970nm IR Led - Page 1
Forum section: electronics / projects

author: diegop
author_rank: Contributor
timestamp: July 01, 2017, 06:18:45 pm
content: Hello everyone.Does anyone know where to buy a 970nm wavelength led?I have been looking in digikey and mouser, but I have only found 940 and 950 nm leds.

author: Kleinstein
author_rank: Super Contributor
timestamp: July 01, 2017, 07:42:09 pm
content: The normal IR LEDs are something like 950 nm. However they are not single wavelength, but have quite a bandwidth which extends even to beyond 980 nm.There might be sources for special longer wavelenght LEDs, but these cold be exotic and thus expensive (thus like dollars instead of cents). What is the purpose for these LEDs ?

author: diegop
author_rank: Contributor
timestamp: July 02, 2017, 08:43:12 pm
content: They are to measure water in the body. Water hasvthe highest absorption of IR light at the 970 nm wavelength. For this reason am looking for this type of led.All I could find that had this wavelength is a led from osram that emitted light from around 700nm to 1100nm.

author: Siwastaja
author_rank: Super Contributor
timestamp: July 07, 2017, 04:34:44 pm
content: There is no such a thing as "950 nm LED" or "970 nm LED".Look at theactualcurves of a few products (can be 940 or 950 nm nominal) and see if they do the job. Note that the actual wavelength curve is also a function of:(a) current(b) temperature(c) individual part; in some cases, you can found them binned to get better control."950 nm LEDs" all produce good amounts of 970nm, even if the peak was at 950nm. If you need to, you could use an optical filter to remove sub-970 nm wavelengths (including the 950 nm peak) if it disturbs your application. But if you only need 970 nm, and other unwanted wavelengths do not cause an issue, just get one which gives you the optical power you need at 970 nm, at suitable price and efficiency.Looking at some graphs on water absorption, it seems the peak absorption is somewhat wide, and the peak is only maybe 20-30% higher than, say, +/- 30 nm band around it, so maybe the 950 nm LED will perform just fine. If you need tight peak, you'll need optical filteranyway, so the actual LED peak is then only a matter of efficiency, i.e., losing least amount of light in the optical filter. Then you need to calculate the system (LED + filter) as a whole, because LED efficiency between different products can differ by factor of 100x easily!

author: mjs
author_rank: Regular Contributor
timestamp: July 07, 2017, 08:49:38 pm
content: Roithner Lasertechnik has a good selection of all kinds of LEDs from a single place:http://www.roithner-laser.com/led_diverse.html

author: dhillman
author_rank: Contributor
timestamp: July 07, 2017, 11:56:58 pm
content: I have ordered from Marubeni America for through hole 750nm units. They will work with smaller orders (50+) and have a huge selection. You will likely have to wait for the shipment from Japan. They seem to show 950 and 970 centered units.http://www.tech-led.com/product/molded-led/

author: diegop
author_rank: Contributor
timestamp: July 08, 2017, 05:13:57 pm
content: Thank you all for you responses.My mistake on wording, what I meant by 970nm led is that the led has its peak wavelength at 970nm.After doing a little bit of research, as Siwastaja said, a 950nm led should also work.I'm going to test with this led from vishayVSMS3700and this photodiode from OSRAMBP 104 FS.