BIBO Crystal Research Articles

An improved Schlieren method for the sensitive and spatially resolved measurement of the quality of optical crystals with small apertures

We present an improved Schlieren method to measure the optical quality of crystals, defined by it’s optical homogeneity and the surface roughness of it’s facets. The method is based on a combination of Schlieren, interferometric and tilting angle measurements. It is especially appropriate for the optical characterization of crystals with small clear apertures. The theory and an application of this improved technique on a BIBO crystal are given. Spatial resolution and sensitivity of the method are mainly defined by the Schlieren setup, which offers a spatial resolution as high as 27 μm and a minimum deflection angle as low as 2.3×10-6.

Multi-stage pulse compression by use of cascaded quadratic nonlinearity

In this paper, the multi-stage compression of picosecond pulses by cascaded quadratic nonlinearity is studied theoretically, and the dependence of pulse compression on phase-mismatch, laser intensity, and crystal characteristics has been discussed in detail. We demonstrate that the multi-stage pulse compression is much more efficient than the single-stage with a same total crystal length. Pulses as short as ∼150 fs can be generated by compressing 30-ps initial pulses in a two-stage configuration under the realistic crystal and laser conditions, and shorter pulses of ∼30 fs may be obtained by three-stage compression. Pulse compression performances with BiBO and BBO crystals are compared and discussed finally.

Intra-cavity second harmonic generation with Nd:YVO 4/BIBO laser at 542 nm

We report, for the first time, an efficient intra-cavity second-harmonic generation (SHG) at 1084 nm in a nonlinear optical crystal, BiB 3O 6(BIBO) at the direction of ( θ, ϕ) = (170.1°, 90°), performed with a LD end-pumped cw Nd:YVO 4 laser. With 590 mW diode pump power, a continuous-wave (cw) SHG output power of 19 mW at 542 nm yellow–green color has been obtained using a 1.5 mm-thick BIBO crystal. The optical conversion efficiency was 3.22%. It was found that the output wavelength could be 532 nm, 537 nm or 542 nm according to regulating the angle of BIBO.

2.41 W compact efficient CW blue light generation by intra-cavity frequency doubling of a compact Nd:YAG laser

We report on a laser diode end-pumped Nd:YAG blue laser using a three-mirror-folded cavity. Three different crystals cut for type-I critical phase matching are used for the intra-cavity frequency doubling of the laser: 10-mm-long LiB 3O 5 (LBO), 15-mm-long LBO, and 10-mm-long BiB 3O 6 (BIBO). Up to 2.41 W of continuous wave output power in the blue spectral range at 473 nm is achieved with BIBO crystal (1.89 W with LBO) at the incident pump power of 16 W, the light-to-light conversion efficiency is about 15.1%.

Optical properties of BiB3O6 with different phase matching orientations

Basic optical properties of the new nonlinear crystal BiB3O6 (BIBO) are measured for second harmonic generation (SHG) of 1064 nm radiation. These properties include the effective nonlinearities for different phase matching orientations, the corresponding acceptance bandwidths and the optical losses. Effective nonlinearities of up to 3.2 pm/V (ϕ=90°, θ=-11°) and losses of less than 0.1 %/cm at 1064 nm indicate that BIBO is a promising new nonlinear crystal for SHG of 1064 nm radiation. A two-dimensional measurement with high spatial resolution of the SHG efficiency and the optical homogeneity, clearly demonstrate the high optical quality of BIBO crystals now available.

UV-Induced Nonlinear Absorption in Lanthanum Calcium Borate Single Crystals

It has been revealed that lanthanum calcium borate (La2CaB10O19) crystals show two-photon absorption (TPA) induced by a UV laser field. UV-induced TPA measurements were performed in the spectral range of 475-1130 nm using as fundamental beam the third harmonics of the 28 ps Nd-YAG pulsed laser as a pumping beam for LiB3O5 optical parametrized generator using Z-scan method. Investigations performed by the Z-scan method were done during illumination by a Xe-F laser (lambda = 217 nm) as a photoinducing (pumping) beam. The pumping laser beam created a thin surface layer (about 80-90 nm) that was the source of the observed photoinduced TPA. The highest values of the TPA beta coefficients were achieved for polarization of the pumping light directed along the second-order crystallographic axis of the investigated crystals. The obtained values of the TPA coefficients were higher than those for the BiB3O6 crystals investigated earlier by us.

