Wednesday, May 19, 2010

IR CCD arrays for spectroscopy?

The charge-coupled device, or CCD, was the gadget behind part of this past year's Nobel prize in physics.  Far and away, the most common CCDs out there are based on silicon, and these devices are highly efficient from the visible out to the near-infrared, with efficiency really taking a major hit at wavelengths longer than about 1100 nm.  One advantage of CCDs is that generally their total efficiency is high:  an incident photon stands a good chance of producing some charge on a pixel, and that charge can be collected well, so that getting a "count" on a particular pixel requires only a couple of photons.  It turns out that one can also get CCDs based on InGaAs, a semiconductor with a smaller band gap than Si, and therefore sensitive to longer wavelengths, typically from around 950 nm out to 1700 nm or so.  I have been thinking about trying to get such a gadget for a few reasons, Raman spectroscopy in particular, and I would welcome reader recommendations.  For our application we really would like something with CCD-like sensitivity (as opposed to a linear array of photodiodes, which is considerably cheaper, but requires on the order of 100 photons to produce a single "count").  Feedback would be greatly appreciated.  I know that Princeton Instruments sells one gadget (though really for imaging rather than spectroscopy), and Newport appears (from press releases)  to offer something with more pixels, though it doesn't show up on their website....

9 comments:

JJ said...

I know that Sionyx has been promising to make a much-more-efficient IR CCD for a few years now. I don't know if they've got a product yet, but it's probably worth checking.
www.sionyx.com

Doug Natelson said...

Thanks, JJ. These are the folks basing devices on the Harvard work on "black Si", right? For those less familiar, "black Si" is made by a combination of very shallow pn junctions plus a pulsed laser process that micro/nanostructures the Si surface. It doesn't get to 1700 nm, but does go out well beyond conventional Si. I've seen papers about this, but never a commercial array device....

JJ said...

Yep, it's the Harvard black silicon spin-off company. I work on black silicon myself, but as a photovoltaic material rather than as a photodector. I don't know whether Sionyx has a commercial product yet, but I've heard nice promises over the years.

Jonah said...

I have used both 1D OMA V's (the 512 element and 1024 element) and the 2D. The 2D is ~10-20x more sensitive as far as number of electrons it takes to generate a count, but I recall it having a higher dark current. I thought of it as diode array though as each pixel has its own amplifier and readout though. Princeton isn't allowed to sell it outside of the states actually due to weaponization or something… so we don't have one here in Bordeaux.
We do have a TE cooled version of the 2D (same chip, different electronics), but it's not as nice as the Princeton cryo-cooled version. Also had to write my own software for that, which I really can't recommend doing if you are on a schedule.

I know that there are several groups (i can think of at least 3 in eke, physics, and chem) at Rice that have the 2D-OMA V. Perhaps you'll find a colleague that would be willing to let you test it out for your application. Obviously don't want to volunteer anyone, but my former advisor is a nice guy and has both the 1D-1024 and 2D. ;)

Doug Natelson said...

Hi Jonah - The problem is that the 1d photodiode array sensitivities are just not very good for what we want to do. The 2d is a possibility, but because it's comparatively few pixels across, for the kind of Raman we want it's unlikely to work well. I'm trying to talk to these guys. Turns out that the Oriel InstaSpec IR is no longer sold, and was originally made by the DeltaNu people.

Anonymous said...

Andor has some InGaAs arrays. Don't know whether its sensitivity is sufficient for you.

http://www.andor.com/scientific_cameras/idus-ingaas/

I would also look through Hamamatsu products.

http://sales.hamamatsu.com/en/products/solid-state-division/image-sensors/ingaas.php

DanM said...

Are the InGaAs devices ITAR restricted? Will you have permission to take it out of the box on campus? Ask these questions before purchasing.

Charles Day said...

On a recent visit to NIST-Boulder, I learnt from Kent Irwin that transition edge sensors (TES), coupled to SQUID amplifiers, provide impressive spectral sensitivity over most of the EM spectrum

Doug Natelson said...

Hi Charles - I know Kent (though he probably doesn't remember me) from Stanford, when he was working on transition edge sensors for the dark matter search. Yeah, they're amazing, though not exactly available as a commercial product....