500 THz (Tera Hertz) Amateur Radio Transceiver

I became an elk (see the picture below) when I get the idea to build a 500 THz Amateur Radio Transmitter and Receiver. In real, it is no problem to talk via a LASER beam in the same case then to talk via short wave or VHF frequencies.  

You will find the principle description how to build the transmitter and receiver. In the future I will describe my solution of a realized system in detail.


DF2IR as an elk
DF2IR as an elk, just developing the transceiver

The Transmitter Principle

The schematism below shows the principle of the transmitter.  Usually a cheap HeNe LASER is not polarize. So you need a linear polarizer between the LASER and the Faraday Modulator. If you have a linear polarize LASER the polarizer between the LASER and the Faraday Modulator is not necessary.

How the Transmitter works

The HeNe Laser produce a continuous red LASER beam.  It is not possible to change the intensity of the beam in the LASER source. That is possible with diode LASER only. The polarizer allows only one polarity of the light wave to go through the filter. The Faraday modulator has the ability to rotate the polarization. The rotation angle is less then one degree. In the receiver is a second polarizer. And after that is a light sensitive diode. The small change in the light intensity will be amplified and connected to a earphone.      

The Faraday Modulator in Detail

The hart of the modulator is the Nd:YAG rod. It is a glass rod and in normal case used to generate a LASER beam for high power industrial LASER. May be you do not have the opportunity to get a Nd:YAG rod, so you can use a quartz glass rod too. The ends of the rod must be plain. In my experiment the rod was 70 mm long and 4 mm in diameter. Around the rod is a coil. The coil is made by 1 mm Cu wire isolated with lac. Do not turn the wire directly around the glass rod.  This will destroy the rod. Use a holder. The coil must be powered with an high power audio amplifier. The number of coil turns depends on the output impedance of your amplifier. I used a 100 W integrated circuit audio amplifier TDA 7294. 

The Receiver Principle

The schematism below shows the principle of the receiver.  

Last modification: April 12 - 2009   DF2IR