Frequency Modulation Detection and its Application to Absorption Line Shape Parameters

1982 ◽  
Vol 36 (3) ◽  
pp. 227-235 ◽  
Author(s):  
J. P. M. de Vreede ◽  
S. C. Mehrotra ◽  
A. Tal ◽  
H. A. Dijkerman
Keyword(s):  
Absorption Line ◽  
Frequency Modulation ◽  
Second Harmonic ◽  
Modulation Depth ◽  
Theoretical Calculations ◽  
Harmonic Signal ◽  
Rotational Transition ◽  
Center Frequency ◽  
Line Center ◽  
Harmonic Detection

The theory for frequency modulation given by Karplus has been extended to include Doppler broadening and arbitrarily large modulation depths. It is shown that the detection limit for second harmonic detection is of the same order as for first harmonic detection: the modulation depth must be approximately the full linewidth of the line profile. Procedures are discussed for extracting from experimental data the linewidth and center frequency of an absorption line with a Voigt profile. At zero detuning information about collisional line broadening can be obtained from the dependence of the second harmonic signal upon the modulation depth. Some experimental examples in the microwave region are presented as a test of the theory. Measurements on the rotational transition J = 2 → 3 (ν2 = 1) of OCS yield collisional self-shift and self-broadening parameters of −0.14 (±0.01) and 5.97 (±0.01) MHz/Torr, respectively; these values are in accordance with literature but are more accurate. For the line center at zero pressure a much more accurate value of 36 571 422.0 ± 0.7 kHz has been found, which is in agreement with recent theoretical calculations.

Contrast Harmonic Detection with Chirp Excitation in 3f0 Transmit Phasing

2008 ◽  
Vol 30 (4) ◽  
pp. 251-261 ◽  
Author(s):  
Che-Chou Shen ◽  
Hong-Wei Wang ◽  
Yi-Yuan Chiu
Keyword(s):  
Second Harmonic ◽  
Signal To Noise Ratio ◽  
Harmonic Signal ◽  
Harmonic Imaging ◽  
Frequency Difference ◽  
Background Suppression ◽  
Harmonic Suppression ◽  
Harmonic Detection ◽  
Third Harmonic

The method of third harmonic (3 f0) transmit phasing is capable of providing effective tissue background suppression for contrast-to-tissue ratio (CTR) improvement in harmonic imaging. With the additional 3 f0 transmit signal to generate both the frequency-sum and the frequency-difference components of harmonic signal, the tissue suppression is achieved when the two components are opposite in phase and mutually cancel out. One major problem in 3 f0 transmit phasing is the limited signal-to-noise ratio (SNR) due to the constraint on transmit amplitude. Chirp excitation can be applied in contrast harmonic imaging to enhance the SNR with minimal destruction of the microbubbles. In this paper, the effect of chirp waveform in combination with the 3 f0 transmit phasing was studied using both in-vitro experiments and simulations. Our results indicate that, though the chirp transmit pulse can increase the SNR of harmonic imaging in 3 f0 transmit phasing (3 dB, p<0.001), it suffers from degraded tissue harmonic suppression and thus provides less CTR improvement as compared to a conventional pulse. The spectral mismatch between the frequency-sum and the frequency-difference components of tissue harmonic signal is particularly evident in the off-center region of second harmonic band, leading to significant residue tissue background. Consequently, with the chirp waveform, the improvement of CTR decreases from 9.5 dB to 5.9 dB (p<0.0006) and thus a tradeoff exists between the SNR improvement and the CTR improvement in 3 f0 transmit phasing.

scholarly journals Magnetic particle imaging signal acquisition using second harmonic detection of magnetic nanoparticles

2019 ◽  
Vol 15 (1) ◽  
pp. 221
Author(s):  
Muhammad Mahadi Abdul Jamil ◽  
Abdulkadir Abubakar Sadiq ◽  
Muhammad Shukri Ahmad ◽  
Noordin Asimi Mohd Noor ◽  
Nur Adilah Abd Rahman ◽  
...  
Keyword(s):  
Magnetic Particle ◽  
Second Harmonic ◽  
Harmonic Signal ◽  
Signal Amplitude ◽  
Gradient Field ◽  
Pickup Coil ◽  
Harmonic Detection ◽  
Magnetic Particle Imaging ◽  
Particle Imaging ◽  
Second Harmonic Signal

