Intense THz Spectroscopy System, Turnkey, > 10 MV/cm Peak Field

Overview

The Intense THz Spectroscopy System integrates a femtosecond ytterbium driver, a few-cycle multi-pass-cell compressor and an intense terahertz time-domain spectrometer into a single pre-aligned platform. It is built for groups that need field-driven, nonlinear and high-dynamic-range terahertz spectroscopy without assembling and stabilising the beamline themselves.

What sets the source apart is the shape of its spectrum. Most terahertz sources spike at one frequency and fall away either side, so a measurement is strong at the peak and noisy everywhere else. The STFT output instead stays within 10 dB of its peak right across 1.0 to 4.6 THz - 3.6 THz wide, 2.2 octaves - and arrives in a single pulse. One scan gives even quality across the band, with no favoured colour.

The HELIOS-HE laser delivers up to 2 mJ at 10 to 100 kHz, and the HYPERION-G-HE gas-filled multi-pass cell compresses it to a typical 29.2 fs at better than 90 % transmission. That clean, round, few-cycle drive is what turns pump energy into peak terahertz field: above 10 MV/cm the pulse does not merely look at a sample, it drives it.

Key highlights

Flat top, not a spike: 1.0 - 4.6 THz held within 10 dB, 2.2 octaves, usable span out to 12 THz.
Above 10 MV/cm in everyday operation with a guaranteed floor of 8 MV/cm - comparable to the field holding electrons to atoms.
Field, not power: the peak field is measured by Kerr rotation in diamond and has been cross-checked against an independent calibration on another source to within about 8 %.
Few-cycle drive: HELIOS-HE at 1 - 2 mJ compressed to a typical 29.2 fs in the HYPERION-G-HE multi-pass cell, with a round, single-lobed beam rather than the butterfly profile familiar from OPA-driven sources.
Two focus stations: 0.14 mm for the strongest field and 0.26 mm where the sample needs room, with terahertz and laser cameras at both.

Four configurations on one bench

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

Optical pump, terahertz probe - a laser flash creates carriers and the terahertz pulse reads the conductivity that appears: photoconductivity, carrier lifetime, transient screening.
Optical pump, optical probe - conventional transient absorption using the two laser arms already on the bench.
Terahertz pump, terahertz probe - the strong pulse drives the sample and a second terahertz pulse reads it: nonlinear terahertz response, field-driven phase changes, saturation.
Terahertz pump, optical probe - the terahertz field distorts the sample and the laser reads the induced birefringence.

What is included

STFT flat-top terahertz source in the Terabullet enclosure, 120 x 90 cm footprint, dry-purged beam path with two focus stations.
HELIOS-10W-HE or 20W-HE femtosecond ytterbium driver, 1 - 2 mJ at 10 - 100 kHz.
HYPERION-G-HE gas-filled multi-pass-cell compressor, typical 29.2 fs output, optional hollow-core fibre cascade for few-cycle operation.
Motorised delay line with 0.015 ps finest step, electro-optic sampling detection, lock-in amplifier and optical chopper.
Real-time terahertz camera with f/0.7 imaging objective, plus built-in terahertz and laser cameras at both focus stations.
Control and acquisition software, cabling and documentation.

Applications

Nonlinear and high-field terahertz spectroscopy. Field-driven material control in two-dimensional materials, semiconductors and correlated systems. Ultrafast optical-pump / THz-probe carrier dynamics - the switch-on of a semiconductor shows more than 90 % signal change with a sub-picosecond edge. High-dynamic-range THz-TDS material characterisation. Real-time terahertz imaging and non-destructive inspection through plastic, paper, ceramics and composites.

Delivery and acceptance

Every unit is factory integrated, aligned and acceptance tested before shipment, then commissioned on site, so the system is experiment-ready on hand-over. The performance figures quoted here are 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, and final figures are confirmed at on-site acceptance.

Components used in this system

The subsystems below are the same parts WaveQuanta supplies individually, so a bench built around this platform can be extended or serviced from the standard catalogue.

• off-axis parabolic mirrors — the terahertz relay is built from these
• GaP electro-optic sampling crystals — detection measures field, not power
• RIGI S2X real-time terahertz camera — the imaging channel of this system
• optical chopper — paired with the lock-in amplifier
• fibre-coupled optical delay line — an alternative to the motorised stage