Nonlinear absorption edge properties of 1.3-μm GaInNAs saturable absorbers

Abstract

GaInNAs 1.3-μm quantum-well saturable absorber mirrors are characterized with spectrally resolved nonlinear reflectivity measurements over 70nm around the broadened band edge. All important parameters such as saturation fluence Fsat, modulation depth ΔR, and nonsaturable loss ΔRns are obtained relative to the photoluminescence (PL) peak. Fsat has a minimum of 4μJ∕cm2 10nm above the PL peak and ΔR scales with the linear absorption even in the bandtail. The product ΔR∙Fsat important to suppress Q-switching instabilities in mode-locked lasers decreases linearly with wavelength and reaches a minimum 20nm above the PL peak. We observed wavelength-independent nonsaturable losses of only about 10% of the maximum linear absorption. These results increase the understanding of optical and electronic properties of GaInNAs around the band edge.

Parameter tunable GaInNAs saturable absorbers for mode locking of solid-state lasers

“…The saturation fluence and nonsaturable losses of SESAMs are important parameters that have to be tightly controlled. The product F sat  DR must be low to suppress Q-switched mode locking [7]. DR denotes the modulation depth of the SESAM, which is the difference in reflectivity between the fully saturated and the recovered states of the SESAM.…”

“…The nonlinear optical parameters of the SESAM strongly depend on the position of the absorption edge with respect to the laser wavelength [7]. Therefore, postgrowth wavelength tuning is very useful.…”

Wideband-tuneable, nanotube mode-locked, fibre laser

“…Mode-locked fibre lasers are convenient and powerful sources of ultrashort pulses 4 , and the inclusion of a broadband saturable absorber as a passive optical switch inside the laser cavity may offer tuneability over a range of wavelengths 5 . Semiconductor saturable absorber mirrors are widely used in fibre lasers [4][5][6] , but their operating range is typically limited to a few tens of nanometres 7,8 , and their fabrication can be challenging in the 1.3 -1.5 mm wavelength region used for optical communications 9,10 . Single-walled carbon nanotubes are excellent saturable absorbers because of their subpicosecond recovery time, low saturation intensity, polarization insensitivity, and mechanical and environmental robustness [11][12][13][14][15][16] .…”

Optical switching in a resonant Fabry–Perot saturable absorber

“…The A-FPSA also exhibits negligible group delay dispersion (GDD) with less than 20 fs 2 over the entire high-reflectivity bandwidth (800-1100 nm). Consequently, A-FPSAs have been extensively investigated and developed [3][4][5][6][7][8][9] for application in passively mode-locked solid-state lasers [7,9,10], while the R-FPSAs or near R-FPSAs [10] introduce considerable GDD in the laser cavity and they are incompatible with solid-state laser technology. However, the longer effective interaction length of the optical field in the R-FPSA leads to greater nonlinearity.…”