Photoconductive Cw THz receiver with 20-fold increased THz conversion efficiency

Photoconductive cw THz receivers with buried interdigital finger contacts feature a 20-fold higher conversion efficiency than their planar counterpart. Applied to a 1.5 mum cw THz photomixing system, a SNR up to 95 dB @ 100 GHz was achieved

High Speed Coherent CW Terahertz Spectrometer

In-fibre wavelength selective modulation of the optical phase enables the electro-optic control of the terahertz phase in continuous-wave photomixing terahertz systems without any free-space optics. Using a fully fibre-coupled terahertz setup, a coherent scan of a frequency range of 1.5 THz with 100 MHz resolution in less than 24 s is demonstrated. This sample rate of 1.6 ms/sample is more than 20 times faster than any previous broadband scans reported

Improved InGaAs/InAlAs photoconductive THz receivers: 5.8 THz bandwidth and 80 dB dynamic range

We investigate optimal Be-doping conditions of low-temperature-grown InGaAs/InAlAs photoconductive antennas with respect to their carrier lifetimes and carrier mobility. Employed as THz-TDS receiver bandwidths of 5.8 THz with a dynamic range of up to 80 dB is achieved

First absolute power measurement of a terahertz time domain spectroscopy system based on InGaAs/InAlAs photoconductors

We present the first absolute power measurement of a photoconductive terahertz (THz) emitter developed for time domain spectroscopy. The broadband THz radiation is generated by a high mobility InGaAs/InAlAs multilayer heterostructure photoconductive emitter packaged into a fiber-coupled housing. For detection a recently developed ultrathin pyroelectric thin-film detector with special conductive electrodes is employed. The detector signal is traceable to the International System of Units since the power responsivity of the detector was calibrated with a standard detector at the German national metrology Institute (PTB). Absolute THz power exceeding 0.1 mW was detected

Fiber coupled THz QTDS at 1550 nm

We present a THz quasi time-domain spectroscopy (QTDS) system based on fiber coupled antennas operating at 1550 nm excitation wavelength. Frequency components up to 950 GHz can be generated with this setup. The signal to noise ratio of a single shot measurement is around 60 dB between 40 GHz and 240 GHz

Photoconductive terahertz near-field detectors for operation with 1550-nm pulsed friber lasers

We present a new generation of photoconductive (PC) terahertz (THz) near-field probes based on freestanding Beryllium-doped low-temperature-grown InGaAs/InAlAs cantilevers. The PC probes are compatible to optical gating with a femtosecond laser having a center wavelength of 1550 nm. Therefore, they are well suited for a cost-efficient direct integration with fiber-coupled THz time-domain spectroscopy (TDS) systems. The photoconductor material features electron lifetimes of 500 fs allowing for broadband detection up to 2 THz, which is comparable to existing LT-GaAs-based near-field detectors, which require 800-nm wavelength excitation. We demonstrate the detector operation in a state-of-the-art fiber-based TDS system with fast and coherent data acquisition and show obtained sheet-resistance mappings of conductive thin-films featuring subwavelength resolution

Fully-integrated THz transceiver with 4.5 THz bandwidth and 70 dB dynamic range

We present a fully-integrated, fiber-coupled transceiver module for THz time domain spectroscopy. The transceiver combines emitter and receiver in a compact, 25 mm housing, which allows for THz reflection measurements under normal incidence. With a bandwidth of 4.5 THz and a peak dynamic range of 70 dB this THz reflection head is a versatile tool for material inspection and non-destructive testing

Terahertz quasi time-domain spectroscopy based on telecom technology for 1550 nm

We present a fiber-coupled terahertz quasi time-domain spectroscopy system driven by a laser with a central wavelength of 1550 nm. By using a commercially available multimode laser diode in combination with state-of-the-art continuous wave antennas, a bandwidth of more than 1.8 THz is achieved. The peak signal-to-noise ratio is around 60 dB. A simulation based on the optical spectrum of the laser diode and the transfer function of the THz path is in agreement with the experimental results. The system is used to extract the refractive index from two different samples and the results indicate that the performance is up to 1.8 THz comparable to a terahertz time-domain spectroscopy system

Thermal behavior of InGaAs-THz photoconductive antennas

While most scientific experiments take place in a controlled laboratory environment systems for industrial applications have to cope with instable temperatures. We investigate the performance of InGaAs/InAlAs THz antennas for the temperature from -20 to 80 degrees Celsius

Fiber-coupled transceiver for terahertz reflection measurements with a 4.5 THz bandwidth

We present a fiber-coupled transceiver for THz time-domain spectroscopy, which combines an emitter and a receiver on a single photoconductive chip. With a bandwidth of 4.5 THz and a peak dynamic range larger than 70 dB, it allows for THz reflection measurements under normal incidence. This THz reflection head is a promising device for applications in such fields as material inspection and nondestructive testing