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lifespan of lasers

ixfd64

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Lasers are sometimes quoted to have a lifespan of over 80,000 hours. However Justin from LaserGlow says the actual lifespan is closer to 5,000-10,000 hours. According to Justin, the 80,000-hour figure applies only to ideal lab conditions. Does this mean that a laser can theoretically last 80,000+ hours if you take perfect care of it?

Also, what part of a laser is more likely to break first? The pump diode? The driver? The crystal?
 

Razako

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ixfd64 said:
Lasers are sometimes quoted to have a lifespan of over 80,000 hours. However Justin from LaserGlow says the actual lifespan is closer to 5,000-10,000 hours. According to Justin, the 80,000-hour figure applies only to ideal lab conditions. Does this mean that a laser can theoretically last 80,000+ hours if you take perfect care of it?

Also, what part of a laser is more likely to break first? The pump diode? The driver? The crystal?
Taking perfect care of it means you only run it on a regulated dc power supply, only run it at ideal temperatures and a bunch of other impractical stuff. Probably the pump diode will be the first part of a good laser to break. Bad crystals would probably burn out early in the laser's life and a good driver shouldn't ever break unless it's overdriven.
 

Razako

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ixfd64 said:
Are pump diodes and crystals easy to replace?
If you have the right equipment they might be, but unless you work in a laser factory you're out of luck.
 
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There are two initial modes DPSS lasers operate in: 1) They fail almost immediately, and 2) They live a good long life. There are very few in between. Proper manufacturer testing and burn-in eliminate those that give up the ghost early but there are some stragglers out there that die in the hands of their new owners. Lab lasers tend to operate in the same environment over and over with the only real stress placed on the laser a function of thermal cycling.

Now, do not take that as gospel when it comes to pointers mainly because their cooling is based on conduction with the initial temperature related to ambient temperature and, shock and vibration, varying humidity, and a higher probability of electrostatic fields. All these things contribute to an early demise of any laser but the very nature of a portable laser lends itself to these issues. Varying temperatures stress the pump diode as well as the crystal set. Lasers are happiest when their operating temperature is constant which is why there are often output feedback systems in higher end models. Shock and vibration are good methods of ending a lasers life. Of course physical shock from a fall could mis-align the precise resonator to a point where it does not operate. Furthermore, an operating system is hot in the crystal set and the pump diode and becomes even more susceptible to shock. Humidity can play a huge factor due primarily to the chemistry of many non-linear optics. They tend to be hydrophillic and are salts. Finally, static discharges across the pump diode are more common in portable lasers and the diode will punch out instantly.

Now how do they keep a pump diode from burning out early. The best way is to install a large pump diode and operate it below its maximum output. This reduces the thermal stresses and the probability that an over current situation will exist across the diode junction. Try a 650nm out of a 20X DVD player. Hook it up and run it at 25mW. The thing will literally run forever. The second way to extend longevity is to insure the crystal set is AR coated for 808nm to minimize the output of the pump diode from being reflected back into the diode. In lab systems the pump diodes tend to be located a decent distance from the crystal set but in portables this is not the case.

Finally, why all the hoopla about <10,000 hours or >10,000 hours? Keep in mind that laser warranties tend to last no more than a year. How many hours are there in a year? 8766 hours. The warranty always expires before the 10,000 hours of use. The 10,000 hours is absolutely arbitrary and represents a marketing position.

What does this all mean? What it means is you get what you pay for. Higher end manufacturers apply real engineering to minimize environmental effects on their equipment. Higher power diodes, better coatings, better crystal sets go hand-in-hand with higher prices. There is just no way around it. Cheaper systems allow the manufacturer a higher margin which in turn allows them to replace defective lasers found in the field. Do you ever wonder how companies such as DX can replace a single customer's laser 5 times? They have high margins for what they pay the manufacturer plus I'm sure they have a return policy with the manufacturer. There is always a cost associated with any purchase. You can buy the best, get the very best in customer service and receive something that will last a good long time, or you can purchase cheap, get decent customer service and spend a lot of your time dealing with RMA's and the postal service. Any time you have to spend extra time dealing with something that should not be happening it is taking away from something else you could be doing. It is an economic concept called utility. I do not fault anyone for buying a less expensive item but there is always a utility cost to be paid.

Now can you replace a crystal set or a pump diode? Yes you can. But, here's the kicker, if you get it working they just never seem to operate the same. If it was very expensive let the retailer fix it for you. If it was cheap, try to fix it if you want to try it, but you will most likely toss it out and get another. It's that sign you see on electronics quite often: No Serviceable Parts Inside.
 

ixfd64

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Thanks for the detailed post. I never knew there were so many factors involved!

I guess the saying "you get what you pay for" certainly applies here!

I've also heard that underdriving a laser by just a few percent can increase its lifespan by significant amount. I think this is what LaserGlow does.
 
L

likewhat

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I have worked with diode lasers that were left on continuously for years, so yes, they can last 10s of thousands of hours. Those lasers were also temperature regulated and had high precision current supplies and were run at approximately 80 percent of the max safe current.

Of course some of the diode lasers died randomly after as little as a few minutes, some of them lasted for months (these were CD burner lasers BTW, purchased, not harvested).

As the Frothy Chimp said above, a pointer is basically the opposite of those controlled ideal conditions, so I wouldnt expect it to last as long. But who uses a pointer for 10000 hrs anyways?
 

Razako

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Basically they are like LEDS.
If you overdrive a Q5 LED and you don't provide proper heatsinking it will die way before it reaches the manufacturer rated 50,000 hours.
If you only run it at 50% of capacity and it's heatsinked properly you can expect it to last 100,000 hours or more.
 

Cyparagon

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At my company, we use lasers (class II) to read the OD of cable. These are emitting 24 hours a day, five days a week. We have had these systems for at least ten years and have yet to replace a head for diode failure.



But very few people have had a portable laser and use it long enough to reach 10 thousand hours assuming some other fate doesn't befall it.
 




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