Transcript Slide 1
Detection Methods • Coherent ↔ Incoherent • Photon Detection ↔ Bolometric • Photon Counting ↔ Integrating Radio Telescopes • Typical Designs • Heterodyne Receivers Jansky’s First Radio Telescope 1933 Grote Reber: 1937 Radio Telescope The Arecibo Radio Telescope Heterodyne Receivers • Mix signal and local oscillator • Mixed signal contains “intermediate frequency” f_signal – f_local but also the sum of the frequencies Heterodyne Signal Detection MM and Sub-MM Telescopes • Use both coherent and incoherent detection • Heterodyne receivers for emission-lines • Mostly bolometers for continuum Millimeter Valley on Mauna Kea NGC 6334 SMA Receivers Bolometers • Absorb and thermalize photons • Measure temperature change • Balance between heating and cooling results in long time constants • Typically used in chopped operation Transition Edge Sensors: Extreme sensitivity to small temperature changes allows to build very sensitive bolometer arrays Photocathods • The photoelectric effect • Quantum nature of light • Photomultipliers, channel plates … Photocathod Devices • • • • Cathods Photomultiplier Image intensifiers Microchannel plates Physics of Semiconductors Basic Quantum Physics Solids Semiconductors PN Junctions Semiconductors • Conduction in semiconductors • Doping PN Junctions • Formation of pn junction • Rectifying properties • Charge separating properties Electronics • • • • • • PN junctions and photodiodes Field Effect transistors Logic devices Analog switches Operational amplifiers A practical example Field Effect Transistor • Junction FET (JFET) • Metal-Oxide-Semiconductor FET (MOSFET) • CMOS circuits (Complementary Oxide Semiconductor) Fabrication of Integrated Circuits • • • • Doping Depositing metal Growing oxides (as isolators) All controlled by photoresist masking HAWAII-2: Photolithographically Abut 4 CMOS Reticles to Produce Each 20482 ROIC Twelve 20482 ROICs per 8” Wafer Submicron Stepper Options Canon 16mm x 14 mm GCA 20mm x 20 mm ASML 22mm x 27.4 mm Reticle-Stitching: 2048x2048 ROIC 20482 Readout Provides Low Read Noise for Visible and MWIR 3-D Barrier to Prevent Glow from Reaching the Detector p-type HgCdTe Detector n+ Indium Interconnect L o w -N o is e C M O S M u ltip le x e r Overglass Metal 3 Analog Capacitor Metal 2 Metal 1 Poly 1 CMOS (LOCOS)