Heating 405nm diodes to increase luminance

[mccarrot]

Would it be possible to increase the nm of a 405nm diode by heating the diode?

I have red on the forum diodes will have a wavelength increase 0,3nm/degrees.

so if a diode emits 405nm @ 20 degrees, and we heat this diode with 30 degrees extra upto 50 degrees total in theory it will laser at 0,3nm x 30 = 9nm + 405nm = 414nm

Now what is the difference in luminous flux

1W of 405nm got 3.18 lm
1W of 414nm got 7.35 lm

So in theory the heated diode lasing at 414nm got a double the visibility compared to the 405nm.

will this theory work?

[cyberb0b]

why dont you try it, and tell us

[sugeek]

will this theory work?

It really depends on where theory meets thermal breakdown. If I were to test this I would get the highest power blu-ray burner diode, and under-drive it rather than over driving. If you want to thermally tune a diode I think you want as little stress on it as possible.

My guess based on no math or data to back it up at all is you may be able to get to 408-410nm before stability issues or extra short life-time occurs.

-Adam

[ElektroFreak]

Would it be possible to increase the nm of a 405nm diode by heating the diode?

I have red on the forum diodes will have a wavelength increase 0,3nm/degrees.

so if a diode emits 405nm @ 20 degrees, and we heat this diode with 30 degrees extra upto 50 degrees total in theory it will laser at 0,3nm x 30 = 9nm + 405nm = 414nm

Now what is the difference in luminous flux

1W of 405nm got 3.18 lm
1W of 414nm got 7.35 lm

So in theory the heated diode lasing at 414nm got a double the visibility compared to the 405nm.

will this theory work?

This is quite possible, since all laser diodes are temperature tunable. This is one of the best features of laser diodes as it allows you to tune diodes directly to the peak absorption bands of laser crystals in DPSS systems. Without this ability, many types of DPSS lasers wouldn't even be possible.

Regarding the visibility of your 405nm diode, heating it will increase the visibility very slightly, but always at the expense of lifetime. Because of this, when selecting DPSS pump diodes, it is always best to get diodes that need to be cooled to tune to the crystals (wavelength a little long) rather than heated (wavelength little short of the peak absorption band).

I know you aren't talking about DPSS systems, but the theory behind your question plays into DPSS a great deal, so I think it's relevant to helping you see that your scenario is possible, and at what cost.

[mccarrot]

Regarding the visibility of your 405nm diode, heating it will increase the visibility very slightly.

According to the Croma program a increase of 7nm will result in a double luminance.

example:
200mW 405nm = 0,63 lm
200mw 412nm = 1,22 lm

Looking at white balance

100mw 532nm, 300mW 655nm and 200mW 412nm will give you white

But to get white with 405nm you need:

100mw 532nm, 300mW 655nm and 400mW 405nm

So I think increasing the wavelength up by 7nm will give a huge (double) difference.

So IF a bluray diode also increases with 0,3nm/C and the Chroma program is correct we will only need to heat it up 24 degrees to double its efficiency.

Looking at a datasheet of a diode they can operate upto 70 degrees, so running the diode at 44 degrees shouldn't be a problem I think.

If we only had someone who could measue the wavelength of a diode and then heat it to plot a graph...

[ElektroFreak]

According to the Croma program a increase of 7nm will result in a double luminance.

example:
200mW 405nm = 0,63 lm
200mw 412nm = 1,22 lm

Looking at white balance

100mw 532nm, 300mW 655nm and 200mW 412nm will give you white

But to get white with 405nm you need:

100mw 532nm, 300mW 655nm and 400mW 405nm

So I think increasing the wavelength up by 7nm will give a huge (double) difference.

So IF a bluray diode also increases with 0,3nm/C and the Chroma program is correct we will only need to heat it up 24 degrees to double its efficiency.

Looking at a datasheet of a diode they can operate upto 70 degrees, so running the diode at 44 degrees shouldn't be a problem I think.

If we only had someone who could measue the wavelength of a diode and then heat it to plot a graph...

Chroma will tell you that you'll get double luminance, but that's all very subjective. There is no accurate mathematics that applies to individual color sensitivity, especially at the fringes of the sensitivity range, so I highly doubt that you will actually see it and say to yourself: "Wow, it looks twice as bright". That's my main problem with Chroma is that it tries to quantify something that varies so much from person to person that it is impossible to quantify. It might give you a rough estimate, but thats a far cry from a precise value.

Also, it has nothing to do with efficiency, rather it has to do with the actual lengthening and shortening of the laser diode chip itself through expansion and contraction. This expansion and contraction is what causes the wavelength shift. You do not get any more power from a diode by changing its temperature.

Tell us how it goes.. seems like you've been working very hard to figure this out mathematically, so now you've got to see if your math works..

[mccarrot]

I agree the beam will probably not look twice as bright, and even some people will not see the beam at all. But I think it is still a fact you need half the power to get a good white when using 412nm

So when we use bluray as addition to 473nm to get a nicer white it make sense to heat the diode.

Look at the HUGE difference 200mW of 412nm can have on my projector.

[ElektroFreak]

I like the idea of adding 405nm to a projector for more vivid color tone overall, but I hesitate to take Chroma at face value since there is too much subjectivity to the idea of "good" white balance.

Your idea might get you the ability to use less power and get more visibility from your 405nm diode, but I'm of the opinion that it might be too much effort for not enough gain. It is a very simple matter to tweak the white level of an RGB system in your software without much loss as long as your lasers are close to the proper ratio without even adding 405. A touch of 405 would help make many colors more vivid, but whether or not it would be worth the effort of temperature tuning the 405nm diode I don't know. I'll be interested to see how this works out for you.

[LesioQ]

So IF a bluray diode also increases with 0,3nm/C and the Chroma program is correct we will only need to heat it up 24 degrees to double its efficiency.
If we only had someone who could measue the wavelength of a diode and then heat it to plot a graph...

Nichia's data sheet for 120mW 405nm GaN laser diode shows graph of wavelength / temperature dependance and it's slope is about 15 deg per nanometer, so not as favourable as GaAs diodes

Piotr.K

[sugeek]

If we only had someone who could measue the wavelength of a diode and then heat it to plot a graph...

We do have someone with these tools, Laserben has a usb spectrometer, and Kevin at junktronics just traded for an ocean optics spectrometer too. I have been wanting one of those nifty boxes for awhile! At least with your new powermeter you will be able to get a graph in realtime via USB but that is just power... If you can get one of those two to take some time to do this it would spread some light on the situation.

-Adam