Detection Methods

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Detection Methods

• Coherent ? Incoherent
• Photon Detection ? Bolometric
• Photon Counting ? Integrating

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Radio Telescopes

• Typical Designs
• Heterodyne Receivers

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Janskys First Radio Telescope 1933
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Grote Reber 1937 Radio Telescope
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The Arecibo Radio Telescope
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Heterodyne Receivers

• Mix signal and local oscillator
• Mixed signal contains
• intermediate frequency
• f_signal f_local
• but also the sum of the frequencies

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Heterodyne Signal Detection
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MM and Sub-MM Telescopes

• Use both coherent and incoherent detection
• Heterodyne receivers for emission-lines
• Mostly bolometers for continuum

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Millimeter Valley on Mauna Kea
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NGC 6334
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SMA Receivers
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Bolometers

• Absorb and thermalize photons
• Measure temperature change
• Balance between heating and cooling results in
  long time constants
• Typically used in chopped operation

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Transition Edge Sensors Extreme sensitivity to
small temperature changes allows to build very
sensitive bolometer arrays
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Photocathods

• The photoelectric effect
• Quantum nature of light
• Photomultipliers, channel plates

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Photocathod Devices

• Cathods
• Photomultiplier
• Image intensifiers
• Microchannel plates

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Physics of Semiconductors

• Basic Quantum Physics
• Solids
• Semiconductors
• PN Junctions

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Semiconductors

• Conduction in semiconductors
• Doping

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PN Junctions

• Formation of pn junction
• Rectifying properties
• Charge separating properties

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Electronics

• PN junctions and photodiodes
• Field Effect transistors
• Logic devices
• Analog switches
• Operational amplifiers
• A practical example

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Field Effect Transistor

• Junction FET (JFET)
• Metal-Oxide-Semiconductor FET (MOSFET)
• CMOS circuits (Complementary Oxide Semiconductor)

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Fabrication of Integrated Circuits

• Doping
• Depositing metal
• Growing oxides (as isolators)
• All controlled by photoresist masking

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HAWAII-2 Photolithographically Abut 4 CMOS
Reticles to Produce Each 20482 ROIC
Twelve 20482 ROICs per 8 Wafer
20482 Readout Provides Low Read Noise for Visible
and MWIR
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3-D Barrier to Prevent Glow from Reaching the
Detector
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