Photon etc. is a Canadian manufacturer of infrared cameras, widely tunable optical filters, hyperspectral imaging and spectroscopic scientific instruments for academic and industrial applications. Its main technology is based on volume Bragg gratings, which are used as filters either for swept lasers or for global imaging.
History As a spin-off of the California Institute of Technology, the company was founded in 2003 by Sébastien Blais-Ouellette who was working on narrow band imaging tunable filters for the detection of hydroxyl groups in the Earth atmosphere. This is how he developed the main technology of the company, a patented volume Bragg grating for filtering purposes. The company was first established in the J.-Armand Bombardier Incubator at Université de Montréal where it benefited from a complete infrastructure and proximity to researchers. After 5 years, Photon etc. moved to its actual location at the "Campus des technologies de la santé″ in the Rosemont district of Montréal. Photon etc. has 25 employees in Canada and has received several awards and recognition (Québec Entrepreneur of the Year (finalist), CCFC (winner), Fondation Armand-Frappier (winner - prix émergence), Prism Award (finalist) ). In the last ten years, the company has developed numerous collaborations, filed several patents and created spin-off companies in various domains: Photonic Knowledge (mining exploration), Nüvü Cameras (EMCCD cameras) and Optina Diagnostics (retinal imaging). More recently, in June 2015, Photon etc. expanded its expertise in nanotechnology and launched a new division, Photon Nano. Photon Nano provides Raman, fluorescence and plasmonic labels synthesized by top research laboratories. Those labels are mainly employed in multiplexing applications for cellular imaging.
Technology Photon etc.'s core technology is a continuously tunable filter based on volume Bragg gratings. It consists of a photo-thermo-refractive glass with a periodically varying index of refraction in which the modulation structure can be orientated to transmit or reflect incident light. In order to select a particular wavelength that will be filtered (diffracted), the angle of the filter is adjusted to meet Bragg condition:
λ B = 2 n Λ sin ( θ + φ ) , {\displaystyle \lambda _{B}=2n\Lambda \sin(\theta +\varphi )\,,}
where n is an integer, λB is the wavelength that will be diffracted, Λ is the step of the grating, θ is the angle between the incident beam and the normal of the entrance surface and φ is the angle between the normal and the grating vector. For transmission gratings, Bragg planes are perpendicular to the entrance surface (φ=π/2) while for reflection gratings, Bragg plans are parallel to the entrance surface (φ=0). If the beam does not meet the Bragg condition, it passes through the filter, undiffracted. In a Bragg filter, the incoming collimated light is first diffracted by a volume filter and only a small fraction of the spectrum is affected. Then, by using a second parallel filter with the same modulation period, light can be recombined and an image can be reconstructed.
Hyperspectral imaging The company commercializes hyperspectral imaging systems based on volume Bragg gratings. This technique combines spectroscopy and imaging: each image is acquired on a narrow band of wavelengths (as small as 0.3 nm). The monochromatic images acquired from a hyperspectral data cube, which contains both the spatial (x- and y-axes) and spectral (z-axis) information of a sample. In this technique, global imaging is used in order to acquire a large area of a sample without damaging it. In global imaging, the whole field of view of the microscope objective is acquired at the same time compared to point-by-point techniques where either the sample or the excitation laser needs to be moved in order to reconstruct a map. When combined to microscopy, darkfield or brightfield illumination can be employed and various experiments can be carried out such as:
Tunable filters The volume Bragg grating technology is also used to design tunable bandpass filters for various light sources. This technology combines an out-of-band rejection of <-60 dB and an optical density higher than OD 6 with a tunability over the visible and near infrared regions of the electromagnetic spectrum.
Tunable lasers The Bragg grating filtering technology can be coupled to a supercontinuum laser in order to generate a tunable laser source. Supercontinuum sources are usually a high-power fibre laser which delivers ultra-broadband radiation and can be used for steady-state or lifetime experiments. This ultra broad radiation is obtained when a laser is directed through a nonlinear medium. From there, a collection of highly nonlinear optical processes (e.g.: four-wave mixing, Raman shifting of the solitons) add up together which create the supercontinuum emission. Coupled with the proper filter it can deliver a quasi-monochromatic output over a spectral range going from 400 nm to 2,300 nm. This tool can be used in several experiments and fields of research which includes:
Infrared cameras Photon etc. designs and manufactures low noise infrared cameras sensitive from 850 nm to 2,500 nm. Their HgCdTe (MCT) focal plane array (FPA) were first developed for faint flux measurements and are now used for astronomy, spectroscopy, quality control and sorting.
Applications
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