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What is optical parametric chirped pulse amplification (OPCPA)?

The basis of Class 5 Photonics’ high-power femtosecond laser technology is the nonlinear amplifier concept called optical parametric chirped pulse amplification (OPCPA).

The concept of OPCPA combines the laser chirped-pulse amplification (CPA) scheme with optical parametric amplification (OPA). With this powerful combination, the advantages of both methods are merged. Ultrashort femtosecond pulses can be amplified to high pulse energies at high repetition rates.

Class 5 Photonics’ products are complete system integrations comprising a commercial Yb-based pump laser, a White Light Generation (WLG) to generate a broad-band seed pulse, a stretcher to optimize bandwidth and temporal overlap between seed and pump pulse, an optical parametric amplifier (OPA) to amplify the seed pulse, and a compressor to compress the amplified pulse to its Fourier transform limit.

How does optical parametric amplification (OPA) work?

The energy of an intense laser pulse (pump pulse) is down-converted to a signal and an idler pulse using a nonlinear optical crystal. In contrast to conventional laser amplifiers, no population inversion and thus no energy storage within the medium is required for the amplification. As the photon energy difference is carried away by the idler radiation, no quantum defect exists, which makes the system highly scalable in average power. Furthermore, non-collinear phase-matching in OPA (NOPA) offers a large amplification bandwidth and hence access to few-cycle pulse durations.

What is white light generation (WLG)?

White Light Generation (WLG) is used to generate the broadband seed pulse for the optical parametric amplification (OPA) process. For this a small fraction of the pump laser is used to generate via filamentation in bulk a white light continuum. Class 5 Photonics has conducted extensive development into the stability of the WLG process. Class 5 Photonics’ patented white light generation technology (WLG) provides maintenance free and stable operation.


High average powers

Owing to the instantaneous nature of the nonlinear parametric response, no energy storage within the medium is required for amplification. Consequently, the absorption of photons is reduced by several orders of magnitude. This enables unprecedented average powers and repetition rates, limited only by the residual absorption of signal, idler and pump pulses.

Few-cycle pulse durations

Broad gain bandwidth offers few-cycle pulse durations (< 9 fs) or a broad wavelength tunability range. The amplification of a full optical octave is possible in a single amplification stage, using non-collinear phase-matching in a sufficiently short crystal, pumped at sufficiently high intensity. The amplification bandwidth is limited by phase-matching.

Passive CEP stability

The idler in a colinear OPA stage has a stable CEO (carrier envelope offset) due to the constant phase relation between seed and pump originating from the same fundamental (Yb-based pump laser). Further optical parametric amplification processes inherit this passive CEP stability. Passive CEP stability is a great benefit for robustness, reliability and stability and offered in Class 5 Photonics’ systems.

High single-pass gain

A high single-pass gain can be achieved with only a few millimeters of nonlinear crystal. This relaxes the design complexity of the amplifier stages, whereas conventional laser amplifiers require multi-pass or regenerative amplifiers. Class 5 Photonics’ products are designed for a compact laser architectures at highest power levels.

Spectral tunability

The amplified bandwidth and central frequency can be adjusted by several degrees of freedom. For example by varying the delay between pump pulse and seed, phase-matching angle or the temperature.

Excellent temporal contrast

The gain window in OPCPA is confined temporally by overlapping the high power pump pulse with the seed pulse and hence no amplified spontaneous emission (ASE) occurs.


  • February 27, 2020
    Femtosecond OPCPAs from UV to short-wave IR wavelengths for ultrafast dynamics experiments from condensed matter to atoms, molecules, and clusters,” Proc. SPIE 11278, Ultrafast Phenomena and Nanophotonics XXIV, 112781A
  • February 1, 2021
    Optical properties of Li-based nonlinear crystals for high power mid-IR OPCPA pumped at 1 µm under realistic operational conditions,” Opt. Mater. Express 11, 231-239 (2021)