If we look at Meyers constructions, the Gas Processor, Injectors and WFC basicly use the same type of photon radiation, and Meyer used red led's, that was what he could get he's hands on at that time. Having said that, also remember that Meyer spoke of the KISS method so advancing to LASER is in this case unproven.
Now, what are you looking for? I'm gona guess here and say Photonization and what does that do for us? If you use a 635nm photon this will infact interact whit the electron (I will get back on that one.)
To ionize:
13.617 eV = 109833 cm-1 = 1313.9 kj/mol for oxygen and 13.598 eV = 109674 cm-1 = 1312.0 kj/mol for hydrogen (one ionization level for the oxygen) and that is hard to do whit one type of photon.
So, the next best thing is to use feild ionization together whit photon interaction, now one can also use multiphotonization, but that is more advanced. Feild ionization in this case is our HV feild in the WFC so, we kinda want to find a frequensy that interacts and HELP (partual ionization). So we do not need to go all the way and use a photon that will do this on a stand alone basis. So lets look at a photon taht will aid in the process.
Using the Hydrogen Atom Simulator online we can find that a photon whit an energy of 657nm (1,9eV) will elongate the electron one level IF the electron already is elongated (L1>L2), so how can we get the electron to move from L1 to L2 to L3 etc? Answer; Feild Ionization which you allready have.
The HV feild in your capacitor creates an electromotive force on the electron and this changes the electron orbite, kinda makes the orbite wobble (oval shaped) and it is when the electron is the most furthest away from its nuclei that the photon have the higest change of interacting, meaning that the ionization energy is lower = easy for a photon whit less energy to interact.
Now, the simulator does not count for feild ionization, so we have to imagen that part and that the electron is in L2 or L3 just to get an idea of what a red led can do for us, also take into acount that Meyer talked about diffused light, not concentrated like in a LASER (dont focus on the word LASER primed which he used to much) just the pricniple.
You want the light source to spread in the capacitor dont you??
So that is my 2 cent right now. If we go further we can talk about Pre-Charged Water and UVC, but for the WFC, I think that a red led will give you the result you are looking for and also remember that you can use LED's that will have a very high luminessens, mugh higher than Meyer could get hold of (= more photons) and of curse it needs to be pulsed. Circuits for this exist and are not that expensive and yes, Stifflers SEC could work whit this I pressume.
Hydrogen Atom Simulator
Hydrogen Atom Simulator - Hydrogen Energy Levels - NAAP
Ps; You can learn alot from h2opowers tread "Stanley Meyer Explained", so there we go, now I mentioned it.