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The applicability of layers of ion-implanted polymethyl methacrylate (PMMA) for beam splitting of laser light at the telecommunications wavelength of 1.55 [micro]m is examined. Bulk PMMA is studied, subjected to low-energy (50 keV) silicon ion implantation at various ion fluences in the range from [10.sup.14] to [10.sup.17] [cm.sup.-2]. The formed ultrathin near-surface ion-implanted layer of a thickness of about 100 nm, buried in a depth of ~100nm, can be used to split (or combine) laser beams at 1.55 [micro]m with a low absorption loss. OCIS codes: 130.1750, 230.1360, 240.1485.

A laser spectroscopy experiment is reported. It involves the excitation of a potassium atom through K(4S arrow 5S) magnetic-dipole transition. This results in stimulated emission at 1.25 micrometer which is explained by a chain-type nonlinear optical process of amplification. The latter consists of magnetic dipole Raman scattering and an electric-dipole four wave parametric emission.