An investigation into non-linear optical processes using high power picosecond laser pulses
An investigation into non-linear optical processes using high power picosecond laser pulses
The design of a high power, synchronously pumpled dye laser is described. The laser is pumped using a Q-switched and modelocked Nd:YAG laser and the performance with both rhodamine 6G and DCM dyes is described. High efficiency is achieved by using a stable resonator design for the oscillator. The time-bandwidth product is 0.63 and the pulse duration is ≃ 70 ps. The output beam is confirmed to be near-diffraction limited. The cavity length tuning characteristics are described. It is shown that the optimum cavity length corresponds to a minimum pulse duration, maximum energy and a maximum energy stability. The design of a longitudinally pumped dye amplifier is described. Pulse energies of up to 1 mJ are obtained in rhodamine 6G and 250 μJ in DCM. A mathematical model for a pulsed synchronously pumped dye laser is described. The effect of cavity mismatch is calculated. The results show that for longer cavities the pulses are smoother but longer in duration. For shorter cavities, the pulses shape is dominated by amplification of the leading edge of the pulses which results in pulse structure. The effect of a longer pump train is described. The resultant pulses are substantially shorter with comparable peak power. The effect of longitudinal pumping is described. The results show that the laser has comparable efficiency while the pulse profiles are smoother and more symmetrical than for transverse pumping. Stimulated Raman scattering (SRS) in H2, D2 and CH4 using picosecond pulses from a Nd:YAG laser is described. The experimental results using focussed and waveguided pump geometries are described. Good agreement with theory is found. The design of a Raman oscillator/amplifier using 100 ps pulses at 1.064 μm is described. Using CH_4 at approximately 30 atm pressure, lst Stokes generation at 1.54 μm is measured with an energy efficiency of 30%. SRS in four organic liquids with Raman shifts in the region of 2900 cm-1, is described. A maximum energy efficiency of 82% is achieved in acetone with 532 nm pump pulses. Raman thresholds are measured using 1.064 μm pump pulses and the experimental results exhibit an intensity-length dependence. Multiple SRS in CH_4 using tunable dye laser pulses is described. An efficiency of 72% is measured for 1st Stokes generation. An efficiency of 5.7% was measured to 3rd Stokes. The tuning range was 1.09 μm to 1.186 μm. Non-linear processes in single mode optical fibres are described. The stimulated Raman threshold is measured and the Raman conversion is shown to limit the power throughput. Four photon mixing (FPM) in birefringent fibres is described. Using a tunable dye laser, Stokes and anti-Stokes components with shifts of 2200 cm^-1 are measured. The FPM threshold exhibits a coherence length effect. A conversion efficiency of 18% is measured. FPM is described using 100 ps pulses at 1.064 μm from a Nd:YAG laser. Using a fibre having a birefringence of 3 x 10-4, a frequency shift of 2073 cm-1 is measured with an energy conversion efficiency of 1%.
University of Southampton
Pointer, David James
5094206c-26df-4030-852a-2a031d929aa6
1987
Pointer, David James
5094206c-26df-4030-852a-2a031d929aa6
Pointer, David James
(1987)
An investigation into non-linear optical processes using high power picosecond laser pulses.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The design of a high power, synchronously pumpled dye laser is described. The laser is pumped using a Q-switched and modelocked Nd:YAG laser and the performance with both rhodamine 6G and DCM dyes is described. High efficiency is achieved by using a stable resonator design for the oscillator. The time-bandwidth product is 0.63 and the pulse duration is ≃ 70 ps. The output beam is confirmed to be near-diffraction limited. The cavity length tuning characteristics are described. It is shown that the optimum cavity length corresponds to a minimum pulse duration, maximum energy and a maximum energy stability. The design of a longitudinally pumped dye amplifier is described. Pulse energies of up to 1 mJ are obtained in rhodamine 6G and 250 μJ in DCM. A mathematical model for a pulsed synchronously pumped dye laser is described. The effect of cavity mismatch is calculated. The results show that for longer cavities the pulses are smoother but longer in duration. For shorter cavities, the pulses shape is dominated by amplification of the leading edge of the pulses which results in pulse structure. The effect of a longer pump train is described. The resultant pulses are substantially shorter with comparable peak power. The effect of longitudinal pumping is described. The results show that the laser has comparable efficiency while the pulse profiles are smoother and more symmetrical than for transverse pumping. Stimulated Raman scattering (SRS) in H2, D2 and CH4 using picosecond pulses from a Nd:YAG laser is described. The experimental results using focussed and waveguided pump geometries are described. Good agreement with theory is found. The design of a Raman oscillator/amplifier using 100 ps pulses at 1.064 μm is described. Using CH_4 at approximately 30 atm pressure, lst Stokes generation at 1.54 μm is measured with an energy efficiency of 30%. SRS in four organic liquids with Raman shifts in the region of 2900 cm-1, is described. A maximum energy efficiency of 82% is achieved in acetone with 532 nm pump pulses. Raman thresholds are measured using 1.064 μm pump pulses and the experimental results exhibit an intensity-length dependence. Multiple SRS in CH_4 using tunable dye laser pulses is described. An efficiency of 72% is measured for 1st Stokes generation. An efficiency of 5.7% was measured to 3rd Stokes. The tuning range was 1.09 μm to 1.186 μm. Non-linear processes in single mode optical fibres are described. The stimulated Raman threshold is measured and the Raman conversion is shown to limit the power throughput. Four photon mixing (FPM) in birefringent fibres is described. Using a tunable dye laser, Stokes and anti-Stokes components with shifts of 2200 cm^-1 are measured. The FPM threshold exhibits a coherence length effect. A conversion efficiency of 18% is measured. FPM is described using 100 ps pulses at 1.064 μm from a Nd:YAG laser. Using a fibre having a birefringence of 3 x 10-4, a frequency shift of 2073 cm-1 is measured with an energy conversion efficiency of 1%.
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Published date: 1987
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Local EPrints ID: 461844
URI: http://eprints.soton.ac.uk/id/eprint/461844
PURE UUID: c6c26c2f-1098-4f03-85b1-3819e05d1a03
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Date deposited: 04 Jul 2022 18:57
Last modified: 23 Jul 2022 00:34
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Author:
David James Pointer
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