Ultrahigh precision nonlinear reflectivity measurement system for saturable absorber mirrors with self-referenced fluence characterization

Abstract

Measurement of nonlinear optical reflectivity of saturable absorber devices is discussed. A setup is described that enables absolute accuracy of reflectivity measurements better than 0.3%. A repeatability within 0.02% is shown for saturable absorbers with few-percent modulation depth. The setup incorporates an in situ knife-edge characterization of beam diameters, making absolute reflectivity estimations and determination of saturation fluences significantly more reliable. Additionally, several measures are discussed to substantially improve the reliability of the reflectivity measurements. At its core, the scheme exploits the limits of state-of-the-art digital lock-in technology but also greatly benefits from a fiber-based master-oscillator power-amplifier source, the use of an integrating sphere, and simultaneous comparison with a linear reflectivity standard.

CNT-based saturable absorbers with scalable modulation depth for Thulium-doped fiber lasers operating at 1.9 μm

“…The measured modulation depth and saturation fluence values, together with the values used for the best possible fitting, are summarized in Table 1. The F sat values were determined from the measured curves, as a point where the transmission increases by 1/e factor of the modulation depth40. Due to the fact, that in all cases we do not reach the theoretical modulation depth, the F sat values read from the graph are approximately two times smaller than the calculated.…”

All-fiber wavelength-tunable picosecond nonlinear reflectivity measurement setup for characterization of semiconductor saturable absorber mirrors

“…Several methods to measure nonlinear reflectivity were suggested [36,37]. Most of these methods were realized using lockin amplifiers and solid state lasers.…”

“…Most of these methods were realized using lockin amplifiers and solid state lasers. More recently, nonlinear reflectivity measurement system was introduced which used a fiber laser as an ultrashort optical pulse source [37]. All-in-fiber setup is a convenient tool to investigate passive saturable absorbers for fiber lasers as these devices are usually integrated with the optical fiber.…”

Absolute SESAM characterization via polarization-resolved non-collinear equivalent time sampling

“…A potential source of error in the measurements comes from the beam size measurement for the fluence. This is a combination of the uncertainty when placing the beam-profiler (BR2-IGA, DataRay Inc.) in the focus as well as the uncertainty when placing the sample [ 47 ]. We estimate an error of 10% for the combined uncertainty.…”