Photoinduced non-linear optical effects in lanthanum calcium borate single crystals

We have revealed that lanthanum calcium borate (La2CaB10O19) crystals show two-photon absorption (TPA) favored by UV laser field. UV-induced TPA measurements were performed under illumination of a Xe-F laser (λ = 217nm) as a photoinducing (pumping) beam. This pumping laser beam created a thin surface layer (about 85 nm) that was a source of the observed photoinduced TPA. Use of the longer photoinducing wavelength leads to a substantial decrease of the photoinduced TPA. The performed DFT calculations of the band energy dispersion clearly show that the effect observed is due to specific band energy dispersion between the sub-bands. The Raman shifted Nd-YAG laser radiation (λ = 1.9 μm) as well as its second and fourth harmonics (λ = 950 and λ = 475 nm, respectively) were used as fundamental (probing) beams of the TPA. The highest values of the TPA β coefficient were achieved for polarization of the pumping light directed along the second-order crystallographic axis. The obtained values of TPA coefficients are higher than for BiBO crystals that were also investigated by us.

Tunable intra-cavity SHG of CW Ti:Sapphire lasers around 785 nm and 810 nm in BiBO-crystals

Phasematch curves as well as sensitivity to angular and wavelength misalignment for generation of second-harmonic of 785 nm and 810 nm in Bi(3)BO(6) crystal was calculated. Measurements were done for intra-cavity CW SHG in a Ti:Sapphire laser. The BiBO crystal was found to be excellent for this application. Temperature dependance was uncritical for both crystals, while power stability was good. Maximum blue output was 53 mW at 392 nm and 100 mW at 405 nm; corresponding to pump-to-blue optical conversion efficiencies of 0.96% and 1.82% respectively.

An extended cavity diode-pumped femtosecond Yb:KGW laser for applications in optical DNA sensor technology based on fluorescence lifetime measurements

A reliable and power-scalable extended cavity diode-pumped passively mode-locked Yb:KGW laser generating ~200 fs long pulses at a repetition rate of 15 MHz was developed and characterized. The laser delivered up to 150 mW of average power at fundamental wavelength of 1040 nm, corresponding to a pulse energy of 10 nJ. The laser radiation was frequency-doubled in a single pass configuration within a nonlinear BIBO crystal to produce femtosecond green radiation at 520 nm with peak power of ~200 W. The generated second harmonic served as excitation source for optical DNA biosensor based on fluorescence lifetime measurements obtained using the time-correlated single photon counting technique.

990 mW average power, 52% efficient, high-repetition-rate picosecond-pulse generation in the blue with BiB_3O_6

Efficient single-pass second-harmonic generation (SHG) of tunable high-repetition-rate picosecond pulses into the blue is reported in the nonlinear crystal BiB3O6. Using 2.4 ps fundamental pulses from a mode-locked Ti:sapphire laser at 76 MHz and a 10 mm crystal cut for type I (e + e --> o) phase matching in the optical yz plane, second-harmonic average powers as high as 990 mW with excellent stability have been generated at 52% conversion efficiency, and a tunable range of 370-450 nm is demonstrated. From measurements of single-pass SHG in the continuous-wave regime an effective nonlinear coefficient of 3.7 pm/V has been verified for BiB3O6, and direct comparison with beta-BaB2O4 confirms a SHG power enhancement of approximately 23% for the same crystal length. Autocorrelation measurements in a 200 microm crystal of beta-BaB2O4 result in durations of 2.8 ps for the second-harmonic blue pulses.

Characterization of bismuth triborate single crystal using Brillouin and Raman spectroscopy

AbstractThe bismuth triborate (BiB3O6; BIBO) single crystal has been studied by Brillouin and Raman spectroscopy. Using Brillouin spectroscopy the propagation of the acoustic phonons in [100], [010], [001], [110] and [011] directions has been analyzed. The influence of birefringent and optical activity of BIBO crystal on some acoustic phonons has been discussed. The Raman spectra of the crystal in different scattering geometries have been recorded in the 50–1500 cm‐1 spectral range at room temperature. The number and symmetry of Raman active modes was determined on the basis of site symmetry group analysis. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

UV-induced two-photon absorption in BiB 3O 6 single crystals

We show that BiB 3O 6 (BiBO) crystals, well known for their excellent second harmonic generation (SHG) properties, may also be of interest for third-order optical phenomena, particularly for two-photon absorption (TPA). Photoinduced TPA measurements were performed under illumination of excimer Xe–F laser ( λ = 217 nm) as a photoinducing (pumping) beam. It created a thin surface layer (about 85 nm) that was a source of the observed photoinduced TPA. Raman shifted Nd-YAG laser radiation ( λ = 1.9 μm) as well as its second and fourth harmonics ( λ = 950 and λ = 475 nm, respectively) were used as fundamental (probing) beams of the TPA. The highest values of the TPA β coefficient were achieved for a polarization of the pumping light directed along crystallographic axis b. Quantum chemical simulations indicate on substantial contribution of UV-induced electron–phonon anharmonicity to the observed TPA. The obtained values of TPA coefficients indicate a possibility of using BiBO crystals as UV-operated optical limiters in a wide spectral range.

