The first from OSA:
Visual sensitivity of the eye to infrared laser radiation
David H.Sliney, Robert T Wangemann, James K Franks (all U.S. Army Environmental Hygiene Agency, Aberdeen Proving Ground, Maryland) and Myron L Wolbarsht (Duke University Eye Center, Durham, North Carolina)
JOSA, Vol 66, Issue 4, pp. 339-341 (1976)
You can find the paper online (membership/paywall) on the Optics Infobase
The abstract reads:
The foveal sensitivity to several near-infrared laser wavelengths was measured. It was found that the eye could respond to radiation at wavelengths at least as far as 1064 nm. A continuous 1064 nm laser source appeared red, but a 1060 nm pulsed laser source appeared green, which suggests the presence of second harmonic generation in the retina.
Similarly, but more recent and with open access is ...
Perception of the Laser Radiation for the Near Infrared Range
D. Kecika, J. Kasprzaka, (both Department and Ophthalmology Clinic, I Medicine Faculty, Medical University of Warsaw) and A. Zając (Institute of Optoelectronics, Military University of Technology, Warsaw)
ACTA PHYSICA POLONICA A, Vol 120, No 4, pp 686-687
This paper is available as a PDF.
This abstract reads:
During the diagnostic research done by means of optical devices equipped with radiation sources from the near infrared range the phenomena indicating the perception possibility of this range by a human eye were observed. In this contribution the initial results of the research of this phenomenon were presented. Sources of radiation applied in laser polarimeters (785 nm) and devices designed for optical coherent tomography (820, 850 nm) were taken into particular consideration. Perception tests with the use of a laser diode generating at the wavelength of 940 nm were also carried out. It was stated that the radiation from the range examined can be recorded by a human eye giving a colour sensation — in practice independently of the wavelength of the radiation beam falling into a retina.I suspect this kind of experiment with lasers falls into the don't try this at home category but it demonstrates that the usual limits quoted for human visual sensitivity are not necessarily the only ones.
There's some interesting notes about this also in the Wikipedia entry on light.
The final word may have to go to a paper I found in the Proceedings of the National Academy of Sciences of the United States of America (PNAS vol 111 no 50) with (sorry) too many authors to list (let's just say Palczewska et al) and with the title Human infrared vision is triggered by two-photon chromophore isomerization. Almost totally out of my area of expertise but if you have the knowledge then you can access the paper (paywall) via this link. I'll leave it to the report's authors to have the final word ... quoted from their 'significance'.
This study resolves a long-standing question about the ability of humans to perceive near infrared radiation (IR) and identifies a mechanism driving human IR vision.
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