Impact of BaB2O4 growth method on frequency conversion to the deep ultra-violet

Abstract

To cite this version:Loic Deyra, Alain Maillard, R Maillard, D Sangla, F Salin, et al.. Impact of BaB 2 O 4 growth method on frequency conversion to the deep ultra-violet. Solid State Sciences, Elsevier, 2015, 50, pp.97-100. 10 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Czochralski and TSSG β-BBO crystals are compared for high power UV (266nm) in second harmonic generation. Impurities from flux decrease the efficiency of harmonic generation at high power (40%). Corresponding author : A Maillard, alain.maillard@univ-lorraine.fr M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT Impact of BaBAbstract: In this article, we report how the growth method used for barium beta-borate β−BaB2O4 (BBO) impacts its high power second harmonic generation properties in the deep-UV. We compared a BBO crystal grown by flux (Top Seeded Solution Growth or TSSG) and a BBO crystal grown by the Czochralski (CZ) method. We first characterized their transparency properties, then we measured their single-pass second harmonic conversion efficiencies with both a low average power and a high average power nanosecond pulsed lasers. We show that both crystals have comparable linear absorption and conversion efficiencies at low power, whereas in a high power experiment, the CZ-grown BBO yields higher conversion efficiency than the TSSG grown BBO. With a 30 W, 150 kHz, 8ns green laser, the use of a CZ BBO led at best to a 40% increase in available average output power at 257 nm.Keywords: Borates, Nonlinear optical, Czochralski growth, Solution growth, Second harmonic generation. IntroductionThe material machining industry has continuously looked to process more and more types of materials efficiently. For some of them such as silicon, glass, sapphire, the ultraviolet lasers (UV) were developed in order to increase the material absorption [1,2]. While UV lasers around 350 nm obtained by third harmonic generation (THG) are now commonly used in material processing, deep-UV lasers obtained by fourth harmonic generation (FHG) around 260 nm are still challenging to realize. The nonlinear material quality is a key parameter in order to reach high and stable conversion efficiency by reducing thermal dephasing and degradation effects. Beta-barium borate β-BaB2O4 (BBO) is a nonlinear crystal that has good properties for frequency conversion to the UV, such as a high nonlinearity or a short cut-off wavelength in the UV around 190nm [3]. It is available commercially, and is usually grown by top-seeded solution growth (TSSG) assisted with either a Na2O or NaF flux [4]. BBO can be also grown without flux by the Czochralski (CZ) method, but...

High Average Power Near‐Infrared Few‐Cycle Lasers

“…Furthermore, the maximum photon energy of the pump wave should be kept well below 50% of the UV‐band gap energy to avoid two‐photon absorption. Additionally, the process of crystal growth could be optimized aiming for a minimum amount of impurities and inclusions to reduce the residual absorption . Note that cooling of the side surfaces of the nonlinear crystal will reduce the peak temperature, however, not the gradients within the crystal.…”

Optical properties and 532nm to 266nm second harmonic generation in bulk β-BBO crystals grown from the BaB2O4-NaBaBO3-V2O5 system

“…Consequently, the primary method for growing β-BBO crystals involves solution-melt crystallization, utilizing the topseeded solution growth technique to grow a seed crystal in the near-surface layer of a solution-melt [1]. However, the challenge of obtaining high-optical-quality β-BBO crystals arises due to the specific properties inherent to bariumborate systems, most notably, the high viscosity of their melts [3].…”

Phase equilibria in the ternary reciprocal system Li, Ba // BO2, F and growth of bulk β-BaB2O4 crystals

“…The main method for growing -BaB 2 O 4 crystals is the top-seeded solution growth technique (Ivleva et al, 1989;Feigelson et al, 1989;Itoh et al, 1990;Kouta et al, 1991;Kim et al, 1989). However, the growth of BBO crystals of high optical quality is hampered by a number of difficulties owing to the specific properties of barium borate melts (Deyra et al, 2015), primarily high viscosity. In spite of the availability of advanced technologies for growing BBO crystals, research on new solvents that improve crystal growth technology is still imperative, as the requirements regarding the size and quality of the crystals constantly increase (Nikolov & Peshev, 1992;Fedorov et al, 2008;Perlov et al, 2011;Jiang et al, 1986).…”