TY - JOUR

T1 - Potential of sub-THz-wave generation in Li2B4O7 nonlinear crystal at room and cryogenic temperatures

AU - Ezhov, Dmitry

AU - Turgeneva, Snezhana

AU - Nikolaev, Nazar

AU - Mamrashev, Alexander

AU - Mikerin, Sergei

AU - Minakov, Fedor

AU - Simanchuk, Andrey

AU - Antsygin, Valery

AU - Svetlichnyi, Valery

AU - Losev, Valery

AU - Andreev, Yury

N1 - Funding Information: Funding: The research was funded by the Russian Science Foundation, project № 19–19–00241. Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

PY - 2021/11

Y1 - 2021/11

N2 - Due to their high optical damage threshold, borate crystals can be used for the efficient nonlinear down-conversion of terawatt laser radiation into the terahertz (THz) frequency range of the electromagnetic spectrum. In this work, we carried out a thorough study of the terahertz optical properties of the lithium tetraborate crystal (Li2 B4 O7; LB4) at 295 and 77 K. Approximating the terahertz refractive index in the form of Sellmeier’s equations, we assessed the possibility of converting the radiation of widespread high-power laser sources with wavelengths of 1064 and 800 nm, as well as their second and third harmonics, into the THz range. It was found that four out of eight types of three-wave mixing processes are possible. The conditions for collinear phase matching were fulfilled only for the o − e → o type of interaction, while cooling the crystal to 77 K did not practically affect the phase-matching curves. However, a noticeable increase of birefringence in the THz range with cooling (from 0.12 to 0.16) led to an increase in the coherence length for o − o → e and e − e → e types of interaction, which are potentially attractive for the down-conversion of ultrashort laser pulses.

AB - Due to their high optical damage threshold, borate crystals can be used for the efficient nonlinear down-conversion of terawatt laser radiation into the terahertz (THz) frequency range of the electromagnetic spectrum. In this work, we carried out a thorough study of the terahertz optical properties of the lithium tetraborate crystal (Li2 B4 O7; LB4) at 295 and 77 K. Approximating the terahertz refractive index in the form of Sellmeier’s equations, we assessed the possibility of converting the radiation of widespread high-power laser sources with wavelengths of 1064 and 800 nm, as well as their second and third harmonics, into the THz range. It was found that four out of eight types of three-wave mixing processes are possible. The conditions for collinear phase matching were fulfilled only for the o − e → o type of interaction, while cooling the crystal to 77 K did not practically affect the phase-matching curves. However, a noticeable increase of birefringence in the THz range with cooling (from 0.12 to 0.16) led to an increase in the coherence length for o − o → e and e − e → e types of interaction, which are potentially attractive for the down-conversion of ultrashort laser pulses.

KW - Absorption coefficient

KW - Down-conversion

KW - Lithium tetraborate

KW - Refractive index

KW - Temperature dependence

KW - Terahertz spectroscopy

UR - http://www.scopus.com/inward/record.url?scp=85118938127&partnerID=8YFLogxK

U2 - 10.3390/cryst11111321

DO - 10.3390/cryst11111321

M3 - Article

AN - SCOPUS:85118938127

VL - 11

JO - Crystals

JF - Crystals

SN - 2073-4352

IS - 11

M1 - 1321

ER -