Abstract
Terahertz (THz) technology is promising in several applications such as imaging, spectroscopy and communications. Among several methods in the generation and detection of THz waves, a THz time-domain system that is developed using photoconductive antennas (PCA) as emitter and detector presents several advantages such as simple alignment, low cost, high performance etc. In this work, we report the design, fabrication and characterization of a 2-D PCA array that is capable of detecting both the amplitude and phase of the THz pulse. The PCA array is fabricated using LT-GaAs and has 8 channels with 64 pixels ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8 \times 8$ </tex-math></inline-formula> ). A novel approach using a spatial light modulator (SLM) to steer and focus the infrared probe beam towards pixels of the PCA array is presented. Each channel records the photocurrent generated by the THz signal (amplitude and phase) separately and frequencies up to 1.4 THz can be detected. Furthermore, the parameters such as directional time delay of the THz pulse, crosstalk between the channels etc., were characterized. Finally, we show that the proposed 2D PCA array design is flexible and can be used for accelerated THz spectral image acquisition.
Highlights
Terahertz (THz) frequency band (0.1 to 10 THz) has received a lot of attention in recent years due to increasing number of technological applications in the fields of telecommunications, imaging and sensing [1]–[7]
The locations of optimal interrogation of the individual H-antennas in the detector array are mapped by steering the probe beam using Spatial Light Modulator
Calibration of the photoconductive antennas (PCA) array was performed by recording THz time traces for an empty system
Summary
Terahertz (THz) frequency band (0.1 to 10 THz) has received a lot of attention in recent years due to increasing number of technological applications in the fields of telecommunications, imaging and sensing [1]–[7]. To further improve the image acquisition speed in THz time-domain systems, the multipixel detectors such as bolometer arrays [35] and Complementary Metal Oxide Semiconductor (CMOS) cameras [36] are proposed In these approaches, only the amplitude of the THz electric field is detected, while phase information is lost. One of them is non-mechanic fast optical beam steering with the possibility of using multiple focal spots in order to interrogate multiple antennas simultaneously In this case, antennas are grouped into separate channels (in our case 8 channels) that can be interrogated in parallel (i.e. by using ‘N’ transimpedance amplifiers for ‘N’ number of channels), speeding up image acquisition, and dramatically simplifying the on-chip wiring. By combining the proposed technique with the fast optical delay scanning [24] (rotary delay line for example [43]), the image acquisition speed can be further improved
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