A new interpretation of the strain-splitting of bound-exciton lines in CdS

A theory recently given by Litton, Reynolds and Collins to explain the observed strain-splitting of bound-exciton lines in CdS is shown to be wrong since it is incompatible with Kramers' theorem. A new explanation is given based on the fact that CdS has two molecules in the unit cell.     

Laser-excited broadband violet emission from sodium molecules

We report strong broadband violet (420–457 nm) emission from sodium vapor upon excitation in the Na₂ C ← X band (310–380 nm). Contrary to a recent interpretation the emission is ascribed to bound → free Na₂ transitions. Its potential use for tunable violet laser action is discussed.     

Polarization tomography of metallic nanohole arrays

We report polarization tomography experiments on metallic nanohole arrays with square and hexagonal symmetry. As a main result we find that a fully polarized input beam is partly depolarized after transmission through a nanohole array. This loss of polarization coherence is found to be anisotropic; i.e., it depends on the polarization state of the input beam. The depolarization is ascribed to a combination of two factors: (i) the nonlocal response of the array as a result of surface-plasmon propagation and (ii) the non-plane-wave nature of a practical input beam.     

Photon statistics of a laser with slow inversion

We have measured the photon number probability distribution of a laser in which the inversion is not slaved to the field. For the experiments, we have used a Nd(3+):YVO(4) laser which has a sufficiently slow inversion to allow measurement of the photon fluctuations at a time scale much shorter than that of the relaxation oscillations. The photon distribution function becomes highly nonstandard (i.e., non-Poissonian) in such a laser; this is consistent with available theoretical work. We point out the relevance of our results for the case of the semiconductor microlaser.     

Equivalence of transverse modes in Raman amplifiers and microchip lasers

It is shown that the transverse modes of a Raman amplifier with Gaussian pump are equivalent to those of a microchip laser with combined quadratic index guiding and Gaussian gain guiding. This equivalence allows for considerable cross-fertilization between these two hitherto separate fields.     

Effect of a near-resonant intermediate level on doppler-free versus doppler-broadened two-photon absorption

The effect of a near-resonant intermediate level on the ratio of strengths of Doppler-free and Doppler-broadened two-photon absorption has been studied for the 16 601.88 cm^-1 Na₂ two-photon transition.