Amplified spontaneous emission

Source: Wikipedia, the free encyclopedia.

Amplified spontaneous emission (ASE) or superluminescence is

gain medium. It is inherent in the field of random lasers
.

Origins

ASE is produced when a

gain medium will be depleted by the incoherent ASE rather than by the desired coherent laser radiation. ASE is especially problematic in lasers with short and wide optical cavities, such as disk lasers (active mirrors).[1]

ASE can also be a desirable effect, finding use in broadband light sources. If the cavity has no optical feedback, lasing will be inhibited, resulting in a broad emission bandwidth due to the bandwidth of the gain medium. This results in low

Spatial coherence can be high, however, allowing for tight focusing of the radiation. These characteristics make such sources useful for fiber optic systems and optical coherence tomography. Examples of such sources include superluminescent diodes and doped fiber amplifiers
.

In organic dye lasers

ASE in pulsed organic dye lasers can have very broad spectral characteristics (as much as 40–50 nm wide) and presents, as such, a serious challenge in the design and operation of tunable narrow-linewidth dye lasers. In order to suppress ASE, in favor of pure laser emission, researchers use various approaches including optimized laser cavity designs.[2]

In disk lasers: Controversy

According to some publications, at the

power scaling of disk lasers, the round-trip gain should be reduced,[3] which means hardening[clarification needed] of requirement on the background loss. Other researchers believe the existing disk lasers work far from such a limit, and the power scaling can be achieved without modification of existing laser materials.[4]

In self healing dye doped polymers

In 2008, a group at Washington state university observed reversible photodegradation or simply, self healing in organic dyes like Disperse orange 11[5] when doped in polymers. They used amplified spontaneous emission as a probe to study self healing properties.[6]

In high-power short-pulse laser systems

In high-power CPA-laser systems with a peak power of several terawatt or petawatt, e.g. the POLARIS laser system, the ASE limits the temporal intensity contrast. After the compression of the laser pulse, which is temporally stretched during the amplification, the ASE causes a quasi-continuous pedestal which is partly located at times before the compressed laser pulse.[7] Due to the high intensities within the focal spot of up to 10^22 W/cm2 the ASE is often sufficient to significantly disturb the experiment or even make the desired laser-target interaction impossible.

See also

References

  1. doi:10.1364/JOSAB.22.001605
    .
  2. ISBN 978-0-12-222700-4
    .
  3. doi:10.1364/JOSAB.23.001074. Retrieved 2007-01-26.; [1][permanent dead link
    ]
  4. S2CID 121158745
    .
  5. ^ http://www.sigmaaldrich.com/catalog/ProductDetail.do?D7=0&N5=SEARCH_CONCAT_PNO%7CBRAND_KEY&N4=217093%7CSIAL&N25=0&QS=ON&F=SPEC Archived January 19, 2012, at the Wayback Machine
  6. ^ Natnael B. Embaye, Shiva K. Ramini, and Mark G. Kuzyk, J. Chem. Phys. 129, 054504 (2008) https://arxiv.org/abs/0808.3346
  7. PMID 27134684
    .
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