SAM – saturable absorber mirror

The RSAM is a strong nonlinear optical device. The absorptance A of the absorber layer and the reflectance R of theRSAM depend on the incoming light intensity I. Due to the resonance condition of the Gires–Tournois interferometer atthe working wavelength the effective saturation intensity I sat,eff of the device shifts by a factor of about (π/F) 2 (F -finesse of the Gires–Tournois interferometer) to lower values in relation to the intrinsic material value I sat , which isvalid for non-resonant saturable absorber mirrors (SAM).The absorptance A of a RSAM with a not too small finesse F > 10 can be estimated byeq.(3)withΑ absorptanceA 0 small signal absorptance (saturable absorption)I light intensity (measured in W/m 2 )I sat intrinsic material saturation intensityF finesse of the RSAMThe effective saturation fluence Φ sat,eff of a RSAM can be estimated using the relaxation time τ and the effectivesaturation intensity I sat,effeq.(4)withΦ sat,effI sat,effτeffective saturation fluence of the RSAMeffective saturation intensity of the RSAMrelaxation time of the absorber materialWith typical values for a non-resonant SAM● I sat = 10 MW/cm 2●τ = 10 ps● Φ sat = 100 µJ/cm 2the relevant parameters for a RSAM with a finesse F = 20 can be estimated to● I sat,eff = 250 kW/cm 2● Φ sat,eff = 2.5 µJ/cm 2In this way the effective saturation values can be decreased to very low values at the expense of a small usuablespectral bandwidth.> Intensity dependent reflectanceSeongKyeong Photonics 20 info@skphotonics.com