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So, this question's been asked one too many times, and most of the time the forum search function doesn't work properly either, and these answers get lost. I'm going to try and get a sticky for this thread too, if that isn't too much to ask for.
Why is my green laser only putting out red light?
You've just bought a new laser pointer from some site, and you've just opened it up, and put the batteries in. You press the button, and instead of seeing a green beam, you see a faint red dot. What's happening?
NEVER look into the laser at the dim red light- you run the risk of sustaining permanent, instantaneous retinal burns
To understand why this is happening, first you need to understand how a green laser pointer works.
As you can see, it's not a straightforward process, as is the case with red and violet laser pointers.
In a green laser pointer, 808nm laser radiation from a pump diode is used to generate 1064nm light in the gain medium (in this case, the YAG or YVO4). This 1064nm light is then doubled by the KTP to from 532nm light. There's no colour filters involved, it's a laser-pumped laser.
To achieve even a low-power output requires large amounts of 808nm IR pump radiation. For example, the pump diodes found in a 50mW green laser pointer will often average around 300mW IR output.
The human eye isn't very sensitive to 808nm IR- and it's barely visible. It takes several watts of 808nm to achieve visual parity with 1mW of 650nm. As a result, what is mistaken as a dim red light is easily capable of causing instantaneous eye damage.
Although this diagram shows an IR filter (which would cut out all of the infrared from the green beam), most cheap pointers and modules lack this IR filter.
The most common causes of this type of pointer failure are either driver/pump diode failure, or crystal set failure. In most cases, these are not user-serviceable, and the best option would be to return the defective pointer to the store for a refund or exchange.
Why is my green laser only putting out red light?
You've just bought a new laser pointer from some site, and you've just opened it up, and put the batteries in. You press the button, and instead of seeing a green beam, you see a faint red dot. What's happening?
NEVER look into the laser at the dim red light- you run the risk of sustaining permanent, instantaneous retinal burns
To understand why this is happening, first you need to understand how a green laser pointer works.
As you can see, it's not a straightforward process, as is the case with red and violet laser pointers.
In a green laser pointer, 808nm laser radiation from a pump diode is used to generate 1064nm light in the gain medium (in this case, the YAG or YVO4). This 1064nm light is then doubled by the KTP to from 532nm light. There's no colour filters involved, it's a laser-pumped laser.
To achieve even a low-power output requires large amounts of 808nm IR pump radiation. For example, the pump diodes found in a 50mW green laser pointer will often average around 300mW IR output.
The human eye isn't very sensitive to 808nm IR- and it's barely visible. It takes several watts of 808nm to achieve visual parity with 1mW of 650nm. As a result, what is mistaken as a dim red light is easily capable of causing instantaneous eye damage.
Although this diagram shows an IR filter (which would cut out all of the infrared from the green beam), most cheap pointers and modules lack this IR filter.
The most common causes of this type of pointer failure are either driver/pump diode failure, or crystal set failure. In most cases, these are not user-serviceable, and the best option would be to return the defective pointer to the store for a refund or exchange.
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