Best material for IR absorption

In summary, the conversation discusses the search for the best material for IR absorption, specifically for telecom wavelengths of 1550 nm or 1310 nm. Various materials such as plastics, semiconductors, and metals are mentioned, with the need for multi-layer anti-reflection coatings for thin films. The conversation also touches on the difficulty of achieving single photon sensitivity without using more complex designs, such as avalanche photo diodes or superconducting nanowire detectors. Ultimately, it is suggested that it would be more feasible to obtain a complete system from a company or university group rather than attempting to build one independently.
  • #1
physengineer
21
0
Hi all,

I am looking for the best material for IR (infra red) absorption, preferably something that I can make it into a thin film; any material that would work from semiconductors, metals to more exotic materials like graphene or...

I appreciate your help.

Thank you
 
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  • #2
It is not that simple.
If you just want to e.g. make an optical filter that blocks IR (for e.g. a window in a cryostat) various plastics work well (I know people who literally use pieces of a plastic bags from the supermarket).
However, if you want "high-end" absorbtion you need to know the wavelength you are looking at because I don't think there is a single material that works well for the whole IR part of the spectra.
If you are using thin films you will also need to use multi-layer anti-reflection coatings in order to reduce the reflectivity. If this is done you can even use various metals as the actual absorber (IR bolometers can use all sorts of materials as the absorber, even gold).
 
  • #3
f95toli said:
It is not that simple.
if you want "high-end" absorbtion you need to know the wavelength you are looking at because I don't think there is a single material that works well for the whole IR part of the spectra.
If you are using thin films you will also need to use multi-layer anti-reflection coatings in order to reduce the reflectivity. If this is done you can even use various metals as the actual absorber (IR bolometers can use all sorts of materials as the absorber, even gold).


Thank you, f95toli! In fact, I am interested in telecom wavelengths: 1550 nm or 1310 nm. Since the number of photons are very limited we need to absorb as much as we can.
 
  • #4
Are you measuring the intensity of radiation to/from cell phones?
 
  • #5
So you want some kind of detector?

What are your requirements? Do you need spatial resolution? Temporal resolution? Will you be able to cool it to reduce noise? Do you need spectral resolution? Do you need single photon sensitivity?

If you want something like a photo diode, InGaAs, Ge or InSb are some of the obvious choices for the IR.
 
  • #6
ThereIam said:
Are you measuring the intensity of radiation to/from cell phones?

Hi ThereIam, No, not cell phones. Just detecting few photons of 1550nm or 1310nm photons at the end of an optical fiber.
Thanks
 
  • #7
Cthugha said:
So you want some kind of detector?

What are your requirements? Do you need spatial resolution? Temporal resolution? Will you be able to cool it to reduce noise? Do you need spectral resolution? Do you need single photon sensitivity?

If you want something like a photo diode, InGaAs, Ge or InSb are some of the obvious choices for the IR.

Thank you, Cthugha! Yes, I want it for a detector. I can cool it down to 4.2K too. Single photon sensitivity is also required. I need the maximum absorption for the thinnest possible film, say a few nano meter. Spectral resolution is not an issue as long as either telecom freqs i.e. 1310 or 1550 is covered. The higher the bandwidth, even the better.
Thanks
 
  • #8
If you really need single photon sensitivity, this will be hard to achieve using just a thin film of a material without using something more complicated.

One way to achieve single photon sensitivity in the IR is an avalanche photo diode design. Here, InGaAs and InP are typical materials. A different and relatively new way are Superconducting nanowire single-photon detectors. They are typically made of NbN or something similar. You might want to google these. I am not quite up to date what the most efficient designs of these are.
 
  • #9
Cthugha said:
A different and relatively new way are Superconducting nanowire single-photon detectors. They are typically made of NbN or something similar. You might want to google these. I am not quite up to date what the most efficient designs of these are.

They are generally made from thin (a few nm) NbN films. However, in order to increase the absolute efficienty they also use multi-layer anti-reflection coating which is what I mentioned above.

If you want single photon sensitivity I am afraid this is one of those "if you have to ask" questions, there is simply no way you will be able to do this yourself.
Your best bet is to get a complete system from somewhere, either a company or a university group.
 
  • #10
f95toli said:
If you want single photon sensitivity I am afraid this is one of those "if you have to ask" questions, there is simply no way you will be able to do this yourself.
Your best bet is to get a complete system from somewhere, either a company or a university group.

I should have made this more clear, but this is my opinion, too. Unless the guy who opened this thread works in a group specialized in building detectors, this is not a do-it-yourself thing. Right now, there are many groups studying potential single photon sources at telecom wavelengths. If this is about that topic, too, the easiest way to demonstrate single photon emission lies in getting two good avalanche photo diodes in the IR and a good coincidence counting circuit and work with these. For the cost of the working time a typical PhD student will need to design something even remotely similar, you can buy a lot of these devices for sure.
 

1. What is the best material for IR absorption?

The best material for IR absorption depends on the specific wavelength range of interest and the application. Generally, materials such as germanium, silicon, and gallium arsenide are good choices for IR absorption due to their strong absorption coefficients in the IR range.

2. How does the thickness of a material affect its IR absorption?

The thickness of a material can greatly affect its IR absorption. Thicker materials typically have a higher absorption coefficient, meaning they can absorb more IR radiation. However, too thick of a material can also cause self-absorption, where the material's own absorption of IR radiation reduces the amount that can pass through.

3. Can any material absorb all wavelengths of IR radiation?

No, no single material can absorb all wavelengths of IR radiation. The absorption of IR radiation is dependent on the material's chemical composition and physical properties, such as thickness and crystal structure. Therefore, a combination of materials may be needed for complete IR absorption.

4. What is the difference between reflective and absorptive materials for IR radiation?

Reflective materials for IR radiation are those that reflect or bounce off IR radiation, while absorptive materials absorb the radiation. Reflective materials are typically used in IR mirrors and filters, while absorptive materials are used in IR detectors and sensors.

5. How can I determine the best material for IR absorption for my specific application?

The best way to determine the best material for IR absorption for your application is to consult with a materials scientist or engineer. They can help identify the specific requirements and characteristics needed for your application and recommend the most suitable materials for your needs.

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