Henry H. Hogue

Multiphoton detection using visible light photon counter

Visible light photon counters feature noise-free avalanche multiplication and narrow pulse height distribution for single photon detection events. Such a well-defined pulse height distribution for a single photon detection event, combined with the fact that the avalanche multiplication is confined to a small area of the whole detector, opens up the possibility for the simultaneous detection of two photons. In this letter, we investigated this capability using twin photons generated by parametric down conversion, and present a high quantum efficiency (∼47%) detection of two photons with good time resolution (∼2 ns), which can be distinguished from a single-photon incidence with a small bit-error rate (∼0.63%).

Development of a high-quantum-efficiency single-photon counting system

A high-quantum-efficiency single-photon counting system has been developed. In this system, single photons were detected by a visible light photon counter operated at 6.9 K. The visible light photon counter is a solid state device that makes use of avalanches across a shallow impurity conduction band in silicon. Threefold tight shielding and viewports that worked as infrared blocking filters were used to eliminate the dark count caused by room-temperature radiation. Corrected quantum efficiencies as high as 88.2%±5% (at 694 nm) were observed, which we believe is the highest reported value for a single-photon detector. The dark count increased as the exponential of the quantum efficiency with changing temperature or bias voltage, and was 2.0×104 cps at the highest quantum efficiency.

Noise-free avalanche multiplication in Si solid state photomultipliers

Si solid state photomultipliers utilize impact ionization of shallow impurity donor levels to create an avalanche multiplication when triggered by a photoexcited hole. The distribution of pulse height from a single photon detection event shows narrow dispersion, which implies that the avalanche multiplication process in these devices is inherently noise-free. We have measured the excess noise factor using two different techniques, digital pulse height analysis and analog noise power measurement. The results demonstrate nearly noise-free avalanche multiplication accomplished in these devices.

Single-Photon Detection Timing Jitter in a Visible Light Photon Counter

Visible light photon counters (VLPCs) offer many attractive features as photon detectors, such as high quantum efficiency and photon number resolution. We report measurements of the single-photon timing jitter in a VLPC, a critical performance factor in a time-correlated single-photon counting measurement, in a fiber-coupled closed-cycle cryocooler. The measured timing jitter is 240 ps full-width-at-half-maximum at a wavelength of 550 nm, with a dark count rate of 25×103 counts per second. The timing jitter increases modestly at longer wavelengths to 300 ps at 1000 nm, and increases substantially at lower bias voltages as the quantum efficiency is reduced.

Space mid-IR detectors from DRS

The Blocked Impurity Band (BIB) detector was invented in the early 1980s and subsequently developed by our team. The original arsenic-doped silicon (Si:As) detectors addressed the need for low-noise, radiation-tolerant, mid-IR detectors for defense surveillance from space. We have since developed large-format BIB focal plane arrays to address high-background requirements of ground-based telescopes and missile interceptors, low-background requirements of the Space Infrared Telescope Facility (SIRTF), and very low background requirements of the mid-IR instruments for the Next Generation Space Telescope (NGST) and Terrestrial Planet Finder. Most of these applications employ Si:As BIB detectors, but antimony-doped silicon (Si:Sb) BIB detectors are used for some SIRTF bands. Other demonstrated types including phosphorus (Si:P) and gallium-doped (Si:Ga) BIB detectors may have application niches. We have proposed development of a BIB detector type utilizing both Si:As and Si:P layers to optimize dark current vs. wavelength performance. Wavelength response for silicon BIB detectors extend to a maximum of ~40 microns (Si:Sb), but we have also demonstrated germanium BIB detectors for wavelengths extending to several hundred microns. We are currently developing germanium BIB detector arrays for astrophysics applications, including space telescopes beyond NGST.

Enhanced quantum efficiency of the visible light photon counter in the ultraviolet wavelengths

The visible light photon counter (VLPC) is a very high quantum efficiency (QE, 88% at 694 nm) single photon detector in the visible wavelengths. The QE in the ultraviolet (UV) wavelenghths is poor in these devices due to absorption in the degenerate front contact. We introduce the ultraviolet photon counter (UVPC), where the QE in the near UV wavelength range (300-400 nm) is dramatically enhanced. The degenerate Si front contact of the VLPC is replaced with a Ti Schottky contact, which reduces the absorption of incident photons within the contact layer. We demonstrate a system QE of 5.3% at 300 nm and 11% at 370 nm for a UVPC with a Ti Schottky contact and a single layer MgF(2) antireflection coating.

