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Home/Products/Special Products/STFT Flat-Top THz Source
STFT Flat-Top THz Source
STFT flat top — within 10 dB
0.10.3131030STFT FLAT-TOP THZ SOURCE
Flat top 1.0–4.6 THz2.2 octaves within 10 dB> 10 MV/cm peak fieldFour pump–probe configurations
Special Products · Flat top 1–4.6 THz, > 10 MV/cm

STFT Flat-Top THz Source

Swiss THz Flat Top Bullet Source

A terahertz source whose output stays within 10 dB of its peak right across the working band, instead of spiking at one frequency and falling away either side. The STFT flat top runs 1.0 to 4.6 THz — 3.6 THz wide, 2.2 octaves — and arrives in a single pulse. Above 10 MV/cm the pulse does not merely look at a sample, it drives it.

STFT flat top1.0 – 4.6 THz
Peak electric field> 10 MV/cm
Energy per pulse4 µJ
Focus size0.14 mm (station 1)
Applications
  • Nonlinear terahertz spectroscopy
  • Optical-pump terahertz-probe — photoconductivity, carrier lifetime, transient screening
  • Terahertz-pump terahertz-probe — field-driven phase changes, saturation
  • Terahertz-pump optical-probe — field-induced birefringence
  • Ultrafast switching measurements, ≈ 1 ps resolution
  • Terahertz imaging and non-destructive inspection
Price on request
Configured to order — request a quotation
Ships from Zürich
Lead time on request

Online prices are for budgetary purposes only. Exact prices can be up to 20% higher depending on the current exchange rate — please request a formal quotation.

Why the flat top matters — Most terahertz sources spike at one frequency and fall away either side, so a measurement is strong at the peak and noisy everywhere else. A flat top holds usable strength right across the band — one scan, even quality, no favoured colour.

Four configurations — Pump and probe can each be the terahertz pulse or the laser, and the bench is laid out so that all four pairings are reachable without rebuilding. The choice sets what you learn. The laser addresses electrons across the band gap; the terahertz field addresses what moves slowly — carriers, phonons, spins, bonds.

Two focus stations, either way round — Whichever configuration you run, the beams meet at one of two foci. Station 1 is the tight focus, smallest spot and strongest field, at 0.14 mm. Station 2 is the sample station, with more room around the sample, at 0.26 mm.

How the field is measured — A strong terahertz pulse briefly distorts a diamond crystal, and the height of the resulting Kerr rotation gives the field strength directly, with no power meter involved. The method has been checked against a completely independent calibration on another source and the two agreed to within about 8 %. For scale, 10 MV/cm is comparable to the field holding electrons to atoms, which is why the pulse can drive a material rather than just probe it.

Watching electrons switch on — Sweeping the delay between the two pulses turns the horizontal axis into a clock. In a semiconductor turning conductive, the signal drops by more than 90 % as the electrons appear, and the edge is under a picosecond wide — fast enough to follow the switching itself, not just its aftermath.

Seeing through things — Terahertz light passes through plastic, paper, ceramics and clothing but stops at metal and water, which makes it useful for looking inside sealed packages, coatings and composites without opening or damaging them. The STFT flat top helps here too — every frequency in the band arrives with usable signal, so contrast does not collapse away from one favoured colour.

  • ▸ Values are from commissioning measurements on this system with the beam path in open air. Purging the path raises them. Full measurement records, methods and uncertainties are available on request.
  • ▸ Water vapour absorbs terahertz light, which is why the beam path is normally purged.
At a glance
STFT flat-top band1.0 – 4.6 THz
Flat-top width2.2 octaves
Strongest at3.4 THz
Usable spanout to 12 THz
Peak electric field> 10 MV/cm
Guaranteed floor8 MV/cm
Energy per pulse4 µJ
Conversion efficiency0.6 – 0.9 %
Pump pulse energy≈ 0.7 mJ
Driving laser1030 nm, ytterbium
Focus size, station 1 / 20.14 / 0.26 mm
DetectionField, not power
Built-in camerasTerahertz + laser
Delay rangeMotorised, ps steps
Beam height135 mm
Footprint120 × 90 cm (Terabullet enclosure)
Four configurations
OpticalTerahertzA laser flash creates carriers; the terahertz pulse reads the conductivity that appears. Photoconductivity, carrier lifetime, transient screening.
OpticalOpticalConventional transient absorption, using the two laser arms already on the bench. Population dynamics above the band gap.
TerahertzTerahertzThe strong pulse drives the sample and a second terahertz pulse reads it. Nonlinear terahertz response, field-driven phase changes, saturation.
TerahertzOpticalThe terahertz field distorts the sample and the laser reads the induced birefringence. This is the route used for the field measurement.

Pump and probe can each be the terahertz pulse or the laser, and all four pairings are reachable without rebuilding the bench.

Switching measurement
Signal change on switching> 90 %
Time resolution≈ 1 ps
Finest delay step0.015 ps
Terahertz imaging
CameraReal time
Objectivef/0.7
Feature size shown3 mm
Documentation & figures
STFT in the Terabullet enclosure — 120 × 90 cm footprint
STFT in the Terabullet enclosure — 120 × 90 cm footprint
The STFT flat top, measured. A — the electric field arriving, recorded directly in time. B — the same pulse in dry and in humid air, scaled to the same height. C — the flat top itself, 3.6 THz within 10 dB. D — the full span, with the detector's own noise floor; SNR above 10 dB out to 12.3 THz. Green is a dry beam path, orange is ordinary room air.
The STFT flat top, measured. A — the electric field arriving, recorded directly in time. B — the same pulse in dry and in humid air, scaled to the same height. C — the flat top itself, 3.6 THz within 10 dB. D — the full span, with the detector's own noise floor; SNR above 10 dB out to 12.3 THz. Green is a dry beam path, orange is ordinary room air.
Two focus stations. Every frame is a real camera image — terahertz, laser, and the two overlaid, at each station. Station 1 at 0.14 mm, station 2 at 0.26 mm.
Two focus stations. Every frame is a real camera image — terahertz, laser, and the two overlaid, at each station. Station 1 at 0.14 mm, station 2 at 0.26 mm.
The pulse passing through diamond. The height of this Kerr rotation peak gives the field strength directly — no power meter involved.
The pulse passing through diamond. The height of this Kerr rotation peak gives the field strength directly — no power meter involved.
A semiconductor turning conductive. A laser flash frees electrons; the terahertz pulse arrives a controlled instant later and finds it almost opaque. Two scans, two step sizes, same answer.
A semiconductor turning conductive. A laser flash frees electrons; the terahertz pulse arrives a controlled instant later and finds it almost opaque. Two scans, two step sizes, same answer.
A terahertz photograph — a 3 mm hole and a metal blade, imaged straight onto a terahertz camera. Single short exposure, nothing corrected.
A terahertz photograph — a 3 mm hole and a metal blade, imaged straight onto a terahertz camera. Single short exposure, nothing corrected.
Applications
Nonlinear spectroscopy
Ultrafast carrier dynamics
Field-driven material control
Terahertz imaging