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Oscillateur Parametrique OPO


An optical parametric oscillator is a laser device in which in a nonlinear process one short wavelength pump photon is split into two longer wavelength photons (Signal and Idler). The wavelength of Signal and Idler are not independent from each other, but can be tuned in wavelength, making the OPO a tunable laser source.

They can be directly operated with laser oscillators without additional amplifiers as pump source. The OPOs are manufactured in different versions to cover various output parameters.


An optical parametric oscillator 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).

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

  • Whereas many lasers can be operated with spatially incoherent pump sources, a parametric oscillator requires relatively high spatial coherence of its pump. In most cases, a diode-pumped solid-state laser is used.
  • Whereas the emission wavelength of most lasers can be tuned only in a narrow range, many parametric oscillators offer the potential for wavelength tuning with extremely wide tuning ranges. These may span regions in the visible, near or mid-infrared part of the electromagnetic spectrum. Particularly in the mid-infrared region, OPOs are very commonly used, because there is little competition from mid-IR lasers.
  • The parametric amplification process requires phase matching to be efficient. The phase-matching details also determine the oscillation wavelength. Wavelength tuning is in most cases achieved by influencing the phase-matching conditions, e.g. by changing the crystal temperature, the angular orientation of the crystal (for critical phase matching), or the poling period (for quasi-phase matching in periodically poled crystals). Within the phase-matching bandwidth, tuning is also possible with an intracavity optical filter. The tuning range can be limited either by restrictions of phase matching (see below), or by the transparency region of the nonlinear material or by the spectral region with high reflectivity of the resonator mirrors.
  • The parametric amplification occurs only in the direction of the pump beam (as another consequence of phase matching), which means that a unidirectional operation in a ring resonator is automatically obtained. (In fact, ring resonators are often used, due to various advantages.)
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