Streak camera

From Wikipedia, the free encyclopedia
Jump to: navigation, search
For other uses, see Streak.

A streak camera is an instrument for measuring the variation in a pulse of light's intensity with time. They are used to measure the pulse duration of some ultrafast laser systems and for applications such as time-resolved spectroscopy and LIDAR.

Operation[edit]

A streak camera operates by transforming the temporal profile of a light pulse into a spatial profile on a detector, by causing a time-varying deflection of the light across the width of the detector. In particular, a light pulse enters the instrument through a narrow slit along one direction. It then gets deflected in the perpendicular direction so that photons that arrive first hit the detector at a different position compared to photons that arrive later.[1]

The resulting image forms a "streak" of light, from which the duration, and other temporal properties, of the light pulse can be inferred. Usually, in order to record periodic phenomena, a streak camera needs to be triggered accordingly, similarly to an oscilloscope.

Mechanical types[edit]

Mechanical streak cameras use a rotating mirror or moving slit system to deflect the light beam. They are limited in their maximum scan speed and thus temporal resolution.

Optoelectronic type[edit]

Optoelectronic streak cameras work by directing the light onto a photocathode, which when hit by photons produces electrons via the photoelectric effect. The electrons are accelerated in a cathode ray tube and pass through an electric field produced by a pair of plates, which deflects the electrons sideways. By modulating the electric potential between the plates, the electric field is quickly changed to give a time-varying deflection of the electrons, sweeping the electrons across a phosphor screen at the end of the tube. A linear detector, such as a charge-coupled device (CCD) array is used to measure the streak pattern on the screen, and thus the temporal profile of the light pulse. [2]

The time-resolution of the best optoelectronic streak cameras is around 100 femtoseconds[citation needed] [3] . Measurement of pulses shorter than this duration requires other techniques such as optical autocorrelation and frequency-resolved optical gating (FROG).

In December 2011, a team at MIT released images combining the use of a streak camera with repeated laser pulses to simulate a movie with a frame rate of one trillion frames per second.[4]

See also[edit]

References[edit]

  1. ^ "Hamamatsu: Interactive Java Tutorials - Streak Camera". Retrieved 2006-10-15. 
  2. ^ "Guide to streak cameras". Retrieved 2011-12-14. 
  3. ^ Akira Takahashi et al.: "New femtosecond streak camera with temporal resolution of 180 fs" Proc. SPIE 2116, Generation, Amplification, and Measurement of Ultrashort Laser Pulses, 275 (May 16, 1994); http://dx.doi.org/10.1117/12.175863
  4. ^ "MIT's trillion frames per second light-tracking camera". BBC News. 2011-12-13. Retrieved 2011-12-14.