During the eight weeks I spent at the NASA COSI sponsored 2004 Summer High School Research Program at City College I was able to learn numerous things. Each student was given a project that current City College scientists were working on for NASA. The students would assist the scientists in any way needed. The project assigned to me was Terahertz Imaging. The spectral range, 0.1 THz to 10 THz, has been retrieved in recent times using ultra-fast laser based Terahertz systems. Having a spatial and depth resolution that is better than 1um, it is a possible contender for detecting mines. Having a spatial and depth resolution better than 1um means that it can detect mines from other similarly shaped objects. Also, the spectral information of the transmitted and scattered radiation could be used to identify different objects hidden underground, possibly destructive ones.

Terahertz beams can infiltrate materials that optical beams can’t. Many larger molecules have their rotational and vibration energy levels in the Terahertz range (.1 to 10 THz). I read texts that dealt with the origins and principles of lasers and laser information. I learned that lasers are created by concentrating the photons emitted by excited atoms that are returning to their relaxed states. This light from the photons can be concentrated by placing them through a partially reflective mirror and a fully reflective mirror until concentrated into a straight beam rather than scattered light. After learning the formation of a laser, I learned the main setup from my project, the Terahertz Generation Setup. It requires the use of an IMRA Laser with wavelengths .78um and 1.56um 48MHz. Although the setup was rarely used besides for testing purposes with a regular laser pointer because of it was being reconstructed with newly purchased components by Professor R. R. Alfano and other professors. I also learned the importance and meaning of each component of the setup: Parabolic Mirrors (these mirrors help send beams into the sample), Beam Splitters (these are semi-transparent mirrors), Times Delay (these create a delay of the laser continuing to the next phase of the setup), ZnTe Crystal (this crystal is required in the setup because of its unqiue optical properties), Lock-in Amplifier (this is a machine that analyzes the incoming laser), Balanced Detectors (These receive the two altered incoming beams and sends them into the Lock-In Amplifier and computer for data analyzing/storing), and the Lens (these are used to magnify and concentrate the laser into the sample). Besides learning the setup, I also studied the importance of discovering new ways to produce images using Terahertz Pulses. Terahertz Pulses is a safe and efficient method because, unlike using X-Rays to produce an image, there is no excess radiation being shown onto the specimen being studied. Terahertz imaging simply creates an image from the natural Terahertz rays emitted by every object. Therefore, there is no harmful radiation being shown from a foreign source. It can also be used to make airports and postal offices more secure by allowing them to safely see through a possible terrorist or terrorist package and find the harmful object. It is also used to analyze certain materials and objects. If an unknown object is found, it’s wavelengths can be measured using the Terahertz Generation Setup and the material can then be identified from its “fingerprints” or it’s designated wavelength. Therefore, it can be concluded that any terrestrial object can be analyzed using the Terahertz Generation Setup and its composition can ultimately be found. This is a diagram I created of Terahertz Generation Setup using Microsoft PowerPoint computer software.

As seen in the picture below, a fully clothed man was analyzed using the Generation Setup. As you can see, the gun can be detected despite being fully clothed an with a full body outer jacket. This is a breakthrough in Terahertz Imaging because once this is perfected, people going through airports can be scanned without harmful radiation waves going through their bodies. Since their bodies naturally emit Terahertz waves, the Lock-In Amplifier can analyze the body without any destruction. As of today, many teams of scientists working on the Terahertz Imaging project are all trying to make a more compact, more portable unit of the setup. The first known unit of the setup so far has can be seen in the picture below. Scientist Derek Jenkins, one of the members of the StarTiger Team, which developed the setup and a new camera in the setup, is picutred.