<p class="Abstract">This paper presents an approach for acquiring a magnetic particle imaging (MPI) signal, by utilizing the second harmonic detection of the magnetic nanoparticles tracers. An MPI signal with high signal-to-noise ratio (SNR) is crucial for high spatial resolution images that reveals the distribution of the tracers in a target area. Samples of Resovist and Perimag nanoparticles tracers were prepared in liquid and immobilised form, which were placed at some distances under the receiver coil of the single-sided MPI scanner. The samples were exposed to the excitation magnetic field generated at 22.8 kHz and a static gradient field generated with a direct current of 2 A. The non-linear magnetization response of the tracers for each spatial position is recorded in the form of voltage signal by a gradiometer pickup coil, with the second harmonic signal being extracted by a resonance circuit. The results obtained revealed that a sufficient signal from the tracers is recorded at up to 25 mm under the pickup coil, with Perimag samples inducing higher signals as compared to Resovist. The dependence of the DC gradient field on the second harmonic signal shows that the peak signal amplitude for Resovist and Perimag particles as ±5 mT and ±6 mT respectively. Additionally, the second harmonic signal amplitude increases exponentially with an increase in the excitation magnetic field. Thus, the results obtained shows the potential of this approach in acquiring high SNR MPI signals at low excitation frequency, which could be vital in reconstructing the contour images of the tracers, particularly in sentinel lymph node biopsy (SLNB) for breast cancer diagnosis.</p>

Frequency modulation spectroscopy with second harmonic detection

1985 ◽  
Vol 24 (20) ◽  
pp. 3318 ◽  
Author(s):  
Gary Janik ◽  
Clint Carlisle ◽  
Thomas F. Gallagher
Keyword(s):  
Frequency Modulation ◽  
Second Harmonic ◽  
Harmonic Detection ◽  
Modulation Spectroscopy

scholarly journals Effect of UV-Irradiation and ZnO Nanoparticles on Nonlinear Optical Response of Specific Photochromic Polymers

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 492
Author(s):  
Karolina Waszkowska ◽  
Tarek Chtouki ◽  
Oksana Krupka ◽  
Vitaliy Smokal ◽  
Viviana Figà ◽  
...  
Keyword(s):  
Harmonic Generation ◽  
Uv Irradiation ◽  
Zno Nanoparticles ◽  
Nonlinear Optical ◽  
Second Harmonic ◽  
Theoretical Calculations ◽  
Harmonic Signal ◽  
Third Harmonic Generation ◽  
Laser Source ◽  
Third Harmonic

A series of methacrylic styrylquinoline polymers have been synthesized and characterized by spectroscopic and nonlinear optical (NLO) investigations. The NLO properties of studied polymer compounds in the form of thin films prepared by a spin coating method have been investigated by means of second and third harmonic generation via Maker fringe setup with a laser source at 1064 nm and a pulse duration of 30 ps. The results show strong second harmonic signal dependence on polarization configurations. This second harmonic generation (SHG) response was enhanced by UV-irradiation at 366 nm and doping by ZnO nanoparticles (NPs) (100 nm), while the opposite effect was achieved for a third harmonic generation experiment. Thus, values of second and third order nonlinear susceptibilities were determined by theoretical calculations based on comparative models. The remarkable NLO results presented in this paper expose potential optoelectronic and photonic applications.

scholarly journals Sub-ppm-Level Ammonia Detection Using Photoacoustic Spectroscopy with an Optical Microphone Based on a Phase Interferometer

Sensors ◽  
2019 ◽  
Vol 19 (13) ◽  
pp. 2890 ◽  
Author(s):  
Oscar E. Bonilla-Manrique ◽  
Julio E. Posada-Roman ◽  
Jose A. Garcia-Souto ◽  
Marta Ruiz-Llata
Keyword(s):  
Absorption Line ◽  
Photoacoustic Spectroscopy ◽  
Limit Of Detection ◽  
Second Harmonic ◽  
Laser Doppler Vibrometer ◽  
Fibre Laser ◽  
Harmonic Detection ◽  
Common Path ◽  
Ammonia Detection ◽  
Path Topology

