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Optical Parametric Oscillators

Acronym: OPO

Definition: coherent light sources based on parametric amplification within an optical resonator

German: optische parametrische Oszillatoren

Categories: nonlinear optics, photonic devices

How to cite the article; suggest additional literature

An optical parametric oscillator (OPO) [1, 2] is a light source similar to a laser, also using a kind of laser resonator, but based on optical gain from parametric amplification in a nonlinear crystal rather than from stimulated emission. Like a laser, such a device exhibits a threshold for the pump power, below which there is negligible output power (only some parametric fluorescence).

optical parametric oscillator
Figure 1: Schematic of an optical parametric oscillator.

A main attraction of OPOs is that the signal and idler wavelengths, which are determined by a phase-matching condition, can be varied in wide ranges. Thus it is possible to access wavelengths (e.g. in the mid-infrared, far-infrared or terahertz spectral region) which are difficult or impossible to obtain from any laser, and wide wavelength tunability (often by affecting the phase-matching condition) is also often possible. This makes OPOs very valuable, for example, for laser spectroscopy.

A limitation is that any OPO requires a pump source with high optical intensity and relatively high spatial coherence. Therefore, a laser is essentially always required for pumping an OPO, and as the direct use of a laser diode is in most cases not possible, the system becomes relatively complex, consisting e.g. of laser diodes, a diode-pumped solid-state laser, and the actual OPO.

optical parametric oscillator
Figure 2: Setup of a typical optical parametric oscillator with a ring resonator. The pump beam is injected through a dichroic mirror. The signal beam is resonant, whereas the idler is usually ejected by at least of the resonator mirrors.

Comparison with Lasers

Although parametric oscillators are in many respects similar to lasers, there are also a couple of important differences:

Singly Resonant Versus Doubly Resonant OPOs

Most OPOs are singly resonant, i.e., they have a resonator which is resonant at either the signal or the idler wavelength, but not for both. (For the non-resonant wave, dichroic resonator mirrors or some polarizing optics lead to high resonator losses, so that there is very little optical feedback.) However, there are also doubly resonant OPOs, where both signal and idler are resonant. The latter makes sense only with a single-frequency pump laser.

The advantage of doubly resonant OPOs is that the threshold pump power can be much lower. This is interesting particularly for continuous-wave operation. However, the tuning behavior is complicated: when the crystal temperature or pump wavelength is changed, the signal and idler wavelengths undergo jumps, and the tuning is generally non-monotonous. This is because the operation wavelengths are determined primarily by the requirement for simultaneous resonance for signal and idler (mode clusters), and not only by a phase-matching condition.

Another possibility is resonant enhancement of the pump wave, which is sometimes applied when the pump laser is a single-frequency device. In a triply resonant OPO, pump, signal and idler waves are resonant at the same time. Such a device is delicate to operate, however. A simpler option is to make an intracavity pumped OPO, where the nonlinear crystal is placed within the resonator of the pump laser, exploiting the high intracavity power.

Pumping of OPOs

There are basically three different options for pumping optical parametric oscillators:

In most cases, the pump light for an OPO comes either directly from some near-infrared laser or from a frequency doubler, generating e.g. green light. In less common cases, OPOs are pumped with ultraviolet or mid-infrared light.

Types of OPOs

The following list shows that there is a wide variety of OPOs:

Applications of OPOs

The potential application areas of OPOs are very diverse. Some examples are:

Problems for Commercial Realization

Despite their amazing capabilities, as demonstrated in years of interesting research, optical parametric oscillators have so far not found widespread use in commercial products. Some of the reasons for this are briefly discussed in the following:


The RP Photonics Buyer's Guide contains 25 suppliers for optical parametric oscillators. Among them:


