Continuous-wave terahertz field imaging based on photonics-based self-heterodyne electro-optic detection

Abstract

We demonstrate a photonics-based self-heterodyne electro-optic field imaging technique at terahertz (THz) frequency. An optical intensity beat generated by mixing two frequency-detuned free-running lasers is used for both the generation and the detection. The frequency of the beat for detection is shifted by an optical frequency shifter to realize coherent heterodyne measurement with free-running lasers. Neither mechanical delay lines nor phase-locked synthesizers are required for the amplitude and the phase imaging of the THz field, and the system simplicity is thus improved. The amplitude and phase of the THz field (125 GHz) radiated from a horn antenna are simultaneously imaged, and the standard deviation of the phase measurement is found to be 0.18 rad.

Electric field visualization system for antenna characterization at terahertz frequency based on a nonpolarimetric self-heterodyne EO technique

“…The lock-in time constant was τ = 30 ms. The deviation of the phase measurement is reduced to about 1/2 compared to the previous result obtaiend based on the conventional polarimetric technique[7].…”

“…Recently, we proposed and demonstrated electrooptic (EO) field visualization system based on a self-heterodyne technique [6] in which free-running lasers can be used both for the THz wave generation and the EO detection [7]. In this proof-of-concept, the THz signal was read out through the polarization state of the probe beam.…”

Photonics for Millimeter-Wave and Terahertz Sensing and Measurement

“…2 (b) [17], [18]. In this case, the electro-optic (EO) crystal is used as an electric-field sensor in the detection.…”

Self-Heterodyne Spectrometer Using Uni-Traveling-Carrier Photodiodes for Terahertz-Wave Generators and Optoelectronic Mixers

“…In the free-space configuration, we measure the system response within a 200 to 1450 GHz range to show the present system would be applicable to the specific applications such as label-free genetic sensing [2]. Our spectrometer is based on a self-heterodyne technique [10], [17], which enables precise phase measurement using free-running LDs. This would be a key technology to realize stable and compact fully integrated CW-THz spectrometer chips, where no optical phase-locked loop is needed.…”