United States Patent Application 20170307520
Inventors:
Hepp, Christian (Ettlingen, DE)
Luettjohann, Stephan (Karlsruhe, DE)
http://www.freepatentsonline.com/y2017/0307520.html
The invention relates to a method for measuring and determining a THz spectrum of a sample (17),
wherein two laser beams (1a, 2a) are superimposed, such that two parts (11, 12) of a superimposed laser radiation are generated, which have a beat frequency in the THz range,
wherein the first part (11) is introduced into an emitter (13) for generating a THz radiation (14), wherein the THz radiation (14) passes through the sample (17) and the characteristic transmission radiation (18) thus obtained is forwarded to a detector (15), wherein the detector (15) is activated by the second part (12) of the superimposed laser radiation,
wherein, by repetition with different beat frequencies, a measurement signal I(f) of the form I(f)=A(f)·cos[Φ(f)] is obtained for the sample (17),
wherein an auxiliary signal Ĩ(f) shifted by 90° is determined from the measurement signal I(f), with Ĩ(f)=A(f)·cos[Φ(f)±90°],
and wherein the THz spectrum S(f) of the sample (17) is determined by means of the auxiliary signal Ĩ(f), with S(f)=|z(f)|=|I(f)+iĨ(f)|. The invention provides a method for measuring and determining a THz spectrum in which an improved spectral resolution can be achieved in a simple manner.
wherein the first part (11) is introduced into an emitter (13) for generating a THz radiation (14), wherein the THz radiation (14) passes through the sample (17) and the characteristic transmission radiation (18) thus obtained is forwarded to a detector (15), wherein the detector (15) is activated by the second part (12) of the superimposed laser radiation,
wherein, by repetition with different beat frequencies, a measurement signal I(f) of the form I(f)=A(f)·cos[Φ(f)] is obtained for the sample (17),
wherein an auxiliary signal Ĩ(f) shifted by 90° is determined from the measurement signal I(f), with Ĩ(f)=A(f)·cos[Φ(f)±90°],
and wherein the THz spectrum S(f) of the sample (17) is determined by means of the auxiliary signal Ĩ(f), with S(f)=|z(f)|=|I(f)+iĨ(f)|. The invention provides a method for measuring and determining a THz spectrum in which an improved spectral resolution can be achieved in a simple manner.
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