[HN Gopher] The terahertz gap: into the dead zone ___________________________________________________________________ The terahertz gap: into the dead zone Author : losfair Score : 48 points Date : 2022-12-04 17:14 UTC (5 hours ago) (HTM) web link (www.chemistryworld.com) (TXT) w3m dump (www.chemistryworld.com) | rich_sasha wrote: | Why would THz waves offer higher resolution in imaging that IR? I | understood that the shorter the wave, the higher the (lower bound | on) attainable resolution? | | Also, unrelated but no point in commenting twice: millimetre wave | astronomy is a big topic of the last decade or two. How does the | THz technology described here link to what's used in mm wave | detection? | was_a_dev wrote: | > It beats infrared light for resolving power because it | suffers less Rayleigh scattering, imaging details less than 1 | millimetre wide. | | While the wavelength of THz is larger than IR, and hence leads | to a worse spatial resolution due to diffraction. This comment | is about the scattering of light through a medium, which acts | as a low pass filter leading to loss of higher spatial | frequencies and therefore lower spatial resolution. | | > millimetre wave astronomy is a big topic of the last decade | or two. How does the THz technology described here link to | what's used in mm wave detection? | | They are effecitevely the same band (1mm ~ 0.3THz). The | difference between astronomy and other applications is photon | flux. Distant astronomical objects are faint, therefore | detection methods only need to detect a small number of | photons/s. One popular detector is cryogenic bolometers, which | measure a temperature increase due to absorbed energy from a | THz photon. These work well in low-flux applications. | adrian_b wrote: | I do not know if this claim is true, but in the article it is | said that infrared light imaging is affected by Rayleigh | scattering, which limits its resolution. | | According to this claim, many common materials would diffuse | the infrared light so that the image would look like looking to | something through translucent glass or through fog, which would | diminish the resolution. | | I assume that this refers to imaging through visually opaque | materials, i.e. through clothes, like for airport security, not | to looking through the air with an infrared camera. | can16358p wrote: | Technically speaking, what should EM in that range called? | | Not visible light, as it's not visible. | | Not exactly microwave either, or is it? | downvotetruth wrote: | Metric: centimicrometer | was_a_dev wrote: | 0.3-3.0THz is given usually named just THz, given surrounding | bands are already named. | | Another convention is sub-mm, given the wavelength is just | that, being on the order of microns. | boulos wrote: | (2007) | | Can people comment on what has happened since? 15 years is a long | time in the research world. Did the hoped for things come to | pass? | wolfram74 wrote: | If I'm remembering correctly, most of the interesting work in | archaeology recovering palimpsests (reused canvas/media for | multiple works) has been done with THz stuff, so that's one | place it's come up. ___________________________________________________________________ (page generated 2022-12-04 23:00 UTC)