Apparatus and method for measuring terahertz wave

• US 8,207,501 B2
• Filed: 01/16/2009
• Issued: 06/26/2012
• Est. Priority Date: 01/18/2008
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Katagiri, Takashi, Itsuji, Takeaki
• Primary Examiner(s): Gaworecki, Mark R
• Application Number:
  US12/742,905
• Publication Number:
  US 20100288928A1
• Time in Patent Office: 1,257 Days
• Field of Search: 250/338.1, 250/338.4, 250/339.06, 250/341.1, 250/341.8
• US Class Current: 250/341.1
• CPC Class Codes: G01J 11/00 Measuring the characteristics of individual optical pulses or of optical pulse trains
• CPC Class Codes: G01J 3/42 Absorption spectrometry; Double beam spectrometry; Flicker spectrometry; Reflection spectrometry beam switching arrangements G01J3/08
• CPC Class Codes: G01N 21/3581 using far infrared light; using Terahertz radiation

Abstract

An apparatus for measuring a terahertz wave includes a dispersing section 103 for chirping the terahertz wave 104 generated from a generating section 101. A detecting section 102 detects waveform information on the terahertz wave chirped by the dispersing section 103. As a result, it is possible to acquire frequency information included in the waveform information. Therefore, it is possible to acquire spectral information including amplitude information of each frequency component and intensity information on each frequency or wavelength from the time waveform without Fourier-transforming the time waveform.

Claims

1. An apparatus, comprising:

a generating section for generating a terahertz wave;

a dispersing section for dispersing the terahertz wave generated by the generating section so that a time waveform of the terahertz wave has an electric field intensity distribution relative to frequency, by delaying the terahertz wave depending on frequency; and

a detecting section for detecting an electric field intensity of the terahertz wave dispersed by the dispersing section,

wherein the apparatus is so configured as to be capable of acquiring an electric field intensity for each frequency from a relation between time and frequency of the time waveform obtained by using a dispersion characteristic of the dispersing section.

2. The apparatus according to claim 1, further comprising:

a delaying section for varying a timing of generating or detecting the terahertz wave; and

an adjusting section for adjusting the timing so as to obtain the electric field intensity at a predetermined frequency by using the relation between time and frequency of the time waveform.

3. The apparatus according to claim 1, wherein

the detecting section includes a detector that is capable of following the terahertz wave dispersed by the dispersing section on a real time basis, and

the electric field intensity detected by the detecting section is an envelope of the time waveform of the terahertz wave dispersed by the dispersing section.

4. The apparatus according to claim 1, further comprising:

an irradiation section for irradiating an object with a terahertz pulse which is generated by irradiating the generating section with pump light; and

a probe light irradiation section for collectively irradiating a two-dimensional region of an electro-optic crystal with probe light to be used for irradiating the detection section, the probe light irradiation section being so arranged as to collectively irradiating a two-dimensional region of the object with the terahertz pulse, the two-dimensional region of the electro-optic crystal corresponding to the two-dimensional region of the object, in order to detect an electric field intensity of the terahertz pulse transmitted through or reflected by the object, wherein

the detecting section is formed by;

the electro-optic crystal;

an analyzer section for extracting a specific polarized component of the probe light whose polarized state is modulated by the terahertz pulse transmitted through the electro-optic crystal; and

a detector for collectively detecting the probe light extracted by the analyzer section in a two-dimensional region corresponding to the two-dimensional region of the object.

5. The apparatus according to claim 4, wherein the dispersing section is a waveguide structure arranged between the generating section and the object or between the object and the detecting section.

6. The apparatus according to claim 1, wherein

the dispersing section makes a group delay dispersion dτ

(f)/df show the same sign in a frequency region to be observed, where τ

(f) is a group delay characteristic of the dispersing section and f is frequency.

7. A method, comprising steps of:

generating a first terahertz wave;

dispersing the generated first terahertz wave so that a time waveform of the first terahertz has an electric field intensity distribution relative to frequency, by delaying the first terahertz wave depending on frequency;

detecting an electric field intensity of the dispersed first terahertz wave;

altering a timing of generating or detecting the first terahertz wave;

generating a second terahertz wave;

dispersing the generated second terahertz wave so that a time waveform of the second terahertz has an electric field intensity distribution relative to frequency, by delaying the first terahertz wave depending on frequency;

detecting an electric field intensity of the dispersed second terahertz wave; and

acquiring an electric field intensity at a predetermined frequency,

wherein the timing is altered so as to obtain the electric field intensity at the predetermined frequency by using a relation between time and frequency of a time waveform that is obtained by using the dispersion characteristic.

8. A measuring apparatus for acquiring information on an object, comprising:

a terahertz pulse generator for generating a terahertz pulse;

a terahertz pulse detector for detecting an electric field intensity of the terahertz pulse;

a first optical system for guiding the terahertz pulse from the terahertz pulse generator to the object; and

a second optical system for guiding the terahertz pulse from the object to the terahertz pulse detector,

wherein the first optical system or the second optical system includes a dispersing section for temporally stretching the terahertz pulse by delaying the terahertz pulse depending on frequency.