A sensitive optical microphone for photoacoustic spectroscopy based on the common path topology of a fibre laser Doppler vibrometer (FLDV) using phase-generated carrier demodulation and a slim diaphragm as an acoustic wave transducer was demonstrated. A resonant gas cell was adapted to enhance gas-detection performance and simultaneously provide efficient cancellation of the window background acoustic signal. Ammonia (NH3) was selected as the target gas. The absorption line was experimentally identified using a distributed feedback laser diode emitting at 1530 nm. The linearity and sensitivity of the gas sensor were measured using wavelength modulation spectroscopy with second harmonic detection. A Teflon diaphragm was used to implement the optical microphone, along with the FLDV, showing a minimum detectable pressure of 79.5 μPa/Hz1/2. The noise-equivalent absorption sensitivity for NH3 detection at the absorption line at 1531.7 nm was 1.85 × 10−8 W cm−1 Hz−1/2, and the limit of detection was 785 ppbv.

Investigation of Transition Metal-Xanthate Complexes for Nonlinear Optical Applications

1998 ◽  
Vol 519 ◽  
Author(s):  
David E. Zelmon ◽  
Zewdu Gebeyehu ◽  
David Tomlin ◽  
Thomas M. Cooper
Keyword(s):  
Nonlinear Optical ◽  
Second Harmonic ◽  
Frequency Doubling ◽  
Harmonic Signal ◽  
Metal Salts ◽  
Potassium Salts ◽  
Metal Xanthate ◽  
Optical Applications ◽  
Nonlinear Optical Applications ◽  
Second Harmonic Signal

AbstractWe have synthesized several metal xanthate complexes from metal salts and xanthate potassium salts. Powders of several of the materials were sorted and tested for their nonlinear optical properties. Cadmium xanthate demonstrated phase matchability for frequency doubling of 1.06 micron light and generated a very strong second harmonic signal.

SECOND HARMONIC GENERATION IN ZnO NANORODS

2010 ◽  
Vol 19 (03) ◽  
pp. 445-458 ◽  
Author(s):  
MALYAJ DAS ◽  
SHIVANI RANA ◽  
PRATIMA SEN
Keyword(s):  
Second Harmonic Generation ◽  
Comparative Study ◽  
Harmonic Generation ◽  
Nd:Yag Laser ◽  
Second Harmonic ◽  
Zno Nanorods ◽  
Harmonic Signal ◽  
Pulsed Nd:Yag Laser ◽  
Micro Particles ◽  
Second Harmonic Signal

A comparative study of the second harmonic generation in ZnO micro particles and nanorods has been experimentally studied by Kurtz technique using nanosecond pulsed Nd:YAG laser. The results have been theoretically explained by taking into account the quadrupole moment as well as surface nonlinearity. It was observed that the nanorods yield polarized second harmonic signal while the second harmonic signal obtained from the micro particles was unpolarized.

Efficient Second Harmonic Generation in Hydrazone, Derivatives of Substituted Aromatic Aldehydes

1989 ◽  
Vol 173 ◽  
Author(s):  
Richard S. Potember ◽  
Robert C. Hoffman ◽  
Karen A. Stetyick
Keyword(s):  
Second Harmonic Generation ◽  
Harmonic Generation ◽  
Second Harmonic ◽  
Harmonic Signal ◽  
Aromatic Aldehydes ◽  
Dihydrogen Phosphate ◽  
Ammonium Dihydrogen Phosphate ◽  
Harmonic Signals ◽  
Derivatives Of ◽  
Second Harmonic Signal

ABSTRACTHydrazone, 1,1-dimethylhydrazone, methylhydrazone, phenylhydrazone and p-nitrophenyl hydrazone derivatives of substituted aromatic aldehydes were prepared and screened for second harmonic generation using the Kurtz powder technique. One compound, 4-nitro-3-methoxybenzaldehyde hydrazone exhibited a second harmonic signal up to 32 times that of ammonium dihydrogen phosphate (ADP) and 4-nitrobenzaldehyde hydrazone exhibited a second harmonic signal five times higher than previously reported, up to 40 times that of ADP. 3-methyl-4-nitrobenzaldehyde hydrazone, 4-nitrobenzaldehyde phenylhydrazone, 1-naphthaldehyde phenylhydrazone, 1-pyrenecarboxaldehyde phenylhydrazone exhibited second harmonic signals 25, 2.5, 5 and 20 times that of an ADP standard.

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