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

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

Detection Methods Coherent ↔ Incoherent Photon Detection ↔ Bolometric Photon Counting ↔ Integrating

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 …

Detection Methods Coherent ↔ Incoherent Photon Detection ↔ Bolometric Photon Counting ↔ Integrating

Photocathod Devices Cathods Photomultiplier Image intensifiers Microchannel plates

In 1907 Joel Stebbins pioneered the use of photoelectric devices in Astronomy

Photomultiplier tubes: pile up errors Each detected photon produces a pulse of finite duration, t 0, which causes a dead time in the detector. The number of pulses (exposure time) is reduced by the amount of overlapping deadtimes. N = n/(1–t 0 n) N is the true rate, and n the apparent rate Pile-up errors System blocks completely at high light levels

1840 J.W. Draper makes a photograph of the moon. Followed by photographs of the Sun by Foucault and Fizeau Sunspots photographed in 1858 by W. De La Rue Jansen and Lockyer in the 1870s photographed the solar spectrum and discovered the spectral lines of Helium. Ainsee Common photographed Orion Nebula and these revealed stars and details you could not see in a telescope Photographs by Hubble in the early 1900‘s established that some nebula where „island universes“ (i.e. galaxies). His spectral observations of galaxies (exposures of more than one night) led to the discovery of the expansion of the Universe. For 100 years photographic plates/film dominated the field of astronomical detectors. A Revolution in Detectors: Photographic Plates

Detection Methods Coherent ↔ Incoherent Photon Detection ↔ Bolometric Photon Counting ↔ Integrating

Physics of Semiconductors Basic Quantum Physics Solids Semiconductors PN Junctions

Semiconductors Conduction in semiconductors Doping

Detection Methods Coherent ↔ Incoherent Photon Detection ↔ Bolometric Photon Counting ↔ Integrating

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 ROIC Twelve ROICs per 8” Wafer Readout Provides Low Read Noise for Visible and MWIR

3-D Barrier to Prevent Glow from Reaching the Detector