scholarly journals Mode-Converting Corrugations for Cavities of Second-Harmonic Gyrotrons with Improved Performance

2021 ◽  
Keyword(s):  
Second Harmonic ◽  
Single Mode ◽  
Operating Mode ◽  
Coupling Coefficients ◽  
Optimal Parameters ◽  
Output Section ◽  
Ohmic Losses ◽  
Mode Purity ◽  
Improved Performance ◽  
Harmonic Gyrotron

Mode-converting longitudinal corrugations are used as a means of improving the selectivity properties of cavities for second-harmonic gyrotrons. As an example, 100-kW 0.3-THz second-harmonic gyrotron is considered. For the operating second-harmonic mode and most dangerous first-harmonic competing modes, the eigenvalues, ohmic losses and beam-wave coupling coefficients are investigated with respect to dimensions of a corrugated cavity. The most optimal parameters are found for a gyrotron cavity with mode-converting corrugations, which ensure the widest range of a single mode operation for the 0.3-THz second-harmonic gyrotron. It is shown that, in this range, the gyrotron output power can be increased up to 180 kW. It is found that output mode purity of the 0.3-THz second-harmonic gyrotron falls off due to mode-converting corrugations, which induce undesirable coupling of the operating mode with neighboring Bloch harmonics in the output section of the gyrotron cavity.

scholarly journals MODE SELECTION BY OHMIC LOSSES IN LONGITUDINALLY CORRUGATED CAVITIES OF SUB-THz SECOND-HARMONIC GYROTRONS

2019 ◽  
pp. 31-34
Author(s):  
T.I. Tkachova ◽  
V.I. Shcherbinin ◽  
V.I. Tkachenko
Keyword(s):  
Second Harmonic ◽  
Mode Selection ◽  
Operating Mode ◽  
Mode Frequency ◽  
Geometrical Parameters ◽  
Harmonic Mode ◽  
Maximum Enhancement ◽  
Ohmic Losses ◽  
Wall Losses ◽  
Harmonic Gyrotron

Ohmic wall losses are proposed as a means for improving the mode selection in a cylindrical gyrotron cavity with longitudinal wedge-shaped corrugations. Such losses depend on mode frequency and geometrical parameters of the corrugations. For cavity of the 0.4-THz second-harmonic gyrotron we find the corrugation depth, which corresponds to maximum ohmic losses of the competing modes excited at the first (fundamental) cyclotron resonance, as well as to reasonably low losses of the operating mode. For this depth, we determine the number of corrugations and their width, which ensure the maximum enhancement of the ohmic wall losses of the fundamental modes with respect to those of the operating second-harmonic mode, together with minimum conversion of the operating second-harmonic mode to higher Bloch harmonics. Parameters of the corrugations in hand are practicable.

scholarly journals “Seeing Is Believing”—In-Depth Analysis by Co-Imaging of Periodically-Poled X-Cut Lithium Niobate Thin Films

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 288
Author(s):  
Sven Reitzig ◽  
Michael Rüsing ◽  
Jie Zhao ◽  
Benjamin Kirbus ◽  
Shayan Mookherjea ◽  
...  
Keyword(s):  
Lithium Niobate ◽  
Second Harmonic ◽  
Imaging Techniques ◽  
Piezoresponse Force Microscopy ◽  
Periodically Poled ◽  
Near Surface ◽  
Domain Structures ◽  
Depth Analysis ◽  
Improved Performance ◽  
Quantum Optical

Nonlinear and quantum optical devices based on periodically-poled thin film lithium niobate (PP-TFLN) have gained considerable interest lately, due to their significantly improved performance as compared to their bulk counterparts. Nevertheless, performance parameters such as conversion efficiency, minimum pump power, and spectral bandwidth strongly depend on the quality of the domain structure in these PP-TFLN samples, e.g., their homogeneity and duty cycle, as well as on the overlap and penetration depth of domains with the waveguide mode. Hence, in order to propose improved fabrication protocols, a profound quality control of domain structures is needed that allows quantifying and thoroughly analyzing these parameters. In this paper, we propose to combine a set of nanometer-to-micrometer-scale imaging techniques, i.e., piezoresponse force microscopy (PFM), second-harmonic generation (SHG), and Raman spectroscopy (RS), to access the relevant and crucial sample properties through cross-correlating these methods. Based on our findings, we designate SHG to be the best-suited standard imaging technique for this purpose, in particular when investigating the domain poling process in x-cut TFLNs. While PFM is excellently recommended for near-surface high-resolution imaging, RS provides thorough insights into stress and/or defect distributions, as associated with these domain structures. In this context, our work here indicates unexpectedly large signs for internal fields occurring in x-cut PP-TFLNs that are substantially larger as compared to previous observations in bulk LN.

