Total Cavity Loss Research Articles

Oscillator strengths and laser effect in Na2Nd2Pb6(PO4)6Cl2 (chloroapatite), a new high-Nd-concentration laser material

Chloroapatite (Na2Nd2Pb6(PO4)6Cl2), a Nd3+ compound with 3.4×1021 ions cm−3 has been shown recently to possess a high fluorescence efficiency. Measurements on single-crystal samples show that the oscillator strengths and the fluorescence quenching are both slightly smaller than in Nd pentaphosphate (NPP). Laser effect with longitudinal Ar* laser excitation is reported for the first time in this material on two lines at 1.0585 and 1.0675 μm, which have orthogonal polarizations and equal thresholds, in agreement with fluorescence spectra. The laser threshold (absorbed power for a given total cavity loss) is nearly equal to that of a NPP crystal in the same cavity.

Efficient frequency doubling of cw dye laser radiation

An efficient conversion of the tunable cw dye laser radiation to the UV region was achieved by intracavity SHG. The conversion efficiency depends strongly on the total cavity loss. This paper gives a survey on conventional and thermally induced loss mechanisms and discusses ways of loss reduction. A system is described that yields 50 mW and 4 mW of tunable UV radiation in multimode and single mode operation, respectively, where the wavelength can be varied from 285–315 nm.

Saturation effects and lamb-dip formation in molecular lasers

With the use of velocity-dependent kinetic equations to account properly for collisional relaxation behavior in molecular lasers, new results for gain saturation formulas have been obtained for intermediate values of pressure. These results, for a traveling-wave field, are exact and, in proper limits, reduce to known results. Further, a more complete description of the behavior of the Lamb dip as a function of molecular parameters has been obtained, and it is shown how the Lamb dip depends not only upon molecular parameters, but upon the total cavity loss parameter itself.

Isotope effects in the two-mode operation of a He-Ne laser

Isotope effects in the two-mode operation of a 633 nm He-Ne laser are investigated with due allowance for soft collisions. A theory is developed for the power of and beat frequency between two modes as a function of cavity detuning with and without soft collisions. Experiments were performed with Ne20∶Ne22 isotope ratios of 98∶2, 95∶5 and 91∶9. The experimental data fit the theoretical curves which include the effects of soft collisions qualitatively for the mode intensities and quantitatively for the beat frequency provided the total cavity loss is assumed to be 3.5%. The output power of the 98∶2 tube with 1.1 Torr of helium is symmetrical about line centre; the power of the 95∶5 tube shows an asymmetry opposite to that of a single isotope tube. The lower frequency mode oscillates in a narrower region in the case of natural neon than for a 95∶5 mixture.

Time variations in the far-field diffraction patterns of spatial modes from electron-beam-pumped semiconductor lasers

Detailed observations of the far-field radiation patterns from electron-beam-pumped GaAs and CdSe lasers reveal angular deviations of the patterns from the laser axis at angles greater than 25°. Moreover, these angular deviations are observed to decrease monotonically as a function of time during each output pulse. A simple model for the near-field laser modes predicts such angular deviations. Furthermore, the model allows the time-varying angular deviations to be accounted for in terms of a time-varying refractive index difference between the pumped and unpumped regions of the laser cavity. Two major sources of sufficient index variations are identified, viz., heating by the electron beam and index changes related to the presence of gain. The relative magnitudes of the two effects have been determined for GaAs and CdSe. The inherent time dependence of these effects proves adequate to account for the observed ``angular tuning'' of the spatial modes. Spatial variations in the refractive index have consequences other than angular tuning of the far-field modes. In particular, it is found that the diffraction losses associated with the spatial modes are strongly dependent on the refractive index difference. The impact on laser dynamics of the consequent time-varying total cavity loss is discussed.

Measurement of Diffraction Loss in a Solid State Laser

The measurement of oscillation losses in solid state lasers has long been used as a method of evaluating the quality of the laser material. Most of these active loss measurements provide a measure of the total cavity loss, from which other losses such as mirror reflectivity losses must be subtracted to give a figure for the internal loss of the laser material. Diffraction losses are also present but the question of their exact contribution to the total cavity loss is frequently ignored. This is because material distortions and filamentary oscillation can make prediction of diffraction loss rather uncertain unless lengthy calculations are made, taking account of the distortions which prevail in each particular laser system.

Losses in a Pulsed Ruby Laser*

The total cavity loss in several ruby lasers has been determined experimentally from a set of threshold measurements. Scattering loss and end-mirror reflectance were measured separately and the difference between these losses and the total attributed to diffraction. Both plane-parallel and confocal resonators were employed. Diffraction loss in the plane-parallel cavities was 25 ± 8% per pass while diffraction loss in the confocal cavity was 8 ± 8%. These values are in agreement with theoretical analysis within experimental error.