High performance terahertz imaging devices have drawn wide attention due to their significant application in healthcare, security of food and medicine, and nondestructive inspection, as well as national security applications. Here we demonstrate a broadband terahertz photon-type up-conversion imaging device, operating around the liquid helium temperature, based on the gallium arsenide homojunction interfacial workfunction internal photoemission (HIWIP)-detector-LED up-converter and silicon CCD. Such an imaging device achieves broadband response in 4.2–20 THz and can absorb the normal incident light. The peak responsivity is 0.5 AW −1 . The light emitting diode leads to a 72.5% external quantum efficiency improvement compared with the one widely used in conventional up-conversion devices. A peak up-conversion efficiency of 1.14 × 10 −2 is realized and the optimal noise equivalent power is 29.1 pWHz −1/2 . The up-conversion imaging for a 1000 K blackbody pin-hole is demonstrated. This work provides a different imaging scheme in the terahertz band.
High-performance terahertz (THz) detectors are in great need in the applications of security, medicine, as well as in astronomy. A high responsivity p-GaAs homojunction interfacial workfunction internal photoemission (HIWIP) detector was demonstrated for a specific frequency (5 THz) below the frequency of the Reststrahlen band. The experimental results indicate that the optimized detector shows significant enhancement of the response below the Reststrahlen band in contrast to the conventional detectors. With the bottom gold layer serving as a perfect reflector, nearly 50% increment of responsivity and quantum efficiency was obtained further due to the cavity effect. Though very simple, such reflector design shows a satisfactory effect and is easy to be realized in practical applications. The resultant peak responsivity of the detector with a bottom reflector could be as high as 6.8 A/W at 1 V bias. The noise equivalent power is 2.3×10−12W/Hz1/2. Due to the absorption ability to normal incident light and high responsivity, the p-GaAs HIWIP detector is promising for the focal plane array and large-scale pixelless imaging applications.
High performance single photon detector at the wavelength of 1550 nm has drawn wide attention and achieved vast improvement due to its significant application in quantum information, quantum key distribution, as well as cosmology. A novel infrared up-conversion single photon detector (USPD) at 1550 nm was proposed to work in free-running regime based on the InGaAs/ InP photodetector (PD)- GaAs/AlGaAs LED up-converter and Si single photon avalanche diode (SPAD). In contrast to conventional In0.53Ga0.47As SPAD, the USPD can suppress dark count rate and afterpulsing efficiently without sacrificing the photon detection efficiency (PDE). A high PDE of ~45% can be achieved by optical adhesive coupling between up-converter and Si SPAD. Using a developed analytical model we gave a noise equivalent power of 1.39 × 10−18 WHz1/2 at 200 K for the USPD, which is better than that of InGaAs SPAD. This work provides a new single photon detection scheme for telecom band.
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