Theoretical analysis of the multi-rotational line TEA CO2 laser

A theoretical model for the multiline TEA CO₂ laser has been developed which takes into account the overlap of the P(20) line of (00⁰1) (10⁰0) regular band transition with the R(23) line of (01¹1) (11¹0) hot band transition. The model is used for the study of the influence of different parameters like laser gas temperature, gas mixture and pump rates on laser intensities of different rotational lines. This study explains the experimental results of the high power multiline TEA CO₂ laser very well.     

Effect of electrode material on sealing wax thermo-electret charge

Thermo-electrets of sealing wax have been prepared using different metal electrodes: tin, aluminium, nickel, copper, lead and zinc (Series A) and pairs of metallic — tin and non-metallicmica (Series B) keeping other preparative parameters to be the same in each series. Surface charge has been measured on anode side of each thermo-electret. Surface charge characteristics have been discussed in the light of the results obtained in earlier studies on sealing wax thermo-electrets by the authors and existing views on the origin of charges. These results suggest that origin of homocharge in thermo-electrets is due to injection of charge carriers supplied by the electrodes into the dielectric surface and freezing in near the surface and getting trapped in the surface levels. The origin of heterocharge is due to inhomogeneous distribution of charge carriers originating in the bulk on account of their trapping.     

Relaxation oscillation studies in Nd: YAG laser—Some new results

The study of transient behaviour of a pulse pumped solid state laser system has assumed importance on account of SLM generation by self-seeding with the pre-lase signal. This paper reports on the observations of seed pulses for two different Nd: YAG laser rods, one with anti-reflection coating (AR) on end faces and the other without. The latter displays single longitudinal mode behaviour in each of the relaxation pulse train while the former displays multimode behaviour. Our observations are well explained by the ‘active etalon concept’ introduced earlier.     

Proposed method of spike suppression in solid-state lasers

A method is proposed to suppress the spikes in the output of solid-state lasers, using passive negative feedback. A saturable absorber, normally used for Q-switching the laser, is used in a modified laser resonator, so that the resonator losses increase with laser intensity. The rate equations of a laser with such a loss mechanism are solved numerically. Numerical results for a ruby laser are presented.     

Mode conversion in optical second harmonic generation: Theory and experiment

Kingston and McWhorter's theory of mode conversion in second harmonic generation with a thin crystal [1] has been extended to include all positions of the crystal relative to the focus of the fundamental beam. Phase differences between the harmonic modes are predicted which depend upon the crystal position. Experiments to test these predictions have been performed with a 1.15 m helium-neon laser and non-critical phase-matching in lithium niobate. Results are presented for a number of fundamental modes.     

Multifunctional polymers as multi-role materials for photonics

Multifunctional polymers can play multi-roles such as laser light source, passive interconnects, optical signal processing and optical data storage in the development of photonics technology. In this paper, two approaches to achieve nanostructure control to introduce multifunctionality at both molecular and bulk levels are presented. A novel concept of multiphasic nanostructured composites is discussed. Various applications of a specific multifunctional property introduced by strong two-photon absorption and efficient fluorescence are presented. The combined action of these two functions produces upconverted emission. Specific applications discussed are upconversion lasing, optical data storage, confocal microscopy, and photodynamic therapy.     

Performance characteristics of a Nd: glass laser amplifier from fluorescence emission studies

The dependence of cavity transfer efficiency of a Nd: glass laser amplifier on flashlamp current density is obtained from the analysis of amplified fluorescence. The cavity transfer efficiency decreases as the current density through the flashlamps is increased. The use of the fluorescence method in optimizing the flashlamp pulse duration for achieving maximum gain in the amplifier is illustrated.     

Operator algebras and a theorem of Dieudonne

LetA be aC*-algebra with second dualA″. Let (φ _n)(n=1,...) be a sequence in the dual ofA such that limφ _n(a) exists for eacha εA. In general, this does not imply that limφ _n(x) exists for eachx εA″. But if limφ _n(p) exists whenever p is the range projection of a positive self-adjoint element of the unit ball ofA, then it is shown that limφ _n(x) does exist for eachx inA″. This is a non-commutative generalisation of a celebrated theorem of Dieudonné. A new proof of Dieudonné’s theorem, for positive measures, is given here. The proof of the main result makes use of Dieudonné’s original theorem.