Yi Qiu

Phase-locking principle of axisymmetric structural CO 2 laser and theoretical study of the influences of parameters-changes on phase-locking

Based on the injection-locking principle, the phase-locking mechanisms of axisymmetricfold combination CO2 lasers are analyzed. Then influences of parameters-changes on phase-locking are studied in detail, such as changes of cavity length and curvature radius, linewidth, phase error, and coherence time. It is shown that these factors almost do not influence the degree of mode coupling, but they could influence distribution of light intensity to some degree. Phase-locking can improve the value of maximum light intensity significantly; what is more, the numerical calculation indicates that the higher the fringe visibility the better the coherence.

Influences of misalignment of control mirror of axisymmetric-structural CO2 laser on phase locking.

Based on the principle of phase locking of an axisymmetric-fold combination CO2 laser under the normal state condition, the mechanisms of phase locking are analyzed when the control mirror is misaligned. Then the overlapping rate (OR) of the mode volume is introduced: the main influences on phase locking are the OR, the average life of the light wave, the root mean square phase error, and the mode coupling coefficient; these influences on phase locking are studied. The distribution of the light intensity reflects the effect of phase locking. It is shown that the misaligned angle has little influence on the phase locking if it is within tolerance.

Phase-locking of an axisymmetric-fold combination cavity CO2 laser using the back surface of the output-mirror

The principle of phase-locking of an axisymmetric fold combination cavity CO2 laser, fulfilled by the reflection–injection of the back surface of the output-mirror, has been studied in detail. Variation of the equiphase surface and the influence of some characteristic parameters on phase-locking are analyzed—for example, phase error, changes in the cavity length and curvature radius, line-width and temperature. It is shown that the injected beam can excite a stable mode in the cavities, and the value of the energy coupling coefficient directly reflects the degree of phase-locking. Therefore, the output beams have a fixed phase relation between each other, and good coherent beams can be obtained by using the phase-locking method.

Light intensity distributions of the Gaussian laser beam through an aperture team

Based on the propagating theory of the laser beam, the propagating characteristics of the Gaussian beam through an aperture team that comprises two apertures and a convergent lens, are studied. The approximate expressions for the field distribution are derived by the diffracted integral equation in detail under the condition of approximations. In comparison with the approximate expression and the precise expression, we know that there are the approximate same results for the two expressions if the radius of the second aperture is not too large. The numerical examples are given to confirm the correctness of our calculated results.