Optically Pumped Gas Lasers

This article traces the development of stabilized lasers from the Massachusetts Institute of Technology passive-stabilization experiments of the early 19609s up through the current epoch of highly stabilized helium-neon and carbon dioxide and continuous wave dye lasers. The utility, present performance, and limitations of stabilized lasers as standards of length or frequency for precision measurements are discussed. Examples considered of laser applications to physical measurements of outstanding scientific interest include determination of the speed of light, redefinition of the meter, resolution of the photon recoil-induced spectral doubling, use of optical "Ramsey" interference fringes from ultrahigh-resolution spectroscopy, and two improved tests of special relativity.

https://science.sciencemag.org/content/sci/202/4364/147.full.pdf

Stabilized Lasers and Precision Measurements

Molecular bromine has been observed to lase when optically pumped on individual vibration–rotation lines. With no dispersive elements in the laser cavity the output consists of several doublets, corresponding to P‐ and R‐branch transitions from the excited (B) state populated by the pump pulse to various vibrational levels of the ground state. The insertion of an intracavity prism causes a single doublet to lase, with a corresponding reduction in output power. In the current experiments the output wavelength was tunable from 550 nm in the green to 750 nm in the red for each transition pumped near 532 nm. The broadband efficiency was a few tenths of a percent, with the single‐line output efficiency one‐tenth of that. The theoretical gain at 10 torr and 300 K was estimated to be 0.05–0.40 per cm. This system offers a quasicontinuous tunable source of radiation ranging from the visible to 3.5 μm in the infrared.

An optically pumped molecular bromine laser

Lasers and Electro-optics by Christopher C. Davis

Optically-pumped group IIB atomic vapor lasers emitting at discrete wavelengths shorter than 230 nm are disclosed. This laser device utilizes an active medium comprising a mixture of a group IIB atomic vapor and one or more buffer gases placed within a doubly-resonant optical cavity that enables the realization of a population inversion between the first 1 P 1 level and the 1 S 0 ground level of the group IIB atoms. The laser may operate in a pure continuous-wave mode, or in a high-repetition pulsed mode, at DUV wavelengths of ˜185 nm (mercury), ˜229 nm (cadmium) and ˜214 nm (zinc).

Optically-pumped DUV atomic vapor lasers

The optically pumped Hg laser at 546.1 nm, first developed by Djeu and Burnham, has now been operated as a sealed‐off rather than continuously flowing system, and with dc‐excited rather than rf‐excited pump lamps in both elliptically focused and close‐wrapped configurations. Laser power outputs of ∼1 mW cw have been obtained with ∼100 W excitation into two commercial Hg germicidal lamps, and a power output of ≳3 mW has been obtained from a sealed‐off tube with ∼300 W into a single low‐pressure ’’Toronto arc’’ pump lamp. Sealed‐off operation appears to be stable and long lived, and substantial further performance improvements are expected.

dc‐excited and sealed‐off operation of the optically pumped 546.1‐nm Hg laser

An optically pumped laser wherein the optical pumping means is in the form of a mercury discharge lamp and a radio-frequency excited coil surrounding the lamp. The discharge lamp is constructed in the form of a closed loop and is inductively excited by the high power radio-frequency coil. The coil forms the primary coil and the lamp the secondary coil of an air-core transformer. Current in the lamp is excited entirely by the radio frequency magnetic fields passing through the plane of the lamp thereby optically pumping the lasing medium.

RF excited mercury laser lamp

A single isolated saturated‐absorption feature in 127I2 using the optically pumped 5461‐nm Hg laser has been observed with low (∼6 MHz) resolution The 3S1→3P2 Hg laser transition can be centered exactly on this feature by varying the N2 buffer gas pressure using the measured pressure tuning rate of −94 MHz/Torr This may provide an attractive laser system for absolute wavelength stabilization

Max Artusy

Papers

dc‐excited and sealed‐off operation of the optically pumped 546.1‐nm Hg laser

RF excited mercury laser lamp

Saturable absorber overlap of iodine 127 with the optically pumped 546‐nm mercury laser