桥链七甲川菁的合成及光性能

菁是一种具有多功能用途的染料,除用作卤化银感光材料及有机光导材料的光谱增感剂、光记录材料中记录介质外,还可作为染料激光器中用的激光染料.我们曾合成了四甲川苯乙烯菁、五甲川(艹粦)及五甲川吡喃鎓等红外染料作为激光染料,测定了它们的光性能.本文合成了具有桥链的七甲川菁,研究了这些桥链七甲川菁的吸收光谱及荧光光谱,并以YAG激光倍频(532nm)作泵浦源,测定了它们的激光调谐范围、中心波长及激光转换效率.     

Spontaneous emission in Ĉerenkov FEL devices: a preliminary theoretical analysis

Summary The main features of the spectral characteristics of the spontaneously emitted Ĉerenkov light in circular and rectangular wave guides filled with dielectric are discussed. The characteristics of the radiation emitted by an electron beam moving near and parallel to the surface of a dielectric slab are also analysed. Finally, the relevance of these results to a possible FEL-Ĉerenkov operation is briefly discussed.

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Riassunto In questo lavoro si discutono le caratteristiche dello spettro della radiazione Ĉerenkov, emessa in guide d'onde circolari e rettangolari riempite con dielettrico. Si analizzano inoltre le proprietà della radiazione emessa da un fascio di elettroni in moto in prossimità e parallelamente alla superficie di una ?slab? di dielettrico. Si discute, infine, brevemente, l'importanza di questi risultati per la realizzazione di un possibile FEL-Ĉerenkov.

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Резюме Обсуждаются основиые особенности спектральных характеристик спонтанного черенковского излучения в круговых и прямоугольных волноводах, заполненных диэлектриком. Также анализируются характеристики излучения, испущенного электронным пучком, движущимся вблизи и пораллелйно поверхности диэлектрической пластинки. В заключение, вкратце обсуждется применимость полученных результатов в возможных FEL-черенковских приборах.

     

Helium-free operations in mini-TEA CO2 lasers

Summary Large helium-free emissions are obtained in two mini-TEA CO₂ lasers, by using always a corona preionization without additives and with a maximum energy density of 900J/l in the discharge. In general, helium-free emissions are more stable, but the best condition in efficiency, energy and peak power is observed always with a small He content added to the laser mixture.

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Riassunto L'uso di una piú efficiente preionizzazione a corona ha permesso l'operazione di un laser a CO₂ senza elio a pressione atmosferica con elevate densità di energia nella scarica (900 J/l) e grande efficienza di conversione dell'energia elettrica in radiazione laser.

     

Phase-dependent properties for absorption and dispersion in a closed equispaced three-level ladder system

It is shown that in a closed equispaced three-level ladder system, by controlling the relative phase of two applied coherent fields, the conversion from absorption with inversion to lasing without inversion (LWI) can be realized; a large index of the refraction with zero absorption can be gotten; considerable increasing of the spectrum region and value of the LWI gain can be achieved. Our study also reveals that the incoherent pumping will produce a remarkable effect on the phase-dependent properties of the system. Modifying value of the incoherent pumping can change the property of the system from absorption to amplification and enhance significantly LWI gain. If the incoherent pumping is absent, we cannot get any gain for any value of the relative phase.     

Search for efficient,near UV lasing dyes. III. Monocyclic and miscellaneous dyes

A potential new class of “monocyclic” lasing dyes is discussed and four families out of nine within the class are examined. The 2,6-diaminopyridines in acid are found to lase under flashlamp excitation but show low slope efficiencies and lower stabilities than the “bicyclic” dyes described previously. Other, miscellaneous dyes show oxygen quenching of laser action rather than enhancement and the best of these produces short pulses under long pulse excitation. This study was supported under contract SANL 284 from the Lawrence Livermore Laboratory.     

Search for efficient,near UV lasing dyes. II. Aza substitution in bicyclic dyes

Two new families of lasing dyes, the 8-azacoumarins and the 8-azaquinolones are described and are found to operate blue-shifted from the coumarins and quinolones. Like the quinolones, they have higher thresholds and lower slope efficiencies than the coumarins. All have yielded long output pulses on long pulse excitation. This study was supported under contract SANL 284 from the Lawrence Livermore Laboratory.     

Stability of Optically Injected Two‐State Quantum‐Dot Lasers

Simultaneous two‐state lasing is a unique property of semiconductor quantum‐dot (QD) lasers. This not only changes steady‐state characteristics of the laser device but also its dynamic response to perturbations. In this paper we investigate the dynamic stability of QD lasers in an external optical injection setup. Compared to conventional single‐state laser devices, we find a strong suppression of dynamical instabilities in two‐state lasers. Furthermore, depending on the frequency and intensity of the injected light, pronounced areas of bistability between both lasing frequencies appear, which can be employed for fast optical switching in all‐optical photonic computing applications. These results emphasize the suitability of QD semiconductor lasers in future integrated optoelectronic systems where a high level of stability is required.     

Synthesis and Properties of a New Two-photon-absorbed Material Heasps

Abstract

A new dye Trans-4-[p-(N-hydroxyethyl-N-ethyiamino)styryl]-N-methylpyridinium p-toluene sulfonate (HEASPS) was synthesized, and the two-photon absorption (TPA), TPA-induced frequency up-conversion emission, and two-photon pumped (TPP) frequency up-converted lasing properties of this new dye were experimentally studied. This new dye has a moderate TPA cross-section of\sigma₂ = 4.7 × 10^?48 cm⁴ .s/photon at 1064nm, but exhibits a high lasing efficiency. The net conversion efficiency from the absorbed 1064 nm pump pulse energy to the 626 nm up-converted lasing energy is 18.2% at the pump energy level of 1.9 mJ.     

High-pressure,high-repetition-rate RF CO2 laser

Summary In this work we report the physical properties of a radiofrequency supplied waveguide CO₂ laser operating with different standard mixtures at high pressures up to 1.5 bar, with about 10% electrical efficiency. We describe some problems to obtain a complete RF matching in the discharge and we analyse the conditions for a better efficiency, gain and peak power in different mixtures, both to obtain a larger mode tuning and to eliminate the he contents so that the laser running costs are largely reduced. Work partially supported by the Progetto Finalizzato Optoelettronica of the Italian National Research Council (CNR). The authors of this paper have agreed to not receive the proofs for correction.     

First room temperature lasing from the fundamental state of V-grooved quantum wire lasers

Lasing from the ground state electron and heavy-hole-like transition of quantum wire (QWR) is demonstrated for the first time at room temperature, with an oxide-isolated V-grooved GaAs/AlGaAs triple QWR laser grown by flow-rate modulation epitaxy (FME). The lasing peaks at all temperatures (4–300 K) are in reasonably good agreement with both the photon energies of the peaks of the photoluminescence curves and the numerical calculation of the electronic sub-band energy states of the corresponding QWR structure. These results are considered to be responsible for the reduced heterointerface inhomogeneities (the Stokes shift 0.3 meV) of the FME grown QWR, giving a low-loss wave guide in the QWR laser.