Room-temperature mid-infrared single-photon spectral imaging

Abstract

The spectral imaging and detection of mid-infrared wavelengths is emerging as an enabling technology of great technical and scientific interest, primarily because important chemical compounds display unique and strong mid-infrared spectral fingerprints that reveal valuable chemical information. Modern quantum cascade lasers have evolved as ideal coherent mid-infrared excitation sources, but simple, low-noise, room-temperature detectors and imaging systems lag behind. We address this need by presenting a novel, field-deployable, upconversion system for sensitive, two-dimensional, midinfrared spectral imaging. A room-temperature dark noise of 0.2 photons/spatial element/second is measured, which is a billion times below the dark noise level of cryogenically cooled InSb cameras. Single-photon imaging and a resolution of up to 200 3 100 spatial elements are obtained with a record-high continuous-wave quantum efficiency of ∼20% for polarized incoherent light at 3 mm. The proposed method is relevant for existing and new mid-infrared applications such as gas analysis and medical diagnostics.O ptical spectroscopy within the ultraviolet, visible and nearinfrared regimes has for decades been an indispensable method for the identification and quantization of chemical analytes. However, emerging mid-infrared applications in environmental gas monitoring or the life sciences call for improved detection systems that challenge today's capabilities in terms of sensitivity and/or imaging functionality. For example, in the face of global warming, mid-infrared detectors capable of measuring minute gas concentrations are required, because important greenhouse gases such as CO 2 , CO, CH 4 and N 2 O have fundamental absorption bands located in the mid-infrared 1 . For example, CO requires a detection sensitivity on the order of 100 ppb (parts per billion) 2 . Monitoring atmospheric trace molecules at these levels provides important inputs for the climate models used for studying global warming and its consequences for life on Earth 3 . In life science, the spectral regime from 0.3 to 2 mm has already been utilized for fundamental studies of breath analysis. However, significant improvements can be expected from using mid-infrared spectroscopy 4,5 . The on-line detection of the numerous different molecules (.1,000) in exhaled human breath may lead to new non-invasive diagnostics tool for doctors. However, such biomarkers are frequently below ppb levels. Indeed, the exhaled concentration of ethane (at 3.3 mm), which is used as a marker for asthma and chronic obstructive pulmonary disease, is found at 100 ppt (parts per trillion) levels, clearly demonstrating the requirement for highly sensitive methods 5 . Similarly, 1-butanol and 3-hydroxy-2-butanone in breath could be useful biomarkers for lung cancer 6 .In the 3-15 mm wavelength regions, two-dimensional mid-infrared spectral imaging demonstrates potential for identifying cancerous tissue, providing a new tool for cancer diagnostics. In this wavelength region, each organic compound an...

An upconverted photonic nonvolatile memory

“…I nfrared (IR) light is in the electromagnetic spectrum between the visible and microwave portions, and exhibits extensive applications in thermography, night vision, energy conversion, spectroscopy, medical and telecommunication [1][2][3][4][5] . Near-IR energy (750-1,000 nm) can also be further applied in implantable electronic devices since its long wavelength allows it to penetrate deep into tissues, and its low energy is not harmful to healthy cells 6,7 .…”

Low-noise mid-IR upconversion detector for improved IR-degenerate four-wave mixing gas sensing

“…Alternative methods based on nonlinear upconversion in periodically poled lithium niobate (PPLN) waveguides have been demonstrated around 1550 nm [2,3] and 2 μm [4] with high efficiencies, allowing for the use of low-noise visible light avalanche photodiodes for detection of infrared (IR) light. The same principles have been applied for the upconversion of incoherent mid-IR images by Dam et al [5] using a continuous wave intracavity PPLN mixing scheme.…”

“…However, no quantitative comparison of detector performance and the (signal-to-noise ratio) SNR of the upconversion-based system was made relative to traditional cryogenically cooled InSb detectors. Using a setup similar to the one in [5,10], this Letter quantifies a 500 times improvement in SNR compared to a conventional cryogenic InSb detector, using continuous wave upconversion detection. Furthermore, a threefold improvement, down to 1 ppm in the detection of acetylene concentration, is demonstrated, compared to previous results reported with a DFWM setup using upconversion [10] and more than a 10 times improvement compared to InSb-based detection.…”

“…The beam waist of the mixing laser inside the PPLN crystal is 180 μm, defining the effective detector area. The upconversion module is described in greater detail in [5], the only change being that the pump diode for the Nd:YVO 4 laser has been exchanged with an 880 nm laser diode to separate the pump wavelength from the visible signal wavelength. This will allow for more efficient filtering and thus minimize the 800 nm light reaching the CCD chip as spill light from the pump.…”

A four-pixel single-photon pulse-position array fabricated from WSi superconducting nanowire single-photon detectors

“…Arrays of single-photon detectors have potential applications in infrared spectroscopy 1 and optical communications in the so-called "photon starved" regime. 2,3 One example is interplanetary communications where the mass and power limitations of the laser transmitter result in single-photon light levels at the receiver.…”