Detectors InGaAs

Optical receiver noise can arise partly from fundamental photon noise and partly from thermal noise in the receiver circuit. For CO2 detection, it was assumed that the optical receiver was an extended InGaAs detector, followed... 

Figure 24.8 Experimental schematic of the multiplexed diode-laser sensor system used to measure CO, CO2, CH4, and H2O absorption by sampling hot combustion gases 1 ECDL 1.49-1.58 pm 2 optical isolator 3 — fiber coupler 4 — 1x2 fiber splitter 5 — etalon 6 — InGaAs detector 7 — DEB 1.65 pm 8 — 2 x 1 fiber combiner 9 optical fiber 10 fiber pitch 11 — concave mirror 12 — multipass...

Figure 24.10 Schematic diagram of the combustion-control experiment at China Lake 1 — primary air 2 — primary air driver sin(27r/ot) 3 — pyrolysis gases N2 -h C2H4 4 — secondary air 5 — secondary air drivers sin(27r/ot- -0) 6 — demultiplexing box 7 — sampling probe 8 — multipass fast-sample cell (36-meter path) 9 — InGaAs detector 10 — multiplexed beam and 11 — data acquisition and control computer...

Several other detectors are available for use in the near-IR. Cooled PbS, Ge, InGaAs, InSb, and platinum silicide have been investigated as detectors for use in FT-Raman. Present commercial instrumentation uses an InGaAs detector. For a discussion on detectors for use in FT-Raman, see Refs. 5 and 9. 

Figure 24.14 The left panel is a plan of the testing area near the LENS (reflected shock) tunnel 1 — 8 test section 2 — TDL probe 3 — 4 nozzle M = 8-16 4 — 8" reflected shock tube 5 — fiber optic and signal line conduit 6 — data acquisition and 7 — TDL system optical table. The right panel is a schematic diagram of the setup used to record water-vapor absorption in high-enthalpy flows 1 — InGaAs detectors 2 — tunable diode laser Ai = 1400.74 nm 3 — ring interferometer 4 — tunable diode laser A2 = 1395.69 nm and 5 — HoO reference cell...

The most common detectors in IR are thermal, i.e. thermocouples, thermistors and bolometers. A thermocouple is based on the use of two different conductors connected by a junction. When a temperature difference is experienced at the junction, a potential difference can be measured. A series of thermocouples together is called a thermopile. Thermistors and bolometers are based on a change in resistance with temperature. They have a faster response time than thermocouples. With a Fourier Transform IR (FTIR), where rapid response and improved sensitivity is key, lead sulflde and InGaAs detectors are used as for NIR. Some arrays are also used. 

Upon transiting the boiler, the beams entered the detector optics enclosure, also mounted to a flange on the boiler. Here the beams were separated using a beam splitter and passed through interference filters to reduce background radiation and crossfalk befween fhe two channels. The 1.56 and 0.813 pm beams were then directed to a thermoelectrically cooled InGaAs detector and uncooled silicon photodiode, respectively. 

The conventional Raman spectra were obtained on a Perkin Elmer 2000 NIR-FT Raman spectrometer equipped with an InGaAs detector. The lasing medium was an Nd-YAG crystal pumped by a high-pressure krypton lamp, resulting in an excitation wavelength of 1064 run (9385 cm ). The power output was ca. 1000 mW. Samples were examined as such or contacted with solutions. 

InGaAs detector Big. 9.28 NIR transmission through a blend wafer. 

Transmission, mid-IR cw-spectra of GP were obtained by employing KBr pellets with GP powder homogenously embedded in the pellets. Reflectance NIR spectra of GP were obtained from purified powders (without KBr) on a Perkin-Elmer Spectrum ONE NTS spectrometer equipped with an integrating sphere and an extended-range InGaAs detector. 

Photomultiplier tubes and CCD detectors are the dominant detectors for Raman spectroscopy. Less common detectors include avalanche photodiodes for specialized applications in the near-infrared, single element photovoltaic detectors such as germanium or InGaAs detectors for FT-Raman measurements, and single element silicon photovoltaic detectors for stimulated Raman measurements. 

This is beyond the detection range of the materials used in array detectors. The detector for an NIR-laser-based FT-Raman systan is a liquid nitrogen-cooled photoconductive detector such as Ge or InGaAs. InGaAs detectors that do not require cooling are also available. 

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