Locking of cw dye laser emission onto the wavelength of molecular fluorescence by intracavity gain: Example I2

Abstract

A cw dye laser can be locked onto wavelengths corresponding to iodine (I2) fluorescence when the fluorescing samples are placed inside the dye laser cavity. The sensitivity of the dye laser to intracavity gains is analogous to its well-known sensitivity to intracavity losses. Gains as low as 0.0001 were detected. In particular, the 5145 Å emission of an Ar+ laser was used to excite I2 molecules inside of a tunable dye laser cavity to the v′=43, J′=12 and/or 16 level (s) of the B 3Π0u+ ground electronic state. The dye laser was then progressively tuned to stimulate emission to the v′′=10–15,J′′=11, 13 and or 15, 17 levels of the X1 Σ0g+ ground electronic state. The efficiency of the dye laser assisted I2 laser was 1–2 orders of magnitude higher than for the Ar+ pumped cw I2 laser. The locking of the dye laser to the I2 fluorescence frequencies was found to be a function of the specific vibrational and rotational quantum numbers. When the dye laser is operated above threshold, spatial hole burning severely limits the fraction of the laser power locked onto I2 fluorescence wavelengths.