[1]R. H. Kingston, “Parametric amplification and oscillation at optical frequencies”, Proc. IRE 50, 472 (1962) (an early theoretical investigation)
[2]J. A. Giordmaine and R. C. Miller, “Tunable coherent parametric oscillation in LiNbO3 at optical frequencies”, Phys. Rev. Lett. 14 (24), 973 (1965) (first experimental demonstration of an optical parametric oscillator)
[3]A. Laubereau et al., “Intense tunable picosecond pulses in the infrared”, Appl. Phys. Lett. 25, 87 (1974)
[4]A. Piskarskas et al., “Continuous parametric generation of picosecond light pulses”, Sov. J. Quantum Electron. 18 (2), 155 (1988)
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[8]J. D. Kafka et al., “Synchronously pumped optical parametric oscillators with LiB3O5”, J. Opt. Soc. Am. B 12 (11), 2147 (1995)
[9]Special feature on optical parametric oscillators, JOSA B 12 (11), 1995
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[12]S. D. Butterworth et al., “High power, broadly tunable all-solid-state synchronously-pumped lithium triborate optical parametric oscillator”, J. Opt. Soc. Am. B 12 (11), 2158 (1995)
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[14]W. R. Bosenberg et al., “Continuous-wave singly resonant optical parametric oscillator based on periodically poled LiNbO3”, Opt. Lett. 21 (10), 713 (1996) (first singly resonant continuous-wave OPO)
[15]M. A. Arbore and M. M. Fejer, “Singly resonant optical parametric oscillation in periodically poled lithium niobate waveguides”, Opt. Lett. 22 (3), 151 (1997)
[16]R. G. Batchko et al., “Continuous-wave 532-nm-pumped singly resonant optical parametric oscillator based on periodically poled lithium niobate”, Opt. Lett. 23 (3), 168 (1998)
[17]S. Guha, “Focusing dependence of the efficiency of a singly resonant optical parametric oscillator”, Appl. Phys. B 66 (6), 663 (1998)
[18]M. E. Klein et al., “Singly resonant continuous-wave optical parametric oscillator pumped by a diode laser”, Opt. Lett. 24 (16), 1142 (1999)
[19]M. H. Dunn and M. Ebrahimzadeh, “Parametric generation of tunable light from continuous-wave to femtosecond pulses”, Science 286, 1513 (1999)
[20]A. V. Smith et al., “Numerical models of broad-bandwidth nanosecond optical parametric oscillators”, J. Opt. Soc. Am. B 16 (4), 609 (1999)
[21]G. Arisholm, “Quantum noise initiation and macroscopic fluctuations in optical parametric oscillators”, J. Opt. Soc. Am. B 16 (1), 117 (1999)
[22]L. Lefort et al., “Generation of femtosecond pulses from order-of-magnitude pulse compression in a synchronously pumped optical parametric oscillator based on periodically poled lithium niobate”, Opt. Lett. 24 (1), 28 (1999)
[23]T. Südmeyer et al., “Femtosecond fiber-feedback OPO”, Opt. Lett. 26 (5), 304 (2001)
[24]D. C. Hanna et al., “Synchronously pumped optical parametric oscillator with diffraction-grating tuning”, J. Phys. D 34, 2440 (2001)
[25]T. Südmeyer et al., “Novel ultrafast parametric systems: high repetition rate single-pass OPG and fiber-feedback OPO”, J. Phys. D: Appl. Phys. 34 (16), 2433 (2001)
[26]U. Strößner et al., “Singly-frequency continuous-wave optical parametric oscillator system with an ultrawide tuning range of 550 to 2830 nm”, J. Opt. Soc. Am. B 19 (6), 1419 (2002)
[27]S. Lecomte et al., “Synchronously pumped optical parametric oscillator with a repetition rate of 81.8 GHz”, IEEE Photon. Technol. Lett. 17, 483 (2005)
[28]M. Ghotbi et al., “Broadly tunable, sub-30 fs near-infrared pulses from an optical parametric amplifier based on BiB3O6”, Opt. Lett. 35 (13), 2139 (2010)
[29]F. Kienle et al., “Compact, high-pulse-energy, picosecond optical parametric oscillator”, Opt. Lett. 35 (21), 3580 (2010)
[30]G. Rustad et al., “Effect of idler absorption in pulsed optical parametric oscillators”, Opt. Express 19 (3), 2815 (2011)
[31]G. Van der Westhuizen and J. Nilsson, “Fiber optical parametric oscillator for large frequency-shift wavelength conversion”, IEEE J. Quantum Electron. 47 (11), 1396 (2011)
[32]A. Herzog et al., “Wavelength conversion of nanosecond pulses to the mid-IR in photonic crystal fibers”, Opt. Lett. 37 (1), 82 (2012)
[33]S. Li et al., “High efficiency terahertz-wave photonic crystal fiber optical parametric oscillator”, Appl. Opt. 51 (22), 5579 (2012)
[34]T. Gottschall et al., “Ultra-short pulse fiber optical parametric oscillator”, Opt. Lett. 42 (17), 3423 (2017)

(Suggest additional literature!)

See also: optical parametric amplifiers, parametric amplification, nonlinear crystal materials, nonlinear frequency conversion, tunable lasers, synchronous pumping, mid-infrared laser sources, Spotlight article 2006-07-30, Spotlight article 2006-09-03, Spotlight article 2006-09-21, Spotlight article 2007-08-23
and other articles in the categories nonlinear optics, photonic devices

Dr. R. Paschotta

This encyclopedia is authored by Dr. Rüdiger Paschotta, the founder and executive of RP Photonics Consulting GmbH. Contact this distinguished expert in laser technology, nonlinear optics and fiber optics, and find out how his technical consulting services (e.g. product designs, problem solving, independent evaluations, or staff training) and software could become very valuable for your business!

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