ABSTRACT
Experiments were performed on a CO(2) laser with an annular resonator. The objective of these experiments was to control the polarization in an annular laser and to verify computer code predictions. A Mylar pellicle was placed in the annular leg, and its angular orientation with respect to the optical axis was varied. The pellicle had different transmittances for horizontal and vertical polarizations and also had stress-induced birefringence. At small angles of incidence in the pellicle, the birefringence dominated, and the output had a complicated nature. However, at large angles of incidence, the transmittance difference forced the laser into a well-defined mode for which the near field was horizontally polarized at the top and bottom and the two sides and vertically polarized at intermediate locations. The experimental results were in good agreement with the computer code calculations.
ABSTRACT
For precision optical systems, the focus and tilt errors caused by coating thickness nonuniformity can be a serious concern. These errors are wavelength dependent and hence cannot be compensated in an IR optical system by aligning and focusing with an auxiliary visible alignment laser. It is shown here that the coating design can be modified so as to make the aberrations caused by coating thickness nonuniformity approximately equal at the IR design wavelength and the wavelength of the auxiliary laser. In that case, focusing and alignment with an auxiliary laser can substantially correct the effect of coating nonuniformity.
ABSTRACT
Previous measurements of electric field induced second harmonic generation indicated that the confocal parameter for a laser beam as calculated from the second harmonic intensity profile was in disagreement with that calculated from the measured beam diameter. In this paper, we show that this discrepancy is caused by the departure of the beam from the pure TEM(00) mode. We expand a distorted beam in terms of the component modes by using the experimental beamscan and calculate the second harmonic profile using this expansion. This calculational procedure is found to be consistent with experimental observations.
