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Electro-optic field sensors for cohe...

Wu, Qi.

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Electro-optic field sensors for coherent detection from DC to mid-infrared.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Electro-optic field sensors for coherent detection from DC to mid-infrared./
Author:	Wu, Qi.
Description:	110 p.
Notes:	Adviser: Xi-Cheng Zhang.
Contained By:	Dissertation Abstracts International59-02B.
Subject:	Engineering, Electronics and Electrical. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9823692
ISBN:	0591757672

Electro-optic field sensors for coherent detection from DC to mid-infrared.
Wu, Qi.

Electro-optic field sensors for coherent detection from DC to mid-infrared. - 110 p.

Adviser: Xi-Cheng Zhang.

Thesis (Ph.D.)--Rensselaer Polytechnic Institute, 1997.

This dissertation presents a pioneering study on the application of electro-optic sampling to the coherent detection of freely-propagating THz electromagnetic pulses. Free-space electro-optic sampling (FSEOS) utilizes the ultrafast nonlinear response of electro-optic (EO) materials with proper implementation of velocity-matching between the optical sampling pulse and the THz wave. We addressed the design issues of velocity-matched EO sensors and developed a theoretical framework for modeling the frequency response functions. The mismatching between the group velocity of optical probe pulse and the frequency-dependent phase velocity of THz wave is found to be responsible for the roll-off and dips in the high frequency response of the EO sensor. This effect presents a trade-off between low-frequency sensitivity and detection bandwidth.

ISBN: 0591757672Subjects--Topical Terms:

626636
Engineering, Electronics and Electrical.

Electro-optic field sensors for coherent detection from DC to mid-infrared.
LDR:04154nam 2200325 a 45 001 926631
005 20110422
008 110422s1997 eng d
020 $a 0591757672
035 $a (UnM)AAI9823692
035 $a AAI9823692
040 $a UnM $c UnM
100 1 $a Wu, Qi. $3 1030532
245 1 0 $a Electro-optic field sensors for coherent detection from DC to mid-infrared.
300 $a 110 p.
500 $a Adviser: Xi-Cheng Zhang.
500 $a Source: Dissertation Abstracts International, Volume: 59-02, Section: B, page: 0714.
502 $a Thesis (Ph.D.)--Rensselaer Polytechnic Institute, 1997.
520 $a This dissertation presents a pioneering study on the application of electro-optic sampling to the coherent detection of freely-propagating THz electromagnetic pulses. Free-space electro-optic sampling (FSEOS) utilizes the ultrafast nonlinear response of electro-optic (EO) materials with proper implementation of velocity-matching between the optical sampling pulse and the THz wave. We addressed the design issues of velocity-matched EO sensors and developed a theoretical framework for modeling the frequency response functions. The mismatching between the group velocity of optical probe pulse and the frequency-dependent phase velocity of THz wave is found to be responsible for the roll-off and dips in the high frequency response of the EO sensor. This effect presents a trade-off between low-frequency sensitivity and detection bandwidth.
520 $a A variety of EO sensors have been experimentally investigated for far-infrared detection. Non-collinear velocity-matching is used for ionic EO crystals such as LiTaO$\sb3$, with which two sensor tips were designed and tested. Semiconductor EO crystals with zincblende structure are found to be well suited for collinear velocity-matching. We have demonstrated velocity-matching in ZnTe when the center wavelength of laser pulse is at 822 nm. Frequency response up to 5 THz is observed from a 0.25 mm thick ZnTe sensor, and the response is limited by the sensor dispersion. THz dispersion and absorption in ZnTe are studied by time-domain-spectroscopy. To further extend the detection bandwidth, we successfully fabricated GaP sensors for EO detection covering form microwave to 7 THz. Other EO sensors including CdTe, CdZnTe, GaAs and DAST are also studied.
520 $a EO sensing in the mid-infrared region, above the reststrahl band of the semiconductor EO crystal, is demonstrated for the first time. Using a 30 $\mu $m thick ZnTe sensor and a 12 fs laser, we obtained a record high frequency response of 37 THz. Our response function modeling shows that a 10 $\mu $m thick ZnTe will be able to cover the region from 7 THz to 50 THz.
520 $a As one of the real-world applications of EO sensors, a focal plane THz imaging system is proposed and studied. This imaging technique takes advantage of a large area EO sensor to transfer the THz image into an optical image for detection with a CCD imager. Instead of the usual quarter wave phase bias. a zero phase bias is used in the EO detection scheme. The ratio between signal and background is boosted by a factor of the square root of the system extinction ratio compared to the quarter wave bias, while the detection remains coherent. With this scheme we have demonstrated a proof-of-principle experiment on the imaging of the spatial distribution of a focused THz spot using a ZnTe sensor. System design issues on imaging optics, spatial resolution and power consumption are addressed.
520 $a Compared to the conventional photoconducting dipole antenna, FSEOS extends the bandwidth of coherent detection by an order of magnitude, while maintaining comparable sensitivity at low frequencies. EO sensors are expected to profoundly contribute to THz optoelectronics, including ultra-wide band THz spectroscopies and real-time THz imaging.
590 $a School code: 0185.
650 4 $a Engineering, Electronics and Electrical. $3 626636
650 4 $a Physics, Optics. $3 1018756
690 $a 0544
690 $a 0752
710 2 0 $a Rensselaer Polytechnic Institute. $3 1019062
773 0 $t Dissertation Abstracts International $g 59-02B.
790 $a 0185
790 1 0 $a Zhang, Xi-Cheng, $e advisor
791 $a Ph.D.
792 $a 1997
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9823692