Terahertz cross-correlation spectroscopy driven by incoherent light from a superluminescent diode.

We present a novel terahertz spectroscopy principle by using incoherent light from a super luminescent diode for terahertz cross-correlation spectroscopy. The combless nature of this light source leads to a truly continuous terahertz spectrum. We demonstrate the possibility to influence the terahertz spectral bandwidth of the system by changing the bandwidth of different bandpass filters in the system. Depending on the employed bandpass filter we achieve peak dynamic ranges of 60 dB or a terahertz spectral width of about 1.7 THz. The applicability of the measurement system to spectroscopic terahertz measurement tasks is demonstrated.

Single-laser, polarization-controlled optical sampling system.

Optical sampling systems traditionally require either one mode-locked laser with an external delay line or two mode-locked lasers with a controllable repetition rate difference. In this paper we present a novel polarization-multiplexed laser architecture combining the benefits of both approaches. The laser emits two mode-locked pulse trains sharing only one gain section without any external delay line. The colliding pulses in the laser have orthogonal polarization as well as opposite propagation directions to reduce coupling effects. With this, the two pulse trains can be freely phase controlled to conduct pump-probe measurements. To further analyze the timing stability of the system, we conducted a two-photon-absorption experiment, leading to a timing accuracy of 30 fs. Based on the novel laser architecture, we call this new approach single-laser polarization-controlled optical sampling, or SLAPCOPS.

Single-laser polarization-controlled optical sampling system for THz-TDS.

We demonstrate a polarization-multiplexed, single-laser system for terahertz (THz) time-domain spectroscopy without an external delay line. The fiber laser emits two pulse trains with independently adjustable repetition rates, utilizing only one laser-active section and one pump diode. With a standard fiber-coupled THz setup and a polarization-multiplexed optical amplifier, we are able to measure transients with a spectral bandwidth of 1.5 THz and a dynamic range of 50 dB in a measurement time of 1 s. Based on the novel laser architecture, we call this new approach single-laser polarization-controlled optical sampling, or SLAPCOPS.