Applications of the Mode Locked Near Uv Output from a Krypton Ion Laser in Chemical Analysis

摘要

The two principle requirements for any excitation source are tunability and repetition rate. As a first step in providing a tunable source for the desired region the near uv lines (406.7, 413.1 nm) of the krypton ion laser are mode-locked. The maximum cw power for the 406.7 nm line is 400 mW. The average power when mode-locked is 120 mW, corresponding to a 70 percent reduction. The mode-locked train consists of pulses with 12 ns separation whose width (FWHM) was electronically measured to be 80 ps (detection limited). The linewidth of the 406.7 nm line was measured as 0.082 A (15 GHz) using a 1 m monochromator. Output cw power is 1.3 watts. In the mode-locked condition the linewidth at 413.1 nm is 0.058 A (10 GHz). The 413.1 nm pulsewidth is estimated to be about 80 psec using delta nu delta t = 0.8 and the widened oscilloscope display of 95 psec (detection limited). The broad lasing linewidth is due to isotopic broadening from several naturally abundant krypton isotopes. The use of the mode-locked Kr exp + laser as an excitation source for measuring fluorescence decay times of the fluorescent cytochemical probe, chromomycin is also reported along with its use to measure the fluorescence lifetime of several coumarin laser dyes. The result suggests the absence of significant molecular aggregation. The mode-locked violet lines of the krypton laser are inherently useful or can be used to generate other wavelengths by synchronous pumping. The short temporal width of the violet lines makes this a source well suited to producing tunable picosecond pulses using coumarin dyes as the lasing medium. (ERA citation 03:053193)