scholarly journals Achievement of High Power Sub-Terahertz Radiations with a Second Harmonic Gyrotron

2009 ◽  
Vol 4 ◽  
pp. 011-011 ◽  
Author(s):  
Takashi NOTAKE ◽  
Teruo SAITO ◽  
Yoshinori TATEMATSU ◽  
Akihito FUJII ◽  
Shinya OGASAWARA ◽  
...  
Keyword(s):  
High Power ◽  
Second Harmonic ◽  
Harmonic Gyrotron

Simulation of a 0.33-THz Second Harmonic Gyrotron Based on Double Confocal Cavity

2020 ◽  
Author(s):  
Xiaotong Guan ◽  
Wenjie Fu ◽  
Jiayi Zhang ◽  
Dun Lu ◽  
Xiaolei Zheng ◽  
...  
Keyword(s):  
Second Harmonic ◽  
Confocal Cavity ◽  
Harmonic Gyrotron

A 250-Watts, 0.5-THz continuous-wave second-harmonic gyrotron

2021 ◽  
pp. 1-1
Author(s):  
Mikhail Yu. Glyavin ◽  
Andrey N. Kuftin ◽  
Mikhail V. Morozkin ◽  
Mikhail D. Proyavin ◽  
Andrey P. Fokin ◽  
...  
Keyword(s):  
Continuous Wave ◽  
Second Harmonic ◽  
Harmonic Gyrotron

scholarly journals Metal–dielectric hybrid nanoantennas for efficient frequency conversion at the anapole mode

2018 ◽  
Vol 9 ◽  
pp. 2306-2314 ◽  
Author(s):  
Valerio F Gili ◽  
Lavinia Ghirardini ◽  
Davide Rocco ◽  
Giuseppe Marino ◽  
Ivan Favero ◽  
...  
Keyword(s):  
Frequency Conversion ◽  
Near Infrared ◽  
Strong Field ◽  
Second Harmonic ◽  
Near Field ◽  
Field Enhancement ◽  
High Refractive Index ◽  
Plasmonic Nanostructures ◽  
Ohmic Losses ◽  
Order Of Magnitude

Background: Dielectric nanoantennas have recently emerged as an alternative solution to plasmonics for nonlinear light manipulation at the nanoscale, thanks to the magnetic and electric resonances, the strong nonlinearities, and the low ohmic losses characterizing high refractive-index materials in the visible/near-infrared (NIR) region of the spectrum. In this frame, AlGaAs nanoantennas demonstrated to be extremely efficient sources of second harmonic radiation. In particular, the nonlinear polarization of an optical system pumped at the anapole mode can be potentially boosted, due to both the strong dip in the scattering spectrum and the near-field enhancement, which are characteristic of this mode. Plasmonic nanostructures, on the other hand, remain the most promising solution to achieve strong local field confinement, especially in the NIR, where metals such as gold display relatively low losses. Results: We present a nonlinear hybrid antenna based on an AlGaAs nanopillar surrounded by a gold ring, which merges in a single platform the strong field confinement typically produced by plasmonic antennas with the high nonlinearity and low loss characteristics of dielectric nanoantennas. This platform allows enhancing the coupling of light to the nanopillar at coincidence with the anapole mode, hence boosting both second- and third-harmonic generation conversion efficiencies. More than one order of magnitude enhancement factors are measured for both processes with respect to the isolated structure. Conclusion: The present results reveal the possibility to achieve tuneable metamixers and higher resolution in nonlinear sensing and spectroscopy, by means of improved both pump coupling and emission efficiency due to the excitation of the anapole mode enhanced by the plasmonic nanoantenna.

Low-noise operation (−140 dB/Hz) in close-coupled Nd:YVO_4 second-harmonic lasers pumped by single-mode laser diodes

1993 ◽  
Vol 32 (33) ◽  
pp. 6610 ◽  
Author(s):  
Hideo Nagai ◽  
Masahiro Kume ◽  
Akio Yoshikawa ◽  
Kunio Itoh
Keyword(s):  
Second Harmonic ◽  
Laser Diodes ◽  
Single Mode ◽  
Low Noise ◽  
Mode Laser ◽  
Single Mode Laser
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