Frequency-Tunable Transform-Limited Picosecond Dye-Laser Pulses

Abstract

Picosecond pulses of transform-limited durations (Δt∼3 psec; ΔtΔν∼0.5) have been obtained from a passively mode-locked Rhodamine 6G dye laser, frequency tuned over a range of 230 Å with an intracavity Fabry-Perot filter. Self-phase-modulation frequency broadening at higher powers has also been measured giving a value n2 = 10−18 cm2V−2 for the nonlinear refractive index of the ethanol dye solvent.

Picosecond phase-conjugate reflection from organic dye saturable absorbers

“…The spectral bandwidth of the pulse train was measured to be 2.3 nm which corresponds to a coherence time (or pulse duration for bandwidthlimited pulses) of 0.22 ps for gaussian shaped pulses. The discrepancy probably arises from spectral broadening due to self-phase modulation when the laser is pumped above threshold [14]. This broaden ing increases monotonically along the pulse train so that the recorded time-integrated bandwidth largely comes from pulses towards the end of the pulse train.…”

Generation and measurement of frequency-tunable picosecond pulses from dye lasers

“…Since organic dye solutions are homogeneously broadened the normal broadband spectral output can be easily narrowed, without appreciable energy loss, by the insertion of dispersive elements into the laser cavity [2,28]. Thus it was possible [7] to remove the pulse duration-bandwidth discrepancyby frequency narrowing the mode-locked Rhodamine 6G dye laser with a single intra-cavity Fabry-Perot filter, which also permitted frequency tuning of the picosecond pulses over the 23 nm free spectral range, by rotating the narrow gap (4 to 10 lam) optically contacted interferometer [8 ]. Because of the variations in the gain of the active medium and in the absorption of the mode-locking dye as the operating wavelength was altered, it was necessary to adjust the DODC1 dye concentration for each wavelength to maintain the laser operating just above threshold.…”

“…By employing powerful linear air flashlamps to pump Rhodamine 6G, and immersing one laser cavity mirror in the saturable absorber solution, 100 ~o modulated pulse trains were first achieved [6] in a passively mode-locked dye laser. Frequency tuning was obtained by replacing one of the laser mirrors by a rotatable diffraction grating, employed in auto-collimation, and two-photon fluorescence (TPF) measurements showed [5,7] that pulse durations of ~5 ps could be reliably produced.…”

Picosecond Phase-Conjugation Reflection and Gain in Saturable Absorbers by Degenerate Four-Wave Mixing

“…:1ncwic!tr;-limftec st,.uc~l.ires from tlle inittal intensity fluc~Jaticrs [i; will be preferentiaily ,-eflected in ~u1tiole passes through t"e ~~!Jret1: a:sorce~. The effect of photoisomer generation in COCCI [7] was clearly seen ~ya reflected pulse delay of '.500 ns, compared with tr.e pur.ip pulse, for a DODC: (5 x 10--M) cell pumped by a 617 nm unmade-locked laser puise. At 586 nm :re efficiency reached 150', Y:ith zero delay.…”

“…The half-width of O.Sps, averaged over a cD111plete pulse train, compares with a coherence time of 0.22ps for the 2.3 nm total bandwidth. Self-phase 1110dulation spectral broadening along the dye lasers pulse train [7] accounts for the difference. As expected there was a quadratic dependence of reflectivity upon pump intensity (8,9j.…”