| Terahertz (THz) Transmitter/Receiver Opto-Mechanical Modules |
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The terahertz (THz) region of the electromagnetic spectra, in which research interest has been substantially increasing, is sandwiched between the infrared and microwave spectral bands. The THz wavelength ranges from 100μm to 1000μm (300GHz to 3THz). In this region the photon energies range from 1.2 to 12.4meV and the equivalent black body temperature ranges from 14K to 140K, below the earth's ambient background. The Ultrafast Terahertz Research Group at Oklahoma State University (OSU) in Stillwater, Oklahoma, has put together a THz Time Domain Spectroscopy (THz-TDS) system based on Thorlabs' opto-mechanical components, see the diagram in the Figures tab. Their system includes two FRU modules; one houses a transmitter and the other houses a receiver. In their system a femtosecond laser is used to illuminate the THz-transmitter, biased coplanar transmission lines fabricated on high-resistivity GaAs that has geometry similar to that shown in Figure 3 on the 'Figures' tab. The laser is focused on the edge of the positively biased line and generates a very large number of photo-induced charge carriers in the high electric field region, creating synchronous bursts of THz radiation. Their receiver FRU includes a THz-receiver chip that has antennae structures fabricated on an ion-implanted silicon-on-sapphire (SOS) wafer. The antennae structures have geometries similar to that shown in Figure 2 on the 'Figures' tab. The pulsed THz radiation is focused between the gap of an antenna and induces a transient bias voltage. The portion of the femtosecond laser beam that is directed into the receiver is also focused onto the antenna, inducing a transient photocurrent that synchronously gates the receiver. One can consider this detection process a sub-picosecond boxcar integrator. With this system OSU's Ultrafast Terahertz Research Group has scanned out past 5 THz using this system. Their system generates THz radiation with ~10nW average power with a signal-to-noise ratio of 10,000:1. The generated and detected THz radiation is coherent and the resulting receiver sensitivity is ~1000 times more sensitive than an incoherent liquid helium cooled bolometer. The receiver module of the THz-TDS system is shown above. The transmitter module uses the same opto-mechanical components as the receiver. Thorlabs stocks this kit which that includes all the optomechanical parts needed to mount a transmitter or receiver module and silica lens, which are not included. Please contact Technical Support at Thorlabs to enquire about sourcing the transmitter/ receiver modules and silica lenses. |
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