In this thesis, we describe the development of a time-domain terahertz (THz)
spectrometer driven by two different laser sources: an Er-doped femtosecond fiber
laser and a mode-locked Ti:Sapphire laser. The resulting THz electromagnetic
radiation was generated and detected using photoconductive antenna detection
methods in both systems. In these experiments we characterized the THz power
output for both the fiber laser driven system and the Ti:Sapphire laser driven system.
Emphasis is given throughout this thesis on understanding the working principles
behind time-domain terahertz spectroscopy, applications of THz radiation and
terahertz generation as well as terahertz detection methods.
We calculated the THz power output using two different methods. By using the
&ldquo / Hertzian Dipole&rdquo / method we estimated the generated THz power after the
generation photoconductive antenna. Using this method, we showed that the
v
generated power is on the order of milliwatts, which is far larger than the expected
power typical for these systems. The second, &ldquo / Open-Circuit Voltage&rdquo / method,
allowed us to calculate the received power on the detection photoconductive antenna.
Using this method we were able to show that the THz power generated and detected
in these systems is on the order of microwatts. For the mode-locked fiber laser driven
spectrometer we obtained on average a ~ 4 ps (0.25 THz) pulse length which
corresponded to an average power in the range of 71.8 nW - 70.54 & / #956 / W on a dipole
antenna with a 6 & / #956 / m dipole gap and 44 & / #956 / m dipole length. Using the mode-locked
Ti:Sapphire laser driven spectrometer we observed a ~ 2 ps (0.5 THz) pulse length
and average power in the range of 0.54 nW &ndash / 5.12 & / #956 / W on a different dipole antenna
with a 5 & / #956 / m gap and 40 & / #956 / m dipole length. Since these values agree with expected
values for these systems we believe the &ldquo / Open-Circuit Voltage&rdquo / method is
appropriate when trying to calculate the THz power.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/3/12610440/index.pdf |
| Date | 01 February 2009 |
| Creators | Erozbek Gungor, Ummugul |
| Contributors | Altan, Hakan |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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