We are using flashlamp pumped nanosecond Nd:YAG laser (with SHG, THG, FHG) for laser induced fluorescence in combustion. I was wondering if there are alternative light sources that offer a higher flexibility with respect to wavelength and pulse duration. I found reports about using an Alexandrite laser which can be tuned from 720-800nm in the fundamental with pulse energies comparable to Nd:YAG. Another material that certainly comes into mind is Ti:Sa. However, it seems that there is hardly any commercial system available. What is the reason for this (excited state lifetime? inefficient pumping?)
If you are looking for more tunable excitation wavelength your best solution is to add an optical parametric oscillator (OPO) to your existing Nd:YAG laser. Depending on the model you use it will let you continuously tune the excitation wavelength in the UV, visible and/or NIR. If you need the shorter laser pulses you'd have to go with a pulsed diode laser (~ps pulses but no wavelength tunability) or a Ti:S system. Ti:S lasers are commercially available, they are just generally a lot pricier than Nd:YAG's and not quite so user friendly. Here in the US at least the two big companies for Ti:S systems are Coherent and Spectraphysics.
You are not specific about your pulse energy and tunability requirements. Also, why flash-lamp? Are you going to build it? I got curious about ns Ti:Sapph. A quick search returns: http://photonix.com/series-groups/tu-series/.
It sounds like it might be a Q-switch with a multi-pass amplification and an OPO on top of that. They mention a Ti:Sapph oscillator though ... not sure.
It may be an overkill for you in terms of power and will hardly provide any pulse length flexibility. And will cost you, too. Why not many of them on the market? A lot of demand for fs and ps systems, I suppose.
Thanks for your answers. I am aware of OPO and dye laser systems (worked with the latter a lot). I just recognized that one can in principle get tunability and longer pulses using a single laser: http://lightage.com/web/products/scientific-research/pal-pulsed-alexandrite-laser/
Industrial collaborators are to convince of dye laser (toxic dye etc.) and OPOs are (from my experience) pretty sensitive and operate near the damage thresholds to get high pulse energies (worked a bit with the Continuum Sunlite OPO system).
Pulse energy should be (I think) at least something like 400-500mJ in the fundamental. Certainly diode-pumped would also be feasible but from my experience, high pulse energy laser are mostly flashlamp pumped. Regarding pulse length: it would be advantageous to be longer than 10ns (Nd:YAG is normally something like 4-10ns) since it would be possible to use higher pulse energies without starting to have problems with saturation effects in LIF.
Basically, I was simply wondering if Ti:Sa can be operated at pulse length of 10-100ns with high pulse energies (let's say >300mJ). Repetition rates can be 10Hz although kHz would be awesome.
In the 90s, Candella Laser used to make flash lamp pumped Ti:Sapphire laser for hair and tattoo removal.
One difficulty is the duration of the flash around 3 to 5 micro second (versus 100 or more for Yag).
Here is a paper talking about Candella's flash pumped Ti:Sapphire.
http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=694180
Good luck to you.
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