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Photodiodes. Photons incident on the depletion layer induce a current. In most cases, best response in the NIR. Response is linear over 6 – 7 orders of incident radiant power. Ingle and Crouch, Spectrochemical Analysis. Spectral Response of Photodiodes.
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Photodiodes Photons incident on the depletion layer induce a current. In most cases, best response in the NIR. Response is linear over 6 – 7 orders of incident radiant power Ingle and Crouch, Spectrochemical Analysis
Spectral Response of Photodiodes Shinya Inoue and Kenneth Spring, Video Microscopy, Plenum Press, New York, 1997.
Avalanche Photodiode Hamamatsu Catalog http://micro.magnet.fsu.edu/primer/java/digitalimaging/avalanche/index.html
Photodiode Arrays (PDA or DAD) Simultaneous detection in a spectrophotometer. Douglas A. Skoog and James J. Leary, Principles of Instrumental Analysis, Saunders College Publishing, Fort Worth, 1992.
Charge Coupled Device (CCD) Ingle and Crouch, Spectrochemical Analysis www.piacton.com
CCD Architecture SiO2 backing Pixel Array Image Area serial register amplifier http://micro.magnet.fsu.edu/primer/digitalimaging/concepts/ccdanatomy.html and Bryce Marquis (Haynes Lab)
CCD Architecture “Channel Stops” form horizontal pixel boundaries Top View 3 electrodes form vertical pixel boundaries One pixel Electrode Insulating oxide n-type silicon p-type silicon Cross section Bryce Marquis (Haynes Lab)
Charge Generation/Collection -V +V -V -V +V -V N-type P-type Incident photons excite electron-hole pairs, electrons gather in potential wells in each pixel
CCD Rain Bucket Analogy • 1. Generation • 2. Collection • 3. Transfer • 4. Measurement Shinya Inoue and Kenneth Spring, Video Microscopy, Plenum Press, New York, 1997.
Charge Generation/Collection -V +V -V -V +V -V N-type silica is doped with pentavalent species = excess electrons P-type is doped with trivalent species = excess holes N-type Potential Well P-type One Pixel
1 2 1 2 3 3 Charge Transfer +5V 0V -5V Every third electrode is coupled, charge packets are walked towards serial registry +5V 0V -5V +5V 0V -5V to serial registry Time-slice shown in diagram http://spiff.rit.edu/classes/phys445/lectures/ccd1/ccd1.html
1 2 1 2 3 3 +5V 0V -5V +5V 0V -5V +5V 0V -5V http://spiff.rit.edu/classes/phys445/lectures/ccd1/ccd1.html
1 2 1 2 3 3 +5V 0V -5V +5V 0V -5V +5V 0V -5V http://spiff.rit.edu/classes/phys445/lectures/ccd1/ccd1.html
1 2 1 2 3 3 +5V 0V -5V +5V 0V -5V +5V 0V -5V http://spiff.rit.edu/classes/phys445/lectures/ccd1/ccd1.html
1 2 1 2 3 3 +5V 0V -5V +5V 0V -5V +5V 0V -5V http://spiff.rit.edu/classes/phys445/lectures/ccd1/ccd1.html
1 2 1 2 3 3 +5V 0V -5V +5V 0V -5V +5V 0V -5V http://spiff.rit.edu/classes/phys445/lectures/ccd1/ccd1.html
1 2 1 2 3 3 +5V 0V -5V +5V 0V -5V +5V 0V -5V http://spiff.rit.edu/classes/phys445/lectures/ccd1/ccd1.html
Charge Transportation • Pixels at end of the array dump charge into serial register • Serial register walks charge packets to amplifier, where it is measured. amplifier
Quantum Efficiency www.piacton.com
Noise Sources in CCD • Shot Noise • Statistical variation of signal over time • Increases with the square of the intensity • Dark Signal Noise • Caused by thermal liberation of electrons • Strongly coupled to temperature • Readout Noise • Summation of noise associated with amplification of signal, and conversion from analogue to digital • Increases with the processing speed
Other Issues: Bad Pixels Increasing hot pixels • Hot Pixels • Increased charge accumulation due to variations in chip surface. • Dead Pixels • Defective pixels that do not respond.
Other Issues: Cosmic Rays Noise From Outer Space!!! * indicates cosmic rays
Other Issues: Etaloning Etaloning www.piacton.com
Other Features: Binning • On Chip Pixel Binning • Increases S/N • Shot noise decrease • Increased speed • Less storage space needed • Decreases resolution http://micro.magnet.fsu.edu/primer/digitalimaging/concepts/binning.html
Are you getting the concept? List the advantages and disadvantages of using each of the discussed detectors to achieve single molecule detection.