CC BY
3The 30th International Conference on Advanced Laser Technologies
ALT'23
N-O-3
Periodical generation of sub-THz dissipative solitons based on passive mode-locking in helical-waveguide Gyro-TWTs
I.V. Zotova, N.S. Ginzburg, M.N. Vilkov, A.S. Sergeev
Institute of Applied Physics RAS, 46 Ul'yanov Street, Nizhny Novgorod, 603950, Russia
zotova@ipfran. ru
In laser physics, there exists a well-known principle for production of ultrashort optical pulses (USP), based on the effect of passive mode-locking [1, 2], which is achieved by incorporating a nonlinear element (for example, a Kerr lens) into the laser resonator that absorbs low-amplitude radiation and is transparent periodic trains of ultrashort pulses (USP) can appear at the laser output. From a general point of view, the generated pulses are considered as dissipative solitons [3], the formation of which is due to the balance of amplification, absorption, harmonic generation, and group velocity dispersion effects.
As shown theoretically in [4-6], this method of pulse generation can be developed in microwave electronics, where saturable absorber can be realized based on electron-wave interaction. Feasibility of such approach was confirmed in recent experiments [7], where we implemented the Ka-band pulse generator mode-locked by nonlinear cyclotron resonance absorber, providing periodical trains of 100 kW/ 0.4 ns with repetition rate of 400 MHz. As an active unit, a wide-band helical-waveguide gyro-TWT was used.
In this report, we present the result of a theoretical analysis of the possibility of realization of dissipative soliton generators in higher W and G frequency bands (0.1-0.25 THz), where the developed gyro-TWT mode-locked by saturable absorbers can also be used. In W-band, the cyclotron resonance absorber which is based on interaction with an initially rectilinear electron beam can be used. Generation of USP with peak power of 100 kW is possible (Fig. 1). In G-band, the non-linear absorber can be realized based on a helical gyro-TWT which operates in the Kompfner dip regime.
Note that short-wave USP generators may be of interest for a large number of physical and technical applications, including plasma and solid state diagnostics, spectroscopy, high-resolution communications and radar, etc.
(a)
Amplifier
Saturable absorber
Feedback loop
Partially transparent
b)
(C)
I 0.5
10 20 time (ns)
90 100 110
frequency (GHz)
Fig.1. (a) scheme of a mode-locked microwave oscillator consisting of a helical gyro-TWT with cyclotron resonance absorber, (b) profiles
of microwave pulses, and (c) radiation spectrum.
3 50
0
0
0
30
80
This work is supported by the Russian Scientific Foundation (RSCF), Grant No. 23-12-00291.
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