In laser projection systems the observer in the far field of the image points on the screen will recognize serious speckle noise. There are many methods to reduce or eliminate speckles in the near field by reducing or eliminating temporal or spatial coherence of the laser. But for the far field it is hardly possible to change the coherence properties of laser sources so that speckles will disappear. We propose a new method for eliminating speckles in the far field by using a diffractive optical element. The intensity modulation depth in the far-field speckle pattern can be reduced to a few percent while good beam quality is preserved.

The form factors for the atmospheric backscattering of laser light leaving the exit aperture of a lidar receiving telescope are calculated in the limiting cases of purely geometrical optics and pure TEM(00) laser emission taking axial aperture displacement as well as misalignment of the transmitter axis into account. Some numerical results are plotted, displaying the effects of variations of the telescope's field of view, laser beam divergence, and misalignment.

A mathematical model is presented for the calculation of the 3-D time-dependent temperature distribution in a biological tissue (slab) irradiated by a laser beam of rectangular or Gaussian profile, which takes into account the different thermooptical properties of the tissue. Detailed consideration is given to the phenomenon of redistributive internal scattering, which is of noticeable magnitude in the irradiation by the argon-ion and Nd:YAG lasers commonly used for tissue coagulation in medicine. Satisfactory agreement is found with temperature measurements performed with a thermocamera, and the CO(2) and Nd:YAG lasers are compared qualitatively and quantitatively.

A new resonator design for doubly resonant continuous-wave intracavity sum-frequency mixing is presented. We generated 212 mW of coherent radiation at 618 nm by mixing the radiation of a 1080-nm Nd(3+):YAlO(3) laser and a 1444-nm Nd(3+):YAG laser. Two different mixing resonator setups and several nonlinear-optical crystals were investigated. So far output is limited by unequal performance of the two fundamental lasers and coating problems of the nonlinear crystals.

The safety of the application of the Nd:YAG laser for hemostasis in emergency gastro-endoscopy when its irradiation is properly dosed is demonstrated on the basis of laboratory investigations as well as theoretical calculations on a mathematical model of internal scattering. The increased effectiveness of this laser compared with argon and C 0 2 lasers in producing in-depth volume heating is shown to derive from the fortuitous combination of its low absorptivity with the scattering phenomenon.