Characterization of the NEP of Mid-Infrared Upconversion Detectors

Abstract

We present a scheme to estimate the noise equivalent power (NEP) of the frequency upconversion detectors (UCDs), detecting mid-infrared (MIR) light. The NEP of UCD is a combined contribution of NEPs from the upconversion process and from the photodetector, used for detecting the upconverted signal. The 2 − 5 µm MIR range is particularly investigated in this letter using a bulk periodically poled lithium niobate based CW-intracavity UCD. We measured the NEP of UCD as 20 fW/ √ Hz at MIR wavelength of 3.39 µm. We showed that the limiting factor here is not the noise from the upconversion process (estimated NEP is 2.3 fW/ √ Hz at 3.39 µm), but from the electrical noise in the photodetector itself. We also compared the performance of our UCD with previously published results and with market available direct MIR detectors. Additionally, we measured the optical noise of the UCD over its working spectral range (2.9 − 3.6 µm) and compared with numerical simulation.

Thermal camera based on frequency upconversion and its noise-equivalent temperature difference characterization

“…The NEP remains an important factor of inquiry in the discussion of system NETD. For an MIR detector based on frequency upconversion, the NEP expression can be written as follows based on previous research work: 22 NEP=σRprΔf=σRηupηdethνMIRΔf=σRhνMIRηupηdetΔf,where ηup is the upconversion process quantum efficiency, ηdet is the CMOS camera quantum efficiency, Δf is the noise bandwidth, σR is the total readout noise, and νMIR is the MIR optical frequency. In the upconversion frequency converter, the main sources of noise are the Stokes noise of the shortwave pump, crystal thermal noise, image photon noise, and detector readout noise.…”

“…In previous related work, the focus has often been on the evaluation of noise equivalent power. [21][22][23][24] This parameter is applicable to areas such as spectral detection, but is not intuitive enough for thermal imaging applications. The noise-equivalent temperature difference (NETD) is an important measure of the noise performance of conventional thermal imagers and is defined as the equivalent temperature difference between the target and the background when the signal-to-noise ratio of the image signal is 1.…”

Theoretical Investigation on the Mechanism and Law of Broadband Terahertz Wave Detection Using Rydberg Quantum State

“…In the free space of electromagnetic radiation, the power flux density (PFD) is the power per unit area perpendicular to the direction of electromagnetic wave propagation, and its unit is W/m 2 [40], represented here by S. For the plane wave, power flux density, electric field strength (E) and magnetic field intensity (H) and the free space of the inherent impedance:…”

Parametric upconversion imaging and its applications

“…Typically, higher upconversion efficiency improves the SNR. For detailed calculation steps of SNR and/or NEP see [106], [107]. By calculating or knowing the values of η, both isignal and σdet can be estimated.…”

“…Dam et al [45] demonstrated single-photon imaging at an IR range of 3 µm, where they estimated an up-noise as low as 0.2 photons/spatial element/sec in a PPLN based intracavity upconverter. Very recently, Pedersen et al [107] compared the NEP of an upconversion detector and a cooled HgCdTe detector in the 3 µm range. With their upconversion detector having an overall detection efficiency (upconversion module + silicon detector, ) of 2%, they obtained a NEP of 20 fW/Hz 1/2 at 3.39 µm, which is 50 times better than the state-of-theart cooled HgCdTe detector of much higher efficiency 66%.…”