. Every     green laser pointer    of this kind only needs one AAA button cell battery.
If you already have two mirrors, the radius of curvature R1, R2, want to use them to form a stable cavity, the cavity length of the scope of how to determine? Derived from the known radius of curvature k = R2/R1 into g1, g2 expression, to identify g1, g2 equation, in order to identify the cavity length range. For example, k = 2, which is a slope of 0.5, intercept of 0.5 linear equation of this straight line falls on the line in the stable region for the AE, DF, as shown in Figure (2-3b). The line segments in Figure 2-3 (b) in the AE segment corresponding to the cavity length range 0 <L R1, the range of the segment DF in Figure 2-3 (b) corresponds to the cavity length L, 3R1 for the 2R1.     green laser pointer    is the red laser pen.
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