ULTRAVIOLET TYPE B & C 240nm -340nm Gallium Nitride

[[BEGIN SERMON MODE]]
I must emphasize, protect your eyeballs when using any one of these LEDs. You only get one set of eyes - and if you wreck them, you can't just go down to the local seven-eleven and buy a can of them.
Here is one simple way you can do this:

Most sunglasses and some prescription eyeglasses have some degree of UV protection already; to determine if yours do or not, aim the LED at something that clearly fluoresces (such as those neon green & orange stickers that occasionally show up on your mail, day-glow orange price tags, or painted portions of a blacklight poster), positioning the LED so the object in front of it glows (fluoresces) brightly from the ultraviolet light. Then put the glasses between the face of the LED and the target. If the glow stops or dims dramatically, the glasses are stopping the UV and you can use them as eye protection at least for short-term use.
However, if the glow remains or dims only slightly, look for another pair.

In any case, never look directly at the LED without eye protection - not even for a minute.

Symptoms of UV exposure may not appear immediately; they can be delayed by 30 minutes to several hours. They can include a burning or "sand in the eyes" sensation, and a hazy look around light bulbs and other bright objects. Mild cases are self-correcting within 24 to 36 hours; however if despite my warnings you still stared at the LED from close range for more than a few minutes, it might not be a bad idea to see an eye doctor and tell him you've been exposed to UVB or UVC radiation.

DISCLAIMER: I shall not be held responsible for any damage or loss of eyesight arising from your use or misuse of the information on this page. Thank you for listening.
[[END SERMON MODE]]



*** VERY IMPORTANT!!! ***
The LEDs directly below (the two deep UV LEDs from SET) are more static-sensitive than most (if not all) other LEDs you may have handled. You ***MUST*** excersize static-safe precautions when handling these LEDs; if you do not have ready access to a static-safe work area, then at least ground yourself immediately before handling one of these LEDs and rather frequently during handling!!!



Sensor Electronic Technology, 275nm deep UV LED in TO-39 case, $199.00 apiece
Received & tested 05-01-08

For a number of years now, you could get NUV and UV LEDs at wavelengths as low as 370nm (you could even get 350nm & 360nm LEDs for the last couple of years if you tried); SET now offers LEDs in the deep UV with wavelengths as short at 240nm - this is well into the UVC band! This LED is in the "UVTOP" package, which appears to be a large transistor case with a transparent, water-clear window designed to transmit short UV wavelengths - ordinary epoxy or glass will block them.


This LED (top) compared with a T1 (5mm) (bottom) of fairly recent manufacture.


The LED's visible output is extremely minimal at best; I had to photograph it "head-on" to get any image at all.

The spot of light you see at the center of the LED appears ***MUCH*** brighter here than it does in real life; the actual visible output is probably a whopping 0.005W or somewhere in that general neighbourhood.

This photograph is a bit out of focus because my camera doesn't "do" macros very well.



A photograph of a white baseball hat fluorescing (glowing) in this LED's 275nm radiation.
The hat has very likely been exposed to a chemical called "bluing"; which is commonly found in laundry soap to help "whites look whiter". It is this bluing that is fluorescing in the UV radiation in this photograph.



Spectrographic analysis of this 275nm UV LED.
This analysis was performed with a If of 19.28mA.
Spectrometer's response was narrowed to a range of 190nm to 380nm.



Same as above, but spectrometer's response widened to a range of 180nm to 874nm.

Note the LED's spectral line halfwidth is unusually narrow for an LED; looks like ~10nm to ~15nm to me.

Unable to measure power output with the instruments at my disposal, but according to the supplied spec sheet, should be ~500W (0.50mW).
Beam angle appears to be approximately 92.

This LED is a loaner; I will not have it for too long (to make comparisons with other UV LEDs).



Sensor Electronic Technology, 300nm deep UV LED in TO-39 case, $139.00 apiece
Received & tested 05-01-08

For a number of years now, you could get NUV and UV LEDs at wavelengths as low as 370nm (you could even get 350nm & 360nm LEDs for the last couple of years if you tried); SET now offers LEDs in the deep UV with wavelengths as short at 240nm - this LED radiates at ~300nm in the UVB band - almost into the UVC band! This LED is in the "UVTOP" package, which appears to be a large transistor case with a transparent, water-clear window designed to transmit short UV wavelengths - ordinary epoxy or glass will block them.


This LED (top) compared with a T1 (5mm) (bottom) of fairly recent manufacture.


The LED's visible output is extremely minimal at best; I had to photograph it "head-on" to get any image at all.

The spot of light you see at the center of the LED appears ***MUCH*** brighter here than it does in real life; the actual visible output is probably a whopping 0.005W or somewhere in that general neighbourhood.

This photograph is a bit out of focus because my camera doesn't "do" macros very well.



A photograph of a white baseball hat fluorescing (glowing) in this LED's 300nm radiation.
The hat has very likely been exposed to a chemical called "bluing"; which is commonly found in laundry soap to help "whites look whiter". It is this bluing that is fluorescing in the UV radiation in this photograph.



Spectrographic analysis of this 300nm UV LED.
This analysis was performed with a If of 19.28mA.
Spectrometer's response was narrowed to a range of 190nm to 380nm.

Note the LED's spectral line halfwidth is unusually narrow for an LED; looks like ~10nm to ~15nm to me.



Same as above, but spectrometer's response widened to a range of 180nm to 874nm.

Unable to measure power output with the instruments at my disposal, but according to the supplied spec sheet, should be ~500W (0.50mW).
Beam angle appears to be approximately 92.

This LED is a loaner; I will not have it for too long (to make comparisons with other UV LEDs).



Update 05-06-08:
I have sent these LEDs back to SET; therefore I no longer have them for future comparisons and/or analyses.








[[BEGIN SERMON MODE]]
Again I must emphasize, protect your eyeballs when using one of these LEDs. You only get one set of eyes - and if you wreck them, you can't just go down to the local seven-eleven and buy a can of them.
Here is one simple way you can do this:

Most sunglasses and some prescription eyeglasses have some degree of UV protection already; to determine if yours do or not, aim the LED at something that clearly fluoresces (such as those neon green & orange stickers that occasionally show up on your mail, day-glow orange price tags, or painted portions of a blacklight poster), positioning the LED so the object in front of it glows (fluoresces) brightly from the ultraviolet light. Then put the glasses between the face of the LED and the target. If the glow stops or dims dramatically, the glasses are stopping the UV and you can use them as eye protection at least for short-term use.
However, if the glow remains or dims only slightly, look for another pair.

In any case, never look directly at the LED without eye protection - not even for a minute.

Symptoms of UV exposure may not appear immediately; they can be delayed by 30 minutes to several hours. They can include a burning or "sand in the eyes" sensation, and a hazy look around light bulbs and other bright objects. Mild cases are self-correcting within 24 to 36 hours; however if despite my warnings you still stared at the LED from close range for more than a few minutes, it might not be a bad idea to see an eye doctor and tell him you've been exposed to UVB or UVC radiation.

DISCLAIMER: I shall not be held responsible for any damage or loss of eyesight arising from your use or misuse of the information on this page. Thank you for listening.
[[END SERMON MODE]]




Update 05-06-08:
I have sent these LEDs back to SET; therefore I no longer have them for future comparisons and/or analyses.






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