David W. Gregg

CHEMICAL QUENCHING OF THE TRIPLET STATE IN FLASHLAMP‐EXCITED LIQUID ORGANIC LASERS

Greatly improved lasing of flashlamp‐excited organic dyes has been achieved by collisionally deexciting the triplet state of dye molecules with newly discovered chemical additives. Experimental results show the quantitative improvement of several principal organic lasing compounds when they are placed in solution with chemical additives. An explanation of the deexcitation mechanism is offered; the criteria for selecting proper chemical additives are listed.

Analysis of the CS2–O2 Chemical Laser Showing New Lines and Selective Excitation

We investigated the lasing oscillation resulting from the flash photolysis of carbon disulfide and oxygen and found 270 new lasing lines which all could be ascribed to P‐ and R‐branch, vibrational‐rotational transitions in CO, a reaction product. A measurement of the time of initiation of the lasing lines showed that the CO was being selectively excited at two vibrational levels by two different mechanisms (collision with electronically excited SO2 and chemical formation of excited CO).

Effect of oxygen on flashlamp-pumped organic-dye lasers

Dissolved oxygen was found to dramatically influence the intensity of flashlamp-pumped organic-dye lasers. The relative energy per laser pulse was measured for nine new and 19 previously reported dye solutions in equilibrium with partial pressures of oxygen ranging from 0 to 1 atmosphere.

Nondestructive inspection of transparent microtargets for laser fusion

The method is described for the nondestructive inspection of small (<100‐μm outside diameter) hollow thin (<2‐μm wall thickness) transparent shells used as laser‐fusion targets. Utilizing the interference properties of light, this method enables measurements of sphericity and absolute wall thickness to accuracies better than ±10%. The equipment and calibration procedure are discussed.

Long-pulse dye-laser emission across the visible spectrum

Long-pulse laser emission has been obtained across the visible spectrum using six different organic dyes in solution with triplet-state quenching additives, suggesting many new candidates for CW dye-laser operation.

Plasma Temperatures Generated by Focused Laser Giant Pulses

Plasma temperatures generated by focusing ruby‐laser giant pulses on surfaces of Be, Al, and Pb in a vacuum were measured as a function of time and giant‐pulse intensity. The monochromatic emission intensities of the plasmas (relative to those obtained with a standard source) were measured at wavelengths ranging from 4000 to 10 500 A, and the temperatures were then calculated from the Planck function. It was found that the plasma temperatures achieved with the lighter elements were hotter and had greater rates of increase with laser intensity. However, the rates of increase were proportional to only the 0.5 power of the laser intensity or less, and the difference in temperatures between target materials was not very great. Temperatures as high as 8×105 °K were achieved with beryllium.

Wavelength tunability of new flashlamp-pumped laser dyes

The wavelength tunability of six new flashlamp-pumped laser dyes is presented. The dyes were pumped with linear flashlamps and tuned by using a grating as one mirror of the laser cavity.

A NEW KIND OF RAPID‐SCAN MONOCHROMATOR USEFUL FOR ANALYZING CHEMICAL LASERS

A new rapid‐scan monochromator useful for analyzing chemical lasers has been evaluated. It consists of using a grating as part of the laser cavity and rotating one of the laser mirrors. The lasing lines are individually Q‐switched, increasing their intensities by a factor of 105. No limitation was found in the scan speed, and the theoretical spectral resolution of the grating was achieved. Because of the wavelength selection in the laser cavity, lines are brought out which otherwise would not lase.