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Efficient femtosecond pulse generation in the blue using BiB3O6 #
M. Ghotbi,1 I. V. Kityk,2 A.Majchrowski,3 E. Michalski,3 and M. Ebrahimzadeh1
1
Institut de Ciencies Fotoniques (ICFO), Carrer de Jordi Girona, 08034 Barcelona, Spain
Institute of Technical Physics, Cracow Technological University, ul. Warszawska 24, Poland
3
Institute of Applied Physics, Military University of Technology, 2 Kaliskiego Str., 00-908 Warsaw, Poland
2
Abstract: Efficient second harmonic generation of femtosecond pulses into the blue is
reported in BiB3O6. Single-pass conversion efficiencies of 53% and average powers of 235
mW have been obtained in 50-fs pulses at 85 MHz repetition-rate.
2003 Optical Society of America
OCIS codes: 160.4430, 190.7110, 190.2620
Summary
The nonlinear optical crystal BiB3O6 (BIBO) is a relatively new material that offers great potential for
frequency conversion into the visible and ultraviolet (UV). It combines the advantages of deep UV transparency
(290-2700nm) and high damage tolerance, as in BBO and LBO, with substantially higher nonlinear coefficients
(deff>3 pm/V), comparable to that of KTP [1]. Since the growth of the first single crystal of BIBO for nonlinear
optical applications [2], a number of optical experiments have been performed in this material demonstrating
the promise of this material for second harmonic generation (SHG) of 1.064 µm pulsed laser radiation [3-5].
Here, we report SHG of high-repetition-rate femtosecond pulses in BIBO, for the first time, providing blue
pulses tunable over the 385-420 nm range. High single-pass power efficiencies and practical average powers
have been generated in pulses of 50 fs duration.
The fundamental input pulses were derived from a Kerr-lens-mode-locked Ti:sapphire laser, providing an
average power of 780 mW at 85 MHz repetition rate in transform-limited pulses of 80 fs duration tunable over
770-840 nm. Due to the non-optimised optics, a large total transmission loss of around 44% resulted in a
fundamental power of 440 mW at the input to the crystal. Several BIBO crystals, grown by top-seeded method
and of different lengths, were used for the second harmonic experiments. The crystals were cut for type I phasematching in the optical yz plane (φ=90°) at internal angles close to θ=156° at normal incidence, and the facets
were uncoated. The rotation of the crystal about the normal incidence in the yz plane resulted in the generation
and optimisation of second harmonic power over the tunable wavelength range of 385-420 nm.
Figure 1 shows the second harmonic output power and conversion efficiency as a function of the fundamental
power. For a maximum available input power of 440 mW, we were able to generate 235 mW of second
harmonic power, corresponding to a single-pass conversion efficiency of 53%. As can be ascertained from the
plots, while there is evidence of saturation in conversion efficiency, the second harmonic power can still be
further increased with higher fundamental powers. This, together with the absence of any optical damage to the
crystal, is indicative that power scaling should be attainable, potentially to the several watts regime.
250
0.6
Power
Efficiency
SHG Efficiency
0.4
150
0.3
100
0.2
SHG Power (mW)
200
0.5
50
0.1
0.0
0
100
200
300
400
0
500
Foundamental Input Power (mW)
Fig.1. Second harmonic conversion efficiency and output power as a function of fundamental input power.
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Figure 2 shows a typical interferometric autocorrelation of the generated second harmonic pulses. For input
fundamental pulses of 80 fs duration, second harmonic pulses with durations of 50 fs were generated.
8
τ=50 fs
7
Arbitrary Units
6
5
4
3
2
1
0
-100
-50
0
50
100
Delay (fs)
Fig. 2. Interferometric autocorrelation of typical second harmonic pulse.
The high single-pass conversion efficiencies and average powers generated in this experiment are indicative of
potentially higher nonlinear coefficients (>4 pm/V) in BIBO than previous estimates. This may be a
consequence of the specific physical-chemistry structure of the BIBO crystals [6].
Combined with a high damage tolerance, this makes the material a highly promising candidate for frequency
conversion applications in the visible and UV.
References
1. H. Hellwig, J. Liebertz, and L. Bohatý, "Exceptional large nonlinear optical coefficients in the monoclinic bismuth borate BiB3O6
(BIBO), "Solid State Commun. 109, 249–251 (1999).
2. P. Becker, J. Liebertz, L. Bohatý, "Top-seeded growth of bismuth triborate," J. Cryst. Growth 203, 149-155 (1999).
3. C. Du, Z. Wang, J. Liu, X. Xu, B. Teng, K. Fu, J. Wang, Y. Liu, Z. Shao, "Efficient intracavity second-harmonic generation at 1.06
µm in a BiB3O6 (BIBO) crystal," Appl. Phys. B 73, 215-217 (2001).
4. Z. Wang, B. Teng, K. Fu, X. Xu, R. Song, C. Du, H. Jiang, J. Wang, Z. Shao, "Efficient second harmonic generation of pulsed laser
radiation in BiB3O6 (BIBO) crystal with different phase-matching directions," Opt. Commun. 202, 217-220 (2002).
5. C. Du, B. Teng, Z. Wang, J. Liu, X. Xu, G. Xu, K. Fu, J. Wang, Y. Liu, Z. Shao "Actively Q-switched intracavity second-harmonic
generation of 1.06 µm in BiB3O6 crystal," Optics & Laser Technology 34, 343-346 (2002).
6. I.V.Kityk, W.Imiolek, A.Majchrowski, E.Michalski, "Photoinduced second harmonic generation in partially crystallized BiB3O6 glass,"
Opt.Commun. 219, 421-426 (2003).
# This work was supported, in part, by a NATO Collaborative Linkage Grant (PST.CLG.978742).