Update on blocked impurity band detector technology from DRS

The Blocked Impurity Band (BIB) detector technology team at DRS Sensors and Targeting Systems specializes in providing the highest performance, broadest application range of BIB detector products. These include detectors, Focal Plane Arrays (FPA), and sensor assemblies for ground, airborne and space applications. We offer flight proven low flux Si:As and Si:Sb FPAs in square formats up to 1024x1024. We also offer high-flux FPA systems for ground-based telescopes and airborne applications in several square and rectangular formats, such as 160×640 sensors for push-broom spatial-spectral imaging. NASAs Wide-field Infrared Survey Explorer mission selected DRS 1024×1024 arrays for its the 12 and 24 micron wavelength bands. The Spitzer Space Telescope utilizes DRS 128×128 Si:As and Si:Sb FPAs, and 1024×1024 Si:Sb arrays are being fabricated by DRS for an upgrade to the SOFIA FORCAST instrument. DRS is unique in providing detectors and FPAs in alternate detector materials such as Si:Sb, Si:Ga, and Si:P to optimize wavelength range vs operating temperature. Sensor assemblies include detectors or FPAs packaged with cryogenic cabling and electronics and ambient temperature drive and data acquisition electronics--fully tested, and environmentally qualified. DRS is also unique in extending its conventional BIB detector product line to include novel detector architectures for a variety of applications. Si:As detectors with avalanche gain (~40,000X) function as number-mode photon counters at visible or mid-infrared wavelengths. A recent DRS innovation is the extension of Si:As BIB detectors designs to achieve wavelength extension into the far-infrared (low THz) wavelength region. Wavelength extension to ~50 microns (6 THz) has been demonstrated, with further extension to at least ~100 microns (3 THz) in progress.

Characterization of flight detector arrays for the wide-field infrared survey explorer

The Wide-field Infrared Survey Explorer is a NASA Midex mission launching in late 2009 that will survey the entire sky at 3.3, 4.7, 12, and 23 microns (PI: Ned Wright, UCLA). Its primary scientific goals are to find the nearest stars (actually most likely to be brown dwarfs) and the most luminous galaxies in the universe. WISE uses three dichroic beamsplitters to take simultaneous images in all four bands using four 1024×1024 detector arrays. The 3.3 and 4.7 micron channels use HgCdTe arrays, and the 12 and 23 micron bands employ Si:As arrays. In order to make a 1024×1024 Si:As array, a new multiplexer had to be designed and produced. The HgCdTe arrays were developed by Teledyne Imaging Systems, and the Si:As array were made by DRS. All four flight arrays have been delivered to the WISE payload contractor, Space Dynamics Laboratory. We present initial ground-based characterization results for the WISE arrays, including measurements of read noise, dark current, flat field and latent image performance, etc. These characterization data will be useful in producing the final WISE data product, an all-sky image atlas and source catalog.

Opportunities for single-photon detection using visible light photon counters

Visible light photon counters (VLPCs) are solid-state devices providing high quantum efficiency (QE) photon detection (>88%) with photon number resolving capability and low timing jitter (~250 ps). VLPC features high QE in the 0.4-1.0μm wavelength range, as the main photon absorption mechanism is provided by electron-hole pair generation across the silicon bandgap. In this paper, we will discuss the optical and electrical operating principles of VLPCs, and propose a range of device optimization paths that improves various aspects of VLPC for advanced quantum optics and quantum information processing experiments, both in the UV and the telecom wavelength range.

Characterization of a megapixel mid-infrared array for high background applications

Our group has developed the first 1024×1024 high background Si:As detector array, the Megapixel Mid-Infrared array (MegaMIR). MegaMIR is designed to meet the thermal imaging and spectroscopic needs of the ground-based and airborne astronomical communities. MegaMIR was designed with switchable capacitance and windowing capability to allow maximum flexibility. We report initial test results for the new array.