17 -- A tour of every instrument¶

Every instrument kind used once along one beam line. A 30 fs, 50 nJ pulse at 800 nm (pre-chirped with 300 fs²) goes through:

The overview figure of this example's run (python make_figures.py redraws it; the file is hero.png).

1. a 3 mm fused-silica plate on a radial grid (SPM, weak Kerr lens);
2. 30 cm of air;
3. chirped mirrors;
4. a quarter-wave plate at 15° and a polariser;
5. a non-collinear OPA in BBO pumped by a 515 nm, 40 µJ pulse.

ultrafast run tour.ufs run.json -o results
ultrafast-plot results          # instruments.png: one numbered panel per instrument, located on system.png

where	instruments (kind)	what they show here
input	energyMeter, spectrometer, autocorrelator (interferometric)	50 nJ, 31.4 nm FWHM, 8:1 IAC
after the plate	beamProfile, camera (near field and far field), wavefrontSensor, spaceTime (virtual)	w = 200 µm, M² = 1.000, Kerr-lens wavefront R ≈ 21 m, far field 637 µm at f = 0.5 m
after the air	camera (12-bit)	w = 434 µm
after the chirped mirrors	spectrometer (dB), autocorrelator, frog (SHG and PG), dscan, contrast, scope, compressor, pulseSummary, wigner and fieldProbe (virtual)	FWHM 38 fs vs 30 fs TL; the d-scan optimum is −7.1 mm of extra glass, the ideal compressor wants −254 fs²
after the quarter-wave plate	polarimeter	s = (0.75, 0.43, 0.50), azimuth 15°, ellipticity 15°
after the polariser	powerMeter	87 % transmitted
the OPA	conversion, phaseMatchingCurve, delayScan	70× gain to 3.5 µJ, 1.9 µJ idler, 226 nm phase-matching bandwidth, optimum delay −50 fs

Sampling: what the instrument actually sees¶

Three more instruments look at the beam through an aperture instead of collecting all of it ("sampling", see docs/instruments.md):

instrument	sampling	transmitted	result
spectrum_nf_pinhole	near field after the plate, 20 µm pinhole on axis	2.0 %	FWHM 31.5 nm (whole beam 31.4 nm): the plate's SPM is weak
spectrum_ff_fibre	far field after the air (f = 0.1 m lens), 25 µm fibre, NA 0.22	7.4 %	centroid 799.78 nm, 0.4 nm bluer than the whole beam: the focal spot is smaller at shorter wavelengths, so a fibre couples the blue better
ac_nf_slit	near field after the plate, 30 µm slit	11.9 %	AC FWHM 68 fs

Example 11 shows the same instruments on a beam with strong spatio-temporal coupling, where on-axis and whole-beam measurements differ clearly.

See docs/instruments.md for every parameter.