A high power photodetection system for use with laser interferometric gravitational wave detectors

• Published in: Optics communications 2002-05, Vol.205 (4), p.405-413
• Main Authors: Jennrich, O., Newton, G., Skeldon, K.D., Hough, J.
• Format: Article
• Language: English
• Subjects: Astronomical and space-research instrumentation; Astronomy; Earth, ocean, space; Exact sciences and technology; Fundamental astronomy and astrophysics. Instrumentation, techniques, and astronomical observations; Gravitational radiation detectors; mass spectrometers; and other instrumentation and techniques; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Interferometers; Optical instruments, equipment and techniques; Physics; Spaceborne and space research instruments, apparatus and components (satellites, space vehicles, etc.)
• ISSN: 0030-4018; 1873-0310
• DOI: 10.1016/S0030-4018(02)01368-8

We report on an experiment to develop a high power, large bandwidth, infra-red photodetection system for use with radio frequency optical modulation schemes in the generation of gravitational wave detectors now being constructed. The incident light is split into 16 components by a configuration of 50:50 beam splitters and directed towards an array of InGaAs PIN photodiodes. The radio frequency output from the diodes is combined using ferrite loaded broad-band hybrid coaxial couplers together with coaxial transformers in a cascade, totem-pole, arrangement. The photodetection system has a very wide bandwidth, being shot noise limited to over 100 MHz in less than 150 mA of photocurrent. It has a photocurrent capability of up to 1.5 A which corresponds to an incident light power of about 2.3 W after optical losses are taken into account. The noise contribution from the photodiode array with bias applied is around 1.4×10 −21 W/ Hz .