S. K. Searles

Stimulated emission at 281.8 nm from XeBr

Xenon with 0.10–4% Br2 was excited by an e‐beam device over the range 10–3000 Torr. Stimulated emission was observed on the transition XeBr*→Xe+Br+hν (281.8 nm). Proof of laser emission and mechanistic details are discussed.

Spectroscopic characterization of Er-doped KPb2Cl5 laser crystals

Abstract A discussion of the spectroscopic properties of the low-phonon energy laser host material potassium lead chloride, KPb 2 Cl 5 , doped with trivalent erbium is presented. In this paper we present room temperature spectroscopic measurements and subsequent analysis based on the Judd–Ofelt model. Additionally, Stark level energies of the Er 3+ ions in the crystal were determined from spectroscopic measurements performed at cryogenic temperatures.

Laser emission at 3577 and 3805 Å in electron‐beam‐pumped Ar–N2 mixtures

Experiments were performed with electron‐beam‐pumped Ar–N2 mixtures. Laser emission on the second positive band transitions 3577 A (0–1) and 3805 A (0–2) was observed in an optical cavity fitted with Brewster angle windows. Some exciting preliminary experiments in which the laser windows were mounted at normal incidence were performed. These results indicated superfluorescent emission with an efficiency of 0.4%. The energy pathways in the irradiated mixtures were modeled and compared to the experimental results.

1‐μs laser pulses from XeF

Long‐pulse operation of the XeF laser has been achieved utilizing electron beam excitation of Ar/Xe/NF3 gas mixtures. For a total mixture pressure of 2.5 atm, ∼0.30 J of 350‐nm radiation was obtained in a 1‐μs FWHM pulse.

Laser and spectral properties of Cr, Tm, Ho:YAG at 2.1 mu m

The authors study the loss process in a uniformly pumped amplifier experiment. The impact of the loss mechanism on laser performance is discussed and its dependence on excited state density is considered. An extensive set of measurements was performed on flashlamp pumped YAG crystals doped with chromium, thulium, and holmium. Near-room-temperature laser operation on the 2.1 mu m holmium transitions was characterized using a frequency selective resonator. Small signal gain and stored energy lifetimes were analyzed to determine the strength and dependence of loss mechanisms. The analysis of the thermal lensing experiments demonstrated a high degree of excess heat generation in this material. >

New quenching rates applicable to the KrF laser

Photolysis of KrF2 has been used to measure the rates of collisional quenching of KrF(B) excimers in two‐ and three‐body collisions with Ar, Kr, and F2. In addition, the KrF(B→X) band radiative lifetime was determined to be 6.8±0.2 ns. The results are in good agreement with existing theory and demonstrate the importance of quenching to KrF laser performance.

XeF* (C1/2) radiative lifetime measurement

By monitoring the spontaneous emission from electron‐beam‐excited xenon difluoride (XeF2) plasmas, the radiative lifetime of XeF* [C (1/2)] has been determined. Excited XeF was formed directly through electron‐impact dissociative excitation of XeF2. The time behavior of the subsequent 351‐nm fluorescence displayed two distinct exponential decay regions. The first was characterized by a pressure‐independent decay constant of 16.5±5 ns, the radiative lifetime of XeF* [C (1/2)]. The time constant of the second region was linearly dependent on XeF2 pressure, indicating that C‐state XeF molecules are, in the late afterglow, formed by a two‐body collision process exhibiting a large rate constant (∼3×10−10 cm3 sec−1).

Superfluorescent laser emission from electron‐beam‐pumped Ar–N2 mixtures

Intense superfluorescent laser pulses on the nitrogen second positive transition N2(C)‐N2(B) at 357.7 nm were generated by electron beam excitation of Ar–N2 mixtures at pressures from 600 to 5000 Torr. The pressure range over which the laser operated is explained on the basis of a simple kinetic model. The efficiency of the laser is discussed in detail.

DETERMINATION OF OPTICAL GAIN FOR CO TRANSITIONS IN A CS2–O2 FLAME BY OSCILLATION‐RANGE MEASUREMENTS

Optical gain in the neighborhood of 2% has been measured in CO vibration‐rotation transitions P(12)–P(14) in the bands 8–7, 9–8, and 10–9 in a free‐burning CS2–O2 flame. The flame was inside a single‐transition single‐mode CO laser cavity. Gain was determined from the change in the oscillation range of the frequency‐tuning curve. This method is particularly useful for the measurement of small optical gains and losses.

High-average-power operation of a Q-switched diode-pumped holmium laser

We have investigated high-peak- and high-average-power operation of diode-pumped, thulium-sensitized, holmium 2.1-microm lasers. Free-running laser powers of 14 W at 29 Hz have been demonstrated with 2.6% electrical efficiency. Q-switched operation produced average powers in excess of 11 W in a burst of short pulses. Preliminary optical parametric oscillator frequency conversion of the holmium laser to 4 microm is also reported.