SAM – saturable absorber mirror

The effective saturation fluence Φ sat,eff of a SANOS can be defined in such a way, that the transmittance Tat Φ sat,eff is 50% of the saturated value at a very large fluence Φ >> Φ sat .Corresponding to the finesse of the RSAM Φ sat,eff of a SANOS is smaller than the saturation fluence Φ sat ofthe absorber material inside the RSAM. The finesse also limits the bandwidth FWHM of the resonance dipat the operation wavelength. The figure below shows the relation between the effective saturation fluenceΦ sat,eff as a function of the bandwidth full width of half maximum (FWHM). For decreasing the FWHM theeffective saturation fluence Φ sat,eff is also decreasing if the cavity thickness remains constant. On the otherhand for a fixed FWHM the effective saturation fluence Φ sat,eff is increasing if the optical thickness of theRSAM cavity is increased.The effective saturationfluence Φ sat,eff as a functionof the full width at halfmaximum (FWHM) of theRSAM resonance dip plottedfor different RSAM cavitythicknesses.> Relaxation time constant τDecrease of the transmittance aftersaturation with τ = 10 psThe low temperature grown saturableabsorber layer inside the SANOS has arelaxation time constant τ, which can bevaried over a large region from about 100fs up to 100 ps. A typical value of therelaxation time τ is 1 ps.The relaxation of the carriers and thechange of the transmittance T(t) after thesaturation can be described asSeongKyeong Photonics 24 info@skphotonics.com