High-power intracavity second-harmonic generation of 1.34 µm in BiB3O6 crystal

The phase-matching curve and effective nonlinear optical coefficient distribution for the second-harmonic generation of 1342 nm in BiB3O6 crystal were calculated. High-power intracavity second-harmonic generation of 1.34 microm in BiB3O6 crystals, at a type-I phase-matching direction of (theta, ø)=(9.07 degrees , 0 degrees ), was performed with a LD-end-pumped Nd:YVO4 laser. The maximum continuous-wave (CW) and quasi-CW output powers at 671 nm were obtained to be 1.22 W and 4.38 W, with the corresponding optical conversion efficiency of 4.9% and 9.5%, respectively.

491 nm generation by sum-frequency mixing of diode pumped neodymium lasers

We present three different dual-wavelength laser architectures to obtain cw blue radiations. They are based on diode-pumped Nd-doped crystals lasing on the 4F3/2-4I11/2 and 4F3/2-4I9/2 transitions. Blue radiations were achieved by intracavity sum frequency operation in a BiB3O6 crystal. We report a maximum output blue power of 303 mW at 491 nm for a pump power of 10 W.

Vibrational spectra of crystals of bismuth borates

The vibrational spectra of crystals of bismuth borates Bi24B2O39, Bi4B2O9, BiBO3, and Bi2B8O15 were obtained for the first time, and the spectra of Bi3B5O12 and BiB3O6 crystals measured in the range 30–1600 cm−1 at room temperature were refined. The lines observed were assigned to the corresponding vibrational transitions on the basis of the theoretical group analysis and comparison of the obtained results with the vibrational spectra of borates of different composition. The complication of the structure of bismuth borates with increasing content of B2O3 was traced by the example of vibrational spectra.

Raman study of phonons in bismuth triborate BiB3O6 crystal

A Raman-scattering study of the vibrational modes in a BiB3O6 crystal was conducted at room temperature. The numbers of external and internal modes obtained in experiment are consistent with the results of a group theoretical analysis. The Raman lines below ∼300cm−1 and from ∼300to1600cm−1 are assigned to the external modes of the lattice and internal vibrations of the BO3 and BO4 subunits of the BiB3O6 structure, respectively.

Determining the optimal growth orientation of BiB 3O 6 crystal

Nonlinear optical crystal BiB 3O 6 grown by using seed crystals with different orientations resulted in different morphologies, dimensions and qualities. In order to find out the optimal seed orientation, thermal expansion property of BIBO crystal was investigated. By analyzing the thermal expansion ellipsoid, the optimal seed orientation seems to be [ 1 ¯ 0 1 ] . High-quality BIBO crystals with dimensions up to 30×30×40 mm 3 and weight of 120 g have been grown using [ 1 ¯ 0 1 ] seed under an appropriate growth conditions.

High-average-power femtosecond pulse generation in the blue using BiB_3O_6

Efficient generation of tunable femtosecond pulses in the blue is reported in the nonlinear crystal BiB3O6. By use of fundamental pulses from a mode-locked Ti:sapphire laser at 76 MHz, single-pass second-harmonic average powers of as much as 830 mW have been generated at 50% conversion efficiency, and a tunable range of 375-435 nm in the blue is demonstrated. Temporal measurements using cross correlation of the fundamental and second-harmonic pulses in a 100-microm-thick beta-BaB2O4 crystal result in blue pulse durations of 220 fs for 130-fs fundamental pulses. Direct experimental comparison with beta-BaB2O4 confirms the superior performance BiB3O6 for second-harmonic generation of femtosecond pulses.

Noncollinear second-harmonic generation in BiB_3O_6

Noncollinear second-harmonic generation (SHG) in a BiB3O6 crystal was investigated. Using a picosecond Nd:YAG laser as the fundamental light source, we achieved two efficient types of noncritical noncollinear SHG. A total reflection technique was employed to make the experimental setup quite simple. The noncollinear SHG efficiency could be as high as 49.2%.

Generation of UV light by frequency doubling in BIBO

We consider generation of 384 nm UV radiation by cavity enhanced second harmonic generation. The newly developed BIBO (BiB 3O 6) crystal is compared to a LBO (LiB 3O 5) crystal of the same physical shape. We find that the nonlinearity of BIBO is nine times larger than for LBO and they have similar passive losses. With BIBO, we obtain an internal IR to UV conversion efficiency of 50% at just 130 mW of coupled IR power. Unfortunately, instability in the BIBO crystal induced by the IR cavity field makes cw operation difficult except for low IR power.