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● Autocorrelator for femtosecond laser

Thorlabs' FSAC Interferometric Autocorrelator provides approximate pulse width measurements in the 650 - 1100 nm wavelength range. Well suited for diagnostics of femtosecond Ti:Sapphire lasers, it consists primarily of a modified Michelson interferometer with a nonlinear detector at the output.

A BNC connector outputs the autocorrelation signal, which can be viewed on any oscilloscope with >1.5 MHz bandwidth. An example of the direct output from the FSAC is shown in the graph to the right. A photodiode amplifier with selectable gain from 0 dB to 70 dB provides compatibility with a large range of optical input powers, up to a maximum average power of 150 mW.

Intuitive, easy-to-reach controls on the outside of the enclosure allow the user to optimize the resolution and fringe contrast. The controls for the delay arm enable a full scan range of 50 fs to 10 ps (i.e., ±25 fs to ±5 ps), and a micrometer tunes the detector's position for maximum signal. Detailed usage recommendations and examples are available in the manual.

Item #FSAC
Wavelength range650-100nm
Pulse duration(HWHM)40fs ~ 1ps w/o precompensation
15fs ~ 1ps w/ precompensation
Full scan range50fs ~ 10ps
(±25 fs ~ ±5 ps)
Scan rate5 Hz
Noise-eqivalent sensitivity0.1 W2 at 800 nm for Ø1 mm Beam (1/e2)
Beam Diameter<Ø4 mm (1/e2)
Repetition Rate>300 kHz
Maximum Average Input Power150 mW
Internal DispersionGDD: 230 fs2 at 800 nm (Nominal)
TOD: 345 fs3 at 800 nm (Nominal)
An illustration of a setup that uses chirped mirrors to compensate for the GDD caused by the internal optics of the FSAC. The graph to the right shows the results of a theoretical calculation of the effect of this setup on the autocorrelation measurement of a 15 fs pulse
Calculated Autocorrelation Results: Non-Precompensated and Precompensated Pulses Compared to an Ideal, Unchirped Pulse