SWIR Cameras for Physical Science & Astronomy

Adaptive Optics

Wavefront sensing and correction through Adaptive Optics (AO) instrumentation enables real-time reduction in image distortion caused by atmospheric turbulence. AO systems afford considerable enhancement of both signal-to-noise ratio and spatial resolution for ground-based observations of objects in space. Wavefront sensors record the rapid variation of a wavefront, providing critical inputs to AO control and wavefront correction systems. Wavefront sensing in the SWIR wavelength domain is becoming increasingly prevalent and effective.

The First Light Imaging range for AO includes market-leading SWIR solutions such as the 3500 fps single photon sensitive C-RED One and the 600 fps InGaAs C-RED 2. It also includes a highly cost-effective C-RED 3 solution, delivering 600 fps from a compact, uncooled platform. 

Neptune in the SWIR range with C-RED 2. Courtesy of SCExAO, NAOJ.

Interferometry

A telescope’s ability to spatially resolve astronomical objects is limited by the size of its primary mirror. Interferometry is a technique used to overcome this limitation by precisely combining light collected by an array of small telescopes to achieve the spatial resolving power (without the light collecting capability) equivalent to that of a telescope with a single primary mirror the size of the full array. This technique has a long history in radio astronomy and is increasingly being adopted at visible and infrared observatories to resolve binary stars, planetary systems, and stellar surface features (e.g. starspots). Interferometers need very precise phase matching of light collected across the array, which, owing to atmospheric turbulence, can only be achieved with very short (ms) exposure times. Atmospheric coherence times tend to be slightly longer at SWIR wavelengths, but the photon count per exposure can still be very low.

Capable of 3500 fps full frame readout and electron multiplication, the C-RED One camera from First Light Imaging delivers revolutionary sensitivity and speed for the most demanding SWIR interferometric observations.

Further Reading
A Highly Sensitive Six-telescope Interferometric Imager at the CHARA Array
A high angular resolution K-band imager at CHARA
Advances in Optical/Infrared Interferometry

Typical C-RED One detector readout with six telescope delay from the MIRC-X instrument operating in All-In-One mode at the CHARA array. Photometry is measured at each wavelength channel on the left of the detector readout and interferometric fringes are formed on the right. Fringes from all 15 baselines are superimposed at non-redundant spatial frequencies. (from Setterholm et al. 2022, Proc. SPIE 12183, Optical and Infrared Interferometry and Imaging VIII, 121830B)

Laser Beam Profiling

Laser beam profiling is a technique used to measure and analyse the spatial characteristics of a laser beam. It provides information on intensity distribution, shape, and size. It has multiple applications:

• Monitoring laser quality, this can include measuring spatial intensity distribution and temporal stability.
• Laser beam profiles can be used to gain a better understanding of laser physics and adjust laser parameters for optimal beam shaping.
• Studying the temporal evolution of a beam, for example to assess the impact of environmental parameters (temperature, wind, snow, etc.) on the propagation of a laser beam.

Andor’s C-RED series provide a range of fast and sensitive solutions for beam profiling in the SWIR domain. C-RED 2 Lite and C-RED 3 provide cost-effective solutions for studying temporal characteristics at 600 fps. C-RED One provides temporal resolution at 3500 fps.

Typical top-hat laser power distribution. Acquisition with a C-RED 3 camera

Hyperspectral Imaging

Hyperspectral imaging combines digital imaging with spectroscopy, adding a spectral dimension to conventional imaging. It is a mature technique for the analysis of agricultural fields, forest, or mines. In the past few years, it has emerged as an important tool for the industrial analysis of products (drugs, plastics, food, etc.).

In the SWIR band (900-2500nm), hyperspectral imaging is an emerging technology for production control. The advantages of simultaneous access to spatial and spectral characteristics of an object provide valuable information on the chemical composition of its surface.

Andor’s C-RED camera series presents a wide range of fast and sensitive, cameras for Hyperspectral, across the full SWIR wavelength range. C-RED 2 Lite is a temperature-stabilized, cost-effective solution in the 900-1700nm range, whereas C-RED 2 ER can be very effectively utilized to extend coverage out to 2200nm.

Mixed pills imaged with a visible camera and with a hyperspectral imaging system (false colour display). Courtesy of First Light Imaging.

Advanced Materials

Spectroscopy in the SWIR region can be used to characterise the optical and electronics properties of a wide range of novel engineering materials in the field of solar cells, quantum sources and nano-lasers, optical probes and functionalised molecules for biosensing (using the deeper probing properties of infrared photons in biological media), or Carbon Nanotubes and graphene-based nanostructures.

Impurities/doping, structural stress and defects, emission/absorption properties, bandgap measurement can be probed by a variety of techniques including photoluminescence, electroluminescence, cathodoluminescence, or 1064nm Raman.

The iDus InGaAs spectroscopy detector series offers high sensitivity and high dynamic range detection capabilities from 1-1.7 μm or 2.2 μm. Combined with Andor Kymera/Shamrock spectrographs, cryostat solutions and UV-NIR spectroscopy detectors, it provides seamlessly configurable workhorse platforms to cater for setups with multiple type of spectroscopy modalities and/or material types.

Chemistry

Optical spectroscopy can be used to probe the makeup, transformation processes and behaviour of chemical species in different environments.

1064 nm laser-based Raman diagnostics can be used as a way to greatly minimise unwanted, competing autofluorescence contribution from some organic-based species. Singlet oxygen spectroscopy (with peak emission around 1,270 nm) can be used to probe photochemical reactions.

The iDus InGaAs spectroscopy detector series offers high sensitivity and high dynamic range detection capabilities from 1-1.7 μm. Combined with Andor Kymera spectrographs, cryostat solutions and UV-NIR spectroscopy detectors, it provides seamlessly configurable workhorse platforms to cater for setups with multiple type of spectroscopy modalities and/or material types.