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Silicon
Avalanche Photodiodes (APDs)
The
APD is a unique device that combines the advantages of solid
state photodetectors with those of high gain devices such
as photomultiplier tubes (PMTs). APDs have internal gain that
provides a high signal-to-noise ratio and have high quantum
efficiency. They are fast, compact and rugged, and these properties
make them suitable detectors for important applications such
as LADAR, detection and identification of toxic chemicals
and bio-warfare agents, LIDAR fluorescence detection, stand-off
laser induced breakdown spectroscopy (LIBS), and nuclear detectors
and imagers.
An APD is basically a diode
operated at a very high reverse bias. The physical mechanism
upon which avalanche gain depends, impact ionization, occurs
when the electric field is sufficiently strong so that an
electron colliding with a bound valence electron transfers
sufficient energy to ionize it. This creates an additional
electron-hole pair with obvious current gain.
| TECHNOLOGY/SPECIFICATIONS |
Features
- Gain above 1,000 at an operating condition of best signal-to-noise
ratio (Maximum gain of 10,000)
- Large active area
- High quantum efficiency (QE) extends beyond visible spectrum
- High speed at 1064 nanometer wavelength of YAG lasers
- Pulse counting mode is the most frequent style of use.
- Optical Photon Counting (2-3 photons) when cooled
Devices
| Type # |
Description |
| S0223 |
2 mm x 2 mm active area detector |
| S0814 |
8 mm x 8 mm active area detector |
| S1315 |
13 mm x13 mm active area detector |
| A1604 |
Array of 16 detector pixels. Pixels are
in a 4 x 4 pattern. Each pixel: 2 mm x 2 mm area, 2.48
mm pitch. |
| A6403 |
Array of 64 detector pixels. Pixels are
in an 8 x 8 pattern. Each pixel: 1 mm x 1 mm area, 1.27
mm pitch. |
Specifications
| Parameter |
Typical Value at 22°C |
| Gain (at optimal signal-to-noise ratio)
|
300 to 2000 |
| Capacitance |
0.7 pf/mm2 |
| Bias voltage (device is typically operated
at optimal signal-to-noise ratio) |
1650 to 1750 volts |
| QE at 400 nm |
50% |
| QE at 532 nm |
65% |
| QE at 830 to 905 nm |
75% |
| QE at 1064 nm |
20% |
| Type # |
S0223 |
S0814 |
S1315 |
A1604 |
A6403 |
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Nominal Active Area (if array, of pixel) (mm2)
|
4 |
64 |
169 |
4 |
1 |
|
Rise Time for a charged particle (ns)
|
< 1 |
< 1 |
< 1 |
< 1 |
< 1 |
| Rise Time at 532 nm (ns) |
5 |
8 |
10 |
5 |
5 |
| Rise Time at 1064 nm (ns) |
< 2 |
< 2 |
< 2 |
< 2 |
< 2 |
| Noise Equivalent Power, rms fW/(Hz)1/2 |
19 |
42 |
85 |
19 |
10 |
| Noise, FWHM eV |
200 |
450 |
900 |
200 |
100 |
Applications
- LIDAR, LADAR
- Medical Imaging: PET sensor provides both timing and
energy information
- High Energy Physics: Read-out of optical fibers
- Bio Sensors
- Telecommunications
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