Rapid scanning terahertz time-domain magnetospectroscopy with a table-top repetitive pulsed magnet

Abstract

We have performed terahertz time-domain magnetospectroscopy by combining a rapid scanning terahertz time-domain spectrometer based on the electronically coupled optical sampling method with a table-top mini-coil pulsed magnet capable of producing magnetic fields up to 30 T. We demonstrate the capability of this system by measuring coherent cyclotron resonance oscillations in a high-mobility two-dimensional electron gas in GaAs and interference-induced terahertz transmittance modifications in a magnetoplasma in lightly doped n-InSb.

Observation of cyclotron resonance and measurement of the hole mass in optimally-doped La$_{2-x}$Sr$_{x}$CuO$_4$

“…1b. To rapidly detect the THz waveform at peak field, we used a TDTS system based on electronically-controlled optical sampling (ECOPS) [30,31], wherein the timing delay between the two ultrafast optical pulse trains that drive the THz emitter and receiver can be electronically modulated very quickly (see Fig. 1c).…”

Terahertz cyclotron resonance spectroscopy of an AlGaN/GaN heterostructure using a high-field pulsed magnet and an asynchronous optical sampling technique

“…9 There have also been several reports of cyclotron resonance spectrometers being developed that combine pulsed magnetic fields with broadband laser-based terahertz radiation sources. [10][11][12] Laser-based terahertz spectroscopy is a timedomain technique that typically employs slow scanning mechanical delay stages to acquire the terahertz waveforms through combining time-delayed near-infrared and terahertz pulses in a nonlinear medium or photoconductive antenna. The key challenge in utilizing these sources with pulsed magnetic fields has been in developing a detection scheme that can measure the terahertz waveforms within the several millisecond duration of the magnetic field.…”

“…Approaches to achieving this have included both replacing the slow mechanical delay stage with a fast rotating mirror 10 and using two lasers synchronized with an electronically controlled optical sampling (ECOPS) technique. 12 The ECOPS scheme was the most suitable method for use with short duration magnetic field pulses as Noe II et al 12 showed that it could be used to record four terahertz waveforms during an approximately 14 ms magnetic field pulse.…”

Single-shot terahertz time-domain spectroscopy in pulsed high magnetic fields

“…For our magnet system, because of the wait time between magnet shots, on the order of several minutes for shots up to 30 T [22], this method proves to be unreasonably time-consuming for recording the gate signal at many time delays. To date, reported rapid scanning methods for THz-TDS in pulsed magnets include using a rotating delay line for measurements up to 12 T with a 40 T magnet [23], an electronically controlled optical sampling (ECOPS) method up to 2.5 T with a 30 T magnet [24], and, most recently, an asynchronous optical sampling (ASOPS) method up to 13 T with a 31 T magnet [25] to change the relative timing between the pump and gate pulse for each consecutive pair of laser pulses. This leads to a mapping of the pump/probe delay time to the real measurement time.…”

“…For instance, in Ref. [24], 15 ps of time delay corresponds to 150 µs of measurement time, which provides slightly less than 1% of magnetic field variation at the peak of the magnetic field pulse that varies on a timescale of milliseconds. For shorter-duration magnetic field pulses, for instance µs pulses in a single-turn coil system, required for ultrahigh magnetic field strengths [20], these methods are simply not fast enough, i.e., the magnetic field variation significantly complicates data extraction.…”