RP Photonics logo
VL logo part of the
Virtual
Library

Encyclopedia of Laser Physics and Technology

Integrating Spheres

previous  |  next  |  feedback

Definition: devices with a diffusely reflecting inner surface, used for certain optical measurements

integrating sphere

Figure 1: Integrating sphere for measuring optical powers independent of the spatial beam properties.

An integrating sphere (also called Ulbricht sphere) is an optical device for various purposes such as measuring the optical flux from a laser diode, light-emitting diode (LED) or bulb, or measuring scattering losses from a surface. It is a hollow sphere with a diffusely reflecting internal surface, typically two or more small openings (ports) for introducing light or attaching a photodetector, and often some so-called baffles, which are light barriers used to prevent direct illumination of a detector by a light source. The arrangement causes many diffuse reflections of the introduced light before it reaches a detector, so that the light flux becomes very uniform at the detector, and nearly independent of the spatial and polarization properties of the introduced light: the detected optical power depends only on the total introduced power. In that way, the total output power of a laser diode can be measured, even if the beam divergence is fairly large.

Apart from such measurement purposes, an integrating sphere can be used to illuminate a device very uniformly. This can be important e.g. for testing the homogeneity of digital imaging equipment (e.g. CCD arrays).

Ideally, the coating on the inner side of the integrating sphere has a very high reflectivity over the required wavelength range, and the reflection is very diffuse. If the optical losses in the sphere and through the small ports are low, the multiple reflections can lead to a fairly high optical intensity inside the sphere and consequently to a high optical efficiency, even if the sphere is much larger than the light source and the detector.

See also: photodetectors

Categories: metrology, photonic devices


cover of print encyclopedia

Since October 2008, the Encyclopedia of Laser Physics and Technology is also available in the form of a two-volume book. Maybe you would enjoy reading it also in that form! The print version has a carefully designed layout and can be considered a must-have for any institute library, laser research group, or laser company.

You may order the print version via Wiley-VCH.

arrow
Home New articles Spotlight Feedback Advertising
Categories Search Quiz Glossary Page hits
I

This encyclopedia is provided by
RP Photonics Consulting GmbH.

You can get technical consulting from the author, Dr. Rüdiger Paschotta.

EKSMA logo

EKSMA Optics

Supplier of laser components, including optics, laser crystals and optomechanics.

A.L.S. logo

A.L.S. GmbH

Picosecond laser diodes
<30 ps, 375 – 1600 nm, >1 Wp, single shot – 120 MHz

Onefive logo

Onefive

Low-noise
femtosecond,
picosecond,
and tunable single-frequency lasers for OEM and R&D applications.

RP Fiber Power 2.0

RP Fiber Power

This software is a powerful tool for designing fiber amplifiers and fiber lasers.
See the comprehensive description!

Your Advertisement at This Place

will be seen by many thousands of visitors per month. These banners receive far over 100'000 page hits per month. Check the details.