Semi-Insulating GaAs for Electro-Optic Sampling System

GaAs wafers, with their efficient electro-optical conversion, wide infrared transparent window, excellent high-frequency characteristics, and process compatibility, have become an ideal choice for electro-optical sampling (EOS) systems, especially occupying a core position in the fields of ultrafast optics and terahertz technology. Despite its higher cost than silicon, its performance advantages are irreplaceable in high-end scientific research and industrial applications. PAM-XIAMEN is able to provide semi-insulating GaAs wafer for developing electro-optical sampling systems. For more wafer specification information, please refer to:

https://www.powerwaywafer.com/semi-insulating-gaas-substrate.html

1. About Electro-Optic Sampling

Electro-optic sampling is a terahertz pulse detection technology based on the linear electro-optic effect (Pockels effect), whose core principle is to indirectly characterize the terahertz electric field characteristics through nonlinear crystal refractive index changes. When terahertz pulses interact with synchronized detection laser pulses in nonlinear crystals such as GaAs, ZnTe, and LiNbO3, the terahertz electric field induces crystal birefringence, causing the polarization plane of the laser to rotate. The change in polarization state is then converted into an intensity modulation signal by a polarizer, and finally measured by a photodetector to invert the amplitude, phase, and time-domain waveform information of terahertz pulses.

The implementation of this technology relies on laser wavelength and crystal combinations (like GaAs, ZnTe, and LiNbO3) that meet phase matching conditions, precision polarization systems, and high-sensitivity photodetectors. It has advantages in supporting ultra wideband signal detection, non-contact measurement (to avoid signal attenuation), and femtosecond level time resolution, but it is limited by spectral selectivity caused by phase matching bandwidth limitations, interference from environmental noise on weak signals, and complex system control requirements such as optical path collimation and temperature control.

2. Research on Electro-OpticSampling of Terahertz Waves in GaAs Crystal

Researchers have proposed a non collinear geometric terahertz electro-optic sampling method based on thick GaAs crystals, which breaks through the technical bottleneck of traditional collinear sampling by optimizing the optical path design. It was found that the optimal incident angle of the detection beam on the crystal is 42-50 °, and the optimal crystal thickness is 1-3cm. The core working principle of this electro-optic sampling is that terahertz waves penetrate the GaAs crystal in the vertical direction, and the detection laser pulse is incident at a specific tilt angle and propagates diagonally inside the crystal. This non collinear configuration enables phase synchronization between the terahertz wavefront and the detection light in the direction perpendicular to the wavefront, fundamentally eliminating signal echo interference caused by multiple reflections in collinear structures. Under the action of the electro-optic effect, the terahertz electric field causes a change in the refractive index of GaAs crystals, which modulates the polarization state of the probe light in relation to the terahertz field strength. By capturing this modulation signal through a polarization analysis system, the terahertz time-domain waveform and spectral information can be reconstructed.

This study found that non collinear electro-optic sampling systems based on thick GaAs crystals have the following significant advantages: firstly, thick crystals (compared to traditional thin films) significantly extend the interaction distance between terahertz fields and probe light, making the sampling time window longer and the spectral resolution improved by more than an order of magnitude; Secondly, non collinear configurations effectively suppress echo noise through physical isolation; Finally, active optimization of phase matching conditions can be achieved by dynamically adjusting the incident angle of the detection light, which can further expand the sampling bandwidth.

Whether you need GaAs wafer for research or for industrial applications, please contact us email at [email protected] and [email protected].