Detection Methods

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 PhysicsSolids

SemiconductorsPN 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

20482 Readout Provides Low Read Noise for Visible and MWIR

Canon 16mm x 14 mmGCA 20mm x 20 mm

ASML 22mm x 27.4 mmReticle-Stitching: 2048x2048 ROIC

Submicron Stepper Options

3-D Barrier to Prevent Glow from Reaching the Detector

Metal 1

Metal 2

Metal 3

Poly 1

Analog Capacitor

Low

-Noi

se C

MO

S M

ultip

lexe

r

p-type

n+

HgCdTeDetector

IndiumInterconnect

Overglass

CMOS (LOCOS)