ND YAG Rod Performance

usually a q switched laser is intermittent duty, as a q switched cavity dumps it's energy into the beam when it is switched into resonance. Now you can flash it at a high frequency and get repeated laser spikes. Now this can be often enough to simulate a CW beam, called it pseudo CW, but if you want 80 watts PCW you might need a driving energy source of 100 to 400 times that much, dues to the assorted drive inefficiencies of flashes and how much the ND:YAG glass can be efficient..

You will have problems of heat distortion, possible cracking, drift, etc. That might be why few will quote you.

You may be able to find a true 80 watt CW laser. They are made in various wavelengths, CO2, Argon, etc.

Google is your friend

You should be able to get 100 Watts CW out of an ND:YAG rod. Sounds like your supplier is attempting to boost the power of the rod by Q-switching it. You need to get rid of the Q-switch and go to a slightly larger rod.

Also, you might want to take a look at your arc-lamp and its supply. The pumping power may be down.

One more thing, most rod suppliers furnish specs regarding peak CW power. If your supplier isn't providing that data, I'd be suspicious.

Suppliers of laser rods (including Nd:YAG) do not specify/ assure output power (CW/pulsed) that can be extracted from rod, for the simple reason, that the output power depends on pumping geometry and resonator configuration. Instead data sheets provide you standard details of quality such as laser damage threshold, residual reflection form AR coated surfaces, residual birefringence (extinction ratio), doping concentration of Nd ions(usually ~0.6% doping for CW operation, ~1.1% doping for pulsed operation).

The quality as well as price of laser rods vary over a wide range from manufacturer to manufacturer. Hence my suggestion is to purchase a rod from manufacturer of laser system (as a spare). But if the laser system is discontinued, then you may at least get advice from the manufacturer on suitable supplier of rod.

First, I am at a loss as to why you cite two different diameter (3 and 4 mm) ND:Yag rods.

What is the mfr's rated CW power specification of the laser you are dealing with? Are you only wanting to increase beyond that?

One post above went into various spectrums. Yours is likely 1064 nm.

CW power is typically used as a benchmark reference in these class lasers; where in the Q-switched mode the average power will vary depending on pulse rate and width.

Ensure all other optics (mirrors and q-switch) are clean and without aberation or burns. Also the pump chamber lamp light reflectors.

When replacing the ND:Yag rod, be sure to replace the associated seals/0-rings.

I'd recommend VLOC as a source mfr. www.vloc.com

Bill ML has given you the best information and advice so far.

First I wanted to comment on your statement, "Some time it is required to replace ND:Yag rod due to poor performance in respect of output watt." Are you guys manufacturing the lasers yourselves and selling them? If so, yes, all rods are not created equal - go to the manufacturer with the lowest rate of throw-aways. If you are a laser user and have purchased the laser from someone else and are continuously replacing your rods, STOP. The rods seldom need to be replaced. Unless you have damaged the rod (this will be visible upon inspection), the only problem may be that the end faces are dirty and need cleaning. (Of course over-driving them can cause warping and even oscillation.) Much more likely is that you need to replace the pump lamp. They must be replaced on a continuous basis. Most lamp manufacturers will tell you how many hours of use for the lamp. However, if you find that you have to keep turning up the current to maintain the desired output, you probably need to replace the lamp. If you push the time too long and the current too high, you will shatter the lamp and potentially damage the cooling system as well as having a mess to clean up. Next in line for maintaining efficiency is cleaning the relfectors and the output coupler.

If your lasers with these various rods are standard laser configurations from a laser manufacturer, the manufacturer will tell you the expected output in Watts. If you are manufacturing them, as already mentioned, the output depends on several parameters, most of which you are the ones with control over. Consequently the rod manufacturers are correct that they are not in a position to guarantee output power. You have two choices. Do the math. It is too involved to go into here, but you can find the mathematical procedure and equations in any good book on lasers and it can be found on-line. There are also some good laser design classes out there - software too. If you are designing and manufacturing them, you should have someone around who knows what they're doing. The other option is to try rods of various doping and length and diameter and see what you get - the old experimentalist approach. When you find what you need - go with it. If you can't get the output you need, check your design and go back to the math. It will need to take into account your cavity design, the rod length, diameter and doping at a minimum.

You may want to look into diode-pumped YAGs for significantly lower maintenance needs, easier maintenance, and more stable long term performance.