RP Photonics logo
VL logo part of the
Virtual
Library

Encyclopedia of Laser Physics and Technology

Enhancement Cavities

previous  |  next  |  feedback
Ask RP Photonics for advice on how to design an enhancement cavity, including the automatic feedback system to keep it resonant with the laser.

Definition: optical cavities for exploiting the resonant enhancement of the power of circulating light

An enhancement cavity is an optical cavity (resonator) which is used for resonant enhancement of an optical power or intensity: if the incident light is resonant with the cavity and is mode-matched to it, the intracavity power can be far above the incident power, particularly for a cavity with high finesse.

monolithic frequency doubler

Figure 1: Monolithic resonant frequency doubler with dielectric coatings on the curved end faces.

An enhancement resonator can contain other optical components. For example, a nonlinear crystal can be used for efficient nonlinear frequency conversion, such as frequency doubling [1] or sum frequency generation. As an example, Figure 1 shows a monolithic frequency doubler, as described more in detail in Ref. [5]. It consists of a nonlinear crystal with dielectric coatings on the end faces which make the pump wave (red) resonant. Frequency-doubled light is extracted on the right-hand side. Even if the nonlinear process converts only a small fraction of the circulating optical power, the resonator allows for a kind of recycling of the unused light. The conversion can be very efficient if impedance matching is achieved, i.e. if the input mirror transmission equals all other resonator losses.

Frequency doubling can be efficient at even significantly lower powers (a few milliwatts) by using a doubly resonant scheme, where both pump wave and second-harmonic wave are resonant. However, the double resonance is usually delicate to maintain.

Resonant doubling should not be confused with intracavity frequency doubling, where the nonlinear crystal is placed within the laser cavity, so that there is no need for a separate resonant cavity.

Conditions for Efficient Resonant Enhancement

For efficient operation of an enhancement cavity, several factors have to be considered:

Enhancement Cavities for Mode-locked Lasers

Enhancement cavities are often applied in conjunction with single-frequency lasers, but can also be used with mode-locked lasers. In the latter case, the cavity length has to be chosen such that the cavity round-trip time is an integer multiple of the pulse spacing. In other words, the free spectral range of the cavity must be an integer multiple of the laser's pulse repetition rate, so that all lines of the laser output (→ frequency combs) can be simultaneously resonant. Also, the intracavity chromatic dispersion and nonlinearity should not be too strong [6].

Bibliography

[1]A. Ashkin, G. D. Boyd, and J. M. Dziedzic, “Resonant optical second harmonic generation and mixing”, IEEE J. Quantum Electron. QE-2, 109 (1966)
[2]B. Couillaud, T. W. Hänsch and S. G. MacLean, “High power CW sum-frequency generation near 243 nm using two intersecting enhancement cavities”, Opt. Commun. 50, 127 (1984)
[3]Z. Y. Ou and H. J. Kimble, “Enhanced conversion efficiency for harmonic-generation with double-resonance”, Opt. Lett. 18 (13), 1053 (1993)
[4]K. Fiedler et al., “Highly efficient frequency-doubling with a doubly resonant monolithic total-internal-reflection ring resonator”, Opt. Lett. 18 (21), 1786 (1993)
[5]R. Paschotta et al., “82% efficient continuous-wave frequency doubling of 1.06 μm with a monolithic MgO:LiNbO3 resonator”, Opt. Lett. 19 (17), 1325 (1994)
[6]K. D. Moll et al., “Nonlinear dynamics inside femtosecond enhancement cavities”, Opt. Express 13 (5), 1672 (2005)

See also: cavities, nonlinear frequency conversion, resonant frequency doubling, intracavity frequency doubling

Categories: photonic devices, resonators


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
E

This encyclopedia is provided by
RP Photonics Consulting GmbH.

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

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!

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.

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.