41. At each point the transmitted X-rays are recorded with a detector such as a proportional counter or an avalanche photodiode . 42. Fifteen years later in 1998, this structure was further developed and named the UTC, or uni-travelling carrier photodiode . 43. This beat signal, detectable with a photodiode , includes a difference frequency component, which is the carrier envelope offset frequency. 44. This development was spurred by the discovery of Indium gallium arsenide and the development of the Indium Gallium Arsenide photodiode by Pearsall. 45. Typical transmission of the probe beam as recorded on the photodiode for Rubidium 85 as a function of the laser's wavelength 46. Due to photodiode noise, the laser frequency can be swept across the transition and the photodiode reading averaged over many sweeps. 47. Due to photodiode noise, the laser frequency can be swept across the transition and the photodiode reading averaged over many sweeps. 48. Opto-isolators use an LED combined with a photodiode or phototransistor to provide a signal path with electrical isolation between two circuits. 49. Various detectors are in common use, such as UV / Vis, photodiode array ( PDA ) or based on mass spectrometry. 50. When the photodiode is reverse-biased with an external voltage source, incoming light increases the reverse current flowing through the diode.
