Photodiodes

[shakilabanu]

I am working on a project that requires me to reverse engineer a BioPhotometer and build a new one with modifications. The part where I am stuck is a photodiode that measures wavelengths between 230nm to 600nm.

I know fundamentals of photodiodes, but I was not sure is a single photodiode can measure this range of wavelengths. ?

Or are there special photodiodes (array) that have multiple photodiodes built into them which measure different wavelengths and hence combine to make a broad spectrum photodiode equivalent. ?

Hope I have made this clear.

[ovnr]

No, there are single photodiodes that should do what you want. Here's some. I especially liked this one - $435, and yet the cover glass is taped on!

[SeanB]

That is a cover used to protect during handling, as the only way to get the lower wavelengths is to not use ordinary soda glass, which has absorbtion bands un the UV region, and which may also flouresce with short wavelengths. Bare die only after assembly and just before putting the cover on for the final time.

[shakilabanu]

No, there are single photodiodes that should do what you want. Here's some. I especially liked this one - $435, and yet the cover glass is taped on!

Thanks the first link was useful. However since Digikey  does not ship to India, I'll have to try finding some other source to get these from.

[ovnr]

That is a cover used to protect during handling, as the only way to get the lower wavelengths is to not use ordinary soda glass, which has absorbtion bands un the UV region, and which may also flouresce with short wavelengths. Bare die only after assembly and just before putting the cover on for the final time.

Yeah, I figured as much. Still, it looks pretty sketchy - and you'd think they could come up with a better way to protect their parts, because that doesn't seem terribly reassuring.

Thanks the first link was useful. However since Digikey  does not ship to India, I'll have to try finding some other source to get these from.

... Digikey does ship to India, but it costs $40 in shipping. Mouser has some parts too, but their parametric search stinks so good luck finding the perfect part for your application. Same $40 shipping too, it seems.

[ejeffrey]

UV photodiodes normally have fused silica windows, which work fine in the UV.  Windowless photodiodes are usually either intended to be used where the etalon effects of the window glass cannot be tolerated, or when the diode will be packaged into a sealed enclosure by the end user, for instance if it is to be peltier cooled or used in vacuum.  That particular diode appears to be also designed to detect electrons such as from X-ray photoemission or secondary electrons from an electron microscope, presumably that is why it has no window.

Thorlabs sells a wide variety of photodiodes, here is a wide range silicon diode that is fairly cheap: http://www.thorlabs.us/thorproduct.cfm?partnumber=FDS010